Different compression methods for FPI

From 387fa7d10ecacd0c3c15b0bded769bddc234eb53 Mon Sep 17 00:00:00 2001
From: Andrey Borodin <amborodin@acm.org>
Date: Sat, 27 Feb 2021 09:03:50 +0500
Subject: [PATCH 1/2] Use different compression methods for FPIs

---
 configure                               | 170 ++++++++++++++++++++++++
 configure.ac                            |  20 +++
 src/backend/Makefile                    |   2 +-
 src/backend/access/transam/xlog.c       |  13 ++
 src/backend/access/transam/xloginsert.c |  58 +++++++-
 src/backend/access/transam/xlogreader.c |  74 ++++++++++-
 src/backend/utils/misc/guc.c            |  11 ++
 src/include/access/xlog.h               |   1 +
 src/include/access/xlog_internal.h      |   7 +
 src/include/access/xlogreader.h         |   1 +
 src/include/access/xlogrecord.h         |   7 +-
 src/include/pg_config.h.in              |   3 +
 src/tools/msvc/Solution.pm              |   1 +
 13 files changed, 357 insertions(+), 11 deletions(-)

diff --git a/configure b/configure
index fad817bb38..440d1e8ce5 100755
--- a/configure
+++ b/configure
@@ -699,6 +699,9 @@ with_gnu_ld
 LD
 LDFLAGS_SL
 LDFLAGS_EX
+LZ4_LIBS
+LZ4_CFLAGS
+with_lz4
 with_zlib
 with_system_tzdata
 with_libxslt
@@ -864,6 +867,7 @@ with_libxml
 with_libxslt
 with_system_tzdata
 with_zlib
+with_lz4
 with_gnu_ld
 with_ssl
 with_openssl
@@ -891,6 +895,8 @@ ICU_LIBS
 XML2_CONFIG
 XML2_CFLAGS
 XML2_LIBS
+LZ4_CFLAGS
+LZ4_LIBS
 LDFLAGS_EX
 LDFLAGS_SL
 PERL
@@ -1569,6 +1575,7 @@ Optional Packages:
   --with-system-tzdata=DIR
                           use system time zone data in DIR
   --without-zlib          do not use Zlib
+  --with-lz4              build with LZ4 support
   --with-gnu-ld           assume the C compiler uses GNU ld [default=no]
   --with-ssl=LIB          use LIB for SSL/TLS support (openssl)
   --with-openssl          obsolete spelling of --with-ssl=openssl
@@ -1596,6 +1603,8 @@ Some influential environment variables:
   XML2_CONFIG path to xml2-config utility
   XML2_CFLAGS C compiler flags for XML2, overriding pkg-config
   XML2_LIBS   linker flags for XML2, overriding pkg-config
+  LZ4_CFLAGS  C compiler flags for LZ4, overriding pkg-config
+  LZ4_LIBS    linker flags for LZ4, overriding pkg-config
   LDFLAGS_EX  extra linker flags for linking executables only
   LDFLAGS_SL  extra linker flags for linking shared libraries only
   PERL        Perl program
@@ -8563,6 +8572,137 @@ fi
 
 
 
+#
+# LZ4
+#
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether to build with LZ4 support" >&5
+$as_echo_n "checking whether to build with LZ4 support... " >&6; }
+
+
+
+# Check whether --with-lz4 was given.
+if test "${with_lz4+set}" = set; then :
+  withval=$with_lz4;
+  case $withval in
+    yes)
+
+$as_echo "#define USE_LZ4 1" >>confdefs.h
+
+      ;;
+    no)
+      :
+      ;;
+    *)
+      as_fn_error $? "no argument expected for --with-lz4 option" "$LINENO" 5
+      ;;
+  esac
+
+else
+  with_lz4=no
+
+fi
+
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $with_lz4" >&5
+$as_echo "$with_lz4" >&6; }
+
+
+if test "$with_lz4" = yes; then
+
+pkg_failed=no
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for liblz4" >&5
+$as_echo_n "checking for liblz4... " >&6; }
+
+if test -n "$LZ4_CFLAGS"; then
+    pkg_cv_LZ4_CFLAGS="$LZ4_CFLAGS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"liblz4\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "liblz4") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_LZ4_CFLAGS=`$PKG_CONFIG --cflags "liblz4" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+if test -n "$LZ4_LIBS"; then
+    pkg_cv_LZ4_LIBS="$LZ4_LIBS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"liblz4\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "liblz4") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_LZ4_LIBS=`$PKG_CONFIG --libs "liblz4" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+
+
+
+if test $pkg_failed = yes; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+
+if $PKG_CONFIG --atleast-pkgconfig-version 0.20; then
+        _pkg_short_errors_supported=yes
+else
+        _pkg_short_errors_supported=no
+fi
+        if test $_pkg_short_errors_supported = yes; then
+	        LZ4_PKG_ERRORS=`$PKG_CONFIG --short-errors --print-errors --cflags --libs "liblz4" 2>&1`
+        else
+	        LZ4_PKG_ERRORS=`$PKG_CONFIG --print-errors --cflags --libs "liblz4" 2>&1`
+        fi
+	# Put the nasty error message in config.log where it belongs
+	echo "$LZ4_PKG_ERRORS" >&5
+
+	as_fn_error $? "Package requirements (liblz4) were not met:
+
+$LZ4_PKG_ERRORS
+
+Consider adjusting the PKG_CONFIG_PATH environment variable if you
+installed software in a non-standard prefix.
+
+Alternatively, you may set the environment variables LZ4_CFLAGS
+and LZ4_LIBS to avoid the need to call pkg-config.
+See the pkg-config man page for more details." "$LINENO" 5
+elif test $pkg_failed = untried; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+	{ { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error $? "The pkg-config script could not be found or is too old.  Make sure it
+is in your PATH or set the PKG_CONFIG environment variable to the full
+path to pkg-config.
+
+Alternatively, you may set the environment variables LZ4_CFLAGS
+and LZ4_LIBS to avoid the need to call pkg-config.
+See the pkg-config man page for more details.
+
+To get pkg-config, see <http://pkg-config.freedesktop.org/>.
+See \`config.log' for more details" "$LINENO" 5; }
+else
+	LZ4_CFLAGS=$pkg_cv_LZ4_CFLAGS
+	LZ4_LIBS=$pkg_cv_LZ4_LIBS
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+
+fi
+  LIBS="$LZ4_LIBS $LIBS"
+  CFLAGS="$LZ4_CFLAGS $CFLAGS"
+fi
+
 #
 # Assignments
 #
@@ -13376,6 +13516,36 @@ Use --without-zlib to disable zlib support." "$LINENO" 5
 fi
 
 
+fi
+
+if test "$with_lz4" = yes; then
+  for ac_header in lz4/lz4.h
+do :
+  ac_fn_c_check_header_mongrel "$LINENO" "lz4/lz4.h" "ac_cv_header_lz4_lz4_h" "$ac_includes_default"
+if test "x$ac_cv_header_lz4_lz4_h" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_LZ4_LZ4_H 1
+_ACEOF
+
+else
+  for ac_header in lz4.h
+do :
+  ac_fn_c_check_header_mongrel "$LINENO" "lz4.h" "ac_cv_header_lz4_h" "$ac_includes_default"
+if test "x$ac_cv_header_lz4_h" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_LZ4_H 1
+_ACEOF
+
+else
+  as_fn_error $? "lz4.h header file is required for LZ4" "$LINENO" 5
+fi
+
+done
+
+fi
+
+done
+
 fi
 
 if test "$with_gssapi" = yes ; then
diff --git a/configure.ac b/configure.ac
index 0ed53571dd..780791ae8a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -986,6 +986,21 @@ PGAC_ARG_BOOL(with, zlib, yes,
               [do not use Zlib])
 AC_SUBST(with_zlib)
 
+#
+# LZ4
+#
+AC_MSG_CHECKING([whether to build with LZ4 support])
+PGAC_ARG_BOOL(with, lz4, no, [build with LZ4 support],
+              [AC_DEFINE([USE_LZ4], 1, [Define to 1 to build with LZ4 support. (--with-lz4)])])
+AC_MSG_RESULT([$with_lz4])
+AC_SUBST(with_lz4)
+
+if test "$with_lz4" = yes; then
+  PKG_CHECK_MODULES(LZ4, liblz4)
+  LIBS="$LZ4_LIBS $LIBS"
+  CFLAGS="$LZ4_CFLAGS $CFLAGS"
+fi
+
 #
 # Assignments
 #
@@ -1407,6 +1422,11 @@ failure.  It is possible the compiler isn't looking in the proper directory.
 Use --without-zlib to disable zlib support.])])
 fi
 
+if test "$with_lz4" = yes; then
+  AC_CHECK_HEADERS(lz4/lz4.h, [],
+       [AC_CHECK_HEADERS(lz4.h, [], [AC_MSG_ERROR([lz4.h header file is required for LZ4])])])
+fi
+
 if test "$with_gssapi" = yes ; then
   AC_CHECK_HEADERS(gssapi/gssapi.h, [],
 	[AC_CHECK_HEADERS(gssapi.h, [], [AC_MSG_ERROR([gssapi.h header file is required for GSSAPI])])])
diff --git a/src/backend/Makefile b/src/backend/Makefile
index 0da848b1fd..3af216ddfc 100644
--- a/src/backend/Makefile
+++ b/src/backend/Makefile
@@ -48,7 +48,7 @@ OBJS = \
 LIBS := $(filter-out -lpgport -lpgcommon, $(LIBS)) $(LDAP_LIBS_BE) $(ICU_LIBS)
 
 # The backend doesn't need everything that's in LIBS, however
-LIBS := $(filter-out -lz -lreadline -ledit -ltermcap -lncurses -lcurses, $(LIBS))
+LIBS := $(filter-out -lreadline -ledit -ltermcap -lncurses -lcurses, $(LIBS))
 
 ifeq ($(with_systemd),yes)
 LIBS += -lsystemd
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index e04250f4e9..82cedb0a41 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -99,6 +99,7 @@ bool		EnableHotStandby = false;
 bool		fullPageWrites = true;
 bool		wal_log_hints = false;
 bool		wal_compression = false;
+int			wal_compression_method = PGLZ_COMPRESSION_ID;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
@@ -180,6 +181,18 @@ const struct config_enum_entry recovery_target_action_options[] = {
 	{NULL, 0, false}
 };
 
+/* Note that due to conditional compilation, offsets within the array are not static */
+const struct config_enum_entry wal_compression_options[] = {
+	{"pglz", PGLZ_COMPRESSION_ID, false},
+#ifdef  USE_LZ4
+	{"lz4", LZ4_COMPRESSION_ID, false},
+#endif
+#ifdef  HAVE_LIBZ
+	{"zlib", ZLIB_COMPRESSION_ID, false},
+#endif
+	{NULL, 0, false}
+};
+
 /*
  * Statistics for current checkpoint are collected in this global struct.
  * Because only the checkpointer or a stand-alone backend can perform
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
index 7052dc245e..256931a93d 100644
--- a/src/backend/access/transam/xloginsert.c
+++ b/src/backend/access/transam/xloginsert.c
@@ -33,6 +33,14 @@
 #include "storage/proc.h"
 #include "utils/memutils.h"
 
+#ifdef USE_LZ4
+#include "lz4.h"
+#endif
+
+#ifdef HAVE_LIBZ
+#include <zlib.h>
+#endif
+
 /* Buffer size required to store a compressed version of backup block image */
 #define PGLZ_MAX_BLCKSZ PGLZ_MAX_OUTPUT(BLCKSZ)
 
@@ -113,7 +121,8 @@ static XLogRecData *XLogRecordAssemble(RmgrId rmid, uint8 info,
 									   XLogRecPtr RedoRecPtr, bool doPageWrites,
 									   XLogRecPtr *fpw_lsn, int *num_fpi);
 static bool XLogCompressBackupBlock(char *page, uint16 hole_offset,
-									uint16 hole_length, char *dest, uint16 *dlen);
+									uint16 hole_length, char *dest,
+									uint16 *dlen, CompressionId compression);
 
 /*
  * Begin constructing a WAL record. This must be called before the
@@ -630,11 +639,12 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
 			 */
 			if (wal_compression)
 			{
+				bimg.compression_method = wal_compression_method;
 				is_compressed =
 					XLogCompressBackupBlock(page, bimg.hole_offset,
 											cbimg.hole_length,
 											regbuf->compressed_page,
-											&compressed_len);
+											&compressed_len, bimg.compression_method);
 			}
 
 			/*
@@ -827,7 +837,7 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
  */
 static bool
 XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
-						char *dest, uint16 *dlen)
+						char *dest, uint16 *dlen, CompressionId compression)
 {
 	int32		orig_len = BLCKSZ - hole_length;
 	int32		len;
@@ -853,12 +863,50 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 	else
 		source = page;
 
+	switch (compression)
+	{
+#ifdef USE_LZ4
+	case LZ4_COMPRESSION_ID:
+		len = LZ4_compress_fast(source, dest, orig_len, PGLZ_MAX_BLCKSZ, 1);
+		break;
+#endif
+
+#ifdef HAVE_LIBZ
+	case ZLIB_COMPRESSION_ID:
+		{
+			unsigned long	len_l = PGLZ_MAX_BLCKSZ;
+			if (compress((Bytef*)dest, &len_l, (Bytef*)source, orig_len) != Z_OK)
+			{
+				// XXX: using an interface other than compress() would allow giving a better error message
+				ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("failed compressing zlib")));
+				len_l = -1;
+			}
+			len = len_l;
+			break;
+		}
+#endif
+
+	case PGLZ_COMPRESSION_ID:
+		len = pglz_compress(source, orig_len, dest, PGLZ_strategy_default);
+		break;
+
+	default:
+		/*
+		 * It should be impossible to get here for zlib and lz4, which
+		 * cannot be assigned if they're not enabled at compile time.
+		 */
+		ereport(ERROR,
+			(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			 errmsg("unknown compression method requested: %d", compression)));
+	}
+
 	/*
-	 * We recheck the actual size even if pglz_compress() reports success and
+	 * We recheck the actual size even if compression reports success and
 	 * see if the number of bytes saved by compression is larger than the
 	 * length of extra data needed for the compressed version of block image.
 	 */
-	len = pglz_compress(source, orig_len, dest, PGLZ_strategy_default);
 	if (len >= 0 &&
 		len + extra_bytes < orig_len)
 	{
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index 42738eb940..10e8766e01 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -33,6 +33,14 @@
 #include "utils/memutils.h"
 #endif
 
+#ifdef USE_LZ4
+#include "lz4.h"
+#endif
+
+#ifdef HAVE_LIBZ
+#include <zlib.h>
+#endif
+
 static void report_invalid_record(XLogReaderState *state, const char *fmt,...)
 			pg_attribute_printf(2, 3);
 static bool allocate_recordbuf(XLogReaderState *state, uint32 reclength);
@@ -1286,6 +1294,7 @@ DecodeXLogRecord(XLogReaderState *state, XLogRecord *record, char **errormsg)
 			{
 				COPY_HEADER_FIELD(&blk->bimg_len, sizeof(uint16));
 				COPY_HEADER_FIELD(&blk->hole_offset, sizeof(uint16));
+				COPY_HEADER_FIELD(&blk->compression_method, sizeof(uint8));
 				COPY_HEADER_FIELD(&blk->bimg_info, sizeof(uint8));
 
 				blk->apply_image = ((blk->bimg_info & BKPIMAGE_APPLY) != 0);
@@ -1535,6 +1544,31 @@ XLogRecGetBlockData(XLogReaderState *record, uint8 block_id, Size *len)
 	}
 }
 
+/*
+ * Return a statically allocated string associated with the given compression
+ * method.  This is similar to the guc, but isn't subject to conditional
+ * compilation.
+ */
+static const char *
+wal_compression_name(CompressionId compression)
+{
+	/*
+	 * This could index into the guc array, except that it's compiled
+	 * conditionally and unsupported methods are elided.
+	 */
+	switch (compression)
+	{
+		case PGLZ_COMPRESSION_ID:
+			return "pglz";
+		case LZ4_COMPRESSION_ID:
+			return "lz4";
+		case ZLIB_COMPRESSION_ID:
+			return "zlib";
+		default:
+			return "???";
+	}
+}
+
 /*
  * Restore a full-page image from a backup block attached to an XLOG record.
  *
@@ -1558,8 +1592,44 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 	if (bkpb->bimg_info & BKPIMAGE_IS_COMPRESSED)
 	{
 		/* If a backup block image is compressed, decompress it */
-		if (pglz_decompress(ptr, bkpb->bimg_len, tmp.data,
-							BLCKSZ - bkpb->hole_length, true) < 0)
+		int32 decomp_result = -1;
+		switch (bkpb->compression_method)
+		{
+		case PGLZ_COMPRESSION_ID:
+			decomp_result = pglz_decompress(ptr, bkpb->bimg_len, tmp.data,
+							BLCKSZ - bkpb->hole_length, true);
+			break;
+
+#ifdef USE_LZ4
+		case LZ4_COMPRESSION_ID:
+			decomp_result = LZ4_decompress_safe(ptr, tmp.data, bkpb->bimg_len, BLCKSZ);
+			break;
+#endif
+
+#ifdef HAVE_LIBZ
+		case ZLIB_COMPRESSION_ID:
+		{
+			unsigned long decomp_result_l = 0;
+			decomp_result_l = BLCKSZ - bkpb->hole_length;
+			if (uncompress((Bytef*)tmp.data, &decomp_result_l, (Bytef*)ptr, bkpb->bimg_len) == Z_OK)
+				decomp_result = decomp_result_l;
+			else
+				decomp_result = -1;
+			break;
+		}
+#endif
+
+		default:
+			report_invalid_record(record, "image at %X/%X is compressed with unsupported codec, block %d (%d/%s)",
+								  (uint32) (record->ReadRecPtr >> 32),
+								  (uint32) record->ReadRecPtr,
+								  block_id,
+								  bkpb->compression_method,
+								  wal_compression_name(bkpb->compression_method));
+			return false;
+		}
+
+		if (decomp_result < 0)
 		{
 			report_invalid_record(record, "invalid compressed image at %X/%X, block %d",
 								  LSN_FORMAT_ARGS(record->ReadRecPtr),
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 855076b1fd..42253c11f1 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -508,6 +508,7 @@ extern const struct config_enum_entry archive_mode_options[];
 extern const struct config_enum_entry recovery_target_action_options[];
 extern const struct config_enum_entry sync_method_options[];
 extern const struct config_enum_entry dynamic_shared_memory_options[];
+extern const struct config_enum_entry wal_compression_options[];
 
 /*
  * GUC option variables that are exported from this module
@@ -4721,6 +4722,16 @@ static struct config_enum ConfigureNamesEnum[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"wal_compression_method", PGC_SIGHUP, WAL_SETTINGS,
+			gettext_noop("Set the method used to compress full page images in the WAL."),
+			NULL
+		},
+		&wal_compression_method,
+		PGLZ_COMPRESSION_ID, wal_compression_options,
+		NULL, NULL, NULL
+	},
+
 	{
 		{"dynamic_shared_memory_type", PGC_POSTMASTER, RESOURCES_MEM,
 			gettext_noop("Selects the dynamic shared memory implementation used."),
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index 6d384d3ce6..5f8c5f120e 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -184,6 +184,7 @@ typedef enum RecoveryPauseState
 } RecoveryPauseState;
 
 extern PGDLLIMPORT int wal_level;
+extern PGDLLIMPORT int wal_compression_method;
 
 /* Is WAL archiving enabled (always or only while server is running normally)? */
 #define XLogArchivingActive() \
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index b23e286406..c8768d7dbe 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -324,4 +324,11 @@ extern bool InArchiveRecovery;
 extern bool StandbyMode;
 extern char *recoveryRestoreCommand;
 
+typedef enum CompressionId
+{
+	PGLZ_COMPRESSION_ID = 0,
+	LZ4_COMPRESSION_ID = 1,
+	ZLIB_COMPRESSION_ID = 2,
+} CompressionId;
+
 #endif							/* XLOG_INTERNAL_H */
diff --git a/src/include/access/xlogreader.h b/src/include/access/xlogreader.h
index 21d200d3df..3d19c315d7 100644
--- a/src/include/access/xlogreader.h
+++ b/src/include/access/xlogreader.h
@@ -133,6 +133,7 @@ typedef struct
 	bool		apply_image;	/* has image that should be restored */
 	char	   *bkp_image;
 	uint16		hole_offset;
+	uint8		compression_method;
 	uint16		hole_length;
 	uint16		bimg_len;
 	uint8		bimg_info;
diff --git a/src/include/access/xlogrecord.h b/src/include/access/xlogrecord.h
index 80c92a2498..3a885dc0c2 100644
--- a/src/include/access/xlogrecord.h
+++ b/src/include/access/xlogrecord.h
@@ -129,9 +129,10 @@ typedef struct XLogRecordBlockHeader
  */
 typedef struct XLogRecordBlockImageHeader
 {
-	uint16		length;			/* number of page image bytes */
-	uint16		hole_offset;	/* number of bytes before "hole" */
-	uint8		bimg_info;		/* flag bits, see below */
+	uint16		length;				/* number of page image bytes */
+	uint16		hole_offset;		/* number of bytes before "hole" */
+	uint8		compression_method; /* compression method used for image */
+	uint8		bimg_info;			/* flag bits, see below */
 
 	/*
 	 * If BKPIMAGE_HAS_HOLE and BKPIMAGE_IS_COMPRESSED, an
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index 7a7cc21d8d..0a6422da4f 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -899,6 +899,9 @@
 /* Define to 1 to build with LLVM based JIT support. (--with-llvm) */
 #undef USE_LLVM
 
+/* Define to 1 to build with LZ4 support (--with-lz4) */
+#undef USE_LZ4
+
 /* Define to select named POSIX semaphores. */
 #undef USE_NAMED_POSIX_SEMAPHORES
 
diff --git a/src/tools/msvc/Solution.pm b/src/tools/msvc/Solution.pm
index a4f5cc4bdb..14605371bb 100644
--- a/src/tools/msvc/Solution.pm
+++ b/src/tools/msvc/Solution.pm
@@ -485,6 +485,7 @@ sub GenerateFiles
 		USE_ICU => $self->{options}->{icu} ? 1 : undef,
 		USE_LIBXML                 => undef,
 		USE_LIBXSLT                => undef,
+		USE_LZ4                    => undef,
 		USE_LDAP                   => $self->{options}->{ldap} ? 1 : undef,
 		USE_LLVM                   => undef,
 		USE_NAMED_POSIX_SEMAPHORES => undef,
-- 
2.17.0

From 672a9763121385f6a5b8153b21696e98e6ae724e Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Thu, 11 Mar 2021 17:36:24 -0600
Subject: [PATCH 2/2] default to --with-lz4

this is meant to exercise the new feature in the CIs, and not meant to be
merged
---
 configure                         | 6 ++++--
 configure.ac                      | 4 ++--
 src/backend/access/transam/xlog.c | 2 +-
 src/backend/utils/misc/guc.c      | 4 ++--
 4 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/configure b/configure
index 440d1e8ce5..b411ed1cb4 100755
--- a/configure
+++ b/configure
@@ -1575,7 +1575,7 @@ Optional Packages:
   --with-system-tzdata=DIR
                           use system time zone data in DIR
   --without-zlib          do not use Zlib
-  --with-lz4              build with LZ4 support
+  --without-lz4           build without LZ4 support
   --with-gnu-ld           assume the C compiler uses GNU ld [default=no]
   --with-ssl=LIB          use LIB for SSL/TLS support (openssl)
   --with-openssl          obsolete spelling of --with-ssl=openssl
@@ -8598,7 +8598,9 @@ $as_echo "#define USE_LZ4 1" >>confdefs.h
   esac
 
 else
-  with_lz4=no
+  with_lz4=yes
+
+$as_echo "#define USE_LZ4 1" >>confdefs.h
 
 fi
 
diff --git a/configure.ac b/configure.ac
index 780791ae8a..392784d55c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -990,8 +990,8 @@ AC_SUBST(with_zlib)
 # LZ4
 #
 AC_MSG_CHECKING([whether to build with LZ4 support])
-PGAC_ARG_BOOL(with, lz4, no, [build with LZ4 support],
-              [AC_DEFINE([USE_LZ4], 1, [Define to 1 to build with LZ4 support. (--with-lz4)])])
+PGAC_ARG_BOOL(with, lz4, yes, [build without LZ4 support],
+              [AC_DEFINE([USE_LZ4], 1, [Define to 1 to build without LZ4 support. (--without-lz4)])])
 AC_MSG_RESULT([$with_lz4])
 AC_SUBST(with_lz4)
 
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 82cedb0a41..321558a2c6 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -99,7 +99,7 @@ bool		EnableHotStandby = false;
 bool		fullPageWrites = true;
 bool		wal_log_hints = false;
 bool		wal_compression = false;
-int			wal_compression_method = PGLZ_COMPRESSION_ID;
+int			wal_compression_method = LZ4_COMPRESSION_ID;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 42253c11f1..6aa14694f4 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -1269,7 +1269,7 @@ static struct config_bool ConfigureNamesBool[] =
 			NULL
 		},
 		&wal_compression,
-		false,
+		true,
 		NULL, NULL, NULL
 	},
 
@@ -4728,7 +4728,7 @@ static struct config_enum ConfigureNamesEnum[] =
 			NULL
 		},
 		&wal_compression_method,
-		PGLZ_COMPRESSION_ID, wal_compression_options,
+		LZ4_COMPRESSION_ID, wal_compression_options,
 		NULL, NULL, NULL
 	},
 
-- 
2.17.0

From ac1cf5ed6a22aade34424d6461bbb83ffaba28ba Mon Sep 17 00:00:00 2001
From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Date: Mon, 8 Mar 2021 15:32:30 +0900
Subject: [PATCH 1/8] Run 011_crash_recovery.pl with wal_level=minimal

The test doesn't need that feature and pg_current_xact_id() is better
exercised by turning off the feature.

Copied from: https://www.postgresql.org/message-id/20210308.173242.463790587797836129.horikyota.ntt%40gmail.com
---
 src/test/recovery/t/011_crash_recovery.pl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/test/recovery/t/011_crash_recovery.pl b/src/test/recovery/t/011_crash_recovery.pl
index 10cd98f70a..690655dda2 100644
--- a/src/test/recovery/t/011_crash_recovery.pl
+++ b/src/test/recovery/t/011_crash_recovery.pl
@@ -11,7 +11,7 @@ use Config;
 plan tests => 3;
 
 my $node = get_new_node('primary');
-$node->init(allows_streaming => 1);
+$node->init();
 $node->start;
 
 my ($stdin, $stdout, $stderr) = ('', '', '');
-- 
2.17.0

From b6021740e9a593db2d57db7c394c66eb4cf0253f Mon Sep 17 00:00:00 2001
From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Date: Mon, 8 Mar 2021 15:43:01 +0900
Subject: [PATCH 2/8] Make sure published XIDs are persistent

pg_xact_status() premises that XIDs obtained by
pg_current_xact_id(_if_assigned)() are persistent beyond a crash. But
XIDs are not guaranteed to go beyond WAL buffers before commit and
thus XIDs may vanish if server crashes before commit. This patch
guarantees the XID shown by the functions to be flushed out to disk.

Copied from: https://www.postgresql.org/message-id/20210308.173242.463790587797836129.horikyota.ntt%40gmail.com
---
 src/backend/access/transam/xact.c | 55 +++++++++++++++++++++++++------
 src/backend/access/transam/xlog.c |  2 +-
 src/backend/utils/adt/xid8funcs.c | 12 ++++++-
 src/include/access/xact.h         |  3 +-
 4 files changed, 59 insertions(+), 13 deletions(-)

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 6395a9b240..38e978d238 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -201,7 +201,7 @@ typedef struct TransactionStateData
 	int			prevSecContext; /* previous SecurityRestrictionContext */
 	bool		prevXactReadOnly;	/* entry-time xact r/o state */
 	bool		startedInRecovery;	/* did we start in recovery? */
-	bool		didLogXid;		/* has xid been included in WAL record? */
+	XLogRecPtr 	minLSN;			/* LSN needed to reach to record the xid */
 	int			parallelModeLevel;	/* Enter/ExitParallelMode counter */
 	bool		chain;			/* start a new block after this one */
 	bool		assigned;		/* assigned to top-level XID */
@@ -520,14 +520,46 @@ GetCurrentFullTransactionIdIfAny(void)
  *	MarkCurrentTransactionIdLoggedIfAny
  *
  * Remember that the current xid - if it is assigned - now has been wal logged.
+ *
+ * upto is the LSN up to which we need to flush WAL to ensure the current xid
+ * to be persistent. See EnsureCurrentTransactionIdLogged().
  */
 void
-MarkCurrentTransactionIdLoggedIfAny(void)
+MarkCurrentTransactionIdLoggedIfAny(XLogRecPtr upto)
 {
-	if (FullTransactionIdIsValid(CurrentTransactionState->fullTransactionId))
-		CurrentTransactionState->didLogXid = true;
+	if (FullTransactionIdIsValid(CurrentTransactionState->fullTransactionId) &&
+		XLogRecPtrIsInvalid(CurrentTransactionState->minLSN))
+		CurrentTransactionState->minLSN = upto;
 }
 
+/*
+ *	EnsureCurrentTransactionIdLogged
+ *
+ * Make sure that the current top XID is WAL-logged.
+ */
+void
+EnsureTopTransactionIdLogged(void)
+{
+	/*
+	 * We need at least one WAL record for the current top transaction to be
+	 * flushed out.  Write one if we don't have one yet.
+	 */
+	if (XLogRecPtrIsInvalid(TopTransactionStateData.minLSN))
+	{
+		xl_xact_assignment xlrec;
+
+		xlrec.xtop = XidFromFullTransactionId(XactTopFullTransactionId);
+		Assert(TransactionIdIsValid(xlrec.xtop));
+		xlrec.nsubxacts = 0;
+
+		XLogBeginInsert();
+		XLogRegisterData((char *) &xlrec, MinSizeOfXactAssignment);
+		TopTransactionStateData.minLSN =
+			XLogInsert(RM_XACT_ID, XLOG_XACT_ASSIGNMENT);
+	}
+
+	XLogFlush(TopTransactionStateData.minLSN);
+}
 
 /*
  *	GetStableLatestTransactionId
@@ -616,14 +648,14 @@ AssignTransactionId(TransactionState s)
 	 * When wal_level=logical, guarantee that a subtransaction's xid can only
 	 * be seen in the WAL stream if its toplevel xid has been logged before.
 	 * If necessary we log an xact_assignment record with fewer than
-	 * PGPROC_MAX_CACHED_SUBXIDS. Note that it is fine if didLogXid isn't set
+	 * PGPROC_MAX_CACHED_SUBXIDS. Note that it is fine if minLSN isn't set
 	 * for a transaction even though it appears in a WAL record, we just might
 	 * superfluously log something. That can happen when an xid is included
 	 * somewhere inside a wal record, but not in XLogRecord->xl_xid, like in
 	 * xl_standby_locks.
 	 */
 	if (isSubXact && XLogLogicalInfoActive() &&
-		!TopTransactionStateData.didLogXid)
+		XLogRecPtrIsInvalid(TopTransactionStateData.minLSN))
 		log_unknown_top = true;
 
 	/*
@@ -693,6 +725,7 @@ AssignTransactionId(TransactionState s)
 			log_unknown_top)
 		{
 			xl_xact_assignment xlrec;
+			XLogRecPtr		   endptr;
 
 			/*
 			 * xtop is always set by now because we recurse up transaction
@@ -707,11 +740,13 @@ AssignTransactionId(TransactionState s)
 			XLogRegisterData((char *) unreportedXids,
 							 nUnreportedXids * sizeof(TransactionId));
 
-			(void) XLogInsert(RM_XACT_ID, XLOG_XACT_ASSIGNMENT);
+			endptr = XLogInsert(RM_XACT_ID, XLOG_XACT_ASSIGNMENT);
 
 			nUnreportedXids = 0;
-			/* mark top, not current xact as having been logged */
-			TopTransactionStateData.didLogXid = true;
+
+			/* set minLSN of top, not of current xact if not yet */
+			if (XLogRecPtrIsInvalid(TopTransactionStateData.minLSN))
+				TopTransactionStateData.minLSN = endptr;
 		}
 	}
 }
@@ -2022,7 +2057,7 @@ StartTransaction(void)
 	 * initialize reported xid accounting
 	 */
 	nUnreportedXids = 0;
-	s->didLogXid = false;
+	s->minLSN = InvalidXLogRecPtr;
 
 	/*
 	 * must initialize resource-management stuff first
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index e04250f4e9..e3128564e1 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -1161,7 +1161,7 @@ XLogInsertRecord(XLogRecData *rdata,
 	 */
 	WALInsertLockRelease();
 
-	MarkCurrentTransactionIdLoggedIfAny();
+	MarkCurrentTransactionIdLoggedIfAny(EndPos);
 
 	END_CRIT_SECTION();
 
diff --git a/src/backend/utils/adt/xid8funcs.c b/src/backend/utils/adt/xid8funcs.c
index cc2b4ac797..992482f8c8 100644
--- a/src/backend/utils/adt/xid8funcs.c
+++ b/src/backend/utils/adt/xid8funcs.c
@@ -357,6 +357,8 @@ bad_format:
 Datum
 pg_current_xact_id(PG_FUNCTION_ARGS)
 {
+	FullTransactionId xid;
+
 	/*
 	 * Must prevent during recovery because if an xid is not assigned we try
 	 * to assign one, which would fail. Programs already rely on this function
@@ -365,7 +367,12 @@ pg_current_xact_id(PG_FUNCTION_ARGS)
 	 */
 	PreventCommandDuringRecovery("pg_current_xact_id()");
 
-	PG_RETURN_FULLTRANSACTIONID(GetTopFullTransactionId());
+	xid = GetTopFullTransactionId();
+
+	/* the XID is going to be published, make sure it is psersistent */
+	EnsureTopTransactionIdLogged();
+
+	PG_RETURN_FULLTRANSACTIONID(xid);
 }
 
 /*
@@ -380,6 +387,9 @@ pg_current_xact_id_if_assigned(PG_FUNCTION_ARGS)
 	if (!FullTransactionIdIsValid(topfxid))
 		PG_RETURN_NULL();
 
+	/* the XID is going to be published, make sure it is psersistent */
+	EnsureTopTransactionIdLogged();
+
 	PG_RETURN_FULLTRANSACTIONID(topfxid);
 }
 
diff --git a/src/include/access/xact.h b/src/include/access/xact.h
index 34cfaf542c..a61e4d6da5 100644
--- a/src/include/access/xact.h
+++ b/src/include/access/xact.h
@@ -386,7 +386,8 @@ extern FullTransactionId GetTopFullTransactionId(void);
 extern FullTransactionId GetTopFullTransactionIdIfAny(void);
 extern FullTransactionId GetCurrentFullTransactionId(void);
 extern FullTransactionId GetCurrentFullTransactionIdIfAny(void);
-extern void MarkCurrentTransactionIdLoggedIfAny(void);
+extern void MarkCurrentTransactionIdLoggedIfAny(XLogRecPtr upto);
+extern void EnsureTopTransactionIdLogged(void);
 extern bool SubTransactionIsActive(SubTransactionId subxid);
 extern CommandId GetCurrentCommandId(bool used);
 extern void SetParallelStartTimestamps(TimestampTz xact_ts, TimestampTz stmt_ts);
-- 
2.17.0

From f3425492da3d990cc170c4929e426addfd9e3a25 Mon Sep 17 00:00:00 2001
From: Andrey Borodin <amborodin@acm.org>
Date: Sat, 27 Feb 2021 09:03:50 +0500
Subject: [PATCH 3/8] Allow alternate compression methods for wal_compression

TODO: bump XLOG_PAGE_MAGIC
---
 src/backend/Makefile                    |  2 +-
 src/backend/access/transam/xlog.c       | 10 ++++
 src/backend/access/transam/xloginsert.c | 52 +++++++++++++++++++--
 src/backend/access/transam/xlogreader.c | 62 ++++++++++++++++++++++++-
 src/backend/utils/misc/guc.c            | 11 +++++
 src/include/access/xlog.h               |  1 +
 src/include/access/xlog_internal.h      |  8 ++++
 src/include/access/xlogreader.h         |  1 +
 src/include/access/xlogrecord.h         |  9 ++--
 9 files changed, 144 insertions(+), 12 deletions(-)

diff --git a/src/backend/Makefile b/src/backend/Makefile
index 0da848b1fd..3af216ddfc 100644
--- a/src/backend/Makefile
+++ b/src/backend/Makefile
@@ -48,7 +48,7 @@ OBJS = \
 LIBS := $(filter-out -lpgport -lpgcommon, $(LIBS)) $(LDAP_LIBS_BE) $(ICU_LIBS)
 
 # The backend doesn't need everything that's in LIBS, however
-LIBS := $(filter-out -lz -lreadline -ledit -ltermcap -lncurses -lcurses, $(LIBS))
+LIBS := $(filter-out -lreadline -ledit -ltermcap -lncurses -lcurses, $(LIBS))
 
 ifeq ($(with_systemd),yes)
 LIBS += -lsystemd
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index e3128564e1..0183589b4d 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -99,6 +99,7 @@ bool		EnableHotStandby = false;
 bool		fullPageWrites = true;
 bool		wal_log_hints = false;
 bool		wal_compression = false;
+int			wal_compression_method = WAL_COMPRESSION_PGLZ;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
@@ -180,6 +181,15 @@ const struct config_enum_entry recovery_target_action_options[] = {
 	{NULL, 0, false}
 };
 
+/* Note that due to conditional compilation, offsets within the array are not static */
+const struct config_enum_entry wal_compression_options[] = {
+	{"pglz", WAL_COMPRESSION_PGLZ, false},
+#ifdef  HAVE_LIBZ
+	{"zlib", WAL_COMPRESSION_ZLIB, false},
+#endif
+	{NULL, 0, false}
+};
+
 /*
  * Statistics for current checkpoint are collected in this global struct.
  * Because only the checkpointer or a stand-alone backend can perform
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
index 7052dc245e..ee73bc3afd 100644
--- a/src/backend/access/transam/xloginsert.c
+++ b/src/backend/access/transam/xloginsert.c
@@ -33,6 +33,10 @@
 #include "storage/proc.h"
 #include "utils/memutils.h"
 
+#ifdef HAVE_LIBZ
+#include <zlib.h>
+#endif
+
 /* Buffer size required to store a compressed version of backup block image */
 #define PGLZ_MAX_BLCKSZ PGLZ_MAX_OUTPUT(BLCKSZ)
 
@@ -113,7 +117,8 @@ static XLogRecData *XLogRecordAssemble(RmgrId rmid, uint8 info,
 									   XLogRecPtr RedoRecPtr, bool doPageWrites,
 									   XLogRecPtr *fpw_lsn, int *num_fpi);
 static bool XLogCompressBackupBlock(char *page, uint16 hole_offset,
-									uint16 hole_length, char *dest, uint16 *dlen);
+									uint16 hole_length, char *dest,
+									uint16 *dlen, WalCompression compression);
 
 /*
  * Begin constructing a WAL record. This must be called before the
@@ -630,11 +635,12 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
 			 */
 			if (wal_compression)
 			{
+				bimg.compression_method = wal_compression_method;
 				is_compressed =
 					XLogCompressBackupBlock(page, bimg.hole_offset,
 											cbimg.hole_length,
 											regbuf->compressed_page,
-											&compressed_len);
+											&compressed_len, bimg.compression_method);
 			}
 
 			/*
@@ -827,7 +833,7 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
  */
 static bool
 XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
-						char *dest, uint16 *dlen)
+						char *dest, uint16 *dlen, WalCompression compression)
 {
 	int32		orig_len = BLCKSZ - hole_length;
 	int32		len;
@@ -853,12 +859,48 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 	else
 		source = page;
 
+	switch (compression)
+	{
+	case WAL_COMPRESSION_PGLZ:
+		len = pglz_compress(source, orig_len, dest, PGLZ_strategy_default);
+		break;
+
+#ifdef HAVE_LIBZ
+	case WAL_COMPRESSION_ZLIB:
+		{
+			unsigned long	len_l = PGLZ_MAX_BLCKSZ;
+			int ret = compress2((Bytef*)dest, &len_l, (Bytef*)source, orig_len,
+						Z_DEFAULT_COMPRESSION);
+			if (ret != Z_OK)
+			{
+				// XXX: using an interface other than compress() would allow giving a better error message
+				ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("failed compressing zlib (%d)", ret)));
+				len_l = -1;
+			}
+			len = len_l;
+			break;
+		}
+#endif
+
+	default:
+		/*
+		 * It should be impossible to get here for unsupported algorithms,
+		 * which cannot be assigned if they're not enabled at compile time.
+		 */
+		ereport(ERROR,
+			(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			 errmsg("unknown compression method requested: %d(%s)",
+				 compression, wal_compression_name(compression))));
+
+	}
+
 	/*
-	 * We recheck the actual size even if pglz_compress() reports success and
+	 * We recheck the actual size even if compression reports success and
 	 * see if the number of bytes saved by compression is larger than the
 	 * length of extra data needed for the compressed version of block image.
 	 */
-	len = pglz_compress(source, orig_len, dest, PGLZ_strategy_default);
 	if (len >= 0 &&
 		len + extra_bytes < orig_len)
 	{
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index 42738eb940..143df55fcb 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -33,6 +33,10 @@
 #include "utils/memutils.h"
 #endif
 
+#ifdef HAVE_LIBZ
+#include <zlib.h>
+#endif
+
 static void report_invalid_record(XLogReaderState *state, const char *fmt,...)
 			pg_attribute_printf(2, 3);
 static bool allocate_recordbuf(XLogReaderState *state, uint32 reclength);
@@ -1286,6 +1290,7 @@ DecodeXLogRecord(XLogReaderState *state, XLogRecord *record, char **errormsg)
 			{
 				COPY_HEADER_FIELD(&blk->bimg_len, sizeof(uint16));
 				COPY_HEADER_FIELD(&blk->hole_offset, sizeof(uint16));
+				COPY_HEADER_FIELD(&blk->compression_method, sizeof(uint8));
 				COPY_HEADER_FIELD(&blk->bimg_info, sizeof(uint8));
 
 				blk->apply_image = ((blk->bimg_info & BKPIMAGE_APPLY) != 0);
@@ -1535,6 +1540,29 @@ XLogRecGetBlockData(XLogReaderState *record, uint8 block_id, Size *len)
 	}
 }
 
+/*
+ * Return a statically allocated string associated with the given compression
+ * method.  This is similar to the guc, but isn't subject to conditional
+ * compilation.
+ */
+const char *
+wal_compression_name(WalCompression compression)
+{
+	/*
+	 * This could index into the guc array, except that it's compiled
+	 * conditionally and unsupported methods are elided.
+	 */
+	switch (compression)
+	{
+		case WAL_COMPRESSION_PGLZ:
+			return "pglz";
+		case WAL_COMPRESSION_ZLIB:
+			return "zlib";
+		default:
+			return "???";
+	}
+}
+
 /*
  * Restore a full-page image from a backup block attached to an XLOG record.
  *
@@ -1558,8 +1586,38 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 	if (bkpb->bimg_info & BKPIMAGE_IS_COMPRESSED)
 	{
 		/* If a backup block image is compressed, decompress it */
-		if (pglz_decompress(ptr, bkpb->bimg_len, tmp.data,
-							BLCKSZ - bkpb->hole_length, true) < 0)
+		int32 decomp_result = -1;
+		switch (bkpb->compression_method)
+		{
+		case WAL_COMPRESSION_PGLZ:
+			decomp_result = pglz_decompress(ptr, bkpb->bimg_len, tmp.data,
+							BLCKSZ - bkpb->hole_length, true);
+			break;
+
+#ifdef HAVE_LIBZ
+		case WAL_COMPRESSION_ZLIB:
+		{
+			unsigned long decomp_result_l = 0;
+			decomp_result_l = BLCKSZ - bkpb->hole_length;
+			if (uncompress((Bytef*)tmp.data, &decomp_result_l, (Bytef*)ptr, bkpb->bimg_len) == Z_OK)
+				decomp_result = decomp_result_l;
+			else
+				decomp_result = -1;
+			break;
+		}
+#endif
+
+		default:
+			report_invalid_record(record, "image at %X/%X is compressed with unsupported codec, block %d (%d/%s)",
+								  (uint32) (record->ReadRecPtr >> 32),
+								  (uint32) record->ReadRecPtr,
+								  block_id,
+								  bkpb->compression_method,
+								  wal_compression_name(bkpb->compression_method));
+			return false;
+		}
+
+		if (decomp_result < 0)
 		{
 			report_invalid_record(record, "invalid compressed image at %X/%X, block %d",
 								  LSN_FORMAT_ARGS(record->ReadRecPtr),
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 855076b1fd..8084027465 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -508,6 +508,7 @@ extern const struct config_enum_entry archive_mode_options[];
 extern const struct config_enum_entry recovery_target_action_options[];
 extern const struct config_enum_entry sync_method_options[];
 extern const struct config_enum_entry dynamic_shared_memory_options[];
+extern const struct config_enum_entry wal_compression_options[];
 
 /*
  * GUC option variables that are exported from this module
@@ -4721,6 +4722,16 @@ static struct config_enum ConfigureNamesEnum[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"wal_compression_method", PGC_SIGHUP, WAL_SETTINGS,
+			gettext_noop("Set the method used to compress full page images in the WAL."),
+			NULL
+		},
+		&wal_compression_method,
+		WAL_COMPRESSION_PGLZ, wal_compression_options,
+		NULL, NULL, NULL
+	},
+
 	{
 		{"dynamic_shared_memory_type", PGC_POSTMASTER, RESOURCES_MEM,
 			gettext_noop("Selects the dynamic shared memory implementation used."),
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index 6d384d3ce6..fa2e5c611f 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -117,6 +117,7 @@ extern bool EnableHotStandby;
 extern bool fullPageWrites;
 extern bool wal_log_hints;
 extern bool wal_compression;
+extern int	wal_compression_method;
 extern bool wal_init_zero;
 extern bool wal_recycle;
 extern bool *wal_consistency_checking;
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index b23e286406..b80759ed45 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -324,4 +324,12 @@ extern bool InArchiveRecovery;
 extern bool StandbyMode;
 extern char *recoveryRestoreCommand;
 
+typedef enum WalCompression
+{
+	WAL_COMPRESSION_PGLZ = 0,
+	WAL_COMPRESSION_ZLIB = 1,
+} WalCompression;
+
+extern const char *wal_compression_name(WalCompression compression);
+
 #endif							/* XLOG_INTERNAL_H */
diff --git a/src/include/access/xlogreader.h b/src/include/access/xlogreader.h
index 21d200d3df..3d19c315d7 100644
--- a/src/include/access/xlogreader.h
+++ b/src/include/access/xlogreader.h
@@ -133,6 +133,7 @@ typedef struct
 	bool		apply_image;	/* has image that should be restored */
 	char	   *bkp_image;
 	uint16		hole_offset;
+	uint8		compression_method;
 	uint16		hole_length;
 	uint16		bimg_len;
 	uint8		bimg_info;
diff --git a/src/include/access/xlogrecord.h b/src/include/access/xlogrecord.h
index 80c92a2498..0d4c212f15 100644
--- a/src/include/access/xlogrecord.h
+++ b/src/include/access/xlogrecord.h
@@ -114,7 +114,7 @@ typedef struct XLogRecordBlockHeader
  * present is (BLCKSZ - <length of "hole" bytes>).
  *
  * Additionally, when wal_compression is enabled, we will try to compress full
- * page images using the PGLZ compression algorithm, after removing the "hole".
+ * page images, after removing the "hole".
  * This can reduce the WAL volume, but at some extra cost of CPU spent
  * on the compression during WAL logging. In this case, since the "hole"
  * length cannot be calculated by subtracting the number of page image bytes
@@ -129,9 +129,10 @@ typedef struct XLogRecordBlockHeader
  */
 typedef struct XLogRecordBlockImageHeader
 {
-	uint16		length;			/* number of page image bytes */
-	uint16		hole_offset;	/* number of bytes before "hole" */
-	uint8		bimg_info;		/* flag bits, see below */
+	uint16		length;				/* number of page image bytes */
+	uint16		hole_offset;		/* number of bytes before "hole" */
+	uint8		compression_method; /* compression method used for image */
+	uint8		bimg_info;			/* flag bits, see below */
 
 	/*
 	 * If BKPIMAGE_HAS_HOLE and BKPIMAGE_IS_COMPRESSED, an
-- 
2.17.0

From a1905d4f00ac0d7ce73046cf9c5cc266905abc34 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Thu, 11 Mar 2021 17:36:24 -0600
Subject: [PATCH 4/8] wal_compression_method: default to zlib..

this is meant to exercise the CIs, and not meant to be merged
---
 src/backend/access/transam/xlog.c | 2 +-
 src/backend/utils/misc/guc.c      | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 0183589b4d..8bae73b4ec 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -99,7 +99,7 @@ bool		EnableHotStandby = false;
 bool		fullPageWrites = true;
 bool		wal_log_hints = false;
 bool		wal_compression = false;
-int			wal_compression_method = WAL_COMPRESSION_PGLZ;
+int			wal_compression_method = WAL_COMPRESSION_ZLIB;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 8084027465..c37a8313d3 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -1269,7 +1269,7 @@ static struct config_bool ConfigureNamesBool[] =
 			NULL
 		},
 		&wal_compression,
-		false,
+		true,
 		NULL, NULL, NULL
 	},
 
@@ -4728,7 +4728,7 @@ static struct config_enum ConfigureNamesEnum[] =
 			NULL
 		},
 		&wal_compression_method,
-		WAL_COMPRESSION_PGLZ, wal_compression_options,
+		WAL_COMPRESSION_ZLIB, wal_compression_options,
 		NULL, NULL, NULL
 	},
 
-- 
2.17.0

From 52d2367082e00e70947c7350a4fae9f0624dc116 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Fri, 12 Mar 2021 14:32:10 -0600
Subject: [PATCH 5/8] (re)add wal_compression_method=lz4

---
 configure                               | 176 ++++++++++++++++++++++++
 configure.ac                            |  26 ++++
 src/backend/access/transam/xlog.c       |   3 +
 src/backend/access/transam/xloginsert.c |  12 ++
 src/backend/access/transam/xlogreader.c |  12 ++
 src/include/access/xlog_internal.h      |   1 +
 src/include/pg_config.h.in              |   3 +
 src/tools/msvc/Solution.pm              |   1 +
 8 files changed, 234 insertions(+)

diff --git a/configure b/configure
index fad817bb38..9b590eb432 100755
--- a/configure
+++ b/configure
@@ -699,6 +699,9 @@ with_gnu_ld
 LD
 LDFLAGS_SL
 LDFLAGS_EX
+LZ4_LIBS
+LZ4_CFLAGS
+with_lz4
 with_zlib
 with_system_tzdata
 with_libxslt
@@ -864,6 +867,7 @@ with_libxml
 with_libxslt
 with_system_tzdata
 with_zlib
+with_lz4
 with_gnu_ld
 with_ssl
 with_openssl
@@ -891,6 +895,8 @@ ICU_LIBS
 XML2_CONFIG
 XML2_CFLAGS
 XML2_LIBS
+LZ4_CFLAGS
+LZ4_LIBS
 LDFLAGS_EX
 LDFLAGS_SL
 PERL
@@ -1569,6 +1575,7 @@ Optional Packages:
   --with-system-tzdata=DIR
                           use system time zone data in DIR
   --without-zlib          do not use Zlib
+  --with-lz4              build with LZ4 support
   --with-gnu-ld           assume the C compiler uses GNU ld [default=no]
   --with-ssl=LIB          use LIB for SSL/TLS support (openssl)
   --with-openssl          obsolete spelling of --with-ssl=openssl
@@ -1596,6 +1603,8 @@ Some influential environment variables:
   XML2_CONFIG path to xml2-config utility
   XML2_CFLAGS C compiler flags for XML2, overriding pkg-config
   XML2_LIBS   linker flags for XML2, overriding pkg-config
+  LZ4_CFLAGS  C compiler flags for LZ4, overriding pkg-config
+  LZ4_LIBS    linker flags for LZ4, overriding pkg-config
   LDFLAGS_EX  extra linker flags for linking executables only
   LDFLAGS_SL  extra linker flags for linking shared libraries only
   PERL        Perl program
@@ -8563,6 +8572,137 @@ fi
 
 
 
+#
+# LZ4
+#
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether to build with LZ4 support" >&5
+$as_echo_n "checking whether to build with LZ4 support... " >&6; }
+
+
+
+# Check whether --with-lz4 was given.
+if test "${with_lz4+set}" = set; then :
+  withval=$with_lz4;
+  case $withval in
+    yes)
+
+$as_echo "#define USE_LZ4 1" >>confdefs.h
+
+      ;;
+    no)
+      :
+      ;;
+    *)
+      as_fn_error $? "no argument expected for --with-lz4 option" "$LINENO" 5
+      ;;
+  esac
+
+else
+  with_lz4=no
+
+fi
+
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $with_lz4" >&5
+$as_echo "$with_lz4" >&6; }
+
+
+if test "$with_lz4" = yes; then
+
+pkg_failed=no
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for liblz4" >&5
+$as_echo_n "checking for liblz4... " >&6; }
+
+if test -n "$LZ4_CFLAGS"; then
+    pkg_cv_LZ4_CFLAGS="$LZ4_CFLAGS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"liblz4\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "liblz4") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_LZ4_CFLAGS=`$PKG_CONFIG --cflags "liblz4" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+if test -n "$LZ4_LIBS"; then
+    pkg_cv_LZ4_LIBS="$LZ4_LIBS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"liblz4\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "liblz4") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_LZ4_LIBS=`$PKG_CONFIG --libs "liblz4" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+
+
+
+if test $pkg_failed = yes; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+
+if $PKG_CONFIG --atleast-pkgconfig-version 0.20; then
+        _pkg_short_errors_supported=yes
+else
+        _pkg_short_errors_supported=no
+fi
+        if test $_pkg_short_errors_supported = yes; then
+	        LZ4_PKG_ERRORS=`$PKG_CONFIG --short-errors --print-errors --cflags --libs "liblz4" 2>&1`
+        else
+	        LZ4_PKG_ERRORS=`$PKG_CONFIG --print-errors --cflags --libs "liblz4" 2>&1`
+        fi
+	# Put the nasty error message in config.log where it belongs
+	echo "$LZ4_PKG_ERRORS" >&5
+
+	as_fn_error $? "Package requirements (liblz4) were not met:
+
+$LZ4_PKG_ERRORS
+
+Consider adjusting the PKG_CONFIG_PATH environment variable if you
+installed software in a non-standard prefix.
+
+Alternatively, you may set the environment variables LZ4_CFLAGS
+and LZ4_LIBS to avoid the need to call pkg-config.
+See the pkg-config man page for more details." "$LINENO" 5
+elif test $pkg_failed = untried; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+	{ { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error $? "The pkg-config script could not be found or is too old.  Make sure it
+is in your PATH or set the PKG_CONFIG environment variable to the full
+path to pkg-config.
+
+Alternatively, you may set the environment variables LZ4_CFLAGS
+and LZ4_LIBS to avoid the need to call pkg-config.
+See the pkg-config man page for more details.
+
+To get pkg-config, see <http://pkg-config.freedesktop.org/>.
+See \`config.log' for more details" "$LINENO" 5; }
+else
+	LZ4_CFLAGS=$pkg_cv_LZ4_CFLAGS
+	LZ4_LIBS=$pkg_cv_LZ4_LIBS
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+
+fi
+  LIBS="$LZ4_LIBS $LIBS"
+  CFLAGS="$LZ4_CFLAGS $CFLAGS"
+fi
+
 #
 # Assignments
 #
@@ -13378,6 +13518,42 @@ fi
 
 fi
 
+if test "$with_lz4" = yes; then
+  ac_save_CPPFLAGS=$CPPFLAGS
+  CPPFLAGS="$LZ4_CFLAGS $CPPFLAGS"
+
+  # Verify we have LZ4's header files
+  for ac_header in lz4/lz4.h
+do :
+  ac_fn_c_check_header_mongrel "$LINENO" "lz4/lz4.h" "ac_cv_header_lz4_lz4_h" "$ac_includes_default"
+if test "x$ac_cv_header_lz4_lz4_h" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_LZ4_LZ4_H 1
+_ACEOF
+
+else
+  for ac_header in lz4.h
+do :
+  ac_fn_c_check_header_mongrel "$LINENO" "lz4.h" "ac_cv_header_lz4_h" "$ac_includes_default"
+if test "x$ac_cv_header_lz4_h" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_LZ4_H 1
+_ACEOF
+
+else
+  as_fn_error $? "lz4.h header file is required for LZ4" "$LINENO" 5
+fi
+
+done
+
+fi
+
+done
+
+
+  CPPFLAGS=$ac_save_CPPFLAGS
+fi
+
 if test "$with_gssapi" = yes ; then
   for ac_header in gssapi/gssapi.h
 do :
diff --git a/configure.ac b/configure.ac
index 0ed53571dd..2b3b5676eb 100644
--- a/configure.ac
+++ b/configure.ac
@@ -986,6 +986,21 @@ PGAC_ARG_BOOL(with, zlib, yes,
               [do not use Zlib])
 AC_SUBST(with_zlib)
 
+#
+# LZ4
+#
+AC_MSG_CHECKING([whether to build with LZ4 support])
+PGAC_ARG_BOOL(with, lz4, no, [build with LZ4 support],
+              [AC_DEFINE([USE_LZ4], 1, [Define to 1 to build with LZ4 support. (--with-lz4)])])
+AC_MSG_RESULT([$with_lz4])
+AC_SUBST(with_lz4)
+
+if test "$with_lz4" = yes; then
+  PKG_CHECK_MODULES(LZ4, liblz4)
+  LIBS="$LZ4_LIBS $LIBS"
+  CFLAGS="$LZ4_CFLAGS $CFLAGS"
+fi
+
 #
 # Assignments
 #
@@ -1407,6 +1422,17 @@ failure.  It is possible the compiler isn't looking in the proper directory.
 Use --without-zlib to disable zlib support.])])
 fi
 
+if test "$with_lz4" = yes; then
+  ac_save_CPPFLAGS=$CPPFLAGS
+  CPPFLAGS="$LZ4_CFLAGS $CPPFLAGS"
+
+  # Verify we have LZ4's header files
+  AC_CHECK_HEADERS(lz4/lz4.h, [],
+       [AC_CHECK_HEADERS(lz4.h, [], [AC_MSG_ERROR([lz4.h header file is required for LZ4])])])
+
+  CPPFLAGS=$ac_save_CPPFLAGS
+fi
+
 if test "$with_gssapi" = yes ; then
   AC_CHECK_HEADERS(gssapi/gssapi.h, [],
 	[AC_CHECK_HEADERS(gssapi.h, [], [AC_MSG_ERROR([gssapi.h header file is required for GSSAPI])])])
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 8bae73b4ec..f33355e44a 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -186,6 +186,9 @@ const struct config_enum_entry wal_compression_options[] = {
 	{"pglz", WAL_COMPRESSION_PGLZ, false},
 #ifdef  HAVE_LIBZ
 	{"zlib", WAL_COMPRESSION_ZLIB, false},
+#endif
+#ifdef  USE_LZ4
+	{"lz4", WAL_COMPRESSION_LZ4, false},
 #endif
 	{NULL, 0, false}
 };
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
index ee73bc3afd..38ac5f9e94 100644
--- a/src/backend/access/transam/xloginsert.c
+++ b/src/backend/access/transam/xloginsert.c
@@ -37,6 +37,10 @@
 #include <zlib.h>
 #endif
 
+#ifdef USE_LZ4
+#include "lz4.h"
+#endif
+
 /* Buffer size required to store a compressed version of backup block image */
 #define PGLZ_MAX_BLCKSZ PGLZ_MAX_OUTPUT(BLCKSZ)
 
@@ -884,6 +888,14 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 		}
 #endif
 
+#ifdef USE_LZ4
+	case WAL_COMPRESSION_LZ4:
+		len = LZ4_compress_fast(source, dest, orig_len, PGLZ_MAX_BLCKSZ, 1);
+		if (len == 0)
+			len = -1;
+		break;
+#endif
+
 	default:
 		/*
 		 * It should be impossible to get here for unsupported algorithms,
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index 143df55fcb..920c47e4d7 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -37,6 +37,10 @@
 #include <zlib.h>
 #endif
 
+#ifdef USE_LZ4
+#include "lz4.h"
+#endif
+
 static void report_invalid_record(XLogReaderState *state, const char *fmt,...)
 			pg_attribute_printf(2, 3);
 static bool allocate_recordbuf(XLogReaderState *state, uint32 reclength);
@@ -1558,6 +1562,8 @@ wal_compression_name(WalCompression compression)
 			return "pglz";
 		case WAL_COMPRESSION_ZLIB:
 			return "zlib";
+		case WAL_COMPRESSION_LZ4:
+			return "lz4";
 		default:
 			return "???";
 	}
@@ -1607,6 +1613,12 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 		}
 #endif
 
+#ifdef USE_LZ4
+		case WAL_COMPRESSION_LZ4:
+			decomp_result = LZ4_decompress_safe(ptr, tmp.data, bkpb->bimg_len, BLCKSZ);
+			break;
+#endif
+
 		default:
 			report_invalid_record(record, "image at %X/%X is compressed with unsupported codec, block %d (%d/%s)",
 								  (uint32) (record->ReadRecPtr >> 32),
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index b80759ed45..0993de784e 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -328,6 +328,7 @@ typedef enum WalCompression
 {
 	WAL_COMPRESSION_PGLZ = 0,
 	WAL_COMPRESSION_ZLIB = 1,
+	WAL_COMPRESSION_LZ4 = 2,
 } WalCompression;
 
 extern const char *wal_compression_name(WalCompression compression);
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index 7a7cc21d8d..0a6422da4f 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -899,6 +899,9 @@
 /* Define to 1 to build with LLVM based JIT support. (--with-llvm) */
 #undef USE_LLVM
 
+/* Define to 1 to build with LZ4 support (--with-lz4) */
+#undef USE_LZ4
+
 /* Define to select named POSIX semaphores. */
 #undef USE_NAMED_POSIX_SEMAPHORES
 
diff --git a/src/tools/msvc/Solution.pm b/src/tools/msvc/Solution.pm
index a4f5cc4bdb..14605371bb 100644
--- a/src/tools/msvc/Solution.pm
+++ b/src/tools/msvc/Solution.pm
@@ -485,6 +485,7 @@ sub GenerateFiles
 		USE_ICU => $self->{options}->{icu} ? 1 : undef,
 		USE_LIBXML                 => undef,
 		USE_LIBXSLT                => undef,
+		USE_LZ4                    => undef,
 		USE_LDAP                   => $self->{options}->{ldap} ? 1 : undef,
 		USE_LLVM                   => undef,
 		USE_NAMED_POSIX_SEMAPHORES => undef,
-- 
2.17.0

From db07b79643958bd42d8c55025849d195b3e4d980 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Fri, 12 Mar 2021 15:35:40 -0600
Subject: [PATCH 6/8] Default to LZ4..

this is meant to exercise in the CIs, and not meant to be merged
---
 configure                    | 6 ++++--
 configure.ac                 | 4 ++--
 src/backend/utils/misc/guc.c | 2 +-
 3 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/configure b/configure
index 9b590eb432..3afa1e87e3 100755
--- a/configure
+++ b/configure
@@ -1575,7 +1575,7 @@ Optional Packages:
   --with-system-tzdata=DIR
                           use system time zone data in DIR
   --without-zlib          do not use Zlib
-  --with-lz4              build with LZ4 support
+  --without-lz4           build without LZ4 support
   --with-gnu-ld           assume the C compiler uses GNU ld [default=no]
   --with-ssl=LIB          use LIB for SSL/TLS support (openssl)
   --with-openssl          obsolete spelling of --with-ssl=openssl
@@ -8598,7 +8598,9 @@ $as_echo "#define USE_LZ4 1" >>confdefs.h
   esac
 
 else
-  with_lz4=no
+  with_lz4=yes
+
+$as_echo "#define USE_LZ4 1" >>confdefs.h
 
 fi
 
diff --git a/configure.ac b/configure.ac
index 2b3b5676eb..d62ea5f742 100644
--- a/configure.ac
+++ b/configure.ac
@@ -990,8 +990,8 @@ AC_SUBST(with_zlib)
 # LZ4
 #
 AC_MSG_CHECKING([whether to build with LZ4 support])
-PGAC_ARG_BOOL(with, lz4, no, [build with LZ4 support],
-              [AC_DEFINE([USE_LZ4], 1, [Define to 1 to build with LZ4 support. (--with-lz4)])])
+PGAC_ARG_BOOL(with, lz4, yes, [build without LZ4 support],
+              [AC_DEFINE([USE_LZ4], 1, [Define to 1 to build without LZ4 support. (--without-lz4)])])
 AC_MSG_RESULT([$with_lz4])
 AC_SUBST(with_lz4)
 
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index c37a8313d3..52f9cd0242 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -4728,7 +4728,7 @@ static struct config_enum ConfigureNamesEnum[] =
 			NULL
 		},
 		&wal_compression_method,
-		WAL_COMPRESSION_ZLIB, wal_compression_options,
+		WAL_COMPRESSION_LZ4, wal_compression_options,
 		NULL, NULL, NULL
 	},
 
-- 
2.17.0

From f5319ea642c38a354d42064c29449428099fff64 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Fri, 12 Mar 2021 14:43:53 -0600
Subject: [PATCH 7/8] add wal_compression_method=zstd

---
 configure                               | 163 ++++++++++++++++++++++++
 configure.ac                            |  26 ++++
 src/backend/access/transam/xlog.c       |   3 +
 src/backend/access/transam/xloginsert.c |  20 +++
 src/backend/access/transam/xlogreader.c |  15 +++
 src/include/access/xlog_internal.h      |   1 +
 src/include/pg_config.h.in              |   3 +
 src/tools/msvc/Solution.pm              |   1 +
 8 files changed, 232 insertions(+)

diff --git a/configure b/configure
index 3afa1e87e3..c7c4c951a7 100755
--- a/configure
+++ b/configure
@@ -699,6 +699,9 @@ with_gnu_ld
 LD
 LDFLAGS_SL
 LDFLAGS_EX
+ZSTD_LIBS
+ZSTD_CFLAGS
+with_zstd
 LZ4_LIBS
 LZ4_CFLAGS
 with_lz4
@@ -868,6 +871,7 @@ with_libxslt
 with_system_tzdata
 with_zlib
 with_lz4
+with_zstd
 with_gnu_ld
 with_ssl
 with_openssl
@@ -897,6 +901,8 @@ XML2_CFLAGS
 XML2_LIBS
 LZ4_CFLAGS
 LZ4_LIBS
+ZSTD_CFLAGS
+ZSTD_LIBS
 LDFLAGS_EX
 LDFLAGS_SL
 PERL
@@ -1576,6 +1582,7 @@ Optional Packages:
                           use system time zone data in DIR
   --without-zlib          do not use Zlib
   --without-lz4           build without LZ4 support
+  --with-zstd             build with zstd support
   --with-gnu-ld           assume the C compiler uses GNU ld [default=no]
   --with-ssl=LIB          use LIB for SSL/TLS support (openssl)
   --with-openssl          obsolete spelling of --with-ssl=openssl
@@ -1605,6 +1612,8 @@ Some influential environment variables:
   XML2_LIBS   linker flags for XML2, overriding pkg-config
   LZ4_CFLAGS  C compiler flags for LZ4, overriding pkg-config
   LZ4_LIBS    linker flags for LZ4, overriding pkg-config
+  ZSTD_CFLAGS C compiler flags for ZSTD, overriding pkg-config
+  ZSTD_LIBS   linker flags for ZSTD, overriding pkg-config
   LDFLAGS_EX  extra linker flags for linking executables only
   LDFLAGS_SL  extra linker flags for linking shared libraries only
   PERL        Perl program
@@ -8705,6 +8714,137 @@ fi
   CFLAGS="$LZ4_CFLAGS $CFLAGS"
 fi
 
+#
+# ZSTD
+#
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether to build with zstd support" >&5
+$as_echo_n "checking whether to build with zstd support... " >&6; }
+
+
+
+# Check whether --with-zstd was given.
+if test "${with_zstd+set}" = set; then :
+  withval=$with_zstd;
+  case $withval in
+    yes)
+
+$as_echo "#define USE_ZSTD 1" >>confdefs.h
+
+      ;;
+    no)
+      :
+      ;;
+    *)
+      as_fn_error $? "no argument expected for --with-zstd option" "$LINENO" 5
+      ;;
+  esac
+
+else
+  with_zstd=no
+
+fi
+
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $with_zstd" >&5
+$as_echo "$with_zstd" >&6; }
+
+
+if test "$with_zstd" = yes; then
+
+pkg_failed=no
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for libzstd" >&5
+$as_echo_n "checking for libzstd... " >&6; }
+
+if test -n "$ZSTD_CFLAGS"; then
+    pkg_cv_ZSTD_CFLAGS="$ZSTD_CFLAGS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"libzstd\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "libzstd") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_ZSTD_CFLAGS=`$PKG_CONFIG --cflags "libzstd" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+if test -n "$ZSTD_LIBS"; then
+    pkg_cv_ZSTD_LIBS="$ZSTD_LIBS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"libzstd\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "libzstd") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_ZSTD_LIBS=`$PKG_CONFIG --libs "libzstd" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+
+
+
+if test $pkg_failed = yes; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+
+if $PKG_CONFIG --atleast-pkgconfig-version 0.20; then
+        _pkg_short_errors_supported=yes
+else
+        _pkg_short_errors_supported=no
+fi
+        if test $_pkg_short_errors_supported = yes; then
+	        ZSTD_PKG_ERRORS=`$PKG_CONFIG --short-errors --print-errors --cflags --libs "libzstd" 2>&1`
+        else
+	        ZSTD_PKG_ERRORS=`$PKG_CONFIG --print-errors --cflags --libs "libzstd" 2>&1`
+        fi
+	# Put the nasty error message in config.log where it belongs
+	echo "$ZSTD_PKG_ERRORS" >&5
+
+	as_fn_error $? "Package requirements (libzstd) were not met:
+
+$ZSTD_PKG_ERRORS
+
+Consider adjusting the PKG_CONFIG_PATH environment variable if you
+installed software in a non-standard prefix.
+
+Alternatively, you may set the environment variables ZSTD_CFLAGS
+and ZSTD_LIBS to avoid the need to call pkg-config.
+See the pkg-config man page for more details." "$LINENO" 5
+elif test $pkg_failed = untried; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+	{ { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error $? "The pkg-config script could not be found or is too old.  Make sure it
+is in your PATH or set the PKG_CONFIG environment variable to the full
+path to pkg-config.
+
+Alternatively, you may set the environment variables ZSTD_CFLAGS
+and ZSTD_LIBS to avoid the need to call pkg-config.
+See the pkg-config man page for more details.
+
+To get pkg-config, see <http://pkg-config.freedesktop.org/>.
+See \`config.log' for more details" "$LINENO" 5; }
+else
+	ZSTD_CFLAGS=$pkg_cv_ZSTD_CFLAGS
+	ZSTD_LIBS=$pkg_cv_ZSTD_LIBS
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+
+fi
+  LIBS="$ZSTD_LIBS $LIBS"
+  CFLAGS="$ZSTD_CFLAGS $CFLAGS"
+fi
+
 #
 # Assignments
 #
@@ -13556,6 +13696,29 @@ done
   CPPFLAGS=$ac_save_CPPFLAGS
 fi
 
+if test "$with_zstd" = yes; then
+  ac_save_CPPFLAGS=$CPPFLAGS
+  CPPFLAGS="$ZSTD_CFLAGS $CPPFLAGS"
+
+  # Verify we have zstd's header files
+  for ac_header in zstd.h
+do :
+  ac_fn_c_check_header_mongrel "$LINENO" "zstd.h" "ac_cv_header_zstd_h" "$ac_includes_default"
+if test "x$ac_cv_header_zstd_h" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_ZSTD_H 1
+_ACEOF
+
+else
+  as_fn_error $? "zstd.h header file is required for zstd" "$LINENO" 5
+fi
+
+done
+
+
+  CPPFLAGS=$ac_save_CPPFLAGS
+fi
+
 if test "$with_gssapi" = yes ; then
   for ac_header in gssapi/gssapi.h
 do :
diff --git a/configure.ac b/configure.ac
index d62ea5f742..abac4b28f6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1001,6 +1001,21 @@ if test "$with_lz4" = yes; then
   CFLAGS="$LZ4_CFLAGS $CFLAGS"
 fi
 
+#
+# ZSTD
+#
+AC_MSG_CHECKING([whether to build with zstd support])
+PGAC_ARG_BOOL(with, zstd, no, [build with zstd support],
+              [AC_DEFINE([USE_ZSTD], 1, [Define to 1 to build with zstd support. (--with-zstd)])])
+AC_MSG_RESULT([$with_zstd])
+AC_SUBST(with_zstd)
+
+if test "$with_zstd" = yes; then
+  PKG_CHECK_MODULES(ZSTD, libzstd)
+  LIBS="$ZSTD_LIBS $LIBS"
+  CFLAGS="$ZSTD_CFLAGS $CFLAGS"
+fi
+
 #
 # Assignments
 #
@@ -1433,6 +1448,17 @@ if test "$with_lz4" = yes; then
   CPPFLAGS=$ac_save_CPPFLAGS
 fi
 
+if test "$with_zstd" = yes; then
+  ac_save_CPPFLAGS=$CPPFLAGS
+  CPPFLAGS="$ZSTD_CFLAGS $CPPFLAGS"
+
+  # Verify we have zstd's header files
+  AC_CHECK_HEADERS(zstd.h, [],
+       [AC_MSG_ERROR([zstd.h header file is required for zstd])])
+
+  CPPFLAGS=$ac_save_CPPFLAGS
+fi
+
 if test "$with_gssapi" = yes ; then
   AC_CHECK_HEADERS(gssapi/gssapi.h, [],
 	[AC_CHECK_HEADERS(gssapi.h, [], [AC_MSG_ERROR([gssapi.h header file is required for GSSAPI])])])
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index f33355e44a..f2749ebf45 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -189,6 +189,9 @@ const struct config_enum_entry wal_compression_options[] = {
 #endif
 #ifdef  USE_LZ4
 	{"lz4", WAL_COMPRESSION_LZ4, false},
+#endif
+#ifdef  USE_ZSTD
+	{"zstd", WAL_COMPRESSION_ZSTD, false},
 #endif
 	{NULL, 0, false}
 };
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
index 38ac5f9e94..852e5ef7af 100644
--- a/src/backend/access/transam/xloginsert.c
+++ b/src/backend/access/transam/xloginsert.c
@@ -41,6 +41,10 @@
 #include "lz4.h"
 #endif
 
+#ifdef USE_ZSTD
+#include "zstd.h"
+#endif
+
 /* Buffer size required to store a compressed version of backup block image */
 #define PGLZ_MAX_BLCKSZ PGLZ_MAX_OUTPUT(BLCKSZ)
 
@@ -896,6 +900,22 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 		break;
 #endif
 
+#ifdef USE_ZSTD
+	case WAL_COMPRESSION_ZSTD:
+		len = ZSTD_compress(dest, PGLZ_MAX_BLCKSZ,
+				source, orig_len, ZSTD_CLEVEL_DEFAULT);
+		if (ZSTD_isError(len))
+		{
+			ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("failed compressing zstd: %s",
+						 ZSTD_getErrorName(len))));
+			len = -1;
+		}
+
+		break;
+#endif
+
 	default:
 		/*
 		 * It should be impossible to get here for unsupported algorithms,
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index 920c47e4d7..6ce2fbfb13 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -41,6 +41,10 @@
 #include "lz4.h"
 #endif
 
+#ifdef USE_ZSTD
+#include "zstd.h"
+#endif
+
 static void report_invalid_record(XLogReaderState *state, const char *fmt,...)
 			pg_attribute_printf(2, 3);
 static bool allocate_recordbuf(XLogReaderState *state, uint32 reclength);
@@ -1564,6 +1568,8 @@ wal_compression_name(WalCompression compression)
 			return "zlib";
 		case WAL_COMPRESSION_LZ4:
 			return "lz4";
+		case WAL_COMPRESSION_ZSTD:
+			return "zstd";
 		default:
 			return "???";
 	}
@@ -1619,6 +1625,15 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 			break;
 #endif
 
+#ifdef USE_ZSTD
+		case WAL_COMPRESSION_ZSTD:
+			decomp_result = ZSTD_decompress(tmp.data, BLCKSZ, ptr, bkpb->bimg_len);
+			// XXX: ZSTD_getErrorName
+			if (ZSTD_isError(decomp_result))
+				decomp_result = -1;
+			break;
+#endif
+
 		default:
 			report_invalid_record(record, "image at %X/%X is compressed with unsupported codec, block %d (%d/%s)",
 								  (uint32) (record->ReadRecPtr >> 32),
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index 0993de784e..30f663f448 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -329,6 +329,7 @@ typedef enum WalCompression
 	WAL_COMPRESSION_PGLZ = 0,
 	WAL_COMPRESSION_ZLIB = 1,
 	WAL_COMPRESSION_LZ4 = 2,
+	WAL_COMPRESSION_ZSTD = 3,
 } WalCompression;
 
 extern const char *wal_compression_name(WalCompression compression);
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index 0a6422da4f..ad26393352 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -902,6 +902,9 @@
 /* Define to 1 to build with LZ4 support (--with-lz4) */
 #undef USE_LZ4
 
+/* Define to 1 if you have the `zstd' library (-lzstd). */
+#undef USE_ZSTD
+
 /* Define to select named POSIX semaphores. */
 #undef USE_NAMED_POSIX_SEMAPHORES
 
diff --git a/src/tools/msvc/Solution.pm b/src/tools/msvc/Solution.pm
index 14605371bb..7dfa0f31f6 100644
--- a/src/tools/msvc/Solution.pm
+++ b/src/tools/msvc/Solution.pm
@@ -307,6 +307,7 @@ sub GenerateFiles
 		HAVE_LIBXML2                                => undef,
 		HAVE_LIBXSLT                                => undef,
 		HAVE_LIBZ                   => $self->{options}->{zlib} ? 1 : undef,
+		HAVE_LIBZSTD                => $self->{options}->{zstd} ? 1 : undef,
 		HAVE_LINK                   => undef,
 		HAVE_LOCALE_T               => 1,
 		HAVE_LONG_INT_64            => undef,
-- 
2.17.0

From 9288683238a72ae379d1b444e497285de5c8c28a Mon Sep 17 00:00:00 2001
From: Andrey Borodin <amborodin@acm.org>
Date: Sat, 27 Feb 2021 09:03:50 +0500
Subject: [PATCH 01/10] Allow alternate compression methods for wal_compression

TODO: bump XLOG_PAGE_MAGIC
---
 doc/src/sgml/config.sgml                      | 17 +++++
 src/backend/Makefile                          |  2 +-
 src/backend/access/transam/xlog.c             | 10 +++
 src/backend/access/transam/xloginsert.c       | 52 +++++++++++++--
 src/backend/access/transam/xlogreader.c       | 63 ++++++++++++++++++-
 src/backend/utils/misc/guc.c                  | 11 ++++
 src/backend/utils/misc/postgresql.conf.sample |  1 +
 src/include/access/xlog.h                     |  1 +
 src/include/access/xlog_internal.h            |  8 +++
 src/include/access/xlogreader.h               |  1 +
 src/include/access/xlogrecord.h               |  9 +--
 11 files changed, 163 insertions(+), 12 deletions(-)

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index a218d78bef..7fb2a84626 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -3072,6 +3072,23 @@ include_dir 'conf.d'
       </listitem>
      </varlistentry>
 
+     <varlistentry id="guc-wal-compression-method" xreflabel="wal_compression_method">
+      <term><varname>wal_compressionion_method</varname> (<type>enum</type>)
+      <indexterm>
+       <primary><varname>wal_compression_method</varname> configuration parameter</primary>
+      </indexterm>
+      </term>
+      <listitem>
+       <para>
+        This parameter selects the compression method used to compress WAL when
+        <varname>wal_compression</varname> is enabled.
+        The supported methods are pglz and zlib.
+        The default value is <literal>pglz</literal>.
+        Only superusers can change this setting.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry id="guc-wal-init-zero" xreflabel="wal_init_zero">
       <term><varname>wal_init_zero</varname> (<type>boolean</type>)
       <indexterm>
diff --git a/src/backend/Makefile b/src/backend/Makefile
index 0da848b1fd..3af216ddfc 100644
--- a/src/backend/Makefile
+++ b/src/backend/Makefile
@@ -48,7 +48,7 @@ OBJS = \
 LIBS := $(filter-out -lpgport -lpgcommon, $(LIBS)) $(LDAP_LIBS_BE) $(ICU_LIBS)
 
 # The backend doesn't need everything that's in LIBS, however
-LIBS := $(filter-out -lz -lreadline -ledit -ltermcap -lncurses -lcurses, $(LIBS))
+LIBS := $(filter-out -lreadline -ledit -ltermcap -lncurses -lcurses, $(LIBS))
 
 ifeq ($(with_systemd),yes)
 LIBS += -lsystemd
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index e04250f4e9..04192b7add 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -99,6 +99,7 @@ bool		EnableHotStandby = false;
 bool		fullPageWrites = true;
 bool		wal_log_hints = false;
 bool		wal_compression = false;
+int			wal_compression_method = WAL_COMPRESSION_PGLZ;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
@@ -180,6 +181,15 @@ const struct config_enum_entry recovery_target_action_options[] = {
 	{NULL, 0, false}
 };
 
+/* Note that due to conditional compilation, offsets within the array are not static */
+const struct config_enum_entry wal_compression_options[] = {
+	{"pglz", WAL_COMPRESSION_PGLZ, false},
+#ifdef  HAVE_LIBZ
+	{"zlib", WAL_COMPRESSION_ZLIB, false},
+#endif
+	{NULL, 0, false}
+};
+
 /*
  * Statistics for current checkpoint are collected in this global struct.
  * Because only the checkpointer or a stand-alone backend can perform
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
index 7052dc245e..34e1227381 100644
--- a/src/backend/access/transam/xloginsert.c
+++ b/src/backend/access/transam/xloginsert.c
@@ -33,6 +33,10 @@
 #include "storage/proc.h"
 #include "utils/memutils.h"
 
+#ifdef HAVE_LIBZ
+#include <zlib.h>
+#endif
+
 /* Buffer size required to store a compressed version of backup block image */
 #define PGLZ_MAX_BLCKSZ PGLZ_MAX_OUTPUT(BLCKSZ)
 
@@ -113,7 +117,8 @@ static XLogRecData *XLogRecordAssemble(RmgrId rmid, uint8 info,
 									   XLogRecPtr RedoRecPtr, bool doPageWrites,
 									   XLogRecPtr *fpw_lsn, int *num_fpi);
 static bool XLogCompressBackupBlock(char *page, uint16 hole_offset,
-									uint16 hole_length, char *dest, uint16 *dlen);
+									uint16 hole_length, char *dest,
+									uint16 *dlen, WalCompression compression);
 
 /*
  * Begin constructing a WAL record. This must be called before the
@@ -630,11 +635,12 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
 			 */
 			if (wal_compression)
 			{
+				bimg.compression_method = wal_compression_method;
 				is_compressed =
 					XLogCompressBackupBlock(page, bimg.hole_offset,
 											cbimg.hole_length,
 											regbuf->compressed_page,
-											&compressed_len);
+											&compressed_len, bimg.compression_method);
 			}
 
 			/*
@@ -827,7 +833,7 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
  */
 static bool
 XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
-						char *dest, uint16 *dlen)
+						char *dest, uint16 *dlen, WalCompression compression)
 {
 	int32		orig_len = BLCKSZ - hole_length;
 	int32		len;
@@ -853,12 +859,48 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 	else
 		source = page;
 
+	switch (compression)
+	{
+	case WAL_COMPRESSION_PGLZ:
+		len = pglz_compress(source, orig_len, dest, PGLZ_strategy_default);
+		break;
+
+#ifdef HAVE_LIBZ
+	case WAL_COMPRESSION_ZLIB:
+		{
+			unsigned long	len_l = PGLZ_MAX_BLCKSZ;
+			int ret;
+			ret = compress2((Bytef*)dest, &len_l, (Bytef*)source, orig_len, 1);
+			if (ret != Z_OK)
+			{
+				// XXX: using an interface other than compress() would allow giving a better error message
+				ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("failed compressing zlib (%d)", ret)));
+				len_l = -1;
+			}
+			len = len_l;
+			break;
+		}
+#endif
+
+	default:
+		/*
+		 * It should be impossible to get here for unsupported algorithms,
+		 * which cannot be assigned if they're not enabled at compile time.
+		 */
+		ereport(ERROR,
+			(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			 errmsg("unknown compression method requested: %d(%s)",
+				 compression, wal_compression_name(compression))));
+
+	}
+
 	/*
-	 * We recheck the actual size even if pglz_compress() reports success and
+	 * We recheck the actual size even if compression reports success and
 	 * see if the number of bytes saved by compression is larger than the
 	 * length of extra data needed for the compressed version of block image.
 	 */
-	len = pglz_compress(source, orig_len, dest, PGLZ_strategy_default);
 	if (len >= 0 &&
 		len + extra_bytes < orig_len)
 	{
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index 42738eb940..afca22a26c 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -33,6 +33,10 @@
 #include "utils/memutils.h"
 #endif
 
+#ifdef HAVE_LIBZ
+#include <zlib.h>
+#endif
+
 static void report_invalid_record(XLogReaderState *state, const char *fmt,...)
 			pg_attribute_printf(2, 3);
 static bool allocate_recordbuf(XLogReaderState *state, uint32 reclength);
@@ -1286,6 +1290,7 @@ DecodeXLogRecord(XLogReaderState *state, XLogRecord *record, char **errormsg)
 			{
 				COPY_HEADER_FIELD(&blk->bimg_len, sizeof(uint16));
 				COPY_HEADER_FIELD(&blk->hole_offset, sizeof(uint16));
+				COPY_HEADER_FIELD(&blk->compression_method, sizeof(uint8));
 				COPY_HEADER_FIELD(&blk->bimg_info, sizeof(uint8));
 
 				blk->apply_image = ((blk->bimg_info & BKPIMAGE_APPLY) != 0);
@@ -1535,6 +1540,29 @@ XLogRecGetBlockData(XLogReaderState *record, uint8 block_id, Size *len)
 	}
 }
 
+/*
+ * Return a statically allocated string associated with the given compression
+ * method.  This is similar to the guc, but isn't subject to conditional
+ * compilation.
+ */
+const char *
+wal_compression_name(WalCompression compression)
+{
+	/*
+	 * This could index into the guc array, except that it's compiled
+	 * conditionally and unsupported methods are elided.
+	 */
+	switch (compression)
+	{
+		case WAL_COMPRESSION_PGLZ:
+			return "pglz";
+		case WAL_COMPRESSION_ZLIB:
+			return "zlib";
+		default:
+			return "???";
+	}
+}
+
 /*
  * Restore a full-page image from a backup block attached to an XLOG record.
  *
@@ -1558,8 +1586,39 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 	if (bkpb->bimg_info & BKPIMAGE_IS_COMPRESSED)
 	{
 		/* If a backup block image is compressed, decompress it */
-		if (pglz_decompress(ptr, bkpb->bimg_len, tmp.data,
-							BLCKSZ - bkpb->hole_length, true) < 0)
+		int32 decomp_result = -1;
+		switch (bkpb->compression_method)
+		{
+		case WAL_COMPRESSION_PGLZ:
+			decomp_result = pglz_decompress(ptr, bkpb->bimg_len, tmp.data,
+							BLCKSZ - bkpb->hole_length, true);
+			break;
+
+#ifdef HAVE_LIBZ
+		case WAL_COMPRESSION_ZLIB:
+		{
+			unsigned long decomp_result_l;
+			decomp_result_l = BLCKSZ - bkpb->hole_length;
+			if (uncompress((Bytef*)tmp.data, &decomp_result_l,
+						(Bytef*)ptr, bkpb->bimg_len) == Z_OK)
+				decomp_result = decomp_result_l;
+			else
+				decomp_result = -1;
+			break;
+		}
+#endif
+
+		default:
+			report_invalid_record(record, "image at %X/%X is compressed with unsupported codec, block %d (%d/%s)",
+								  (uint32) (record->ReadRecPtr >> 32),
+								  (uint32) record->ReadRecPtr,
+								  block_id,
+								  bkpb->compression_method,
+								  wal_compression_name(bkpb->compression_method));
+			return false;
+		}
+
+		if (decomp_result < 0)
 		{
 			report_invalid_record(record, "invalid compressed image at %X/%X, block %d",
 								  LSN_FORMAT_ARGS(record->ReadRecPtr),
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 855076b1fd..8084027465 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -508,6 +508,7 @@ extern const struct config_enum_entry archive_mode_options[];
 extern const struct config_enum_entry recovery_target_action_options[];
 extern const struct config_enum_entry sync_method_options[];
 extern const struct config_enum_entry dynamic_shared_memory_options[];
+extern const struct config_enum_entry wal_compression_options[];
 
 /*
  * GUC option variables that are exported from this module
@@ -4721,6 +4722,16 @@ static struct config_enum ConfigureNamesEnum[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"wal_compression_method", PGC_SIGHUP, WAL_SETTINGS,
+			gettext_noop("Set the method used to compress full page images in the WAL."),
+			NULL
+		},
+		&wal_compression_method,
+		WAL_COMPRESSION_PGLZ, wal_compression_options,
+		NULL, NULL, NULL
+	},
+
 	{
 		{"dynamic_shared_memory_type", PGC_POSTMASTER, RESOURCES_MEM,
 			gettext_noop("Selects the dynamic shared memory implementation used."),
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index f46c2dd7a8..ef69a94492 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -213,6 +213,7 @@
 					#   open_sync
 #full_page_writes = on			# recover from partial page writes
 #wal_compression = off			# enable compression of full-page writes
+#wal_compression_method = pglz		# pglz, zlib
 #wal_log_hints = off			# also do full page writes of non-critical updates
 					# (change requires restart)
 #wal_init_zero = on			# zero-fill new WAL files
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index 6d384d3ce6..fa2e5c611f 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -117,6 +117,7 @@ extern bool EnableHotStandby;
 extern bool fullPageWrites;
 extern bool wal_log_hints;
 extern bool wal_compression;
+extern int	wal_compression_method;
 extern bool wal_init_zero;
 extern bool wal_recycle;
 extern bool *wal_consistency_checking;
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index b23e286406..d653839b97 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -324,4 +324,12 @@ extern bool InArchiveRecovery;
 extern bool StandbyMode;
 extern char *recoveryRestoreCommand;
 
+typedef enum WalCompression
+{
+	WAL_COMPRESSION_PGLZ,
+	WAL_COMPRESSION_ZLIB,
+} WalCompression;
+
+extern const char *wal_compression_name(WalCompression compression);
+
 #endif							/* XLOG_INTERNAL_H */
diff --git a/src/include/access/xlogreader.h b/src/include/access/xlogreader.h
index 21d200d3df..3d19c315d7 100644
--- a/src/include/access/xlogreader.h
+++ b/src/include/access/xlogreader.h
@@ -133,6 +133,7 @@ typedef struct
 	bool		apply_image;	/* has image that should be restored */
 	char	   *bkp_image;
 	uint16		hole_offset;
+	uint8		compression_method;
 	uint16		hole_length;
 	uint16		bimg_len;
 	uint8		bimg_info;
diff --git a/src/include/access/xlogrecord.h b/src/include/access/xlogrecord.h
index 80c92a2498..0d4c212f15 100644
--- a/src/include/access/xlogrecord.h
+++ b/src/include/access/xlogrecord.h
@@ -114,7 +114,7 @@ typedef struct XLogRecordBlockHeader
  * present is (BLCKSZ - <length of "hole" bytes>).
  *
  * Additionally, when wal_compression is enabled, we will try to compress full
- * page images using the PGLZ compression algorithm, after removing the "hole".
+ * page images, after removing the "hole".
  * This can reduce the WAL volume, but at some extra cost of CPU spent
  * on the compression during WAL logging. In this case, since the "hole"
  * length cannot be calculated by subtracting the number of page image bytes
@@ -129,9 +129,10 @@ typedef struct XLogRecordBlockHeader
  */
 typedef struct XLogRecordBlockImageHeader
 {
-	uint16		length;			/* number of page image bytes */
-	uint16		hole_offset;	/* number of bytes before "hole" */
-	uint8		bimg_info;		/* flag bits, see below */
+	uint16		length;				/* number of page image bytes */
+	uint16		hole_offset;		/* number of bytes before "hole" */
+	uint8		compression_method; /* compression method used for image */
+	uint8		bimg_info;			/* flag bits, see below */
 
 	/*
 	 * If BKPIMAGE_HAS_HOLE and BKPIMAGE_IS_COMPRESSED, an
-- 
2.17.0

From 43736a30c06ae37b6088fd6ed5da2ec915c91a37 Mon Sep 17 00:00:00 2001
From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Date: Mon, 8 Mar 2021 15:32:30 +0900
Subject: [PATCH 02/10] Run 011_crash_recovery.pl with wal_level=minimal

The test doesn't need that feature and pg_current_xact_id() is better
exercised by turning off the feature.

Copied from: https://www.postgresql.org/message-id/20210308.173242.463790587797836129.horikyota.ntt%40gmail.com
---
 src/test/recovery/t/011_crash_recovery.pl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/test/recovery/t/011_crash_recovery.pl b/src/test/recovery/t/011_crash_recovery.pl
index 10cd98f70a..690655dda2 100644
--- a/src/test/recovery/t/011_crash_recovery.pl
+++ b/src/test/recovery/t/011_crash_recovery.pl
@@ -11,7 +11,7 @@ use Config;
 plan tests => 3;
 
 my $node = get_new_node('primary');
-$node->init(allows_streaming => 1);
+$node->init();
 $node->start;
 
 my ($stdin, $stdout, $stderr) = ('', '', '');
-- 
2.17.0

From 6364eaade0f3b5f2e749bb799b3a8ed99fe4e323 Mon Sep 17 00:00:00 2001
From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Date: Mon, 8 Mar 2021 15:43:01 +0900
Subject: [PATCH 03/10] Make sure published XIDs are persistent

pg_xact_status() premises that XIDs obtained by
pg_current_xact_id(_if_assigned)() are persistent beyond a crash. But
XIDs are not guaranteed to go beyond WAL buffers before commit and
thus XIDs may vanish if server crashes before commit. This patch
guarantees the XID shown by the functions to be flushed out to disk.

Copied from: https://www.postgresql.org/message-id/20210308.173242.463790587797836129.horikyota.ntt%40gmail.com
---
 src/backend/access/transam/xact.c | 55 +++++++++++++++++++++++++------
 src/backend/access/transam/xlog.c |  2 +-
 src/backend/utils/adt/xid8funcs.c | 12 ++++++-
 src/include/access/xact.h         |  3 +-
 4 files changed, 59 insertions(+), 13 deletions(-)

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 6395a9b240..38e978d238 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -201,7 +201,7 @@ typedef struct TransactionStateData
 	int			prevSecContext; /* previous SecurityRestrictionContext */
 	bool		prevXactReadOnly;	/* entry-time xact r/o state */
 	bool		startedInRecovery;	/* did we start in recovery? */
-	bool		didLogXid;		/* has xid been included in WAL record? */
+	XLogRecPtr 	minLSN;			/* LSN needed to reach to record the xid */
 	int			parallelModeLevel;	/* Enter/ExitParallelMode counter */
 	bool		chain;			/* start a new block after this one */
 	bool		assigned;		/* assigned to top-level XID */
@@ -520,14 +520,46 @@ GetCurrentFullTransactionIdIfAny(void)
  *	MarkCurrentTransactionIdLoggedIfAny
  *
  * Remember that the current xid - if it is assigned - now has been wal logged.
+ *
+ * upto is the LSN up to which we need to flush WAL to ensure the current xid
+ * to be persistent. See EnsureCurrentTransactionIdLogged().
  */
 void
-MarkCurrentTransactionIdLoggedIfAny(void)
+MarkCurrentTransactionIdLoggedIfAny(XLogRecPtr upto)
 {
-	if (FullTransactionIdIsValid(CurrentTransactionState->fullTransactionId))
-		CurrentTransactionState->didLogXid = true;
+	if (FullTransactionIdIsValid(CurrentTransactionState->fullTransactionId) &&
+		XLogRecPtrIsInvalid(CurrentTransactionState->minLSN))
+		CurrentTransactionState->minLSN = upto;
 }
 
+/*
+ *	EnsureCurrentTransactionIdLogged
+ *
+ * Make sure that the current top XID is WAL-logged.
+ */
+void
+EnsureTopTransactionIdLogged(void)
+{
+	/*
+	 * We need at least one WAL record for the current top transaction to be
+	 * flushed out.  Write one if we don't have one yet.
+	 */
+	if (XLogRecPtrIsInvalid(TopTransactionStateData.minLSN))
+	{
+		xl_xact_assignment xlrec;
+
+		xlrec.xtop = XidFromFullTransactionId(XactTopFullTransactionId);
+		Assert(TransactionIdIsValid(xlrec.xtop));
+		xlrec.nsubxacts = 0;
+
+		XLogBeginInsert();
+		XLogRegisterData((char *) &xlrec, MinSizeOfXactAssignment);
+		TopTransactionStateData.minLSN =
+			XLogInsert(RM_XACT_ID, XLOG_XACT_ASSIGNMENT);
+	}
+
+	XLogFlush(TopTransactionStateData.minLSN);
+}
 
 /*
  *	GetStableLatestTransactionId
@@ -616,14 +648,14 @@ AssignTransactionId(TransactionState s)
 	 * When wal_level=logical, guarantee that a subtransaction's xid can only
 	 * be seen in the WAL stream if its toplevel xid has been logged before.
 	 * If necessary we log an xact_assignment record with fewer than
-	 * PGPROC_MAX_CACHED_SUBXIDS. Note that it is fine if didLogXid isn't set
+	 * PGPROC_MAX_CACHED_SUBXIDS. Note that it is fine if minLSN isn't set
 	 * for a transaction even though it appears in a WAL record, we just might
 	 * superfluously log something. That can happen when an xid is included
 	 * somewhere inside a wal record, but not in XLogRecord->xl_xid, like in
 	 * xl_standby_locks.
 	 */
 	if (isSubXact && XLogLogicalInfoActive() &&
-		!TopTransactionStateData.didLogXid)
+		XLogRecPtrIsInvalid(TopTransactionStateData.minLSN))
 		log_unknown_top = true;
 
 	/*
@@ -693,6 +725,7 @@ AssignTransactionId(TransactionState s)
 			log_unknown_top)
 		{
 			xl_xact_assignment xlrec;
+			XLogRecPtr		   endptr;
 
 			/*
 			 * xtop is always set by now because we recurse up transaction
@@ -707,11 +740,13 @@ AssignTransactionId(TransactionState s)
 			XLogRegisterData((char *) unreportedXids,
 							 nUnreportedXids * sizeof(TransactionId));
 
-			(void) XLogInsert(RM_XACT_ID, XLOG_XACT_ASSIGNMENT);
+			endptr = XLogInsert(RM_XACT_ID, XLOG_XACT_ASSIGNMENT);
 
 			nUnreportedXids = 0;
-			/* mark top, not current xact as having been logged */
-			TopTransactionStateData.didLogXid = true;
+
+			/* set minLSN of top, not of current xact if not yet */
+			if (XLogRecPtrIsInvalid(TopTransactionStateData.minLSN))
+				TopTransactionStateData.minLSN = endptr;
 		}
 	}
 }
@@ -2022,7 +2057,7 @@ StartTransaction(void)
 	 * initialize reported xid accounting
 	 */
 	nUnreportedXids = 0;
-	s->didLogXid = false;
+	s->minLSN = InvalidXLogRecPtr;
 
 	/*
 	 * must initialize resource-management stuff first
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 04192b7add..0183589b4d 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -1171,7 +1171,7 @@ XLogInsertRecord(XLogRecData *rdata,
 	 */
 	WALInsertLockRelease();
 
-	MarkCurrentTransactionIdLoggedIfAny();
+	MarkCurrentTransactionIdLoggedIfAny(EndPos);
 
 	END_CRIT_SECTION();
 
diff --git a/src/backend/utils/adt/xid8funcs.c b/src/backend/utils/adt/xid8funcs.c
index cc2b4ac797..992482f8c8 100644
--- a/src/backend/utils/adt/xid8funcs.c
+++ b/src/backend/utils/adt/xid8funcs.c
@@ -357,6 +357,8 @@ bad_format:
 Datum
 pg_current_xact_id(PG_FUNCTION_ARGS)
 {
+	FullTransactionId xid;
+
 	/*
 	 * Must prevent during recovery because if an xid is not assigned we try
 	 * to assign one, which would fail. Programs already rely on this function
@@ -365,7 +367,12 @@ pg_current_xact_id(PG_FUNCTION_ARGS)
 	 */
 	PreventCommandDuringRecovery("pg_current_xact_id()");
 
-	PG_RETURN_FULLTRANSACTIONID(GetTopFullTransactionId());
+	xid = GetTopFullTransactionId();
+
+	/* the XID is going to be published, make sure it is psersistent */
+	EnsureTopTransactionIdLogged();
+
+	PG_RETURN_FULLTRANSACTIONID(xid);
 }
 
 /*
@@ -380,6 +387,9 @@ pg_current_xact_id_if_assigned(PG_FUNCTION_ARGS)
 	if (!FullTransactionIdIsValid(topfxid))
 		PG_RETURN_NULL();
 
+	/* the XID is going to be published, make sure it is psersistent */
+	EnsureTopTransactionIdLogged();
+
 	PG_RETURN_FULLTRANSACTIONID(topfxid);
 }
 
diff --git a/src/include/access/xact.h b/src/include/access/xact.h
index 34cfaf542c..a61e4d6da5 100644
--- a/src/include/access/xact.h
+++ b/src/include/access/xact.h
@@ -386,7 +386,8 @@ extern FullTransactionId GetTopFullTransactionId(void);
 extern FullTransactionId GetTopFullTransactionIdIfAny(void);
 extern FullTransactionId GetCurrentFullTransactionId(void);
 extern FullTransactionId GetCurrentFullTransactionIdIfAny(void);
-extern void MarkCurrentTransactionIdLoggedIfAny(void);
+extern void MarkCurrentTransactionIdLoggedIfAny(XLogRecPtr upto);
+extern void EnsureTopTransactionIdLogged(void);
 extern bool SubTransactionIsActive(SubTransactionId subxid);
 extern CommandId GetCurrentCommandId(bool used);
 extern void SetParallelStartTimestamps(TimestampTz xact_ts, TimestampTz stmt_ts);
-- 
2.17.0

From e296fc423fc5862de53ea7e59f3acfa7940044fb Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Thu, 11 Mar 2021 17:36:24 -0600
Subject: [PATCH 04/10] wal_compression_method: default to zlib..

this is meant to exercise the CIs, and not meant to be merged
---
 src/backend/access/transam/xlog.c | 2 +-
 src/backend/utils/misc/guc.c      | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 0183589b4d..8bae73b4ec 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -99,7 +99,7 @@ bool		EnableHotStandby = false;
 bool		fullPageWrites = true;
 bool		wal_log_hints = false;
 bool		wal_compression = false;
-int			wal_compression_method = WAL_COMPRESSION_PGLZ;
+int			wal_compression_method = WAL_COMPRESSION_ZLIB;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 8084027465..c37a8313d3 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -1269,7 +1269,7 @@ static struct config_bool ConfigureNamesBool[] =
 			NULL
 		},
 		&wal_compression,
-		false,
+		true,
 		NULL, NULL, NULL
 	},
 
@@ -4728,7 +4728,7 @@ static struct config_enum ConfigureNamesEnum[] =
 			NULL
 		},
 		&wal_compression_method,
-		WAL_COMPRESSION_PGLZ, wal_compression_options,
+		WAL_COMPRESSION_ZLIB, wal_compression_options,
 		NULL, NULL, NULL
 	},
 
-- 
2.17.0

From aaea36fedb048f0f4f94abc8313a367d7c6b2007 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Fri, 12 Mar 2021 14:32:10 -0600
Subject: [PATCH 05/10] (re)add wal_compression_method: lz4

---
 configure                                     | 176 ++++++++++++++++++
 configure.ac                                  |  26 +++
 doc/src/sgml/config.sgml                      |   3 +-
 src/backend/access/transam/xlog.c             |   3 +
 src/backend/access/transam/xloginsert.c       |  12 ++
 src/backend/access/transam/xlogreader.c       |  13 ++
 src/backend/utils/misc/postgresql.conf.sample |   2 +-
 src/include/access/xlog_internal.h            |   1 +
 src/include/pg_config.h.in                    |   3 +
 src/tools/msvc/Solution.pm                    |   1 +
 10 files changed, 238 insertions(+), 2 deletions(-)

diff --git a/configure b/configure
index fad817bb38..9b590eb432 100755
--- a/configure
+++ b/configure
@@ -699,6 +699,9 @@ with_gnu_ld
 LD
 LDFLAGS_SL
 LDFLAGS_EX
+LZ4_LIBS
+LZ4_CFLAGS
+with_lz4
 with_zlib
 with_system_tzdata
 with_libxslt
@@ -864,6 +867,7 @@ with_libxml
 with_libxslt
 with_system_tzdata
 with_zlib
+with_lz4
 with_gnu_ld
 with_ssl
 with_openssl
@@ -891,6 +895,8 @@ ICU_LIBS
 XML2_CONFIG
 XML2_CFLAGS
 XML2_LIBS
+LZ4_CFLAGS
+LZ4_LIBS
 LDFLAGS_EX
 LDFLAGS_SL
 PERL
@@ -1569,6 +1575,7 @@ Optional Packages:
   --with-system-tzdata=DIR
                           use system time zone data in DIR
   --without-zlib          do not use Zlib
+  --with-lz4              build with LZ4 support
   --with-gnu-ld           assume the C compiler uses GNU ld [default=no]
   --with-ssl=LIB          use LIB for SSL/TLS support (openssl)
   --with-openssl          obsolete spelling of --with-ssl=openssl
@@ -1596,6 +1603,8 @@ Some influential environment variables:
   XML2_CONFIG path to xml2-config utility
   XML2_CFLAGS C compiler flags for XML2, overriding pkg-config
   XML2_LIBS   linker flags for XML2, overriding pkg-config
+  LZ4_CFLAGS  C compiler flags for LZ4, overriding pkg-config
+  LZ4_LIBS    linker flags for LZ4, overriding pkg-config
   LDFLAGS_EX  extra linker flags for linking executables only
   LDFLAGS_SL  extra linker flags for linking shared libraries only
   PERL        Perl program
@@ -8563,6 +8572,137 @@ fi
 
 
 
+#
+# LZ4
+#
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether to build with LZ4 support" >&5
+$as_echo_n "checking whether to build with LZ4 support... " >&6; }
+
+
+
+# Check whether --with-lz4 was given.
+if test "${with_lz4+set}" = set; then :
+  withval=$with_lz4;
+  case $withval in
+    yes)
+
+$as_echo "#define USE_LZ4 1" >>confdefs.h
+
+      ;;
+    no)
+      :
+      ;;
+    *)
+      as_fn_error $? "no argument expected for --with-lz4 option" "$LINENO" 5
+      ;;
+  esac
+
+else
+  with_lz4=no
+
+fi
+
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $with_lz4" >&5
+$as_echo "$with_lz4" >&6; }
+
+
+if test "$with_lz4" = yes; then
+
+pkg_failed=no
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for liblz4" >&5
+$as_echo_n "checking for liblz4... " >&6; }
+
+if test -n "$LZ4_CFLAGS"; then
+    pkg_cv_LZ4_CFLAGS="$LZ4_CFLAGS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"liblz4\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "liblz4") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_LZ4_CFLAGS=`$PKG_CONFIG --cflags "liblz4" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+if test -n "$LZ4_LIBS"; then
+    pkg_cv_LZ4_LIBS="$LZ4_LIBS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"liblz4\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "liblz4") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_LZ4_LIBS=`$PKG_CONFIG --libs "liblz4" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+
+
+
+if test $pkg_failed = yes; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+
+if $PKG_CONFIG --atleast-pkgconfig-version 0.20; then
+        _pkg_short_errors_supported=yes
+else
+        _pkg_short_errors_supported=no
+fi
+        if test $_pkg_short_errors_supported = yes; then
+	        LZ4_PKG_ERRORS=`$PKG_CONFIG --short-errors --print-errors --cflags --libs "liblz4" 2>&1`
+        else
+	        LZ4_PKG_ERRORS=`$PKG_CONFIG --print-errors --cflags --libs "liblz4" 2>&1`
+        fi
+	# Put the nasty error message in config.log where it belongs
+	echo "$LZ4_PKG_ERRORS" >&5
+
+	as_fn_error $? "Package requirements (liblz4) were not met:
+
+$LZ4_PKG_ERRORS
+
+Consider adjusting the PKG_CONFIG_PATH environment variable if you
+installed software in a non-standard prefix.
+
+Alternatively, you may set the environment variables LZ4_CFLAGS
+and LZ4_LIBS to avoid the need to call pkg-config.
+See the pkg-config man page for more details." "$LINENO" 5
+elif test $pkg_failed = untried; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+	{ { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error $? "The pkg-config script could not be found or is too old.  Make sure it
+is in your PATH or set the PKG_CONFIG environment variable to the full
+path to pkg-config.
+
+Alternatively, you may set the environment variables LZ4_CFLAGS
+and LZ4_LIBS to avoid the need to call pkg-config.
+See the pkg-config man page for more details.
+
+To get pkg-config, see <http://pkg-config.freedesktop.org/>.
+See \`config.log' for more details" "$LINENO" 5; }
+else
+	LZ4_CFLAGS=$pkg_cv_LZ4_CFLAGS
+	LZ4_LIBS=$pkg_cv_LZ4_LIBS
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+
+fi
+  LIBS="$LZ4_LIBS $LIBS"
+  CFLAGS="$LZ4_CFLAGS $CFLAGS"
+fi
+
 #
 # Assignments
 #
@@ -13378,6 +13518,42 @@ fi
 
 fi
 
+if test "$with_lz4" = yes; then
+  ac_save_CPPFLAGS=$CPPFLAGS
+  CPPFLAGS="$LZ4_CFLAGS $CPPFLAGS"
+
+  # Verify we have LZ4's header files
+  for ac_header in lz4/lz4.h
+do :
+  ac_fn_c_check_header_mongrel "$LINENO" "lz4/lz4.h" "ac_cv_header_lz4_lz4_h" "$ac_includes_default"
+if test "x$ac_cv_header_lz4_lz4_h" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_LZ4_LZ4_H 1
+_ACEOF
+
+else
+  for ac_header in lz4.h
+do :
+  ac_fn_c_check_header_mongrel "$LINENO" "lz4.h" "ac_cv_header_lz4_h" "$ac_includes_default"
+if test "x$ac_cv_header_lz4_h" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_LZ4_H 1
+_ACEOF
+
+else
+  as_fn_error $? "lz4.h header file is required for LZ4" "$LINENO" 5
+fi
+
+done
+
+fi
+
+done
+
+
+  CPPFLAGS=$ac_save_CPPFLAGS
+fi
+
 if test "$with_gssapi" = yes ; then
   for ac_header in gssapi/gssapi.h
 do :
diff --git a/configure.ac b/configure.ac
index 0ed53571dd..2b3b5676eb 100644
--- a/configure.ac
+++ b/configure.ac
@@ -986,6 +986,21 @@ PGAC_ARG_BOOL(with, zlib, yes,
               [do not use Zlib])
 AC_SUBST(with_zlib)
 
+#
+# LZ4
+#
+AC_MSG_CHECKING([whether to build with LZ4 support])
+PGAC_ARG_BOOL(with, lz4, no, [build with LZ4 support],
+              [AC_DEFINE([USE_LZ4], 1, [Define to 1 to build with LZ4 support. (--with-lz4)])])
+AC_MSG_RESULT([$with_lz4])
+AC_SUBST(with_lz4)
+
+if test "$with_lz4" = yes; then
+  PKG_CHECK_MODULES(LZ4, liblz4)
+  LIBS="$LZ4_LIBS $LIBS"
+  CFLAGS="$LZ4_CFLAGS $CFLAGS"
+fi
+
 #
 # Assignments
 #
@@ -1407,6 +1422,17 @@ failure.  It is possible the compiler isn't looking in the proper directory.
 Use --without-zlib to disable zlib support.])])
 fi
 
+if test "$with_lz4" = yes; then
+  ac_save_CPPFLAGS=$CPPFLAGS
+  CPPFLAGS="$LZ4_CFLAGS $CPPFLAGS"
+
+  # Verify we have LZ4's header files
+  AC_CHECK_HEADERS(lz4/lz4.h, [],
+       [AC_CHECK_HEADERS(lz4.h, [], [AC_MSG_ERROR([lz4.h header file is required for LZ4])])])
+
+  CPPFLAGS=$ac_save_CPPFLAGS
+fi
+
 if test "$with_gssapi" = yes ; then
   AC_CHECK_HEADERS(gssapi/gssapi.h, [],
 	[AC_CHECK_HEADERS(gssapi.h, [], [AC_MSG_ERROR([gssapi.h header file is required for GSSAPI])])])
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 7fb2a84626..257775c83b 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -3082,7 +3082,8 @@ include_dir 'conf.d'
        <para>
         This parameter selects the compression method used to compress WAL when
         <varname>wal_compression</varname> is enabled.
-        The supported methods are pglz and zlib.
+        The supported methods are pglz, zlib, and (if configured when
+        <productname>PostgreSQL</productname> was built) lz4.
         The default value is <literal>pglz</literal>.
         Only superusers can change this setting.
        </para>
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 8bae73b4ec..f33355e44a 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -186,6 +186,9 @@ const struct config_enum_entry wal_compression_options[] = {
 	{"pglz", WAL_COMPRESSION_PGLZ, false},
 #ifdef  HAVE_LIBZ
 	{"zlib", WAL_COMPRESSION_ZLIB, false},
+#endif
+#ifdef  USE_LZ4
+	{"lz4", WAL_COMPRESSION_LZ4, false},
 #endif
 	{NULL, 0, false}
 };
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
index 34e1227381..9fe5c30236 100644
--- a/src/backend/access/transam/xloginsert.c
+++ b/src/backend/access/transam/xloginsert.c
@@ -37,6 +37,10 @@
 #include <zlib.h>
 #endif
 
+#ifdef USE_LZ4
+#include "lz4.h"
+#endif
+
 /* Buffer size required to store a compressed version of backup block image */
 #define PGLZ_MAX_BLCKSZ PGLZ_MAX_OUTPUT(BLCKSZ)
 
@@ -884,6 +888,14 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 		}
 #endif
 
+#ifdef USE_LZ4
+	case WAL_COMPRESSION_LZ4:
+		len = LZ4_compress_fast(source, dest, orig_len, PGLZ_MAX_BLCKSZ, 1);
+		if (len == 0)
+			len = -1;
+		break;
+#endif
+
 	default:
 		/*
 		 * It should be impossible to get here for unsupported algorithms,
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index afca22a26c..fa1e38a810 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -37,6 +37,10 @@
 #include <zlib.h>
 #endif
 
+#ifdef USE_LZ4
+#include "lz4.h"
+#endif
+
 static void report_invalid_record(XLogReaderState *state, const char *fmt,...)
 			pg_attribute_printf(2, 3);
 static bool allocate_recordbuf(XLogReaderState *state, uint32 reclength);
@@ -1558,6 +1562,8 @@ wal_compression_name(WalCompression compression)
 			return "pglz";
 		case WAL_COMPRESSION_ZLIB:
 			return "zlib";
+		case WAL_COMPRESSION_LZ4:
+			return "lz4";
 		default:
 			return "???";
 	}
@@ -1608,6 +1614,13 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 		}
 #endif
 
+#ifdef USE_LZ4
+		case WAL_COMPRESSION_LZ4:
+			decomp_result = LZ4_decompress_safe(ptr, tmp.data,
+					bkpb->bimg_len, BLCKSZ-bkpb->hole_length);
+			break;
+#endif
+
 		default:
 			report_invalid_record(record, "image at %X/%X is compressed with unsupported codec, block %d (%d/%s)",
 								  (uint32) (record->ReadRecPtr >> 32),
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index ef69a94492..76f494cb9b 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -213,7 +213,7 @@
 					#   open_sync
 #full_page_writes = on			# recover from partial page writes
 #wal_compression = off			# enable compression of full-page writes
-#wal_compression_method = pglz		# pglz, zlib
+#wal_compression_method = pglz		# pglz, zlib, lz4
 #wal_log_hints = off			# also do full page writes of non-critical updates
 					# (change requires restart)
 #wal_init_zero = on			# zero-fill new WAL files
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index d653839b97..e70886b81c 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -328,6 +328,7 @@ typedef enum WalCompression
 {
 	WAL_COMPRESSION_PGLZ,
 	WAL_COMPRESSION_ZLIB,
+	WAL_COMPRESSION_LZ4,
 } WalCompression;
 
 extern const char *wal_compression_name(WalCompression compression);
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index 7a7cc21d8d..0a6422da4f 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -899,6 +899,9 @@
 /* Define to 1 to build with LLVM based JIT support. (--with-llvm) */
 #undef USE_LLVM
 
+/* Define to 1 to build with LZ4 support (--with-lz4) */
+#undef USE_LZ4
+
 /* Define to select named POSIX semaphores. */
 #undef USE_NAMED_POSIX_SEMAPHORES
 
diff --git a/src/tools/msvc/Solution.pm b/src/tools/msvc/Solution.pm
index a4f5cc4bdb..14605371bb 100644
--- a/src/tools/msvc/Solution.pm
+++ b/src/tools/msvc/Solution.pm
@@ -485,6 +485,7 @@ sub GenerateFiles
 		USE_ICU => $self->{options}->{icu} ? 1 : undef,
 		USE_LIBXML                 => undef,
 		USE_LIBXSLT                => undef,
+		USE_LZ4                    => undef,
 		USE_LDAP                   => $self->{options}->{ldap} ? 1 : undef,
 		USE_LLVM                   => undef,
 		USE_NAMED_POSIX_SEMAPHORES => undef,
-- 
2.17.0

From fff41a30d241477ed16086bc51a535bf8ec90702 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Fri, 12 Mar 2021 14:32:10 -0600
Subject: [PATCH 05/10] (re)add wal_compression_method: LZ4

---
 configure                               | 176 ++++++++++++++++++++++++
 configure.ac                            |  26 ++++
 doc/src/sgml/config.sgml                |   3 +-
 src/backend/access/transam/xlog.c       |   5 +-
 src/backend/access/transam/xloginsert.c |  12 ++
 src/backend/access/transam/xlogreader.c |  13 ++
 src/include/access/xlog_internal.h      |   1 +
 src/include/pg_config.h.in              |   3 +
 src/tools/msvc/Solution.pm              |   1 +
 9 files changed, 238 insertions(+), 2 deletions(-)

diff --git a/configure b/configure
index fad817bb38..9b590eb432 100755
--- a/configure
+++ b/configure
@@ -699,6 +699,9 @@ with_gnu_ld
 LD
 LDFLAGS_SL
 LDFLAGS_EX
+LZ4_LIBS
+LZ4_CFLAGS
+with_lz4
 with_zlib
 with_system_tzdata
 with_libxslt
@@ -864,6 +867,7 @@ with_libxml
 with_libxslt
 with_system_tzdata
 with_zlib
+with_lz4
 with_gnu_ld
 with_ssl
 with_openssl
@@ -891,6 +895,8 @@ ICU_LIBS
 XML2_CONFIG
 XML2_CFLAGS
 XML2_LIBS
+LZ4_CFLAGS
+LZ4_LIBS
 LDFLAGS_EX
 LDFLAGS_SL
 PERL
@@ -1569,6 +1575,7 @@ Optional Packages:
   --with-system-tzdata=DIR
                           use system time zone data in DIR
   --without-zlib          do not use Zlib
+  --with-lz4              build with LZ4 support
   --with-gnu-ld           assume the C compiler uses GNU ld [default=no]
   --with-ssl=LIB          use LIB for SSL/TLS support (openssl)
   --with-openssl          obsolete spelling of --with-ssl=openssl
@@ -1596,6 +1603,8 @@ Some influential environment variables:
   XML2_CONFIG path to xml2-config utility
   XML2_CFLAGS C compiler flags for XML2, overriding pkg-config
   XML2_LIBS   linker flags for XML2, overriding pkg-config
+  LZ4_CFLAGS  C compiler flags for LZ4, overriding pkg-config
+  LZ4_LIBS    linker flags for LZ4, overriding pkg-config
   LDFLAGS_EX  extra linker flags for linking executables only
   LDFLAGS_SL  extra linker flags for linking shared libraries only
   PERL        Perl program
@@ -8563,6 +8572,137 @@ fi
 
 
 
+#
+# LZ4
+#
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether to build with LZ4 support" >&5
+$as_echo_n "checking whether to build with LZ4 support... " >&6; }
+
+
+
+# Check whether --with-lz4 was given.
+if test "${with_lz4+set}" = set; then :
+  withval=$with_lz4;
+  case $withval in
+    yes)
+
+$as_echo "#define USE_LZ4 1" >>confdefs.h
+
+      ;;
+    no)
+      :
+      ;;
+    *)
+      as_fn_error $? "no argument expected for --with-lz4 option" "$LINENO" 5
+      ;;
+  esac
+
+else
+  with_lz4=no
+
+fi
+
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $with_lz4" >&5
+$as_echo "$with_lz4" >&6; }
+
+
+if test "$with_lz4" = yes; then
+
+pkg_failed=no
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for liblz4" >&5
+$as_echo_n "checking for liblz4... " >&6; }
+
+if test -n "$LZ4_CFLAGS"; then
+    pkg_cv_LZ4_CFLAGS="$LZ4_CFLAGS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"liblz4\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "liblz4") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_LZ4_CFLAGS=`$PKG_CONFIG --cflags "liblz4" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+if test -n "$LZ4_LIBS"; then
+    pkg_cv_LZ4_LIBS="$LZ4_LIBS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"liblz4\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "liblz4") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_LZ4_LIBS=`$PKG_CONFIG --libs "liblz4" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+
+
+
+if test $pkg_failed = yes; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+
+if $PKG_CONFIG --atleast-pkgconfig-version 0.20; then
+        _pkg_short_errors_supported=yes
+else
+        _pkg_short_errors_supported=no
+fi
+        if test $_pkg_short_errors_supported = yes; then
+	        LZ4_PKG_ERRORS=`$PKG_CONFIG --short-errors --print-errors --cflags --libs "liblz4" 2>&1`
+        else
+	        LZ4_PKG_ERRORS=`$PKG_CONFIG --print-errors --cflags --libs "liblz4" 2>&1`
+        fi
+	# Put the nasty error message in config.log where it belongs
+	echo "$LZ4_PKG_ERRORS" >&5
+
+	as_fn_error $? "Package requirements (liblz4) were not met:
+
+$LZ4_PKG_ERRORS
+
+Consider adjusting the PKG_CONFIG_PATH environment variable if you
+installed software in a non-standard prefix.
+
+Alternatively, you may set the environment variables LZ4_CFLAGS
+and LZ4_LIBS to avoid the need to call pkg-config.
+See the pkg-config man page for more details." "$LINENO" 5
+elif test $pkg_failed = untried; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+	{ { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error $? "The pkg-config script could not be found or is too old.  Make sure it
+is in your PATH or set the PKG_CONFIG environment variable to the full
+path to pkg-config.
+
+Alternatively, you may set the environment variables LZ4_CFLAGS
+and LZ4_LIBS to avoid the need to call pkg-config.
+See the pkg-config man page for more details.
+
+To get pkg-config, see <http://pkg-config.freedesktop.org/>.
+See \`config.log' for more details" "$LINENO" 5; }
+else
+	LZ4_CFLAGS=$pkg_cv_LZ4_CFLAGS
+	LZ4_LIBS=$pkg_cv_LZ4_LIBS
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+
+fi
+  LIBS="$LZ4_LIBS $LIBS"
+  CFLAGS="$LZ4_CFLAGS $CFLAGS"
+fi
+
 #
 # Assignments
 #
@@ -13378,6 +13518,42 @@ fi
 
 fi
 
+if test "$with_lz4" = yes; then
+  ac_save_CPPFLAGS=$CPPFLAGS
+  CPPFLAGS="$LZ4_CFLAGS $CPPFLAGS"
+
+  # Verify we have LZ4's header files
+  for ac_header in lz4/lz4.h
+do :
+  ac_fn_c_check_header_mongrel "$LINENO" "lz4/lz4.h" "ac_cv_header_lz4_lz4_h" "$ac_includes_default"
+if test "x$ac_cv_header_lz4_lz4_h" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_LZ4_LZ4_H 1
+_ACEOF
+
+else
+  for ac_header in lz4.h
+do :
+  ac_fn_c_check_header_mongrel "$LINENO" "lz4.h" "ac_cv_header_lz4_h" "$ac_includes_default"
+if test "x$ac_cv_header_lz4_h" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_LZ4_H 1
+_ACEOF
+
+else
+  as_fn_error $? "lz4.h header file is required for LZ4" "$LINENO" 5
+fi
+
+done
+
+fi
+
+done
+
+
+  CPPFLAGS=$ac_save_CPPFLAGS
+fi
+
 if test "$with_gssapi" = yes ; then
   for ac_header in gssapi/gssapi.h
 do :
diff --git a/configure.ac b/configure.ac
index 0ed53571dd..2b3b5676eb 100644
--- a/configure.ac
+++ b/configure.ac
@@ -986,6 +986,21 @@ PGAC_ARG_BOOL(with, zlib, yes,
               [do not use Zlib])
 AC_SUBST(with_zlib)
 
+#
+# LZ4
+#
+AC_MSG_CHECKING([whether to build with LZ4 support])
+PGAC_ARG_BOOL(with, lz4, no, [build with LZ4 support],
+              [AC_DEFINE([USE_LZ4], 1, [Define to 1 to build with LZ4 support. (--with-lz4)])])
+AC_MSG_RESULT([$with_lz4])
+AC_SUBST(with_lz4)
+
+if test "$with_lz4" = yes; then
+  PKG_CHECK_MODULES(LZ4, liblz4)
+  LIBS="$LZ4_LIBS $LIBS"
+  CFLAGS="$LZ4_CFLAGS $CFLAGS"
+fi
+
 #
 # Assignments
 #
@@ -1407,6 +1422,17 @@ failure.  It is possible the compiler isn't looking in the proper directory.
 Use --without-zlib to disable zlib support.])])
 fi
 
+if test "$with_lz4" = yes; then
+  ac_save_CPPFLAGS=$CPPFLAGS
+  CPPFLAGS="$LZ4_CFLAGS $CPPFLAGS"
+
+  # Verify we have LZ4's header files
+  AC_CHECK_HEADERS(lz4/lz4.h, [],
+       [AC_CHECK_HEADERS(lz4.h, [], [AC_MSG_ERROR([lz4.h header file is required for LZ4])])])
+
+  CPPFLAGS=$ac_save_CPPFLAGS
+fi
+
 if test "$with_gssapi" = yes ; then
   AC_CHECK_HEADERS(gssapi/gssapi.h, [],
 	[AC_CHECK_HEADERS(gssapi.h, [], [AC_MSG_ERROR([gssapi.h header file is required for GSSAPI])])])
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 7fb2a84626..257775c83b 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -3082,7 +3082,8 @@ include_dir 'conf.d'
        <para>
         This parameter selects the compression method used to compress WAL when
         <varname>wal_compression</varname> is enabled.
-        The supported methods are pglz and zlib.
+        The supported methods are pglz, zlib, and (if configured when
+        <productname>PostgreSQL</productname> was built) lz4.
         The default value is <literal>pglz</literal>.
         Only superusers can change this setting.
        </para>
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 8bae73b4ec..609d954a3a 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -99,7 +99,7 @@ bool		EnableHotStandby = false;
 bool		fullPageWrites = true;
 bool		wal_log_hints = false;
 bool		wal_compression = false;
-int			wal_compression_method = WAL_COMPRESSION_ZLIB;
+int			wal_compression_method = WAL_COMPRESSION_LZ4;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
@@ -186,6 +186,9 @@ const struct config_enum_entry wal_compression_options[] = {
 	{"pglz", WAL_COMPRESSION_PGLZ, false},
 #ifdef  HAVE_LIBZ
 	{"zlib", WAL_COMPRESSION_ZLIB, false},
+#endif
+#ifdef  USE_LZ4
+	{"lz4", WAL_COMPRESSION_LZ4, false},
 #endif
 	{NULL, 0, false}
 };
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
index 34e1227381..9fe5c30236 100644
--- a/src/backend/access/transam/xloginsert.c
+++ b/src/backend/access/transam/xloginsert.c
@@ -37,6 +37,10 @@
 #include <zlib.h>
 #endif
 
+#ifdef USE_LZ4
+#include "lz4.h"
+#endif
+
 /* Buffer size required to store a compressed version of backup block image */
 #define PGLZ_MAX_BLCKSZ PGLZ_MAX_OUTPUT(BLCKSZ)
 
@@ -884,6 +888,14 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 		}
 #endif
 
+#ifdef USE_LZ4
+	case WAL_COMPRESSION_LZ4:
+		len = LZ4_compress_fast(source, dest, orig_len, PGLZ_MAX_BLCKSZ, 1);
+		if (len == 0)
+			len = -1;
+		break;
+#endif
+
 	default:
 		/*
 		 * It should be impossible to get here for unsupported algorithms,
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index afca22a26c..fa1e38a810 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -37,6 +37,10 @@
 #include <zlib.h>
 #endif
 
+#ifdef USE_LZ4
+#include "lz4.h"
+#endif
+
 static void report_invalid_record(XLogReaderState *state, const char *fmt,...)
 			pg_attribute_printf(2, 3);
 static bool allocate_recordbuf(XLogReaderState *state, uint32 reclength);
@@ -1558,6 +1562,8 @@ wal_compression_name(WalCompression compression)
 			return "pglz";
 		case WAL_COMPRESSION_ZLIB:
 			return "zlib";
+		case WAL_COMPRESSION_LZ4:
+			return "lz4";
 		default:
 			return "???";
 	}
@@ -1608,6 +1614,13 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 		}
 #endif
 
+#ifdef USE_LZ4
+		case WAL_COMPRESSION_LZ4:
+			decomp_result = LZ4_decompress_safe(ptr, tmp.data,
+					bkpb->bimg_len, BLCKSZ-bkpb->hole_length);
+			break;
+#endif
+
 		default:
 			report_invalid_record(record, "image at %X/%X is compressed with unsupported codec, block %d (%d/%s)",
 								  (uint32) (record->ReadRecPtr >> 32),
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index d653839b97..e70886b81c 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -328,6 +328,7 @@ typedef enum WalCompression
 {
 	WAL_COMPRESSION_PGLZ,
 	WAL_COMPRESSION_ZLIB,
+	WAL_COMPRESSION_LZ4,
 } WalCompression;
 
 extern const char *wal_compression_name(WalCompression compression);
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index 7a7cc21d8d..0a6422da4f 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -899,6 +899,9 @@
 /* Define to 1 to build with LLVM based JIT support. (--with-llvm) */
 #undef USE_LLVM
 
+/* Define to 1 to build with LZ4 support (--with-lz4) */
+#undef USE_LZ4
+
 /* Define to select named POSIX semaphores. */
 #undef USE_NAMED_POSIX_SEMAPHORES
 
diff --git a/src/tools/msvc/Solution.pm b/src/tools/msvc/Solution.pm
index a4f5cc4bdb..14605371bb 100644
--- a/src/tools/msvc/Solution.pm
+++ b/src/tools/msvc/Solution.pm
@@ -485,6 +485,7 @@ sub GenerateFiles
 		USE_ICU => $self->{options}->{icu} ? 1 : undef,
 		USE_LIBXML                 => undef,
 		USE_LIBXSLT                => undef,
+		USE_LZ4                    => undef,
 		USE_LDAP                   => $self->{options}->{ldap} ? 1 : undef,
 		USE_LLVM                   => undef,
 		USE_NAMED_POSIX_SEMAPHORES => undef,
-- 
2.17.0

From 0f50e5f58fb4c4c5580f44cc03512a30f08f27f2 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Fri, 12 Mar 2021 15:35:40 -0600
Subject: [PATCH 06/10] Default to LZ4..

this is meant to exercise in the CIs, and not meant to be merged
---
 configure                         | 6 ++++--
 configure.ac                      | 4 ++--
 src/backend/access/transam/xlog.c | 2 +-
 src/backend/utils/misc/guc.c      | 2 +-
 4 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/configure b/configure
index 9b590eb432..3afa1e87e3 100755
--- a/configure
+++ b/configure
@@ -1575,7 +1575,7 @@ Optional Packages:
   --with-system-tzdata=DIR
                           use system time zone data in DIR
   --without-zlib          do not use Zlib
-  --with-lz4              build with LZ4 support
+  --without-lz4           build without LZ4 support
   --with-gnu-ld           assume the C compiler uses GNU ld [default=no]
   --with-ssl=LIB          use LIB for SSL/TLS support (openssl)
   --with-openssl          obsolete spelling of --with-ssl=openssl
@@ -8598,7 +8598,9 @@ $as_echo "#define USE_LZ4 1" >>confdefs.h
   esac
 
 else
-  with_lz4=no
+  with_lz4=yes
+
+$as_echo "#define USE_LZ4 1" >>confdefs.h
 
 fi
 
diff --git a/configure.ac b/configure.ac
index 2b3b5676eb..d62ea5f742 100644
--- a/configure.ac
+++ b/configure.ac
@@ -990,8 +990,8 @@ AC_SUBST(with_zlib)
 # LZ4
 #
 AC_MSG_CHECKING([whether to build with LZ4 support])
-PGAC_ARG_BOOL(with, lz4, no, [build with LZ4 support],
-              [AC_DEFINE([USE_LZ4], 1, [Define to 1 to build with LZ4 support. (--with-lz4)])])
+PGAC_ARG_BOOL(with, lz4, yes, [build without LZ4 support],
+              [AC_DEFINE([USE_LZ4], 1, [Define to 1 to build without LZ4 support. (--without-lz4)])])
 AC_MSG_RESULT([$with_lz4])
 AC_SUBST(with_lz4)
 
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index f33355e44a..609d954a3a 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -99,7 +99,7 @@ bool		EnableHotStandby = false;
 bool		fullPageWrites = true;
 bool		wal_log_hints = false;
 bool		wal_compression = false;
-int			wal_compression_method = WAL_COMPRESSION_ZLIB;
+int			wal_compression_method = WAL_COMPRESSION_LZ4;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index c37a8313d3..52f9cd0242 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -4728,7 +4728,7 @@ static struct config_enum ConfigureNamesEnum[] =
 			NULL
 		},
 		&wal_compression_method,
-		WAL_COMPRESSION_ZLIB, wal_compression_options,
+		WAL_COMPRESSION_LZ4, wal_compression_options,
 		NULL, NULL, NULL
 	},
 
-- 
2.17.0

From b1240bea051f704b6bf024e369a5a83201893c3e Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Fri, 12 Mar 2021 14:43:53 -0600
Subject: [PATCH 07/10] add wal_compression_method: zstd

---
 configure                                     | 163 ++++++++++++++++++
 configure.ac                                  |  26 +++
 doc/src/sgml/config.sgml                      |   2 +-
 src/backend/access/transam/xlog.c             |   3 +
 src/backend/access/transam/xloginsert.c       |  19 ++
 src/backend/access/transam/xlogreader.c       |  16 ++
 src/backend/utils/misc/postgresql.conf.sample |   2 +-
 src/include/access/xlog_internal.h            |   1 +
 src/include/pg_config.h.in                    |   3 +
 src/tools/msvc/Solution.pm                    |   1 +
 10 files changed, 234 insertions(+), 2 deletions(-)

diff --git a/configure b/configure
index 3afa1e87e3..20c6e08c02 100755
--- a/configure
+++ b/configure
@@ -699,6 +699,9 @@ with_gnu_ld
 LD
 LDFLAGS_SL
 LDFLAGS_EX
+ZSTD_LIBS
+ZSTD_CFLAGS
+with_zstd
 LZ4_LIBS
 LZ4_CFLAGS
 with_lz4
@@ -868,6 +871,7 @@ with_libxslt
 with_system_tzdata
 with_zlib
 with_lz4
+with_zstd
 with_gnu_ld
 with_ssl
 with_openssl
@@ -897,6 +901,8 @@ XML2_CFLAGS
 XML2_LIBS
 LZ4_CFLAGS
 LZ4_LIBS
+ZSTD_CFLAGS
+ZSTD_LIBS
 LDFLAGS_EX
 LDFLAGS_SL
 PERL
@@ -1576,6 +1582,7 @@ Optional Packages:
                           use system time zone data in DIR
   --without-zlib          do not use Zlib
   --without-lz4           build without LZ4 support
+  --with-zstd             build with Zstd compression library
   --with-gnu-ld           assume the C compiler uses GNU ld [default=no]
   --with-ssl=LIB          use LIB for SSL/TLS support (openssl)
   --with-openssl          obsolete spelling of --with-ssl=openssl
@@ -1605,6 +1612,8 @@ Some influential environment variables:
   XML2_LIBS   linker flags for XML2, overriding pkg-config
   LZ4_CFLAGS  C compiler flags for LZ4, overriding pkg-config
   LZ4_LIBS    linker flags for LZ4, overriding pkg-config
+  ZSTD_CFLAGS C compiler flags for ZSTD, overriding pkg-config
+  ZSTD_LIBS   linker flags for ZSTD, overriding pkg-config
   LDFLAGS_EX  extra linker flags for linking executables only
   LDFLAGS_SL  extra linker flags for linking shared libraries only
   PERL        Perl program
@@ -8705,6 +8714,137 @@ fi
   CFLAGS="$LZ4_CFLAGS $CFLAGS"
 fi
 
+#
+# ZSTD
+#
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether to build with zstd support" >&5
+$as_echo_n "checking whether to build with zstd support... " >&6; }
+
+
+
+# Check whether --with-zstd was given.
+if test "${with_zstd+set}" = set; then :
+  withval=$with_zstd;
+  case $withval in
+    yes)
+
+$as_echo "#define USE_ZSTD 1" >>confdefs.h
+
+      ;;
+    no)
+      :
+      ;;
+    *)
+      as_fn_error $? "no argument expected for --with-zstd option" "$LINENO" 5
+      ;;
+  esac
+
+else
+  with_zstd=no
+
+fi
+
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $with_zstd" >&5
+$as_echo "$with_zstd" >&6; }
+
+
+if test "$with_zstd" = yes; then
+
+pkg_failed=no
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for libzstd" >&5
+$as_echo_n "checking for libzstd... " >&6; }
+
+if test -n "$ZSTD_CFLAGS"; then
+    pkg_cv_ZSTD_CFLAGS="$ZSTD_CFLAGS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"libzstd\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "libzstd") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_ZSTD_CFLAGS=`$PKG_CONFIG --cflags "libzstd" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+if test -n "$ZSTD_LIBS"; then
+    pkg_cv_ZSTD_LIBS="$ZSTD_LIBS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"libzstd\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "libzstd") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_ZSTD_LIBS=`$PKG_CONFIG --libs "libzstd" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+
+
+
+if test $pkg_failed = yes; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+
+if $PKG_CONFIG --atleast-pkgconfig-version 0.20; then
+        _pkg_short_errors_supported=yes
+else
+        _pkg_short_errors_supported=no
+fi
+        if test $_pkg_short_errors_supported = yes; then
+	        ZSTD_PKG_ERRORS=`$PKG_CONFIG --short-errors --print-errors --cflags --libs "libzstd" 2>&1`
+        else
+	        ZSTD_PKG_ERRORS=`$PKG_CONFIG --print-errors --cflags --libs "libzstd" 2>&1`
+        fi
+	# Put the nasty error message in config.log where it belongs
+	echo "$ZSTD_PKG_ERRORS" >&5
+
+	as_fn_error $? "Package requirements (libzstd) were not met:
+
+$ZSTD_PKG_ERRORS
+
+Consider adjusting the PKG_CONFIG_PATH environment variable if you
+installed software in a non-standard prefix.
+
+Alternatively, you may set the environment variables ZSTD_CFLAGS
+and ZSTD_LIBS to avoid the need to call pkg-config.
+See the pkg-config man page for more details." "$LINENO" 5
+elif test $pkg_failed = untried; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+	{ { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error $? "The pkg-config script could not be found or is too old.  Make sure it
+is in your PATH or set the PKG_CONFIG environment variable to the full
+path to pkg-config.
+
+Alternatively, you may set the environment variables ZSTD_CFLAGS
+and ZSTD_LIBS to avoid the need to call pkg-config.
+See the pkg-config man page for more details.
+
+To get pkg-config, see <http://pkg-config.freedesktop.org/>.
+See \`config.log' for more details" "$LINENO" 5; }
+else
+	ZSTD_CFLAGS=$pkg_cv_ZSTD_CFLAGS
+	ZSTD_LIBS=$pkg_cv_ZSTD_LIBS
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+
+fi
+  LIBS="$ZSTD_LIBS $LIBS"
+  CFLAGS="$ZSTD_CFLAGS $CFLAGS"
+fi
+
 #
 # Assignments
 #
@@ -13556,6 +13696,29 @@ done
   CPPFLAGS=$ac_save_CPPFLAGS
 fi
 
+if test "$with_zstd" = yes; then
+  ac_save_CPPFLAGS=$CPPFLAGS
+  CPPFLAGS="$ZSTD_CFLAGS $CPPFLAGS"
+
+  # Verify we have zstd's header files
+  for ac_header in zstd.h
+do :
+  ac_fn_c_check_header_mongrel "$LINENO" "zstd.h" "ac_cv_header_zstd_h" "$ac_includes_default"
+if test "x$ac_cv_header_zstd_h" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_ZSTD_H 1
+_ACEOF
+
+else
+  as_fn_error $? "zstd.h header file is required for zstd" "$LINENO" 5
+fi
+
+done
+
+
+  CPPFLAGS=$ac_save_CPPFLAGS
+fi
+
 if test "$with_gssapi" = yes ; then
   for ac_header in gssapi/gssapi.h
 do :
diff --git a/configure.ac b/configure.ac
index d62ea5f742..c4956745ce 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1001,6 +1001,21 @@ if test "$with_lz4" = yes; then
   CFLAGS="$LZ4_CFLAGS $CFLAGS"
 fi
 
+#
+# ZSTD
+#
+AC_MSG_CHECKING([whether to build with zstd support])
+PGAC_ARG_BOOL(with, zstd, no, [build with Zstd compression library],
+              [AC_DEFINE([USE_ZSTD], 1, [Define to 1 to build with zstd support. (--with-zstd)])])
+AC_MSG_RESULT([$with_zstd])
+AC_SUBST(with_zstd)
+
+if test "$with_zstd" = yes; then
+  PKG_CHECK_MODULES(ZSTD, libzstd)
+  LIBS="$ZSTD_LIBS $LIBS"
+  CFLAGS="$ZSTD_CFLAGS $CFLAGS"
+fi
+
 #
 # Assignments
 #
@@ -1433,6 +1448,17 @@ if test "$with_lz4" = yes; then
   CPPFLAGS=$ac_save_CPPFLAGS
 fi
 
+if test "$with_zstd" = yes; then
+  ac_save_CPPFLAGS=$CPPFLAGS
+  CPPFLAGS="$ZSTD_CFLAGS $CPPFLAGS"
+
+  # Verify we have zstd's header files
+  AC_CHECK_HEADERS(zstd.h, [],
+       [AC_MSG_ERROR([zstd.h header file is required for zstd])])
+
+  CPPFLAGS=$ac_save_CPPFLAGS
+fi
+
 if test "$with_gssapi" = yes ; then
   AC_CHECK_HEADERS(gssapi/gssapi.h, [],
 	[AC_CHECK_HEADERS(gssapi.h, [], [AC_MSG_ERROR([gssapi.h header file is required for GSSAPI])])])
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 257775c83b..94dd6ef3e9 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -3083,7 +3083,7 @@ include_dir 'conf.d'
         This parameter selects the compression method used to compress WAL when
         <varname>wal_compression</varname> is enabled.
         The supported methods are pglz, zlib, and (if configured when
-        <productname>PostgreSQL</productname> was built) lz4.
+        <productname>PostgreSQL</productname> was built) lz4 and zstd.
         The default value is <literal>pglz</literal>.
         Only superusers can change this setting.
        </para>
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 609d954a3a..9bac79b579 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -189,6 +189,9 @@ const struct config_enum_entry wal_compression_options[] = {
 #endif
 #ifdef  USE_LZ4
 	{"lz4", WAL_COMPRESSION_LZ4, false},
+#endif
+#ifdef  USE_ZSTD
+	{"zstd", WAL_COMPRESSION_ZSTD, false},
 #endif
 	{NULL, 0, false}
 };
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
index 9fe5c30236..5d1ae37dae 100644
--- a/src/backend/access/transam/xloginsert.c
+++ b/src/backend/access/transam/xloginsert.c
@@ -41,6 +41,10 @@
 #include "lz4.h"
 #endif
 
+#ifdef USE_ZSTD
+#include "zstd.h"
+#endif
+
 /* Buffer size required to store a compressed version of backup block image */
 #define PGLZ_MAX_BLCKSZ PGLZ_MAX_OUTPUT(BLCKSZ)
 
@@ -896,6 +900,21 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 		break;
 #endif
 
+#ifdef USE_ZSTD
+	case WAL_COMPRESSION_ZSTD:
+		len = ZSTD_compress(dest, PGLZ_MAX_BLCKSZ, source, orig_len, 1);
+		if (ZSTD_isError(len))
+		{
+			ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("failed compressing zstd: %s",
+						 ZSTD_getErrorName(len))));
+			len = -1;
+		}
+
+		break;
+#endif
+
 	default:
 		/*
 		 * It should be impossible to get here for unsupported algorithms,
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index fa1e38a810..caa1031d63 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -41,6 +41,10 @@
 #include "lz4.h"
 #endif
 
+#ifdef USE_ZSTD
+#include "zstd.h"
+#endif
+
 static void report_invalid_record(XLogReaderState *state, const char *fmt,...)
 			pg_attribute_printf(2, 3);
 static bool allocate_recordbuf(XLogReaderState *state, uint32 reclength);
@@ -1564,6 +1568,8 @@ wal_compression_name(WalCompression compression)
 			return "zlib";
 		case WAL_COMPRESSION_LZ4:
 			return "lz4";
+		case WAL_COMPRESSION_ZSTD:
+			return "zstd";
 		default:
 			return "???";
 	}
@@ -1621,6 +1627,16 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 			break;
 #endif
 
+#ifdef USE_ZSTD
+		case WAL_COMPRESSION_ZSTD:
+			decomp_result = ZSTD_decompress(tmp.data, BLCKSZ-bkpb->hole_length,
+					ptr, bkpb->bimg_len);
+			// XXX: ZSTD_getErrorName
+			if (ZSTD_isError(decomp_result))
+				decomp_result = -1;
+			break;
+#endif
+
 		default:
 			report_invalid_record(record, "image at %X/%X is compressed with unsupported codec, block %d (%d/%s)",
 								  (uint32) (record->ReadRecPtr >> 32),
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 76f494cb9b..d372e2a817 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -213,7 +213,7 @@
 					#   open_sync
 #full_page_writes = on			# recover from partial page writes
 #wal_compression = off			# enable compression of full-page writes
-#wal_compression_method = pglz		# pglz, zlib, lz4
+#wal_compression_method = pglz		# pglz, zlib, lz4, zstd
 #wal_log_hints = off			# also do full page writes of non-critical updates
 					# (change requires restart)
 #wal_init_zero = on			# zero-fill new WAL files
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index e70886b81c..48b16b6083 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -329,6 +329,7 @@ typedef enum WalCompression
 	WAL_COMPRESSION_PGLZ,
 	WAL_COMPRESSION_ZLIB,
 	WAL_COMPRESSION_LZ4,
+	WAL_COMPRESSION_ZSTD,
 } WalCompression;
 
 extern const char *wal_compression_name(WalCompression compression);
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index 0a6422da4f..ad26393352 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -902,6 +902,9 @@
 /* Define to 1 to build with LZ4 support (--with-lz4) */
 #undef USE_LZ4
 
+/* Define to 1 if you have the `zstd' library (-lzstd). */
+#undef USE_ZSTD
+
 /* Define to select named POSIX semaphores. */
 #undef USE_NAMED_POSIX_SEMAPHORES
 
diff --git a/src/tools/msvc/Solution.pm b/src/tools/msvc/Solution.pm
index 14605371bb..fff0212087 100644
--- a/src/tools/msvc/Solution.pm
+++ b/src/tools/msvc/Solution.pm
@@ -486,6 +486,7 @@ sub GenerateFiles
 		USE_LIBXML                 => undef,
 		USE_LIBXSLT                => undef,
 		USE_LZ4                    => undef,
+		USE_ZSTD                   => $self->{options}->{zstd} ? 1 : undef,
 		USE_LDAP                   => $self->{options}->{ldap} ? 1 : undef,
 		USE_LLVM                   => undef,
 		USE_NAMED_POSIX_SEMAPHORES => undef,
-- 
2.17.0

From 033141b4f2e31541c9c3abe0c28b98596ad827d2 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Fri, 12 Mar 2021 15:35:53 -0600
Subject: [PATCH 08/10] Default to zstd..

for CI, not for merge
---
 configure                         | 6 ++++--
 configure.ac                      | 2 +-
 src/backend/access/transam/xlog.c | 2 +-
 src/backend/utils/misc/guc.c      | 2 +-
 4 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/configure b/configure
index 20c6e08c02..dffe70208b 100755
--- a/configure
+++ b/configure
@@ -1582,7 +1582,7 @@ Optional Packages:
                           use system time zone data in DIR
   --without-zlib          do not use Zlib
   --without-lz4           build without LZ4 support
-  --with-zstd             build with Zstd compression library
+  --without-zstd          build without Zstd compression library
   --with-gnu-ld           assume the C compiler uses GNU ld [default=no]
   --with-ssl=LIB          use LIB for SSL/TLS support (openssl)
   --with-openssl          obsolete spelling of --with-ssl=openssl
@@ -8740,7 +8740,9 @@ $as_echo "#define USE_ZSTD 1" >>confdefs.h
   esac
 
 else
-  with_zstd=no
+  with_zstd=yes
+
+$as_echo "#define USE_ZSTD 1" >>confdefs.h
 
 fi
 
diff --git a/configure.ac b/configure.ac
index c4956745ce..780c0e785f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1005,7 +1005,7 @@ fi
 # ZSTD
 #
 AC_MSG_CHECKING([whether to build with zstd support])
-PGAC_ARG_BOOL(with, zstd, no, [build with Zstd compression library],
+PGAC_ARG_BOOL(with, zstd, yes, [build without Zstd compression library],
               [AC_DEFINE([USE_ZSTD], 1, [Define to 1 to build with zstd support. (--with-zstd)])])
 AC_MSG_RESULT([$with_zstd])
 AC_SUBST(with_zstd)
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 9bac79b579..5a8447a525 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -99,7 +99,7 @@ bool		EnableHotStandby = false;
 bool		fullPageWrites = true;
 bool		wal_log_hints = false;
 bool		wal_compression = false;
-int			wal_compression_method = WAL_COMPRESSION_LZ4;
+int			wal_compression_method = WAL_COMPRESSION_ZSTD;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 52f9cd0242..8031e027aa 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -4728,7 +4728,7 @@ static struct config_enum ConfigureNamesEnum[] =
 			NULL
 		},
 		&wal_compression_method,
-		WAL_COMPRESSION_LZ4, wal_compression_options,
+		WAL_COMPRESSION_ZSTD, wal_compression_options,
 		NULL, NULL, NULL
 	},
 
-- 
2.17.0

From b83b0365d68758010f8d45f1019a7749f104a880 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Sun, 14 Mar 2021 17:12:07 -0500
Subject: [PATCH 09/10] Add zstd compression levels

---
 src/backend/access/transam/xlog.c       |  6 +++++-
 src/backend/access/transam/xloginsert.c | 14 +++++++++++++-
 src/backend/access/transam/xlogreader.c |  8 ++++++++
 src/backend/utils/misc/guc.c            |  2 +-
 src/include/access/xlog_internal.h      |  4 ++++
 5 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 5a8447a525..2c6c97c1b3 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -99,7 +99,7 @@ bool		EnableHotStandby = false;
 bool		fullPageWrites = true;
 bool		wal_log_hints = false;
 bool		wal_compression = false;
-int			wal_compression_method = WAL_COMPRESSION_ZSTD;
+int			wal_compression_method = WAL_COMPRESSION_ZSTD_FAST_10;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
@@ -192,6 +192,10 @@ const struct config_enum_entry wal_compression_options[] = {
 #endif
 #ifdef  USE_ZSTD
 	{"zstd", WAL_COMPRESSION_ZSTD, false},
+	{"zstd-1", WAL_COMPRESSION_ZSTD_1, false},
+	{"zstd-fast-10", WAL_COMPRESSION_ZSTD_FAST_10, false},
+	{"zstd-fast-20", WAL_COMPRESSION_ZSTD_FAST_20, false},
+	{"zstd-fast-40", WAL_COMPRESSION_ZSTD_FAST_40, false},
 #endif
 	{NULL, 0, false}
 };
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
index 5d1ae37dae..9e6bc77717 100644
--- a/src/backend/access/transam/xloginsert.c
+++ b/src/backend/access/transam/xloginsert.c
@@ -902,7 +902,18 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 
 #ifdef USE_ZSTD
 	case WAL_COMPRESSION_ZSTD:
-		len = ZSTD_compress(dest, PGLZ_MAX_BLCKSZ, source, orig_len, 1);
+	case WAL_COMPRESSION_ZSTD_1:
+	case WAL_COMPRESSION_ZSTD_FAST_10:
+	case WAL_COMPRESSION_ZSTD_FAST_20:
+	case WAL_COMPRESSION_ZSTD_FAST_40:
+	{
+		int level = compression == WAL_COMPRESSION_ZSTD_1 ? 1 :
+			compression == WAL_COMPRESSION_ZSTD_FAST_10 ? -10 :
+			compression == WAL_COMPRESSION_ZSTD_FAST_20 ? -20 :
+			compression == WAL_COMPRESSION_ZSTD_FAST_40 ? -40 :
+			ZSTD_CLEVEL_DEFAULT;
+
+		len = ZSTD_compress(dest, PGLZ_MAX_BLCKSZ, source, orig_len, level);
 		if (ZSTD_isError(len))
 		{
 			ereport(ERROR,
@@ -913,6 +924,7 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 		}
 
 		break;
+	}
 #endif
 
 	default:
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index caa1031d63..ec795a7b9f 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -1569,6 +1569,10 @@ wal_compression_name(WalCompression compression)
 		case WAL_COMPRESSION_LZ4:
 			return "lz4";
 		case WAL_COMPRESSION_ZSTD:
+		case WAL_COMPRESSION_ZSTD_1:
+		case WAL_COMPRESSION_ZSTD_FAST_10:
+		case WAL_COMPRESSION_ZSTD_FAST_20:
+		case WAL_COMPRESSION_ZSTD_FAST_40:
 			return "zstd";
 		default:
 			return "???";
@@ -1629,6 +1633,10 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 
 #ifdef USE_ZSTD
 		case WAL_COMPRESSION_ZSTD:
+		case WAL_COMPRESSION_ZSTD_1:
+		case WAL_COMPRESSION_ZSTD_FAST_10:
+		case WAL_COMPRESSION_ZSTD_FAST_20:
+		case WAL_COMPRESSION_ZSTD_FAST_40:
 			decomp_result = ZSTD_decompress(tmp.data, BLCKSZ-bkpb->hole_length,
 					ptr, bkpb->bimg_len);
 			// XXX: ZSTD_getErrorName
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 8031e027aa..667fc4c0c1 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -4728,7 +4728,7 @@ static struct config_enum ConfigureNamesEnum[] =
 			NULL
 		},
 		&wal_compression_method,
-		WAL_COMPRESSION_ZSTD, wal_compression_options,
+		WAL_COMPRESSION_ZSTD_FAST_10, wal_compression_options,
 		NULL, NULL, NULL
 	},
 
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index 48b16b6083..affd6defc2 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -330,6 +330,10 @@ typedef enum WalCompression
 	WAL_COMPRESSION_ZLIB,
 	WAL_COMPRESSION_LZ4,
 	WAL_COMPRESSION_ZSTD,
+	WAL_COMPRESSION_ZSTD_1,
+	WAL_COMPRESSION_ZSTD_FAST_10, /* level = -10 */
+	WAL_COMPRESSION_ZSTD_FAST_20, /* level = -20 */
+	WAL_COMPRESSION_ZSTD_FAST_40, /* level = -40 */
 } WalCompression;
 
 extern const char *wal_compression_name(WalCompression compression);
-- 
2.17.0

From e5d4d63a5b785d9d81df7b3aaea8124c396e762c Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Sun, 14 Mar 2021 17:12:07 -0500
Subject: [PATCH 09/10] Add zstd compression levels

---
 src/backend/access/transam/xlog.c       |  6 +++++-
 src/backend/access/transam/xloginsert.c | 14 +++++++++++++-
 src/backend/access/transam/xlogreader.c |  8 ++++++++
 src/backend/utils/misc/guc.c            |  2 +-
 src/include/access/xlog_internal.h      |  4 ++++
 5 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 92023de9f5..b14c7c5929 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -99,7 +99,7 @@ bool		EnableHotStandby = false;
 bool		fullPageWrites = true;
 bool		wal_log_hints = false;
 bool		wal_compression = false;
-int			wal_compression_method = WAL_COMPRESSION_ZSTD;
+int			wal_compression_method = WAL_COMPRESSION_ZSTD_FAST_10;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
@@ -192,6 +192,10 @@ const struct config_enum_entry wal_compression_options[] = {
 #endif
 #ifdef  USE_ZSTD
 	{"zstd", WAL_COMPRESSION_ZSTD, false},
+	{"zstd-1", WAL_COMPRESSION_ZSTD_1, false},
+	{"zstd-fast-10", WAL_COMPRESSION_ZSTD_FAST_10, false},
+	{"zstd-fast-20", WAL_COMPRESSION_ZSTD_FAST_20, false},
+	{"zstd-fast-40", WAL_COMPRESSION_ZSTD_FAST_40, false},
 #endif
 	{NULL, 0, false}
 };
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
index 5d1ae37dae..9e6bc77717 100644
--- a/src/backend/access/transam/xloginsert.c
+++ b/src/backend/access/transam/xloginsert.c
@@ -902,7 +902,18 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 
 #ifdef USE_ZSTD
 	case WAL_COMPRESSION_ZSTD:
-		len = ZSTD_compress(dest, PGLZ_MAX_BLCKSZ, source, orig_len, 1);
+	case WAL_COMPRESSION_ZSTD_1:
+	case WAL_COMPRESSION_ZSTD_FAST_10:
+	case WAL_COMPRESSION_ZSTD_FAST_20:
+	case WAL_COMPRESSION_ZSTD_FAST_40:
+	{
+		int level = compression == WAL_COMPRESSION_ZSTD_1 ? 1 :
+			compression == WAL_COMPRESSION_ZSTD_FAST_10 ? -10 :
+			compression == WAL_COMPRESSION_ZSTD_FAST_20 ? -20 :
+			compression == WAL_COMPRESSION_ZSTD_FAST_40 ? -40 :
+			ZSTD_CLEVEL_DEFAULT;
+
+		len = ZSTD_compress(dest, PGLZ_MAX_BLCKSZ, source, orig_len, level);
 		if (ZSTD_isError(len))
 		{
 			ereport(ERROR,
@@ -913,6 +924,7 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 		}
 
 		break;
+	}
 #endif
 
 	default:
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index caa1031d63..ec795a7b9f 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -1569,6 +1569,10 @@ wal_compression_name(WalCompression compression)
 		case WAL_COMPRESSION_LZ4:
 			return "lz4";
 		case WAL_COMPRESSION_ZSTD:
+		case WAL_COMPRESSION_ZSTD_1:
+		case WAL_COMPRESSION_ZSTD_FAST_10:
+		case WAL_COMPRESSION_ZSTD_FAST_20:
+		case WAL_COMPRESSION_ZSTD_FAST_40:
 			return "zstd";
 		default:
 			return "???";
@@ -1629,6 +1633,10 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 
 #ifdef USE_ZSTD
 		case WAL_COMPRESSION_ZSTD:
+		case WAL_COMPRESSION_ZSTD_1:
+		case WAL_COMPRESSION_ZSTD_FAST_10:
+		case WAL_COMPRESSION_ZSTD_FAST_20:
+		case WAL_COMPRESSION_ZSTD_FAST_40:
 			decomp_result = ZSTD_decompress(tmp.data, BLCKSZ-bkpb->hole_length,
 					ptr, bkpb->bimg_len);
 			// XXX: ZSTD_getErrorName
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 8031e027aa..667fc4c0c1 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -4728,7 +4728,7 @@ static struct config_enum ConfigureNamesEnum[] =
 			NULL
 		},
 		&wal_compression_method,
-		WAL_COMPRESSION_ZSTD, wal_compression_options,
+		WAL_COMPRESSION_ZSTD_FAST_10, wal_compression_options,
 		NULL, NULL, NULL
 	},
 
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index 48b16b6083..affd6defc2 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -330,6 +330,10 @@ typedef enum WalCompression
 	WAL_COMPRESSION_ZLIB,
 	WAL_COMPRESSION_LZ4,
 	WAL_COMPRESSION_ZSTD,
+	WAL_COMPRESSION_ZSTD_1,
+	WAL_COMPRESSION_ZSTD_FAST_10, /* level = -10 */
+	WAL_COMPRESSION_ZSTD_FAST_20, /* level = -20 */
+	WAL_COMPRESSION_ZSTD_FAST_40, /* level = -40 */
 } WalCompression;
 
 extern const char *wal_compression_name(WalCompression compression);
-- 
2.17.0

From 581884bb12f666a1eb6a7f4bd769b1edeba4c563 Mon Sep 17 00:00:00 2001
From: Andrey Borodin <amborodin@acm.org>
Date: Sat, 27 Feb 2021 09:03:50 +0500
Subject: [PATCH 01/10] Allow alternate compression methods for wal_compression

TODO: bump XLOG_PAGE_MAGIC
---
 doc/src/sgml/config.sgml                      | 17 +++++
 src/backend/Makefile                          |  2 +-
 src/backend/access/transam/xlog.c             | 10 +++
 src/backend/access/transam/xloginsert.c       | 52 +++++++++++++--
 src/backend/access/transam/xlogreader.c       | 63 ++++++++++++++++++-
 src/backend/utils/misc/guc.c                  | 11 ++++
 src/backend/utils/misc/postgresql.conf.sample |  1 +
 src/include/access/xlog.h                     |  1 +
 src/include/access/xlog_internal.h            |  8 +++
 src/include/access/xlogreader.h               |  1 +
 src/include/access/xlogrecord.h               |  9 +--
 11 files changed, 163 insertions(+), 12 deletions(-)

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index a218d78bef..7fb2a84626 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -3072,6 +3072,23 @@ include_dir 'conf.d'
       </listitem>
      </varlistentry>
 
+     <varlistentry id="guc-wal-compression-method" xreflabel="wal_compression_method">
+      <term><varname>wal_compressionion_method</varname> (<type>enum</type>)
+      <indexterm>
+       <primary><varname>wal_compression_method</varname> configuration parameter</primary>
+      </indexterm>
+      </term>
+      <listitem>
+       <para>
+        This parameter selects the compression method used to compress WAL when
+        <varname>wal_compression</varname> is enabled.
+        The supported methods are pglz and zlib.
+        The default value is <literal>pglz</literal>.
+        Only superusers can change this setting.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry id="guc-wal-init-zero" xreflabel="wal_init_zero">
       <term><varname>wal_init_zero</varname> (<type>boolean</type>)
       <indexterm>
diff --git a/src/backend/Makefile b/src/backend/Makefile
index 0da848b1fd..3af216ddfc 100644
--- a/src/backend/Makefile
+++ b/src/backend/Makefile
@@ -48,7 +48,7 @@ OBJS = \
 LIBS := $(filter-out -lpgport -lpgcommon, $(LIBS)) $(LDAP_LIBS_BE) $(ICU_LIBS)
 
 # The backend doesn't need everything that's in LIBS, however
-LIBS := $(filter-out -lz -lreadline -ledit -ltermcap -lncurses -lcurses, $(LIBS))
+LIBS := $(filter-out -lreadline -ledit -ltermcap -lncurses -lcurses, $(LIBS))
 
 ifeq ($(with_systemd),yes)
 LIBS += -lsystemd
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index f4d1ce5dea..15da91a8dd 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -99,6 +99,7 @@ bool		EnableHotStandby = false;
 bool		fullPageWrites = true;
 bool		wal_log_hints = false;
 bool		wal_compression = false;
+int			wal_compression_method = WAL_COMPRESSION_PGLZ;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
@@ -180,6 +181,15 @@ const struct config_enum_entry recovery_target_action_options[] = {
 	{NULL, 0, false}
 };
 
+/* Note that due to conditional compilation, offsets within the array are not static */
+const struct config_enum_entry wal_compression_options[] = {
+	{"pglz", WAL_COMPRESSION_PGLZ, false},
+#ifdef  HAVE_LIBZ
+	{"zlib", WAL_COMPRESSION_ZLIB, false},
+#endif
+	{NULL, 0, false}
+};
+
 /*
  * Statistics for current checkpoint are collected in this global struct.
  * Because only the checkpointer or a stand-alone backend can perform
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
index 7052dc245e..34e1227381 100644
--- a/src/backend/access/transam/xloginsert.c
+++ b/src/backend/access/transam/xloginsert.c
@@ -33,6 +33,10 @@
 #include "storage/proc.h"
 #include "utils/memutils.h"
 
+#ifdef HAVE_LIBZ
+#include <zlib.h>
+#endif
+
 /* Buffer size required to store a compressed version of backup block image */
 #define PGLZ_MAX_BLCKSZ PGLZ_MAX_OUTPUT(BLCKSZ)
 
@@ -113,7 +117,8 @@ static XLogRecData *XLogRecordAssemble(RmgrId rmid, uint8 info,
 									   XLogRecPtr RedoRecPtr, bool doPageWrites,
 									   XLogRecPtr *fpw_lsn, int *num_fpi);
 static bool XLogCompressBackupBlock(char *page, uint16 hole_offset,
-									uint16 hole_length, char *dest, uint16 *dlen);
+									uint16 hole_length, char *dest,
+									uint16 *dlen, WalCompression compression);
 
 /*
  * Begin constructing a WAL record. This must be called before the
@@ -630,11 +635,12 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
 			 */
 			if (wal_compression)
 			{
+				bimg.compression_method = wal_compression_method;
 				is_compressed =
 					XLogCompressBackupBlock(page, bimg.hole_offset,
 											cbimg.hole_length,
 											regbuf->compressed_page,
-											&compressed_len);
+											&compressed_len, bimg.compression_method);
 			}
 
 			/*
@@ -827,7 +833,7 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
  */
 static bool
 XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
-						char *dest, uint16 *dlen)
+						char *dest, uint16 *dlen, WalCompression compression)
 {
 	int32		orig_len = BLCKSZ - hole_length;
 	int32		len;
@@ -853,12 +859,48 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 	else
 		source = page;
 
+	switch (compression)
+	{
+	case WAL_COMPRESSION_PGLZ:
+		len = pglz_compress(source, orig_len, dest, PGLZ_strategy_default);
+		break;
+
+#ifdef HAVE_LIBZ
+	case WAL_COMPRESSION_ZLIB:
+		{
+			unsigned long	len_l = PGLZ_MAX_BLCKSZ;
+			int ret;
+			ret = compress2((Bytef*)dest, &len_l, (Bytef*)source, orig_len, 1);
+			if (ret != Z_OK)
+			{
+				// XXX: using an interface other than compress() would allow giving a better error message
+				ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("failed compressing zlib (%d)", ret)));
+				len_l = -1;
+			}
+			len = len_l;
+			break;
+		}
+#endif
+
+	default:
+		/*
+		 * It should be impossible to get here for unsupported algorithms,
+		 * which cannot be assigned if they're not enabled at compile time.
+		 */
+		ereport(ERROR,
+			(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			 errmsg("unknown compression method requested: %d(%s)",
+				 compression, wal_compression_name(compression))));
+
+	}
+
 	/*
-	 * We recheck the actual size even if pglz_compress() reports success and
+	 * We recheck the actual size even if compression reports success and
 	 * see if the number of bytes saved by compression is larger than the
 	 * length of extra data needed for the compressed version of block image.
 	 */
-	len = pglz_compress(source, orig_len, dest, PGLZ_strategy_default);
 	if (len >= 0 &&
 		len + extra_bytes < orig_len)
 	{
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index 42738eb940..afca22a26c 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -33,6 +33,10 @@
 #include "utils/memutils.h"
 #endif
 
+#ifdef HAVE_LIBZ
+#include <zlib.h>
+#endif
+
 static void report_invalid_record(XLogReaderState *state, const char *fmt,...)
 			pg_attribute_printf(2, 3);
 static bool allocate_recordbuf(XLogReaderState *state, uint32 reclength);
@@ -1286,6 +1290,7 @@ DecodeXLogRecord(XLogReaderState *state, XLogRecord *record, char **errormsg)
 			{
 				COPY_HEADER_FIELD(&blk->bimg_len, sizeof(uint16));
 				COPY_HEADER_FIELD(&blk->hole_offset, sizeof(uint16));
+				COPY_HEADER_FIELD(&blk->compression_method, sizeof(uint8));
 				COPY_HEADER_FIELD(&blk->bimg_info, sizeof(uint8));
 
 				blk->apply_image = ((blk->bimg_info & BKPIMAGE_APPLY) != 0);
@@ -1535,6 +1540,29 @@ XLogRecGetBlockData(XLogReaderState *record, uint8 block_id, Size *len)
 	}
 }
 
+/*
+ * Return a statically allocated string associated with the given compression
+ * method.  This is similar to the guc, but isn't subject to conditional
+ * compilation.
+ */
+const char *
+wal_compression_name(WalCompression compression)
+{
+	/*
+	 * This could index into the guc array, except that it's compiled
+	 * conditionally and unsupported methods are elided.
+	 */
+	switch (compression)
+	{
+		case WAL_COMPRESSION_PGLZ:
+			return "pglz";
+		case WAL_COMPRESSION_ZLIB:
+			return "zlib";
+		default:
+			return "???";
+	}
+}
+
 /*
  * Restore a full-page image from a backup block attached to an XLOG record.
  *
@@ -1558,8 +1586,39 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 	if (bkpb->bimg_info & BKPIMAGE_IS_COMPRESSED)
 	{
 		/* If a backup block image is compressed, decompress it */
-		if (pglz_decompress(ptr, bkpb->bimg_len, tmp.data,
-							BLCKSZ - bkpb->hole_length, true) < 0)
+		int32 decomp_result = -1;
+		switch (bkpb->compression_method)
+		{
+		case WAL_COMPRESSION_PGLZ:
+			decomp_result = pglz_decompress(ptr, bkpb->bimg_len, tmp.data,
+							BLCKSZ - bkpb->hole_length, true);
+			break;
+
+#ifdef HAVE_LIBZ
+		case WAL_COMPRESSION_ZLIB:
+		{
+			unsigned long decomp_result_l;
+			decomp_result_l = BLCKSZ - bkpb->hole_length;
+			if (uncompress((Bytef*)tmp.data, &decomp_result_l,
+						(Bytef*)ptr, bkpb->bimg_len) == Z_OK)
+				decomp_result = decomp_result_l;
+			else
+				decomp_result = -1;
+			break;
+		}
+#endif
+
+		default:
+			report_invalid_record(record, "image at %X/%X is compressed with unsupported codec, block %d (%d/%s)",
+								  (uint32) (record->ReadRecPtr >> 32),
+								  (uint32) record->ReadRecPtr,
+								  block_id,
+								  bkpb->compression_method,
+								  wal_compression_name(bkpb->compression_method));
+			return false;
+		}
+
+		if (decomp_result < 0)
 		{
 			report_invalid_record(record, "invalid compressed image at %X/%X, block %d",
 								  LSN_FORMAT_ARGS(record->ReadRecPtr),
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 855076b1fd..8084027465 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -508,6 +508,7 @@ extern const struct config_enum_entry archive_mode_options[];
 extern const struct config_enum_entry recovery_target_action_options[];
 extern const struct config_enum_entry sync_method_options[];
 extern const struct config_enum_entry dynamic_shared_memory_options[];
+extern const struct config_enum_entry wal_compression_options[];
 
 /*
  * GUC option variables that are exported from this module
@@ -4721,6 +4722,16 @@ static struct config_enum ConfigureNamesEnum[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"wal_compression_method", PGC_SIGHUP, WAL_SETTINGS,
+			gettext_noop("Set the method used to compress full page images in the WAL."),
+			NULL
+		},
+		&wal_compression_method,
+		WAL_COMPRESSION_PGLZ, wal_compression_options,
+		NULL, NULL, NULL
+	},
+
 	{
 		{"dynamic_shared_memory_type", PGC_POSTMASTER, RESOURCES_MEM,
 			gettext_noop("Selects the dynamic shared memory implementation used."),
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index f46c2dd7a8..ef69a94492 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -213,6 +213,7 @@
 					#   open_sync
 #full_page_writes = on			# recover from partial page writes
 #wal_compression = off			# enable compression of full-page writes
+#wal_compression_method = pglz		# pglz, zlib
 #wal_log_hints = off			# also do full page writes of non-critical updates
 					# (change requires restart)
 #wal_init_zero = on			# zero-fill new WAL files
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index 6d384d3ce6..fa2e5c611f 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -117,6 +117,7 @@ extern bool EnableHotStandby;
 extern bool fullPageWrites;
 extern bool wal_log_hints;
 extern bool wal_compression;
+extern int	wal_compression_method;
 extern bool wal_init_zero;
 extern bool wal_recycle;
 extern bool *wal_consistency_checking;
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index b23e286406..d653839b97 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -324,4 +324,12 @@ extern bool InArchiveRecovery;
 extern bool StandbyMode;
 extern char *recoveryRestoreCommand;
 
+typedef enum WalCompression
+{
+	WAL_COMPRESSION_PGLZ,
+	WAL_COMPRESSION_ZLIB,
+} WalCompression;
+
+extern const char *wal_compression_name(WalCompression compression);
+
 #endif							/* XLOG_INTERNAL_H */
diff --git a/src/include/access/xlogreader.h b/src/include/access/xlogreader.h
index 21d200d3df..3d19c315d7 100644
--- a/src/include/access/xlogreader.h
+++ b/src/include/access/xlogreader.h
@@ -133,6 +133,7 @@ typedef struct
 	bool		apply_image;	/* has image that should be restored */
 	char	   *bkp_image;
 	uint16		hole_offset;
+	uint8		compression_method;
 	uint16		hole_length;
 	uint16		bimg_len;
 	uint8		bimg_info;
diff --git a/src/include/access/xlogrecord.h b/src/include/access/xlogrecord.h
index 80c92a2498..0d4c212f15 100644
--- a/src/include/access/xlogrecord.h
+++ b/src/include/access/xlogrecord.h
@@ -114,7 +114,7 @@ typedef struct XLogRecordBlockHeader
  * present is (BLCKSZ - <length of "hole" bytes>).
  *
  * Additionally, when wal_compression is enabled, we will try to compress full
- * page images using the PGLZ compression algorithm, after removing the "hole".
+ * page images, after removing the "hole".
  * This can reduce the WAL volume, but at some extra cost of CPU spent
  * on the compression during WAL logging. In this case, since the "hole"
  * length cannot be calculated by subtracting the number of page image bytes
@@ -129,9 +129,10 @@ typedef struct XLogRecordBlockHeader
  */
 typedef struct XLogRecordBlockImageHeader
 {
-	uint16		length;			/* number of page image bytes */
-	uint16		hole_offset;	/* number of bytes before "hole" */
-	uint8		bimg_info;		/* flag bits, see below */
+	uint16		length;				/* number of page image bytes */
+	uint16		hole_offset;		/* number of bytes before "hole" */
+	uint8		compression_method; /* compression method used for image */
+	uint8		bimg_info;			/* flag bits, see below */
 
 	/*
 	 * If BKPIMAGE_HAS_HOLE and BKPIMAGE_IS_COMPRESSED, an
-- 
2.17.0

From 34dd6bdee962ebe923d71dcc60cf68d0c4925ccc Mon Sep 17 00:00:00 2001
From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Date: Mon, 8 Mar 2021 15:32:30 +0900
Subject: [PATCH 02/10] Run 011_crash_recovery.pl with wal_level=minimal

The test doesn't need that feature and pg_current_xact_id() is better
exercised by turning off the feature.

Copied from: https://www.postgresql.org/message-id/20210308.173242.463790587797836129.horikyota.ntt%40gmail.com
---
 src/test/recovery/t/011_crash_recovery.pl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/test/recovery/t/011_crash_recovery.pl b/src/test/recovery/t/011_crash_recovery.pl
index 10cd98f70a..690655dda2 100644
--- a/src/test/recovery/t/011_crash_recovery.pl
+++ b/src/test/recovery/t/011_crash_recovery.pl
@@ -11,7 +11,7 @@ use Config;
 plan tests => 3;
 
 my $node = get_new_node('primary');
-$node->init(allows_streaming => 1);
+$node->init();
 $node->start;
 
 my ($stdin, $stdout, $stderr) = ('', '', '');
-- 
2.17.0

From a5a20274b9ddd3cccd1a090af3419446c9d8bc52 Mon Sep 17 00:00:00 2001
From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Date: Mon, 8 Mar 2021 15:43:01 +0900
Subject: [PATCH 03/10] Make sure published XIDs are persistent

pg_xact_status() premises that XIDs obtained by
pg_current_xact_id(_if_assigned)() are persistent beyond a crash. But
XIDs are not guaranteed to go beyond WAL buffers before commit and
thus XIDs may vanish if server crashes before commit. This patch
guarantees the XID shown by the functions to be flushed out to disk.

Copied from: https://www.postgresql.org/message-id/20210308.173242.463790587797836129.horikyota.ntt%40gmail.com
---
 src/backend/access/transam/xact.c | 55 +++++++++++++++++++++++++------
 src/backend/access/transam/xlog.c |  2 +-
 src/backend/utils/adt/xid8funcs.c | 12 ++++++-
 src/include/access/xact.h         |  3 +-
 4 files changed, 59 insertions(+), 13 deletions(-)

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 6395a9b240..38e978d238 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -201,7 +201,7 @@ typedef struct TransactionStateData
 	int			prevSecContext; /* previous SecurityRestrictionContext */
 	bool		prevXactReadOnly;	/* entry-time xact r/o state */
 	bool		startedInRecovery;	/* did we start in recovery? */
-	bool		didLogXid;		/* has xid been included in WAL record? */
+	XLogRecPtr 	minLSN;			/* LSN needed to reach to record the xid */
 	int			parallelModeLevel;	/* Enter/ExitParallelMode counter */
 	bool		chain;			/* start a new block after this one */
 	bool		assigned;		/* assigned to top-level XID */
@@ -520,14 +520,46 @@ GetCurrentFullTransactionIdIfAny(void)
  *	MarkCurrentTransactionIdLoggedIfAny
  *
  * Remember that the current xid - if it is assigned - now has been wal logged.
+ *
+ * upto is the LSN up to which we need to flush WAL to ensure the current xid
+ * to be persistent. See EnsureCurrentTransactionIdLogged().
  */
 void
-MarkCurrentTransactionIdLoggedIfAny(void)
+MarkCurrentTransactionIdLoggedIfAny(XLogRecPtr upto)
 {
-	if (FullTransactionIdIsValid(CurrentTransactionState->fullTransactionId))
-		CurrentTransactionState->didLogXid = true;
+	if (FullTransactionIdIsValid(CurrentTransactionState->fullTransactionId) &&
+		XLogRecPtrIsInvalid(CurrentTransactionState->minLSN))
+		CurrentTransactionState->minLSN = upto;
 }
 
+/*
+ *	EnsureCurrentTransactionIdLogged
+ *
+ * Make sure that the current top XID is WAL-logged.
+ */
+void
+EnsureTopTransactionIdLogged(void)
+{
+	/*
+	 * We need at least one WAL record for the current top transaction to be
+	 * flushed out.  Write one if we don't have one yet.
+	 */
+	if (XLogRecPtrIsInvalid(TopTransactionStateData.minLSN))
+	{
+		xl_xact_assignment xlrec;
+
+		xlrec.xtop = XidFromFullTransactionId(XactTopFullTransactionId);
+		Assert(TransactionIdIsValid(xlrec.xtop));
+		xlrec.nsubxacts = 0;
+
+		XLogBeginInsert();
+		XLogRegisterData((char *) &xlrec, MinSizeOfXactAssignment);
+		TopTransactionStateData.minLSN =
+			XLogInsert(RM_XACT_ID, XLOG_XACT_ASSIGNMENT);
+	}
+
+	XLogFlush(TopTransactionStateData.minLSN);
+}
 
 /*
  *	GetStableLatestTransactionId
@@ -616,14 +648,14 @@ AssignTransactionId(TransactionState s)
 	 * When wal_level=logical, guarantee that a subtransaction's xid can only
 	 * be seen in the WAL stream if its toplevel xid has been logged before.
 	 * If necessary we log an xact_assignment record with fewer than
-	 * PGPROC_MAX_CACHED_SUBXIDS. Note that it is fine if didLogXid isn't set
+	 * PGPROC_MAX_CACHED_SUBXIDS. Note that it is fine if minLSN isn't set
 	 * for a transaction even though it appears in a WAL record, we just might
 	 * superfluously log something. That can happen when an xid is included
 	 * somewhere inside a wal record, but not in XLogRecord->xl_xid, like in
 	 * xl_standby_locks.
 	 */
 	if (isSubXact && XLogLogicalInfoActive() &&
-		!TopTransactionStateData.didLogXid)
+		XLogRecPtrIsInvalid(TopTransactionStateData.minLSN))
 		log_unknown_top = true;
 
 	/*
@@ -693,6 +725,7 @@ AssignTransactionId(TransactionState s)
 			log_unknown_top)
 		{
 			xl_xact_assignment xlrec;
+			XLogRecPtr		   endptr;
 
 			/*
 			 * xtop is always set by now because we recurse up transaction
@@ -707,11 +740,13 @@ AssignTransactionId(TransactionState s)
 			XLogRegisterData((char *) unreportedXids,
 							 nUnreportedXids * sizeof(TransactionId));
 
-			(void) XLogInsert(RM_XACT_ID, XLOG_XACT_ASSIGNMENT);
+			endptr = XLogInsert(RM_XACT_ID, XLOG_XACT_ASSIGNMENT);
 
 			nUnreportedXids = 0;
-			/* mark top, not current xact as having been logged */
-			TopTransactionStateData.didLogXid = true;
+
+			/* set minLSN of top, not of current xact if not yet */
+			if (XLogRecPtrIsInvalid(TopTransactionStateData.minLSN))
+				TopTransactionStateData.minLSN = endptr;
 		}
 	}
 }
@@ -2022,7 +2057,7 @@ StartTransaction(void)
 	 * initialize reported xid accounting
 	 */
 	nUnreportedXids = 0;
-	s->didLogXid = false;
+	s->minLSN = InvalidXLogRecPtr;
 
 	/*
 	 * must initialize resource-management stuff first
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 15da91a8dd..6eb46ea8a7 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -1172,7 +1172,7 @@ XLogInsertRecord(XLogRecData *rdata,
 	 */
 	WALInsertLockRelease();
 
-	MarkCurrentTransactionIdLoggedIfAny();
+	MarkCurrentTransactionIdLoggedIfAny(EndPos);
 
 	END_CRIT_SECTION();
 
diff --git a/src/backend/utils/adt/xid8funcs.c b/src/backend/utils/adt/xid8funcs.c
index cc2b4ac797..992482f8c8 100644
--- a/src/backend/utils/adt/xid8funcs.c
+++ b/src/backend/utils/adt/xid8funcs.c
@@ -357,6 +357,8 @@ bad_format:
 Datum
 pg_current_xact_id(PG_FUNCTION_ARGS)
 {
+	FullTransactionId xid;
+
 	/*
 	 * Must prevent during recovery because if an xid is not assigned we try
 	 * to assign one, which would fail. Programs already rely on this function
@@ -365,7 +367,12 @@ pg_current_xact_id(PG_FUNCTION_ARGS)
 	 */
 	PreventCommandDuringRecovery("pg_current_xact_id()");
 
-	PG_RETURN_FULLTRANSACTIONID(GetTopFullTransactionId());
+	xid = GetTopFullTransactionId();
+
+	/* the XID is going to be published, make sure it is psersistent */
+	EnsureTopTransactionIdLogged();
+
+	PG_RETURN_FULLTRANSACTIONID(xid);
 }
 
 /*
@@ -380,6 +387,9 @@ pg_current_xact_id_if_assigned(PG_FUNCTION_ARGS)
 	if (!FullTransactionIdIsValid(topfxid))
 		PG_RETURN_NULL();
 
+	/* the XID is going to be published, make sure it is psersistent */
+	EnsureTopTransactionIdLogged();
+
 	PG_RETURN_FULLTRANSACTIONID(topfxid);
 }
 
diff --git a/src/include/access/xact.h b/src/include/access/xact.h
index 34cfaf542c..a61e4d6da5 100644
--- a/src/include/access/xact.h
+++ b/src/include/access/xact.h
@@ -386,7 +386,8 @@ extern FullTransactionId GetTopFullTransactionId(void);
 extern FullTransactionId GetTopFullTransactionIdIfAny(void);
 extern FullTransactionId GetCurrentFullTransactionId(void);
 extern FullTransactionId GetCurrentFullTransactionIdIfAny(void);
-extern void MarkCurrentTransactionIdLoggedIfAny(void);
+extern void MarkCurrentTransactionIdLoggedIfAny(XLogRecPtr upto);
+extern void EnsureTopTransactionIdLogged(void);
 extern bool SubTransactionIsActive(SubTransactionId subxid);
 extern CommandId GetCurrentCommandId(bool used);
 extern void SetParallelStartTimestamps(TimestampTz xact_ts, TimestampTz stmt_ts);
-- 
2.17.0

From 58f1bd3d39adbd2b8ac1312316878c8bd8e61d49 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Thu, 11 Mar 2021 17:36:24 -0600
Subject: [PATCH 04/10] wal_compression_method: default to zlib..

this is meant to exercise the CIs, and not meant to be merged
---
 src/backend/access/transam/xlog.c | 2 +-
 src/backend/utils/misc/guc.c      | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 6eb46ea8a7..f5d4450654 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -99,7 +99,7 @@ bool		EnableHotStandby = false;
 bool		fullPageWrites = true;
 bool		wal_log_hints = false;
 bool		wal_compression = false;
-int			wal_compression_method = WAL_COMPRESSION_PGLZ;
+int			wal_compression_method = WAL_COMPRESSION_ZLIB;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 8084027465..c37a8313d3 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -1269,7 +1269,7 @@ static struct config_bool ConfigureNamesBool[] =
 			NULL
 		},
 		&wal_compression,
-		false,
+		true,
 		NULL, NULL, NULL
 	},
 
@@ -4728,7 +4728,7 @@ static struct config_enum ConfigureNamesEnum[] =
 			NULL
 		},
 		&wal_compression_method,
-		WAL_COMPRESSION_PGLZ, wal_compression_options,
+		WAL_COMPRESSION_ZLIB, wal_compression_options,
 		NULL, NULL, NULL
 	},
 
-- 
2.17.0

From 770904b2fdb7302dd8fa8c1baa8ad078eceaa0db Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Fri, 12 Mar 2021 14:32:10 -0600
Subject: [PATCH 05/10] (re)add wal_compression_method: lz4

---
 configure                                     | 176 ++++++++++++++++++
 configure.ac                                  |  26 +++
 doc/src/sgml/config.sgml                      |   3 +-
 src/backend/access/transam/xlog.c             |   3 +
 src/backend/access/transam/xloginsert.c       |  12 ++
 src/backend/access/transam/xlogreader.c       |  13 ++
 src/backend/utils/misc/postgresql.conf.sample |   2 +-
 src/include/access/xlog_internal.h            |   1 +
 src/include/pg_config.h.in                    |   3 +
 src/tools/msvc/Solution.pm                    |   1 +
 10 files changed, 238 insertions(+), 2 deletions(-)

diff --git a/configure b/configure
index 3fd4cecbeb..fed440adcf 100755
--- a/configure
+++ b/configure
@@ -699,6 +699,9 @@ with_gnu_ld
 LD
 LDFLAGS_SL
 LDFLAGS_EX
+LZ4_LIBS
+LZ4_CFLAGS
+with_lz4
 with_zlib
 with_system_tzdata
 with_libxslt
@@ -864,6 +867,7 @@ with_libxml
 with_libxslt
 with_system_tzdata
 with_zlib
+with_lz4
 with_gnu_ld
 with_ssl
 with_openssl
@@ -891,6 +895,8 @@ ICU_LIBS
 XML2_CONFIG
 XML2_CFLAGS
 XML2_LIBS
+LZ4_CFLAGS
+LZ4_LIBS
 LDFLAGS_EX
 LDFLAGS_SL
 PERL
@@ -1569,6 +1575,7 @@ Optional Packages:
   --with-system-tzdata=DIR
                           use system time zone data in DIR
   --without-zlib          do not use Zlib
+  --with-lz4              build with LZ4 support
   --with-gnu-ld           assume the C compiler uses GNU ld [default=no]
   --with-ssl=LIB          use LIB for SSL/TLS support (openssl)
   --with-openssl          obsolete spelling of --with-ssl=openssl
@@ -1596,6 +1603,8 @@ Some influential environment variables:
   XML2_CONFIG path to xml2-config utility
   XML2_CFLAGS C compiler flags for XML2, overriding pkg-config
   XML2_LIBS   linker flags for XML2, overriding pkg-config
+  LZ4_CFLAGS  C compiler flags for LZ4, overriding pkg-config
+  LZ4_LIBS    linker flags for LZ4, overriding pkg-config
   LDFLAGS_EX  extra linker flags for linking executables only
   LDFLAGS_SL  extra linker flags for linking shared libraries only
   PERL        Perl program
@@ -8563,6 +8572,137 @@ fi
 
 
 
+#
+# LZ4
+#
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether to build with LZ4 support" >&5
+$as_echo_n "checking whether to build with LZ4 support... " >&6; }
+
+
+
+# Check whether --with-lz4 was given.
+if test "${with_lz4+set}" = set; then :
+  withval=$with_lz4;
+  case $withval in
+    yes)
+
+$as_echo "#define USE_LZ4 1" >>confdefs.h
+
+      ;;
+    no)
+      :
+      ;;
+    *)
+      as_fn_error $? "no argument expected for --with-lz4 option" "$LINENO" 5
+      ;;
+  esac
+
+else
+  with_lz4=no
+
+fi
+
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $with_lz4" >&5
+$as_echo "$with_lz4" >&6; }
+
+
+if test "$with_lz4" = yes; then
+
+pkg_failed=no
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for liblz4" >&5
+$as_echo_n "checking for liblz4... " >&6; }
+
+if test -n "$LZ4_CFLAGS"; then
+    pkg_cv_LZ4_CFLAGS="$LZ4_CFLAGS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"liblz4\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "liblz4") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_LZ4_CFLAGS=`$PKG_CONFIG --cflags "liblz4" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+if test -n "$LZ4_LIBS"; then
+    pkg_cv_LZ4_LIBS="$LZ4_LIBS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"liblz4\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "liblz4") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_LZ4_LIBS=`$PKG_CONFIG --libs "liblz4" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+
+
+
+if test $pkg_failed = yes; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+
+if $PKG_CONFIG --atleast-pkgconfig-version 0.20; then
+        _pkg_short_errors_supported=yes
+else
+        _pkg_short_errors_supported=no
+fi
+        if test $_pkg_short_errors_supported = yes; then
+	        LZ4_PKG_ERRORS=`$PKG_CONFIG --short-errors --print-errors --cflags --libs "liblz4" 2>&1`
+        else
+	        LZ4_PKG_ERRORS=`$PKG_CONFIG --print-errors --cflags --libs "liblz4" 2>&1`
+        fi
+	# Put the nasty error message in config.log where it belongs
+	echo "$LZ4_PKG_ERRORS" >&5
+
+	as_fn_error $? "Package requirements (liblz4) were not met:
+
+$LZ4_PKG_ERRORS
+
+Consider adjusting the PKG_CONFIG_PATH environment variable if you
+installed software in a non-standard prefix.
+
+Alternatively, you may set the environment variables LZ4_CFLAGS
+and LZ4_LIBS to avoid the need to call pkg-config.
+See the pkg-config man page for more details." "$LINENO" 5
+elif test $pkg_failed = untried; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+	{ { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error $? "The pkg-config script could not be found or is too old.  Make sure it
+is in your PATH or set the PKG_CONFIG environment variable to the full
+path to pkg-config.
+
+Alternatively, you may set the environment variables LZ4_CFLAGS
+and LZ4_LIBS to avoid the need to call pkg-config.
+See the pkg-config man page for more details.
+
+To get pkg-config, see <http://pkg-config.freedesktop.org/>.
+See \`config.log' for more details" "$LINENO" 5; }
+else
+	LZ4_CFLAGS=$pkg_cv_LZ4_CFLAGS
+	LZ4_LIBS=$pkg_cv_LZ4_LIBS
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+
+fi
+  LIBS="$LZ4_LIBS $LIBS"
+  CFLAGS="$LZ4_CFLAGS $CFLAGS"
+fi
+
 #
 # Assignments
 #
@@ -13381,6 +13521,42 @@ fi
 
 fi
 
+if test "$with_lz4" = yes; then
+  ac_save_CPPFLAGS=$CPPFLAGS
+  CPPFLAGS="$LZ4_CFLAGS $CPPFLAGS"
+
+  # Verify we have LZ4's header files
+  for ac_header in lz4/lz4.h
+do :
+  ac_fn_c_check_header_mongrel "$LINENO" "lz4/lz4.h" "ac_cv_header_lz4_lz4_h" "$ac_includes_default"
+if test "x$ac_cv_header_lz4_lz4_h" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_LZ4_LZ4_H 1
+_ACEOF
+
+else
+  for ac_header in lz4.h
+do :
+  ac_fn_c_check_header_mongrel "$LINENO" "lz4.h" "ac_cv_header_lz4_h" "$ac_includes_default"
+if test "x$ac_cv_header_lz4_h" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_LZ4_H 1
+_ACEOF
+
+else
+  as_fn_error $? "lz4.h header file is required for LZ4" "$LINENO" 5
+fi
+
+done
+
+fi
+
+done
+
+
+  CPPFLAGS=$ac_save_CPPFLAGS
+fi
+
 if test "$with_gssapi" = yes ; then
   for ac_header in gssapi/gssapi.h
 do :
diff --git a/configure.ac b/configure.ac
index 2f1585adc0..8c454128bb 100644
--- a/configure.ac
+++ b/configure.ac
@@ -986,6 +986,21 @@ PGAC_ARG_BOOL(with, zlib, yes,
               [do not use Zlib])
 AC_SUBST(with_zlib)
 
+#
+# LZ4
+#
+AC_MSG_CHECKING([whether to build with LZ4 support])
+PGAC_ARG_BOOL(with, lz4, no, [build with LZ4 support],
+              [AC_DEFINE([USE_LZ4], 1, [Define to 1 to build with LZ4 support. (--with-lz4)])])
+AC_MSG_RESULT([$with_lz4])
+AC_SUBST(with_lz4)
+
+if test "$with_lz4" = yes; then
+  PKG_CHECK_MODULES(LZ4, liblz4)
+  LIBS="$LZ4_LIBS $LIBS"
+  CFLAGS="$LZ4_CFLAGS $CFLAGS"
+fi
+
 #
 # Assignments
 #
@@ -1410,6 +1425,17 @@ failure.  It is possible the compiler isn't looking in the proper directory.
 Use --without-zlib to disable zlib support.])])
 fi
 
+if test "$with_lz4" = yes; then
+  ac_save_CPPFLAGS=$CPPFLAGS
+  CPPFLAGS="$LZ4_CFLAGS $CPPFLAGS"
+
+  # Verify we have LZ4's header files
+  AC_CHECK_HEADERS(lz4/lz4.h, [],
+       [AC_CHECK_HEADERS(lz4.h, [], [AC_MSG_ERROR([lz4.h header file is required for LZ4])])])
+
+  CPPFLAGS=$ac_save_CPPFLAGS
+fi
+
 if test "$with_gssapi" = yes ; then
   AC_CHECK_HEADERS(gssapi/gssapi.h, [],
 	[AC_CHECK_HEADERS(gssapi.h, [], [AC_MSG_ERROR([gssapi.h header file is required for GSSAPI])])])
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 7fb2a84626..257775c83b 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -3082,7 +3082,8 @@ include_dir 'conf.d'
        <para>
         This parameter selects the compression method used to compress WAL when
         <varname>wal_compression</varname> is enabled.
-        The supported methods are pglz and zlib.
+        The supported methods are pglz, zlib, and (if configured when
+        <productname>PostgreSQL</productname> was built) lz4.
         The default value is <literal>pglz</literal>.
         Only superusers can change this setting.
        </para>
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index f5d4450654..984ce39cc7 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -186,6 +186,9 @@ const struct config_enum_entry wal_compression_options[] = {
 	{"pglz", WAL_COMPRESSION_PGLZ, false},
 #ifdef  HAVE_LIBZ
 	{"zlib", WAL_COMPRESSION_ZLIB, false},
+#endif
+#ifdef  USE_LZ4
+	{"lz4", WAL_COMPRESSION_LZ4, false},
 #endif
 	{NULL, 0, false}
 };
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
index 34e1227381..9fe5c30236 100644
--- a/src/backend/access/transam/xloginsert.c
+++ b/src/backend/access/transam/xloginsert.c
@@ -37,6 +37,10 @@
 #include <zlib.h>
 #endif
 
+#ifdef USE_LZ4
+#include "lz4.h"
+#endif
+
 /* Buffer size required to store a compressed version of backup block image */
 #define PGLZ_MAX_BLCKSZ PGLZ_MAX_OUTPUT(BLCKSZ)
 
@@ -884,6 +888,14 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 		}
 #endif
 
+#ifdef USE_LZ4
+	case WAL_COMPRESSION_LZ4:
+		len = LZ4_compress_fast(source, dest, orig_len, PGLZ_MAX_BLCKSZ, 1);
+		if (len == 0)
+			len = -1;
+		break;
+#endif
+
 	default:
 		/*
 		 * It should be impossible to get here for unsupported algorithms,
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index afca22a26c..fa1e38a810 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -37,6 +37,10 @@
 #include <zlib.h>
 #endif
 
+#ifdef USE_LZ4
+#include "lz4.h"
+#endif
+
 static void report_invalid_record(XLogReaderState *state, const char *fmt,...)
 			pg_attribute_printf(2, 3);
 static bool allocate_recordbuf(XLogReaderState *state, uint32 reclength);
@@ -1558,6 +1562,8 @@ wal_compression_name(WalCompression compression)
 			return "pglz";
 		case WAL_COMPRESSION_ZLIB:
 			return "zlib";
+		case WAL_COMPRESSION_LZ4:
+			return "lz4";
 		default:
 			return "???";
 	}
@@ -1608,6 +1614,13 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 		}
 #endif
 
+#ifdef USE_LZ4
+		case WAL_COMPRESSION_LZ4:
+			decomp_result = LZ4_decompress_safe(ptr, tmp.data,
+					bkpb->bimg_len, BLCKSZ-bkpb->hole_length);
+			break;
+#endif
+
 		default:
 			report_invalid_record(record, "image at %X/%X is compressed with unsupported codec, block %d (%d/%s)",
 								  (uint32) (record->ReadRecPtr >> 32),
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index ef69a94492..76f494cb9b 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -213,7 +213,7 @@
 					#   open_sync
 #full_page_writes = on			# recover from partial page writes
 #wal_compression = off			# enable compression of full-page writes
-#wal_compression_method = pglz		# pglz, zlib
+#wal_compression_method = pglz		# pglz, zlib, lz4
 #wal_log_hints = off			# also do full page writes of non-critical updates
 					# (change requires restart)
 #wal_init_zero = on			# zero-fill new WAL files
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index d653839b97..e70886b81c 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -328,6 +328,7 @@ typedef enum WalCompression
 {
 	WAL_COMPRESSION_PGLZ,
 	WAL_COMPRESSION_ZLIB,
+	WAL_COMPRESSION_LZ4,
 } WalCompression;
 
 extern const char *wal_compression_name(WalCompression compression);
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index 7a7cc21d8d..0a6422da4f 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -899,6 +899,9 @@
 /* Define to 1 to build with LLVM based JIT support. (--with-llvm) */
 #undef USE_LLVM
 
+/* Define to 1 to build with LZ4 support (--with-lz4) */
+#undef USE_LZ4
+
 /* Define to select named POSIX semaphores. */
 #undef USE_NAMED_POSIX_SEMAPHORES
 
diff --git a/src/tools/msvc/Solution.pm b/src/tools/msvc/Solution.pm
index a4f5cc4bdb..14605371bb 100644
--- a/src/tools/msvc/Solution.pm
+++ b/src/tools/msvc/Solution.pm
@@ -485,6 +485,7 @@ sub GenerateFiles
 		USE_ICU => $self->{options}->{icu} ? 1 : undef,
 		USE_LIBXML                 => undef,
 		USE_LIBXSLT                => undef,
+		USE_LZ4                    => undef,
 		USE_LDAP                   => $self->{options}->{ldap} ? 1 : undef,
 		USE_LLVM                   => undef,
 		USE_NAMED_POSIX_SEMAPHORES => undef,
-- 
2.17.0

From 4c91dc61ce933f21d7097da4cea28721dc4d7fab Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Fri, 12 Mar 2021 15:35:40 -0600
Subject: [PATCH 06/10] Default to LZ4..

this is meant to exercise in the CIs, and not meant to be merged
---
 configure                         | 6 ++++--
 configure.ac                      | 4 ++--
 src/backend/access/transam/xlog.c | 2 +-
 src/backend/utils/misc/guc.c      | 2 +-
 4 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/configure b/configure
index fed440adcf..8d76be00c1 100755
--- a/configure
+++ b/configure
@@ -1575,7 +1575,7 @@ Optional Packages:
   --with-system-tzdata=DIR
                           use system time zone data in DIR
   --without-zlib          do not use Zlib
-  --with-lz4              build with LZ4 support
+  --without-lz4           build without LZ4 support
   --with-gnu-ld           assume the C compiler uses GNU ld [default=no]
   --with-ssl=LIB          use LIB for SSL/TLS support (openssl)
   --with-openssl          obsolete spelling of --with-ssl=openssl
@@ -8598,7 +8598,9 @@ $as_echo "#define USE_LZ4 1" >>confdefs.h
   esac
 
 else
-  with_lz4=no
+  with_lz4=yes
+
+$as_echo "#define USE_LZ4 1" >>confdefs.h
 
 fi
 
diff --git a/configure.ac b/configure.ac
index 8c454128bb..bfcdc88be0 100644
--- a/configure.ac
+++ b/configure.ac
@@ -990,8 +990,8 @@ AC_SUBST(with_zlib)
 # LZ4
 #
 AC_MSG_CHECKING([whether to build with LZ4 support])
-PGAC_ARG_BOOL(with, lz4, no, [build with LZ4 support],
-              [AC_DEFINE([USE_LZ4], 1, [Define to 1 to build with LZ4 support. (--with-lz4)])])
+PGAC_ARG_BOOL(with, lz4, yes, [build without LZ4 support],
+              [AC_DEFINE([USE_LZ4], 1, [Define to 1 to build without LZ4 support. (--without-lz4)])])
 AC_MSG_RESULT([$with_lz4])
 AC_SUBST(with_lz4)
 
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 984ce39cc7..3657f74de9 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -99,7 +99,7 @@ bool		EnableHotStandby = false;
 bool		fullPageWrites = true;
 bool		wal_log_hints = false;
 bool		wal_compression = false;
-int			wal_compression_method = WAL_COMPRESSION_ZLIB;
+int			wal_compression_method = WAL_COMPRESSION_LZ4;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index c37a8313d3..52f9cd0242 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -4728,7 +4728,7 @@ static struct config_enum ConfigureNamesEnum[] =
 			NULL
 		},
 		&wal_compression_method,
-		WAL_COMPRESSION_ZLIB, wal_compression_options,
+		WAL_COMPRESSION_LZ4, wal_compression_options,
 		NULL, NULL, NULL
 	},
 
-- 
2.17.0

From 1de321c69cc9d66e0694ab7192043b3d69c1f39b Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Fri, 12 Mar 2021 14:43:53 -0600
Subject: [PATCH 07/10] add wal_compression_method: zstd

---
 configure                                     | 163 ++++++++++++++++++
 configure.ac                                  |  26 +++
 doc/src/sgml/config.sgml                      |   2 +-
 src/backend/access/transam/xlog.c             |   3 +
 src/backend/access/transam/xloginsert.c       |  19 ++
 src/backend/access/transam/xlogreader.c       |  16 ++
 src/backend/utils/misc/postgresql.conf.sample |   2 +-
 src/include/access/xlog_internal.h            |   1 +
 src/include/pg_config.h.in                    |   3 +
 src/tools/msvc/Solution.pm                    |   1 +
 10 files changed, 234 insertions(+), 2 deletions(-)

diff --git a/configure b/configure
index 8d76be00c1..81e23418b2 100755
--- a/configure
+++ b/configure
@@ -699,6 +699,9 @@ with_gnu_ld
 LD
 LDFLAGS_SL
 LDFLAGS_EX
+ZSTD_LIBS
+ZSTD_CFLAGS
+with_zstd
 LZ4_LIBS
 LZ4_CFLAGS
 with_lz4
@@ -868,6 +871,7 @@ with_libxslt
 with_system_tzdata
 with_zlib
 with_lz4
+with_zstd
 with_gnu_ld
 with_ssl
 with_openssl
@@ -897,6 +901,8 @@ XML2_CFLAGS
 XML2_LIBS
 LZ4_CFLAGS
 LZ4_LIBS
+ZSTD_CFLAGS
+ZSTD_LIBS
 LDFLAGS_EX
 LDFLAGS_SL
 PERL
@@ -1576,6 +1582,7 @@ Optional Packages:
                           use system time zone data in DIR
   --without-zlib          do not use Zlib
   --without-lz4           build without LZ4 support
+  --with-zstd             build with Zstd compression library
   --with-gnu-ld           assume the C compiler uses GNU ld [default=no]
   --with-ssl=LIB          use LIB for SSL/TLS support (openssl)
   --with-openssl          obsolete spelling of --with-ssl=openssl
@@ -1605,6 +1612,8 @@ Some influential environment variables:
   XML2_LIBS   linker flags for XML2, overriding pkg-config
   LZ4_CFLAGS  C compiler flags for LZ4, overriding pkg-config
   LZ4_LIBS    linker flags for LZ4, overriding pkg-config
+  ZSTD_CFLAGS C compiler flags for ZSTD, overriding pkg-config
+  ZSTD_LIBS   linker flags for ZSTD, overriding pkg-config
   LDFLAGS_EX  extra linker flags for linking executables only
   LDFLAGS_SL  extra linker flags for linking shared libraries only
   PERL        Perl program
@@ -8705,6 +8714,137 @@ fi
   CFLAGS="$LZ4_CFLAGS $CFLAGS"
 fi
 
+#
+# ZSTD
+#
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether to build with zstd support" >&5
+$as_echo_n "checking whether to build with zstd support... " >&6; }
+
+
+
+# Check whether --with-zstd was given.
+if test "${with_zstd+set}" = set; then :
+  withval=$with_zstd;
+  case $withval in
+    yes)
+
+$as_echo "#define USE_ZSTD 1" >>confdefs.h
+
+      ;;
+    no)
+      :
+      ;;
+    *)
+      as_fn_error $? "no argument expected for --with-zstd option" "$LINENO" 5
+      ;;
+  esac
+
+else
+  with_zstd=no
+
+fi
+
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $with_zstd" >&5
+$as_echo "$with_zstd" >&6; }
+
+
+if test "$with_zstd" = yes; then
+
+pkg_failed=no
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for libzstd" >&5
+$as_echo_n "checking for libzstd... " >&6; }
+
+if test -n "$ZSTD_CFLAGS"; then
+    pkg_cv_ZSTD_CFLAGS="$ZSTD_CFLAGS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"libzstd\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "libzstd") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_ZSTD_CFLAGS=`$PKG_CONFIG --cflags "libzstd" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+if test -n "$ZSTD_LIBS"; then
+    pkg_cv_ZSTD_LIBS="$ZSTD_LIBS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"libzstd\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "libzstd") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_ZSTD_LIBS=`$PKG_CONFIG --libs "libzstd" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+
+
+
+if test $pkg_failed = yes; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+
+if $PKG_CONFIG --atleast-pkgconfig-version 0.20; then
+        _pkg_short_errors_supported=yes
+else
+        _pkg_short_errors_supported=no
+fi
+        if test $_pkg_short_errors_supported = yes; then
+	        ZSTD_PKG_ERRORS=`$PKG_CONFIG --short-errors --print-errors --cflags --libs "libzstd" 2>&1`
+        else
+	        ZSTD_PKG_ERRORS=`$PKG_CONFIG --print-errors --cflags --libs "libzstd" 2>&1`
+        fi
+	# Put the nasty error message in config.log where it belongs
+	echo "$ZSTD_PKG_ERRORS" >&5
+
+	as_fn_error $? "Package requirements (libzstd) were not met:
+
+$ZSTD_PKG_ERRORS
+
+Consider adjusting the PKG_CONFIG_PATH environment variable if you
+installed software in a non-standard prefix.
+
+Alternatively, you may set the environment variables ZSTD_CFLAGS
+and ZSTD_LIBS to avoid the need to call pkg-config.
+See the pkg-config man page for more details." "$LINENO" 5
+elif test $pkg_failed = untried; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+	{ { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error $? "The pkg-config script could not be found or is too old.  Make sure it
+is in your PATH or set the PKG_CONFIG environment variable to the full
+path to pkg-config.
+
+Alternatively, you may set the environment variables ZSTD_CFLAGS
+and ZSTD_LIBS to avoid the need to call pkg-config.
+See the pkg-config man page for more details.
+
+To get pkg-config, see <http://pkg-config.freedesktop.org/>.
+See \`config.log' for more details" "$LINENO" 5; }
+else
+	ZSTD_CFLAGS=$pkg_cv_ZSTD_CFLAGS
+	ZSTD_LIBS=$pkg_cv_ZSTD_LIBS
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+
+fi
+  LIBS="$ZSTD_LIBS $LIBS"
+  CFLAGS="$ZSTD_CFLAGS $CFLAGS"
+fi
+
 #
 # Assignments
 #
@@ -13559,6 +13699,29 @@ done
   CPPFLAGS=$ac_save_CPPFLAGS
 fi
 
+if test "$with_zstd" = yes; then
+  ac_save_CPPFLAGS=$CPPFLAGS
+  CPPFLAGS="$ZSTD_CFLAGS $CPPFLAGS"
+
+  # Verify we have zstd's header files
+  for ac_header in zstd.h
+do :
+  ac_fn_c_check_header_mongrel "$LINENO" "zstd.h" "ac_cv_header_zstd_h" "$ac_includes_default"
+if test "x$ac_cv_header_zstd_h" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_ZSTD_H 1
+_ACEOF
+
+else
+  as_fn_error $? "zstd.h header file is required for zstd" "$LINENO" 5
+fi
+
+done
+
+
+  CPPFLAGS=$ac_save_CPPFLAGS
+fi
+
 if test "$with_gssapi" = yes ; then
   for ac_header in gssapi/gssapi.h
 do :
diff --git a/configure.ac b/configure.ac
index bfcdc88be0..d6f6349067 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1001,6 +1001,21 @@ if test "$with_lz4" = yes; then
   CFLAGS="$LZ4_CFLAGS $CFLAGS"
 fi
 
+#
+# ZSTD
+#
+AC_MSG_CHECKING([whether to build with zstd support])
+PGAC_ARG_BOOL(with, zstd, no, [build with Zstd compression library],
+              [AC_DEFINE([USE_ZSTD], 1, [Define to 1 to build with zstd support. (--with-zstd)])])
+AC_MSG_RESULT([$with_zstd])
+AC_SUBST(with_zstd)
+
+if test "$with_zstd" = yes; then
+  PKG_CHECK_MODULES(ZSTD, libzstd)
+  LIBS="$ZSTD_LIBS $LIBS"
+  CFLAGS="$ZSTD_CFLAGS $CFLAGS"
+fi
+
 #
 # Assignments
 #
@@ -1436,6 +1451,17 @@ if test "$with_lz4" = yes; then
   CPPFLAGS=$ac_save_CPPFLAGS
 fi
 
+if test "$with_zstd" = yes; then
+  ac_save_CPPFLAGS=$CPPFLAGS
+  CPPFLAGS="$ZSTD_CFLAGS $CPPFLAGS"
+
+  # Verify we have zstd's header files
+  AC_CHECK_HEADERS(zstd.h, [],
+       [AC_MSG_ERROR([zstd.h header file is required for zstd])])
+
+  CPPFLAGS=$ac_save_CPPFLAGS
+fi
+
 if test "$with_gssapi" = yes ; then
   AC_CHECK_HEADERS(gssapi/gssapi.h, [],
 	[AC_CHECK_HEADERS(gssapi.h, [], [AC_MSG_ERROR([gssapi.h header file is required for GSSAPI])])])
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 257775c83b..94dd6ef3e9 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -3083,7 +3083,7 @@ include_dir 'conf.d'
         This parameter selects the compression method used to compress WAL when
         <varname>wal_compression</varname> is enabled.
         The supported methods are pglz, zlib, and (if configured when
-        <productname>PostgreSQL</productname> was built) lz4.
+        <productname>PostgreSQL</productname> was built) lz4 and zstd.
         The default value is <literal>pglz</literal>.
         Only superusers can change this setting.
        </para>
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 3657f74de9..307eee6626 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -189,6 +189,9 @@ const struct config_enum_entry wal_compression_options[] = {
 #endif
 #ifdef  USE_LZ4
 	{"lz4", WAL_COMPRESSION_LZ4, false},
+#endif
+#ifdef  USE_ZSTD
+	{"zstd", WAL_COMPRESSION_ZSTD, false},
 #endif
 	{NULL, 0, false}
 };
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
index 9fe5c30236..5d1ae37dae 100644
--- a/src/backend/access/transam/xloginsert.c
+++ b/src/backend/access/transam/xloginsert.c
@@ -41,6 +41,10 @@
 #include "lz4.h"
 #endif
 
+#ifdef USE_ZSTD
+#include "zstd.h"
+#endif
+
 /* Buffer size required to store a compressed version of backup block image */
 #define PGLZ_MAX_BLCKSZ PGLZ_MAX_OUTPUT(BLCKSZ)
 
@@ -896,6 +900,21 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 		break;
 #endif
 
+#ifdef USE_ZSTD
+	case WAL_COMPRESSION_ZSTD:
+		len = ZSTD_compress(dest, PGLZ_MAX_BLCKSZ, source, orig_len, 1);
+		if (ZSTD_isError(len))
+		{
+			ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("failed compressing zstd: %s",
+						 ZSTD_getErrorName(len))));
+			len = -1;
+		}
+
+		break;
+#endif
+
 	default:
 		/*
 		 * It should be impossible to get here for unsupported algorithms,
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index fa1e38a810..caa1031d63 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -41,6 +41,10 @@
 #include "lz4.h"
 #endif
 
+#ifdef USE_ZSTD
+#include "zstd.h"
+#endif
+
 static void report_invalid_record(XLogReaderState *state, const char *fmt,...)
 			pg_attribute_printf(2, 3);
 static bool allocate_recordbuf(XLogReaderState *state, uint32 reclength);
@@ -1564,6 +1568,8 @@ wal_compression_name(WalCompression compression)
 			return "zlib";
 		case WAL_COMPRESSION_LZ4:
 			return "lz4";
+		case WAL_COMPRESSION_ZSTD:
+			return "zstd";
 		default:
 			return "???";
 	}
@@ -1621,6 +1627,16 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 			break;
 #endif
 
+#ifdef USE_ZSTD
+		case WAL_COMPRESSION_ZSTD:
+			decomp_result = ZSTD_decompress(tmp.data, BLCKSZ-bkpb->hole_length,
+					ptr, bkpb->bimg_len);
+			// XXX: ZSTD_getErrorName
+			if (ZSTD_isError(decomp_result))
+				decomp_result = -1;
+			break;
+#endif
+
 		default:
 			report_invalid_record(record, "image at %X/%X is compressed with unsupported codec, block %d (%d/%s)",
 								  (uint32) (record->ReadRecPtr >> 32),
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 76f494cb9b..d372e2a817 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -213,7 +213,7 @@
 					#   open_sync
 #full_page_writes = on			# recover from partial page writes
 #wal_compression = off			# enable compression of full-page writes
-#wal_compression_method = pglz		# pglz, zlib, lz4
+#wal_compression_method = pglz		# pglz, zlib, lz4, zstd
 #wal_log_hints = off			# also do full page writes of non-critical updates
 					# (change requires restart)
 #wal_init_zero = on			# zero-fill new WAL files
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index e70886b81c..48b16b6083 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -329,6 +329,7 @@ typedef enum WalCompression
 	WAL_COMPRESSION_PGLZ,
 	WAL_COMPRESSION_ZLIB,
 	WAL_COMPRESSION_LZ4,
+	WAL_COMPRESSION_ZSTD,
 } WalCompression;
 
 extern const char *wal_compression_name(WalCompression compression);
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index 0a6422da4f..ad26393352 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -902,6 +902,9 @@
 /* Define to 1 to build with LZ4 support (--with-lz4) */
 #undef USE_LZ4
 
+/* Define to 1 if you have the `zstd' library (-lzstd). */
+#undef USE_ZSTD
+
 /* Define to select named POSIX semaphores. */
 #undef USE_NAMED_POSIX_SEMAPHORES
 
diff --git a/src/tools/msvc/Solution.pm b/src/tools/msvc/Solution.pm
index 14605371bb..fff0212087 100644
--- a/src/tools/msvc/Solution.pm
+++ b/src/tools/msvc/Solution.pm
@@ -486,6 +486,7 @@ sub GenerateFiles
 		USE_LIBXML                 => undef,
 		USE_LIBXSLT                => undef,
 		USE_LZ4                    => undef,
+		USE_ZSTD                   => $self->{options}->{zstd} ? 1 : undef,
 		USE_LDAP                   => $self->{options}->{ldap} ? 1 : undef,
 		USE_LLVM                   => undef,
 		USE_NAMED_POSIX_SEMAPHORES => undef,
-- 
2.17.0

From e6c3c3080ec7a7f3de1087cf7067b226b4923b16 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Fri, 12 Mar 2021 15:35:53 -0600
Subject: [PATCH 08/10] Default to zstd..

for CI, not for merge
---
 configure                         | 6 ++++--
 configure.ac                      | 2 +-
 src/backend/access/transam/xlog.c | 2 +-
 src/backend/utils/misc/guc.c      | 2 +-
 4 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/configure b/configure
index 81e23418b2..253f028fc4 100755
--- a/configure
+++ b/configure
@@ -1582,7 +1582,7 @@ Optional Packages:
                           use system time zone data in DIR
   --without-zlib          do not use Zlib
   --without-lz4           build without LZ4 support
-  --with-zstd             build with Zstd compression library
+  --without-zstd          build without Zstd compression library
   --with-gnu-ld           assume the C compiler uses GNU ld [default=no]
   --with-ssl=LIB          use LIB for SSL/TLS support (openssl)
   --with-openssl          obsolete spelling of --with-ssl=openssl
@@ -8740,7 +8740,9 @@ $as_echo "#define USE_ZSTD 1" >>confdefs.h
   esac
 
 else
-  with_zstd=no
+  with_zstd=yes
+
+$as_echo "#define USE_ZSTD 1" >>confdefs.h
 
 fi
 
diff --git a/configure.ac b/configure.ac
index d6f6349067..8d72710fa7 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1005,7 +1005,7 @@ fi
 # ZSTD
 #
 AC_MSG_CHECKING([whether to build with zstd support])
-PGAC_ARG_BOOL(with, zstd, no, [build with Zstd compression library],
+PGAC_ARG_BOOL(with, zstd, yes, [build without Zstd compression library],
               [AC_DEFINE([USE_ZSTD], 1, [Define to 1 to build with zstd support. (--with-zstd)])])
 AC_MSG_RESULT([$with_zstd])
 AC_SUBST(with_zstd)
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 307eee6626..92023de9f5 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -99,7 +99,7 @@ bool		EnableHotStandby = false;
 bool		fullPageWrites = true;
 bool		wal_log_hints = false;
 bool		wal_compression = false;
-int			wal_compression_method = WAL_COMPRESSION_LZ4;
+int			wal_compression_method = WAL_COMPRESSION_ZSTD;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 52f9cd0242..8031e027aa 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -4728,7 +4728,7 @@ static struct config_enum ConfigureNamesEnum[] =
 			NULL
 		},
 		&wal_compression_method,
-		WAL_COMPRESSION_LZ4, wal_compression_options,
+		WAL_COMPRESSION_ZSTD, wal_compression_options,
 		NULL, NULL, NULL
 	},
 
-- 
2.17.0

From cbb75085d8755d5db09905a51e12ca47df151775 Mon Sep 17 00:00:00 2001
From: Andrey Borodin <amborodin@acm.org>
Date: Sat, 27 Feb 2021 09:03:50 +0500
Subject: [PATCH 01/10] Allow alternate compression methods for wal_compression

TODO: bump XLOG_PAGE_MAGIC
---
 doc/src/sgml/config.sgml                      | 17 +++++
 src/backend/Makefile                          |  2 +-
 src/backend/access/transam/xlog.c             | 10 +++
 src/backend/access/transam/xloginsert.c       | 67 ++++++++++++++++---
 src/backend/access/transam/xlogreader.c       | 64 +++++++++++++++++-
 src/backend/utils/misc/guc.c                  | 11 +++
 src/backend/utils/misc/postgresql.conf.sample |  1 +
 src/include/access/xlog.h                     |  1 +
 src/include/access/xlog_internal.h            | 16 +++++
 src/include/access/xlogrecord.h               | 11 ++-
 10 files changed, 187 insertions(+), 13 deletions(-)

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index a218d78bef..7fb2a84626 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -3072,6 +3072,23 @@ include_dir 'conf.d'
       </listitem>
      </varlistentry>
 
+     <varlistentry id="guc-wal-compression-method" xreflabel="wal_compression_method">
+      <term><varname>wal_compressionion_method</varname> (<type>enum</type>)
+      <indexterm>
+       <primary><varname>wal_compression_method</varname> configuration parameter</primary>
+      </indexterm>
+      </term>
+      <listitem>
+       <para>
+        This parameter selects the compression method used to compress WAL when
+        <varname>wal_compression</varname> is enabled.
+        The supported methods are pglz and zlib.
+        The default value is <literal>pglz</literal>.
+        Only superusers can change this setting.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry id="guc-wal-init-zero" xreflabel="wal_init_zero">
       <term><varname>wal_init_zero</varname> (<type>boolean</type>)
       <indexterm>
diff --git a/src/backend/Makefile b/src/backend/Makefile
index 0da848b1fd..3af216ddfc 100644
--- a/src/backend/Makefile
+++ b/src/backend/Makefile
@@ -48,7 +48,7 @@ OBJS = \
 LIBS := $(filter-out -lpgport -lpgcommon, $(LIBS)) $(LDAP_LIBS_BE) $(ICU_LIBS)
 
 # The backend doesn't need everything that's in LIBS, however
-LIBS := $(filter-out -lz -lreadline -ledit -ltermcap -lncurses -lcurses, $(LIBS))
+LIBS := $(filter-out -lreadline -ledit -ltermcap -lncurses -lcurses, $(LIBS))
 
 ifeq ($(with_systemd),yes)
 LIBS += -lsystemd
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index f4d1ce5dea..15da91a8dd 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -99,6 +99,7 @@ bool		EnableHotStandby = false;
 bool		fullPageWrites = true;
 bool		wal_log_hints = false;
 bool		wal_compression = false;
+int			wal_compression_method = WAL_COMPRESSION_PGLZ;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
@@ -180,6 +181,15 @@ const struct config_enum_entry recovery_target_action_options[] = {
 	{NULL, 0, false}
 };
 
+/* Note that due to conditional compilation, offsets within the array are not static */
+const struct config_enum_entry wal_compression_options[] = {
+	{"pglz", WAL_COMPRESSION_PGLZ, false},
+#ifdef  HAVE_LIBZ
+	{"zlib", WAL_COMPRESSION_ZLIB, false},
+#endif
+	{NULL, 0, false}
+};
+
 /*
  * Statistics for current checkpoint are collected in this global struct.
  * Because only the checkpointer or a stand-alone backend can perform
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
index 7052dc245e..a93b33464f 100644
--- a/src/backend/access/transam/xloginsert.c
+++ b/src/backend/access/transam/xloginsert.c
@@ -33,8 +33,18 @@
 #include "storage/proc.h"
 #include "utils/memutils.h"
 
+#ifdef HAVE_LIBZ
+#include <zlib.h>
+/* zlib compressBound is not a macro */
+#define ZLIB_MAX_BLCKSZ		BLCKSZ + (BLCKSZ>>12) + (BLCKSZ>>14) + (BLCKSZ>>25) + 13
+#else
+#define ZLIB_MAX_BLCKSZ		0
+#endif
+
 /* Buffer size required to store a compressed version of backup block image */
-#define PGLZ_MAX_BLCKSZ PGLZ_MAX_OUTPUT(BLCKSZ)
+#define PGLZ_MAX_BLCKSZ		PGLZ_MAX_OUTPUT(BLCKSZ)
+
+#define COMPRESS_BUFSIZE	Max(PGLZ_MAX_BLCKSZ, ZLIB_MAX_BLCKSZ)
 
 /*
  * For each block reference registered with XLogRegisterBuffer, we fill in
@@ -58,7 +68,7 @@ typedef struct
 								 * backup block data in XLogRecordAssemble() */
 
 	/* buffer to store a compressed version of backup block image */
-	char		compressed_page[PGLZ_MAX_BLCKSZ];
+	char		compressed_page[COMPRESS_BUFSIZE];
 } registered_buffer;
 
 static registered_buffer *registered_buffers;
@@ -113,7 +123,8 @@ static XLogRecData *XLogRecordAssemble(RmgrId rmid, uint8 info,
 									   XLogRecPtr RedoRecPtr, bool doPageWrites,
 									   XLogRecPtr *fpw_lsn, int *num_fpi);
 static bool XLogCompressBackupBlock(char *page, uint16 hole_offset,
-									uint16 hole_length, char *dest, uint16 *dlen);
+									uint16 hole_length, char *dest,
+									uint16 *dlen, WalCompression compression);
 
 /*
  * Begin constructing a WAL record. This must be called before the
@@ -625,16 +636,26 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
 				cbimg.hole_length = 0;
 			}
 
+			bimg.bimg_info = (cbimg.hole_length == 0) ? 0 : BKPIMAGE_HAS_HOLE;
+
 			/*
 			 * Try to compress a block image if wal_compression is enabled
 			 */
 			if (wal_compression)
 			{
+				int compression;
+				/* The current compression is stored in the WAL record */
+				wal_compression_name(wal_compression_method); /* Range check */
+				compression = walmethods[wal_compression_method].walmethod;
+				Assert(compression < (1 << BKPIMAGE_COMPRESS_BITS));
+				bimg.bimg_info |=
+					compression << BKPIMAGE_COMPRESS_OFFSET_BITS;
 				is_compressed =
 					XLogCompressBackupBlock(page, bimg.hole_offset,
 											cbimg.hole_length,
 											regbuf->compressed_page,
-											&compressed_len);
+											&compressed_len,
+											wal_compression_method);
 			}
 
 			/*
@@ -652,8 +673,6 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
 			rdt_datas_last->next = &regbuf->bkp_rdatas[0];
 			rdt_datas_last = rdt_datas_last->next;
 
-			bimg.bimg_info = (cbimg.hole_length == 0) ? 0 : BKPIMAGE_HAS_HOLE;
-
 			/*
 			 * If WAL consistency checking is enabled for the resource manager
 			 * of this WAL record, a full-page image is included in the record
@@ -827,7 +846,7 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
  */
 static bool
 XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
-						char *dest, uint16 *dlen)
+						char *dest, uint16 *dlen, WalCompression compression)
 {
 	int32		orig_len = BLCKSZ - hole_length;
 	int32		len;
@@ -853,12 +872,42 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 	else
 		source = page;
 
+	switch (compression)
+	{
+	case WAL_COMPRESSION_PGLZ:
+		len = pglz_compress(source, orig_len, dest, PGLZ_strategy_default);
+		break;
+
+#ifdef HAVE_LIBZ
+	case WAL_COMPRESSION_ZLIB:
+		{
+			unsigned long	len_l = COMPRESS_BUFSIZE;
+			int ret;
+			ret = compress2((Bytef*)dest, &len_l, (Bytef*)source, orig_len, 1);
+			if (ret != Z_OK)
+				len_l = -1;
+			len = len_l;
+			break;
+		}
+#endif
+
+	default:
+		/*
+		 * It should be impossible to get here for unsupported algorithms,
+		 * which cannot be assigned if they're not enabled at compile time.
+		 */
+		ereport(ERROR,
+			(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			 errmsg("unknown compression method requested: %d(%s)",
+				 compression, wal_compression_name(compression))));
+
+	}
+
 	/*
-	 * We recheck the actual size even if pglz_compress() reports success and
+	 * We recheck the actual size even if compression reports success and
 	 * see if the number of bytes saved by compression is larger than the
 	 * length of extra data needed for the compressed version of block image.
 	 */
-	len = pglz_compress(source, orig_len, dest, PGLZ_strategy_default);
 	if (len >= 0 &&
 		len + extra_bytes < orig_len)
 	{
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index 42738eb940..0d8830fc50 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -33,6 +33,10 @@
 #include "utils/memutils.h"
 #endif
 
+#ifdef HAVE_LIBZ
+#include <zlib.h>
+#endif
+
 static void report_invalid_record(XLogReaderState *state, const char *fmt,...)
 			pg_attribute_printf(2, 3);
 static bool allocate_recordbuf(XLogReaderState *state, uint32 reclength);
@@ -1535,6 +1539,30 @@ XLogRecGetBlockData(XLogReaderState *record, uint8 block_id, Size *len)
 	}
 }
 
+/* This is a mapping indexed by wal_compression */
+// XXX: maybe this is better done as a GUC hook to assign the 1) method; and 2) level
+struct walcompression walmethods[] = {
+	{"pglz",	WAL_COMPRESSION_PGLZ},
+	{"zlib",	WAL_COMPRESSION_ZLIB},
+};
+
+/*
+ * Return a statically allocated string associated with the given compression
+ * method.
+ * This is here to be visible to frontend tools like pg_rewind.
+ */
+const char *
+wal_compression_name(WalCompression compression)
+{
+	/*
+	 * This could index into the guc array, except that it's compiled
+	 * conditionally and unsupported methods are elided.
+	 */
+	if (compression < sizeof(walmethods)/sizeof(*walmethods))
+		return walmethods[compression].name;
+	return "???";
+}
+
 /*
  * Restore a full-page image from a backup block attached to an XLOG record.
  *
@@ -1557,9 +1585,41 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 
 	if (bkpb->bimg_info & BKPIMAGE_IS_COMPRESSED)
 	{
+		int compression_method = BKPIMAGE_COMPRESSION(bkpb->bimg_info);
 		/* If a backup block image is compressed, decompress it */
-		if (pglz_decompress(ptr, bkpb->bimg_len, tmp.data,
-							BLCKSZ - bkpb->hole_length, true) < 0)
+		int32 decomp_result = -1;
+		switch (compression_method)
+		{
+		case WAL_COMPRESSION_PGLZ:
+			decomp_result = pglz_decompress(ptr, bkpb->bimg_len, tmp.data,
+							BLCKSZ - bkpb->hole_length, true);
+			break;
+
+#ifdef HAVE_LIBZ
+		case WAL_COMPRESSION_ZLIB:
+		{
+			unsigned long decomp_result_l;
+			decomp_result_l = BLCKSZ - bkpb->hole_length;
+			if (uncompress((Bytef*)tmp.data, &decomp_result_l,
+						(Bytef*)ptr, bkpb->bimg_len) == Z_OK)
+				decomp_result = decomp_result_l;
+			else
+				decomp_result = -1;
+			break;
+		}
+#endif
+
+		default:
+			report_invalid_record(record, "image at %X/%X is compressed with unsupported codec, block %d (%d/%s)",
+								  (uint32) (record->ReadRecPtr >> 32),
+								  (uint32) record->ReadRecPtr,
+								  block_id,
+								  compression_method,
+								  wal_compression_name(compression_method));
+			return false;
+		}
+
+		if (decomp_result < 0)
 		{
 			report_invalid_record(record, "invalid compressed image at %X/%X, block %d",
 								  LSN_FORMAT_ARGS(record->ReadRecPtr),
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 855076b1fd..8084027465 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -508,6 +508,7 @@ extern const struct config_enum_entry archive_mode_options[];
 extern const struct config_enum_entry recovery_target_action_options[];
 extern const struct config_enum_entry sync_method_options[];
 extern const struct config_enum_entry dynamic_shared_memory_options[];
+extern const struct config_enum_entry wal_compression_options[];
 
 /*
  * GUC option variables that are exported from this module
@@ -4721,6 +4722,16 @@ static struct config_enum ConfigureNamesEnum[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"wal_compression_method", PGC_SIGHUP, WAL_SETTINGS,
+			gettext_noop("Set the method used to compress full page images in the WAL."),
+			NULL
+		},
+		&wal_compression_method,
+		WAL_COMPRESSION_PGLZ, wal_compression_options,
+		NULL, NULL, NULL
+	},
+
 	{
 		{"dynamic_shared_memory_type", PGC_POSTMASTER, RESOURCES_MEM,
 			gettext_noop("Selects the dynamic shared memory implementation used."),
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index f46c2dd7a8..ef69a94492 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -213,6 +213,7 @@
 					#   open_sync
 #full_page_writes = on			# recover from partial page writes
 #wal_compression = off			# enable compression of full-page writes
+#wal_compression_method = pglz		# pglz, zlib
 #wal_log_hints = off			# also do full page writes of non-critical updates
 					# (change requires restart)
 #wal_init_zero = on			# zero-fill new WAL files
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index 6d384d3ce6..fa2e5c611f 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -117,6 +117,7 @@ extern bool EnableHotStandby;
 extern bool fullPageWrites;
 extern bool wal_log_hints;
 extern bool wal_compression;
+extern int	wal_compression_method;
 extern bool wal_init_zero;
 extern bool wal_recycle;
 extern bool *wal_consistency_checking;
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index b23e286406..b000a21557 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -324,4 +324,20 @@ extern bool InArchiveRecovery;
 extern bool StandbyMode;
 extern char *recoveryRestoreCommand;
 
+struct walcompression
+{
+	char	*name;
+	int	walmethod;	/* Compression method to be stored in WAL */
+};
+
+extern struct walcompression walmethods[];
+
+typedef enum WalCompression
+{
+	WAL_COMPRESSION_PGLZ,
+	WAL_COMPRESSION_ZLIB,
+} WalCompression;
+
+extern const char *wal_compression_name(WalCompression compression);
+
 #endif							/* XLOG_INTERNAL_H */
diff --git a/src/include/access/xlogrecord.h b/src/include/access/xlogrecord.h
index 80c92a2498..7107cf6186 100644
--- a/src/include/access/xlogrecord.h
+++ b/src/include/access/xlogrecord.h
@@ -114,7 +114,7 @@ typedef struct XLogRecordBlockHeader
  * present is (BLCKSZ - <length of "hole" bytes>).
  *
  * Additionally, when wal_compression is enabled, we will try to compress full
- * page images using the PGLZ compression algorithm, after removing the "hole".
+ * page images, after removing the "hole".
  * This can reduce the WAL volume, but at some extra cost of CPU spent
  * on the compression during WAL logging. In this case, since the "hole"
  * length cannot be calculated by subtracting the number of page image bytes
@@ -147,6 +147,15 @@ typedef struct XLogRecordBlockImageHeader
 #define BKPIMAGE_IS_COMPRESSED		0x02	/* page image is compressed */
 #define BKPIMAGE_APPLY		0x04	/* page image should be restored during
 									 * replay */
+#define BKPIMAGE_COMPRESS_METHOD1	0x08	/* bits to encode compression method */
+#define BKPIMAGE_COMPRESS_METHOD2	0x10	/* 0=pglz; 1=zlib; */
+
+/* How many bits to shift to extract compression */
+#define	BKPIMAGE_COMPRESS_OFFSET_BITS	3
+/* How many bits are for compression */
+#define	BKPIMAGE_COMPRESS_BITS		2
+/* Extract the compression from the bimg_info */
+#define	BKPIMAGE_COMPRESSION(info)	((info >> BKPIMAGE_COMPRESS_OFFSET_BITS) & ((1<<BKPIMAGE_COMPRESS_BITS) - 1))
 
 /*
  * Extra header information used when page image has "hole" and
-- 
2.17.0

From b550cbf1176a0172c30755dcf15272dbaaf5c924 Mon Sep 17 00:00:00 2001
From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Date: Mon, 8 Mar 2021 15:32:30 +0900
Subject: [PATCH 02/10] Run 011_crash_recovery.pl with wal_level=minimal

The test doesn't need that feature and pg_current_xact_id() is better
exercised by turning off the feature.

Copied from: https://www.postgresql.org/message-id/20210308.173242.463790587797836129.horikyota.ntt%40gmail.com
---
 src/test/recovery/t/011_crash_recovery.pl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/test/recovery/t/011_crash_recovery.pl b/src/test/recovery/t/011_crash_recovery.pl
index 10cd98f70a..690655dda2 100644
--- a/src/test/recovery/t/011_crash_recovery.pl
+++ b/src/test/recovery/t/011_crash_recovery.pl
@@ -11,7 +11,7 @@ use Config;
 plan tests => 3;
 
 my $node = get_new_node('primary');
-$node->init(allows_streaming => 1);
+$node->init();
 $node->start;
 
 my ($stdin, $stdout, $stderr) = ('', '', '');
-- 
2.17.0

From 5e60c379ad3efa4f6041b75e7e984aa896ac25d9 Mon Sep 17 00:00:00 2001
From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Date: Mon, 8 Mar 2021 15:43:01 +0900
Subject: [PATCH 03/10] Make sure published XIDs are persistent

pg_xact_status() premises that XIDs obtained by
pg_current_xact_id(_if_assigned)() are persistent beyond a crash. But
XIDs are not guaranteed to go beyond WAL buffers before commit and
thus XIDs may vanish if server crashes before commit. This patch
guarantees the XID shown by the functions to be flushed out to disk.

Copied from: https://www.postgresql.org/message-id/20210308.173242.463790587797836129.horikyota.ntt%40gmail.com
---
 src/backend/access/transam/xact.c | 55 +++++++++++++++++++++++++------
 src/backend/access/transam/xlog.c |  2 +-
 src/backend/utils/adt/xid8funcs.c | 12 ++++++-
 src/include/access/xact.h         |  3 +-
 4 files changed, 59 insertions(+), 13 deletions(-)

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 6395a9b240..38e978d238 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -201,7 +201,7 @@ typedef struct TransactionStateData
 	int			prevSecContext; /* previous SecurityRestrictionContext */
 	bool		prevXactReadOnly;	/* entry-time xact r/o state */
 	bool		startedInRecovery;	/* did we start in recovery? */
-	bool		didLogXid;		/* has xid been included in WAL record? */
+	XLogRecPtr 	minLSN;			/* LSN needed to reach to record the xid */
 	int			parallelModeLevel;	/* Enter/ExitParallelMode counter */
 	bool		chain;			/* start a new block after this one */
 	bool		assigned;		/* assigned to top-level XID */
@@ -520,14 +520,46 @@ GetCurrentFullTransactionIdIfAny(void)
  *	MarkCurrentTransactionIdLoggedIfAny
  *
  * Remember that the current xid - if it is assigned - now has been wal logged.
+ *
+ * upto is the LSN up to which we need to flush WAL to ensure the current xid
+ * to be persistent. See EnsureCurrentTransactionIdLogged().
  */
 void
-MarkCurrentTransactionIdLoggedIfAny(void)
+MarkCurrentTransactionIdLoggedIfAny(XLogRecPtr upto)
 {
-	if (FullTransactionIdIsValid(CurrentTransactionState->fullTransactionId))
-		CurrentTransactionState->didLogXid = true;
+	if (FullTransactionIdIsValid(CurrentTransactionState->fullTransactionId) &&
+		XLogRecPtrIsInvalid(CurrentTransactionState->minLSN))
+		CurrentTransactionState->minLSN = upto;
 }
 
+/*
+ *	EnsureCurrentTransactionIdLogged
+ *
+ * Make sure that the current top XID is WAL-logged.
+ */
+void
+EnsureTopTransactionIdLogged(void)
+{
+	/*
+	 * We need at least one WAL record for the current top transaction to be
+	 * flushed out.  Write one if we don't have one yet.
+	 */
+	if (XLogRecPtrIsInvalid(TopTransactionStateData.minLSN))
+	{
+		xl_xact_assignment xlrec;
+
+		xlrec.xtop = XidFromFullTransactionId(XactTopFullTransactionId);
+		Assert(TransactionIdIsValid(xlrec.xtop));
+		xlrec.nsubxacts = 0;
+
+		XLogBeginInsert();
+		XLogRegisterData((char *) &xlrec, MinSizeOfXactAssignment);
+		TopTransactionStateData.minLSN =
+			XLogInsert(RM_XACT_ID, XLOG_XACT_ASSIGNMENT);
+	}
+
+	XLogFlush(TopTransactionStateData.minLSN);
+}
 
 /*
  *	GetStableLatestTransactionId
@@ -616,14 +648,14 @@ AssignTransactionId(TransactionState s)
 	 * When wal_level=logical, guarantee that a subtransaction's xid can only
 	 * be seen in the WAL stream if its toplevel xid has been logged before.
 	 * If necessary we log an xact_assignment record with fewer than
-	 * PGPROC_MAX_CACHED_SUBXIDS. Note that it is fine if didLogXid isn't set
+	 * PGPROC_MAX_CACHED_SUBXIDS. Note that it is fine if minLSN isn't set
 	 * for a transaction even though it appears in a WAL record, we just might
 	 * superfluously log something. That can happen when an xid is included
 	 * somewhere inside a wal record, but not in XLogRecord->xl_xid, like in
 	 * xl_standby_locks.
 	 */
 	if (isSubXact && XLogLogicalInfoActive() &&
-		!TopTransactionStateData.didLogXid)
+		XLogRecPtrIsInvalid(TopTransactionStateData.minLSN))
 		log_unknown_top = true;
 
 	/*
@@ -693,6 +725,7 @@ AssignTransactionId(TransactionState s)
 			log_unknown_top)
 		{
 			xl_xact_assignment xlrec;
+			XLogRecPtr		   endptr;
 
 			/*
 			 * xtop is always set by now because we recurse up transaction
@@ -707,11 +740,13 @@ AssignTransactionId(TransactionState s)
 			XLogRegisterData((char *) unreportedXids,
 							 nUnreportedXids * sizeof(TransactionId));
 
-			(void) XLogInsert(RM_XACT_ID, XLOG_XACT_ASSIGNMENT);
+			endptr = XLogInsert(RM_XACT_ID, XLOG_XACT_ASSIGNMENT);
 
 			nUnreportedXids = 0;
-			/* mark top, not current xact as having been logged */
-			TopTransactionStateData.didLogXid = true;
+
+			/* set minLSN of top, not of current xact if not yet */
+			if (XLogRecPtrIsInvalid(TopTransactionStateData.minLSN))
+				TopTransactionStateData.minLSN = endptr;
 		}
 	}
 }
@@ -2022,7 +2057,7 @@ StartTransaction(void)
 	 * initialize reported xid accounting
 	 */
 	nUnreportedXids = 0;
-	s->didLogXid = false;
+	s->minLSN = InvalidXLogRecPtr;
 
 	/*
 	 * must initialize resource-management stuff first
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 15da91a8dd..6eb46ea8a7 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -1172,7 +1172,7 @@ XLogInsertRecord(XLogRecData *rdata,
 	 */
 	WALInsertLockRelease();
 
-	MarkCurrentTransactionIdLoggedIfAny();
+	MarkCurrentTransactionIdLoggedIfAny(EndPos);
 
 	END_CRIT_SECTION();
 
diff --git a/src/backend/utils/adt/xid8funcs.c b/src/backend/utils/adt/xid8funcs.c
index cc2b4ac797..992482f8c8 100644
--- a/src/backend/utils/adt/xid8funcs.c
+++ b/src/backend/utils/adt/xid8funcs.c
@@ -357,6 +357,8 @@ bad_format:
 Datum
 pg_current_xact_id(PG_FUNCTION_ARGS)
 {
+	FullTransactionId xid;
+
 	/*
 	 * Must prevent during recovery because if an xid is not assigned we try
 	 * to assign one, which would fail. Programs already rely on this function
@@ -365,7 +367,12 @@ pg_current_xact_id(PG_FUNCTION_ARGS)
 	 */
 	PreventCommandDuringRecovery("pg_current_xact_id()");
 
-	PG_RETURN_FULLTRANSACTIONID(GetTopFullTransactionId());
+	xid = GetTopFullTransactionId();
+
+	/* the XID is going to be published, make sure it is psersistent */
+	EnsureTopTransactionIdLogged();
+
+	PG_RETURN_FULLTRANSACTIONID(xid);
 }
 
 /*
@@ -380,6 +387,9 @@ pg_current_xact_id_if_assigned(PG_FUNCTION_ARGS)
 	if (!FullTransactionIdIsValid(topfxid))
 		PG_RETURN_NULL();
 
+	/* the XID is going to be published, make sure it is psersistent */
+	EnsureTopTransactionIdLogged();
+
 	PG_RETURN_FULLTRANSACTIONID(topfxid);
 }
 
diff --git a/src/include/access/xact.h b/src/include/access/xact.h
index 34cfaf542c..a61e4d6da5 100644
--- a/src/include/access/xact.h
+++ b/src/include/access/xact.h
@@ -386,7 +386,8 @@ extern FullTransactionId GetTopFullTransactionId(void);
 extern FullTransactionId GetTopFullTransactionIdIfAny(void);
 extern FullTransactionId GetCurrentFullTransactionId(void);
 extern FullTransactionId GetCurrentFullTransactionIdIfAny(void);
-extern void MarkCurrentTransactionIdLoggedIfAny(void);
+extern void MarkCurrentTransactionIdLoggedIfAny(XLogRecPtr upto);
+extern void EnsureTopTransactionIdLogged(void);
 extern bool SubTransactionIsActive(SubTransactionId subxid);
 extern CommandId GetCurrentCommandId(bool used);
 extern void SetParallelStartTimestamps(TimestampTz xact_ts, TimestampTz stmt_ts);
-- 
2.17.0

From 860116e2edc6ba5399c0d92a349b0850c49a96fe Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Thu, 11 Mar 2021 17:36:24 -0600
Subject: [PATCH 04/10] wal_compression_method: default to zlib..

this is meant to exercise the CIs, and not meant to be merged
---
 src/backend/access/transam/xlog.c | 2 +-
 src/backend/utils/misc/guc.c      | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 6eb46ea8a7..f5d4450654 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -99,7 +99,7 @@ bool		EnableHotStandby = false;
 bool		fullPageWrites = true;
 bool		wal_log_hints = false;
 bool		wal_compression = false;
-int			wal_compression_method = WAL_COMPRESSION_PGLZ;
+int			wal_compression_method = WAL_COMPRESSION_ZLIB;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 8084027465..c37a8313d3 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -1269,7 +1269,7 @@ static struct config_bool ConfigureNamesBool[] =
 			NULL
 		},
 		&wal_compression,
-		false,
+		true,
 		NULL, NULL, NULL
 	},
 
@@ -4728,7 +4728,7 @@ static struct config_enum ConfigureNamesEnum[] =
 			NULL
 		},
 		&wal_compression_method,
-		WAL_COMPRESSION_PGLZ, wal_compression_options,
+		WAL_COMPRESSION_ZLIB, wal_compression_options,
 		NULL, NULL, NULL
 	},
 
-- 
2.17.0

From 1eac7210a16fd74f94f43d25f2c2d19fb377356e Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Fri, 12 Mar 2021 14:32:10 -0600
Subject: [PATCH 05/10] (re)add wal_compression_method: lz4

---
 configure                                     | 176 ++++++++++++++++++
 configure.ac                                  |  26 +++
 doc/src/sgml/config.sgml                      |   3 +-
 src/backend/access/transam/xlog.c             |   3 +
 src/backend/access/transam/xloginsert.c       |  17 +-
 src/backend/access/transam/xlogreader.c       |  12 ++
 src/backend/utils/misc/postgresql.conf.sample |   2 +-
 src/include/access/xlog_internal.h            |   1 +
 src/include/pg_config.h.in                    |   3 +
 src/tools/msvc/Solution.pm                    |   1 +
 10 files changed, 241 insertions(+), 3 deletions(-)

diff --git a/configure b/configure
index 3fd4cecbeb..fed440adcf 100755
--- a/configure
+++ b/configure
@@ -699,6 +699,9 @@ with_gnu_ld
 LD
 LDFLAGS_SL
 LDFLAGS_EX
+LZ4_LIBS
+LZ4_CFLAGS
+with_lz4
 with_zlib
 with_system_tzdata
 with_libxslt
@@ -864,6 +867,7 @@ with_libxml
 with_libxslt
 with_system_tzdata
 with_zlib
+with_lz4
 with_gnu_ld
 with_ssl
 with_openssl
@@ -891,6 +895,8 @@ ICU_LIBS
 XML2_CONFIG
 XML2_CFLAGS
 XML2_LIBS
+LZ4_CFLAGS
+LZ4_LIBS
 LDFLAGS_EX
 LDFLAGS_SL
 PERL
@@ -1569,6 +1575,7 @@ Optional Packages:
   --with-system-tzdata=DIR
                           use system time zone data in DIR
   --without-zlib          do not use Zlib
+  --with-lz4              build with LZ4 support
   --with-gnu-ld           assume the C compiler uses GNU ld [default=no]
   --with-ssl=LIB          use LIB for SSL/TLS support (openssl)
   --with-openssl          obsolete spelling of --with-ssl=openssl
@@ -1596,6 +1603,8 @@ Some influential environment variables:
   XML2_CONFIG path to xml2-config utility
   XML2_CFLAGS C compiler flags for XML2, overriding pkg-config
   XML2_LIBS   linker flags for XML2, overriding pkg-config
+  LZ4_CFLAGS  C compiler flags for LZ4, overriding pkg-config
+  LZ4_LIBS    linker flags for LZ4, overriding pkg-config
   LDFLAGS_EX  extra linker flags for linking executables only
   LDFLAGS_SL  extra linker flags for linking shared libraries only
   PERL        Perl program
@@ -8563,6 +8572,137 @@ fi
 
 
 
+#
+# LZ4
+#
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether to build with LZ4 support" >&5
+$as_echo_n "checking whether to build with LZ4 support... " >&6; }
+
+
+
+# Check whether --with-lz4 was given.
+if test "${with_lz4+set}" = set; then :
+  withval=$with_lz4;
+  case $withval in
+    yes)
+
+$as_echo "#define USE_LZ4 1" >>confdefs.h
+
+      ;;
+    no)
+      :
+      ;;
+    *)
+      as_fn_error $? "no argument expected for --with-lz4 option" "$LINENO" 5
+      ;;
+  esac
+
+else
+  with_lz4=no
+
+fi
+
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $with_lz4" >&5
+$as_echo "$with_lz4" >&6; }
+
+
+if test "$with_lz4" = yes; then
+
+pkg_failed=no
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for liblz4" >&5
+$as_echo_n "checking for liblz4... " >&6; }
+
+if test -n "$LZ4_CFLAGS"; then
+    pkg_cv_LZ4_CFLAGS="$LZ4_CFLAGS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"liblz4\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "liblz4") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_LZ4_CFLAGS=`$PKG_CONFIG --cflags "liblz4" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+if test -n "$LZ4_LIBS"; then
+    pkg_cv_LZ4_LIBS="$LZ4_LIBS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"liblz4\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "liblz4") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_LZ4_LIBS=`$PKG_CONFIG --libs "liblz4" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+
+
+
+if test $pkg_failed = yes; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+
+if $PKG_CONFIG --atleast-pkgconfig-version 0.20; then
+        _pkg_short_errors_supported=yes
+else
+        _pkg_short_errors_supported=no
+fi
+        if test $_pkg_short_errors_supported = yes; then
+	        LZ4_PKG_ERRORS=`$PKG_CONFIG --short-errors --print-errors --cflags --libs "liblz4" 2>&1`
+        else
+	        LZ4_PKG_ERRORS=`$PKG_CONFIG --print-errors --cflags --libs "liblz4" 2>&1`
+        fi
+	# Put the nasty error message in config.log where it belongs
+	echo "$LZ4_PKG_ERRORS" >&5
+
+	as_fn_error $? "Package requirements (liblz4) were not met:
+
+$LZ4_PKG_ERRORS
+
+Consider adjusting the PKG_CONFIG_PATH environment variable if you
+installed software in a non-standard prefix.
+
+Alternatively, you may set the environment variables LZ4_CFLAGS
+and LZ4_LIBS to avoid the need to call pkg-config.
+See the pkg-config man page for more details." "$LINENO" 5
+elif test $pkg_failed = untried; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+	{ { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error $? "The pkg-config script could not be found or is too old.  Make sure it
+is in your PATH or set the PKG_CONFIG environment variable to the full
+path to pkg-config.
+
+Alternatively, you may set the environment variables LZ4_CFLAGS
+and LZ4_LIBS to avoid the need to call pkg-config.
+See the pkg-config man page for more details.
+
+To get pkg-config, see <http://pkg-config.freedesktop.org/>.
+See \`config.log' for more details" "$LINENO" 5; }
+else
+	LZ4_CFLAGS=$pkg_cv_LZ4_CFLAGS
+	LZ4_LIBS=$pkg_cv_LZ4_LIBS
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+
+fi
+  LIBS="$LZ4_LIBS $LIBS"
+  CFLAGS="$LZ4_CFLAGS $CFLAGS"
+fi
+
 #
 # Assignments
 #
@@ -13381,6 +13521,42 @@ fi
 
 fi
 
+if test "$with_lz4" = yes; then
+  ac_save_CPPFLAGS=$CPPFLAGS
+  CPPFLAGS="$LZ4_CFLAGS $CPPFLAGS"
+
+  # Verify we have LZ4's header files
+  for ac_header in lz4/lz4.h
+do :
+  ac_fn_c_check_header_mongrel "$LINENO" "lz4/lz4.h" "ac_cv_header_lz4_lz4_h" "$ac_includes_default"
+if test "x$ac_cv_header_lz4_lz4_h" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_LZ4_LZ4_H 1
+_ACEOF
+
+else
+  for ac_header in lz4.h
+do :
+  ac_fn_c_check_header_mongrel "$LINENO" "lz4.h" "ac_cv_header_lz4_h" "$ac_includes_default"
+if test "x$ac_cv_header_lz4_h" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_LZ4_H 1
+_ACEOF
+
+else
+  as_fn_error $? "lz4.h header file is required for LZ4" "$LINENO" 5
+fi
+
+done
+
+fi
+
+done
+
+
+  CPPFLAGS=$ac_save_CPPFLAGS
+fi
+
 if test "$with_gssapi" = yes ; then
   for ac_header in gssapi/gssapi.h
 do :
diff --git a/configure.ac b/configure.ac
index 2f1585adc0..8c454128bb 100644
--- a/configure.ac
+++ b/configure.ac
@@ -986,6 +986,21 @@ PGAC_ARG_BOOL(with, zlib, yes,
               [do not use Zlib])
 AC_SUBST(with_zlib)
 
+#
+# LZ4
+#
+AC_MSG_CHECKING([whether to build with LZ4 support])
+PGAC_ARG_BOOL(with, lz4, no, [build with LZ4 support],
+              [AC_DEFINE([USE_LZ4], 1, [Define to 1 to build with LZ4 support. (--with-lz4)])])
+AC_MSG_RESULT([$with_lz4])
+AC_SUBST(with_lz4)
+
+if test "$with_lz4" = yes; then
+  PKG_CHECK_MODULES(LZ4, liblz4)
+  LIBS="$LZ4_LIBS $LIBS"
+  CFLAGS="$LZ4_CFLAGS $CFLAGS"
+fi
+
 #
 # Assignments
 #
@@ -1410,6 +1425,17 @@ failure.  It is possible the compiler isn't looking in the proper directory.
 Use --without-zlib to disable zlib support.])])
 fi
 
+if test "$with_lz4" = yes; then
+  ac_save_CPPFLAGS=$CPPFLAGS
+  CPPFLAGS="$LZ4_CFLAGS $CPPFLAGS"
+
+  # Verify we have LZ4's header files
+  AC_CHECK_HEADERS(lz4/lz4.h, [],
+       [AC_CHECK_HEADERS(lz4.h, [], [AC_MSG_ERROR([lz4.h header file is required for LZ4])])])
+
+  CPPFLAGS=$ac_save_CPPFLAGS
+fi
+
 if test "$with_gssapi" = yes ; then
   AC_CHECK_HEADERS(gssapi/gssapi.h, [],
 	[AC_CHECK_HEADERS(gssapi.h, [], [AC_MSG_ERROR([gssapi.h header file is required for GSSAPI])])])
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 7fb2a84626..257775c83b 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -3082,7 +3082,8 @@ include_dir 'conf.d'
        <para>
         This parameter selects the compression method used to compress WAL when
         <varname>wal_compression</varname> is enabled.
-        The supported methods are pglz and zlib.
+        The supported methods are pglz, zlib, and (if configured when
+        <productname>PostgreSQL</productname> was built) lz4.
         The default value is <literal>pglz</literal>.
         Only superusers can change this setting.
        </para>
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index f5d4450654..984ce39cc7 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -186,6 +186,9 @@ const struct config_enum_entry wal_compression_options[] = {
 	{"pglz", WAL_COMPRESSION_PGLZ, false},
 #ifdef  HAVE_LIBZ
 	{"zlib", WAL_COMPRESSION_ZLIB, false},
+#endif
+#ifdef  USE_LZ4
+	{"lz4", WAL_COMPRESSION_LZ4, false},
 #endif
 	{NULL, 0, false}
 };
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
index a93b33464f..3c15286bd8 100644
--- a/src/backend/access/transam/xloginsert.c
+++ b/src/backend/access/transam/xloginsert.c
@@ -41,10 +41,17 @@
 #define ZLIB_MAX_BLCKSZ		0
 #endif
 
+#ifdef USE_LZ4
+#include "lz4.h"
+#define	LZ4_MAX_BLCKSZ		LZ4_COMPRESSBOUND(BLCKSZ)
+#else
+#define LZ4_MAX_BLCKSZ		0
+#endif
+
 /* Buffer size required to store a compressed version of backup block image */
 #define PGLZ_MAX_BLCKSZ		PGLZ_MAX_OUTPUT(BLCKSZ)
 
-#define COMPRESS_BUFSIZE	Max(PGLZ_MAX_BLCKSZ, ZLIB_MAX_BLCKSZ)
+#define COMPRESS_BUFSIZE	Max(Max(PGLZ_MAX_BLCKSZ, ZLIB_MAX_BLCKSZ), LZ4_MAX_BLCKSZ)
 
 /*
  * For each block reference registered with XLogRegisterBuffer, we fill in
@@ -891,6 +898,14 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 		}
 #endif
 
+#ifdef USE_LZ4
+	case WAL_COMPRESSION_LZ4:
+		len = LZ4_compress_fast(source, dest, orig_len, COMPRESS_BUFSIZE, 1);
+		if (len == 0)
+			len = -1;
+		break;
+#endif
+
 	default:
 		/*
 		 * It should be impossible to get here for unsupported algorithms,
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index 0d8830fc50..97165f1bb1 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -37,6 +37,10 @@
 #include <zlib.h>
 #endif
 
+#ifdef USE_LZ4
+#include "lz4.h"
+#endif
+
 static void report_invalid_record(XLogReaderState *state, const char *fmt,...)
 			pg_attribute_printf(2, 3);
 static bool allocate_recordbuf(XLogReaderState *state, uint32 reclength);
@@ -1544,6 +1548,7 @@ XLogRecGetBlockData(XLogReaderState *record, uint8 block_id, Size *len)
 struct walcompression walmethods[] = {
 	{"pglz",	WAL_COMPRESSION_PGLZ},
 	{"zlib",	WAL_COMPRESSION_ZLIB},
+	{"lz4",		WAL_COMPRESSION_LZ4},
 };
 
 /*
@@ -1609,6 +1614,13 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 		}
 #endif
 
+#ifdef USE_LZ4
+		case WAL_COMPRESSION_LZ4:
+			decomp_result = LZ4_decompress_safe(ptr, tmp.data,
+					bkpb->bimg_len, BLCKSZ-bkpb->hole_length);
+			break;
+#endif
+
 		default:
 			report_invalid_record(record, "image at %X/%X is compressed with unsupported codec, block %d (%d/%s)",
 								  (uint32) (record->ReadRecPtr >> 32),
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index ef69a94492..76f494cb9b 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -213,7 +213,7 @@
 					#   open_sync
 #full_page_writes = on			# recover from partial page writes
 #wal_compression = off			# enable compression of full-page writes
-#wal_compression_method = pglz		# pglz, zlib
+#wal_compression_method = pglz		# pglz, zlib, lz4
 #wal_log_hints = off			# also do full page writes of non-critical updates
 					# (change requires restart)
 #wal_init_zero = on			# zero-fill new WAL files
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index b000a21557..b908fa48de 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -336,6 +336,7 @@ typedef enum WalCompression
 {
 	WAL_COMPRESSION_PGLZ,
 	WAL_COMPRESSION_ZLIB,
+	WAL_COMPRESSION_LZ4,
 } WalCompression;
 
 extern const char *wal_compression_name(WalCompression compression);
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index 7a7cc21d8d..0a6422da4f 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -899,6 +899,9 @@
 /* Define to 1 to build with LLVM based JIT support. (--with-llvm) */
 #undef USE_LLVM
 
+/* Define to 1 to build with LZ4 support (--with-lz4) */
+#undef USE_LZ4
+
 /* Define to select named POSIX semaphores. */
 #undef USE_NAMED_POSIX_SEMAPHORES
 
diff --git a/src/tools/msvc/Solution.pm b/src/tools/msvc/Solution.pm
index a4f5cc4bdb..14605371bb 100644
--- a/src/tools/msvc/Solution.pm
+++ b/src/tools/msvc/Solution.pm
@@ -485,6 +485,7 @@ sub GenerateFiles
 		USE_ICU => $self->{options}->{icu} ? 1 : undef,
 		USE_LIBXML                 => undef,
 		USE_LIBXSLT                => undef,
+		USE_LZ4                    => undef,
 		USE_LDAP                   => $self->{options}->{ldap} ? 1 : undef,
 		USE_LLVM                   => undef,
 		USE_NAMED_POSIX_SEMAPHORES => undef,
-- 
2.17.0

From d7a40dda7223adf3443e9cd46d85eb51c5cf0c4c Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Fri, 12 Mar 2021 15:35:40 -0600
Subject: [PATCH 06/10] Default to LZ4..

this is meant to exercise in the CIs, and not meant to be merged
---
 configure                         | 6 ++++--
 configure.ac                      | 4 ++--
 src/backend/access/transam/xlog.c | 2 +-
 src/backend/utils/misc/guc.c      | 2 +-
 4 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/configure b/configure
index fed440adcf..8d76be00c1 100755
--- a/configure
+++ b/configure
@@ -1575,7 +1575,7 @@ Optional Packages:
   --with-system-tzdata=DIR
                           use system time zone data in DIR
   --without-zlib          do not use Zlib
-  --with-lz4              build with LZ4 support
+  --without-lz4           build without LZ4 support
   --with-gnu-ld           assume the C compiler uses GNU ld [default=no]
   --with-ssl=LIB          use LIB for SSL/TLS support (openssl)
   --with-openssl          obsolete spelling of --with-ssl=openssl
@@ -8598,7 +8598,9 @@ $as_echo "#define USE_LZ4 1" >>confdefs.h
   esac
 
 else
-  with_lz4=no
+  with_lz4=yes
+
+$as_echo "#define USE_LZ4 1" >>confdefs.h
 
 fi
 
diff --git a/configure.ac b/configure.ac
index 8c454128bb..bfcdc88be0 100644
--- a/configure.ac
+++ b/configure.ac
@@ -990,8 +990,8 @@ AC_SUBST(with_zlib)
 # LZ4
 #
 AC_MSG_CHECKING([whether to build with LZ4 support])
-PGAC_ARG_BOOL(with, lz4, no, [build with LZ4 support],
-              [AC_DEFINE([USE_LZ4], 1, [Define to 1 to build with LZ4 support. (--with-lz4)])])
+PGAC_ARG_BOOL(with, lz4, yes, [build without LZ4 support],
+              [AC_DEFINE([USE_LZ4], 1, [Define to 1 to build without LZ4 support. (--without-lz4)])])
 AC_MSG_RESULT([$with_lz4])
 AC_SUBST(with_lz4)
 
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 984ce39cc7..3657f74de9 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -99,7 +99,7 @@ bool		EnableHotStandby = false;
 bool		fullPageWrites = true;
 bool		wal_log_hints = false;
 bool		wal_compression = false;
-int			wal_compression_method = WAL_COMPRESSION_ZLIB;
+int			wal_compression_method = WAL_COMPRESSION_LZ4;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index c37a8313d3..52f9cd0242 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -4728,7 +4728,7 @@ static struct config_enum ConfigureNamesEnum[] =
 			NULL
 		},
 		&wal_compression_method,
-		WAL_COMPRESSION_ZLIB, wal_compression_options,
+		WAL_COMPRESSION_LZ4, wal_compression_options,
 		NULL, NULL, NULL
 	},
 
-- 
2.17.0

From 0399525064de6ed86fc5333c75b061ab85857785 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Fri, 12 Mar 2021 14:43:53 -0600
Subject: [PATCH 07/10] add wal_compression_method: zstd

---
 configure                                     | 163 ++++++++++++++++++
 configure.ac                                  |  26 +++
 doc/src/sgml/config.sgml                      |   2 +-
 src/backend/access/transam/xlog.c             |   3 +
 src/backend/access/transam/xloginsert.c       |  18 +-
 src/backend/access/transam/xlogreader.c       |  15 ++
 src/backend/utils/misc/postgresql.conf.sample |   2 +-
 src/include/access/xlog_internal.h            |   1 +
 src/include/pg_config.h.in                    |   3 +
 src/tools/msvc/Solution.pm                    |   1 +
 10 files changed, 231 insertions(+), 3 deletions(-)

diff --git a/configure b/configure
index 8d76be00c1..81e23418b2 100755
--- a/configure
+++ b/configure
@@ -699,6 +699,9 @@ with_gnu_ld
 LD
 LDFLAGS_SL
 LDFLAGS_EX
+ZSTD_LIBS
+ZSTD_CFLAGS
+with_zstd
 LZ4_LIBS
 LZ4_CFLAGS
 with_lz4
@@ -868,6 +871,7 @@ with_libxslt
 with_system_tzdata
 with_zlib
 with_lz4
+with_zstd
 with_gnu_ld
 with_ssl
 with_openssl
@@ -897,6 +901,8 @@ XML2_CFLAGS
 XML2_LIBS
 LZ4_CFLAGS
 LZ4_LIBS
+ZSTD_CFLAGS
+ZSTD_LIBS
 LDFLAGS_EX
 LDFLAGS_SL
 PERL
@@ -1576,6 +1582,7 @@ Optional Packages:
                           use system time zone data in DIR
   --without-zlib          do not use Zlib
   --without-lz4           build without LZ4 support
+  --with-zstd             build with Zstd compression library
   --with-gnu-ld           assume the C compiler uses GNU ld [default=no]
   --with-ssl=LIB          use LIB for SSL/TLS support (openssl)
   --with-openssl          obsolete spelling of --with-ssl=openssl
@@ -1605,6 +1612,8 @@ Some influential environment variables:
   XML2_LIBS   linker flags for XML2, overriding pkg-config
   LZ4_CFLAGS  C compiler flags for LZ4, overriding pkg-config
   LZ4_LIBS    linker flags for LZ4, overriding pkg-config
+  ZSTD_CFLAGS C compiler flags for ZSTD, overriding pkg-config
+  ZSTD_LIBS   linker flags for ZSTD, overriding pkg-config
   LDFLAGS_EX  extra linker flags for linking executables only
   LDFLAGS_SL  extra linker flags for linking shared libraries only
   PERL        Perl program
@@ -8705,6 +8714,137 @@ fi
   CFLAGS="$LZ4_CFLAGS $CFLAGS"
 fi
 
+#
+# ZSTD
+#
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether to build with zstd support" >&5
+$as_echo_n "checking whether to build with zstd support... " >&6; }
+
+
+
+# Check whether --with-zstd was given.
+if test "${with_zstd+set}" = set; then :
+  withval=$with_zstd;
+  case $withval in
+    yes)
+
+$as_echo "#define USE_ZSTD 1" >>confdefs.h
+
+      ;;
+    no)
+      :
+      ;;
+    *)
+      as_fn_error $? "no argument expected for --with-zstd option" "$LINENO" 5
+      ;;
+  esac
+
+else
+  with_zstd=no
+
+fi
+
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $with_zstd" >&5
+$as_echo "$with_zstd" >&6; }
+
+
+if test "$with_zstd" = yes; then
+
+pkg_failed=no
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for libzstd" >&5
+$as_echo_n "checking for libzstd... " >&6; }
+
+if test -n "$ZSTD_CFLAGS"; then
+    pkg_cv_ZSTD_CFLAGS="$ZSTD_CFLAGS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"libzstd\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "libzstd") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_ZSTD_CFLAGS=`$PKG_CONFIG --cflags "libzstd" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+if test -n "$ZSTD_LIBS"; then
+    pkg_cv_ZSTD_LIBS="$ZSTD_LIBS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"libzstd\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "libzstd") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_ZSTD_LIBS=`$PKG_CONFIG --libs "libzstd" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+
+
+
+if test $pkg_failed = yes; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+
+if $PKG_CONFIG --atleast-pkgconfig-version 0.20; then
+        _pkg_short_errors_supported=yes
+else
+        _pkg_short_errors_supported=no
+fi
+        if test $_pkg_short_errors_supported = yes; then
+	        ZSTD_PKG_ERRORS=`$PKG_CONFIG --short-errors --print-errors --cflags --libs "libzstd" 2>&1`
+        else
+	        ZSTD_PKG_ERRORS=`$PKG_CONFIG --print-errors --cflags --libs "libzstd" 2>&1`
+        fi
+	# Put the nasty error message in config.log where it belongs
+	echo "$ZSTD_PKG_ERRORS" >&5
+
+	as_fn_error $? "Package requirements (libzstd) were not met:
+
+$ZSTD_PKG_ERRORS
+
+Consider adjusting the PKG_CONFIG_PATH environment variable if you
+installed software in a non-standard prefix.
+
+Alternatively, you may set the environment variables ZSTD_CFLAGS
+and ZSTD_LIBS to avoid the need to call pkg-config.
+See the pkg-config man page for more details." "$LINENO" 5
+elif test $pkg_failed = untried; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+	{ { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error $? "The pkg-config script could not be found or is too old.  Make sure it
+is in your PATH or set the PKG_CONFIG environment variable to the full
+path to pkg-config.
+
+Alternatively, you may set the environment variables ZSTD_CFLAGS
+and ZSTD_LIBS to avoid the need to call pkg-config.
+See the pkg-config man page for more details.
+
+To get pkg-config, see <http://pkg-config.freedesktop.org/>.
+See \`config.log' for more details" "$LINENO" 5; }
+else
+	ZSTD_CFLAGS=$pkg_cv_ZSTD_CFLAGS
+	ZSTD_LIBS=$pkg_cv_ZSTD_LIBS
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+
+fi
+  LIBS="$ZSTD_LIBS $LIBS"
+  CFLAGS="$ZSTD_CFLAGS $CFLAGS"
+fi
+
 #
 # Assignments
 #
@@ -13559,6 +13699,29 @@ done
   CPPFLAGS=$ac_save_CPPFLAGS
 fi
 
+if test "$with_zstd" = yes; then
+  ac_save_CPPFLAGS=$CPPFLAGS
+  CPPFLAGS="$ZSTD_CFLAGS $CPPFLAGS"
+
+  # Verify we have zstd's header files
+  for ac_header in zstd.h
+do :
+  ac_fn_c_check_header_mongrel "$LINENO" "zstd.h" "ac_cv_header_zstd_h" "$ac_includes_default"
+if test "x$ac_cv_header_zstd_h" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_ZSTD_H 1
+_ACEOF
+
+else
+  as_fn_error $? "zstd.h header file is required for zstd" "$LINENO" 5
+fi
+
+done
+
+
+  CPPFLAGS=$ac_save_CPPFLAGS
+fi
+
 if test "$with_gssapi" = yes ; then
   for ac_header in gssapi/gssapi.h
 do :
diff --git a/configure.ac b/configure.ac
index bfcdc88be0..d6f6349067 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1001,6 +1001,21 @@ if test "$with_lz4" = yes; then
   CFLAGS="$LZ4_CFLAGS $CFLAGS"
 fi
 
+#
+# ZSTD
+#
+AC_MSG_CHECKING([whether to build with zstd support])
+PGAC_ARG_BOOL(with, zstd, no, [build with Zstd compression library],
+              [AC_DEFINE([USE_ZSTD], 1, [Define to 1 to build with zstd support. (--with-zstd)])])
+AC_MSG_RESULT([$with_zstd])
+AC_SUBST(with_zstd)
+
+if test "$with_zstd" = yes; then
+  PKG_CHECK_MODULES(ZSTD, libzstd)
+  LIBS="$ZSTD_LIBS $LIBS"
+  CFLAGS="$ZSTD_CFLAGS $CFLAGS"
+fi
+
 #
 # Assignments
 #
@@ -1436,6 +1451,17 @@ if test "$with_lz4" = yes; then
   CPPFLAGS=$ac_save_CPPFLAGS
 fi
 
+if test "$with_zstd" = yes; then
+  ac_save_CPPFLAGS=$CPPFLAGS
+  CPPFLAGS="$ZSTD_CFLAGS $CPPFLAGS"
+
+  # Verify we have zstd's header files
+  AC_CHECK_HEADERS(zstd.h, [],
+       [AC_MSG_ERROR([zstd.h header file is required for zstd])])
+
+  CPPFLAGS=$ac_save_CPPFLAGS
+fi
+
 if test "$with_gssapi" = yes ; then
   AC_CHECK_HEADERS(gssapi/gssapi.h, [],
 	[AC_CHECK_HEADERS(gssapi.h, [], [AC_MSG_ERROR([gssapi.h header file is required for GSSAPI])])])
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 257775c83b..94dd6ef3e9 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -3083,7 +3083,7 @@ include_dir 'conf.d'
         This parameter selects the compression method used to compress WAL when
         <varname>wal_compression</varname> is enabled.
         The supported methods are pglz, zlib, and (if configured when
-        <productname>PostgreSQL</productname> was built) lz4.
+        <productname>PostgreSQL</productname> was built) lz4 and zstd.
         The default value is <literal>pglz</literal>.
         Only superusers can change this setting.
        </para>
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 3657f74de9..307eee6626 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -189,6 +189,9 @@ const struct config_enum_entry wal_compression_options[] = {
 #endif
 #ifdef  USE_LZ4
 	{"lz4", WAL_COMPRESSION_LZ4, false},
+#endif
+#ifdef  USE_ZSTD
+	{"zstd", WAL_COMPRESSION_ZSTD, false},
 #endif
 	{NULL, 0, false}
 };
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
index 3c15286bd8..4591e476c6 100644
--- a/src/backend/access/transam/xloginsert.c
+++ b/src/backend/access/transam/xloginsert.c
@@ -48,10 +48,17 @@
 #define LZ4_MAX_BLCKSZ		0
 #endif
 
+#ifdef USE_ZSTD
+#include "zstd.h"
+#define ZSTD_MAX_BLCKSZ		ZSTD_COMPRESSBOUND(BLCKSZ)
+#else
+#define ZSTD_MAX_BLCKSZ		0
+#endif
+
 /* Buffer size required to store a compressed version of backup block image */
 #define PGLZ_MAX_BLCKSZ		PGLZ_MAX_OUTPUT(BLCKSZ)
 
-#define COMPRESS_BUFSIZE	Max(Max(PGLZ_MAX_BLCKSZ, ZLIB_MAX_BLCKSZ), LZ4_MAX_BLCKSZ)
+#define COMPRESS_BUFSIZE	Max(Max(Max(PGLZ_MAX_BLCKSZ, ZLIB_MAX_BLCKSZ), LZ4_MAX_BLCKSZ), ZSTD_MAX_BLCKSZ)
 
 /*
  * For each block reference registered with XLogRegisterBuffer, we fill in
@@ -906,6 +913,15 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 		break;
 #endif
 
+#ifdef USE_ZSTD
+	case WAL_COMPRESSION_ZSTD:
+		len = ZSTD_compress(dest, COMPRESS_BUFSIZE, source, orig_len,
+				ZSTD_CLEVEL_DEFAULT);
+		if (ZSTD_isError(len))
+			len = -1;
+		break;
+#endif
+
 	default:
 		/*
 		 * It should be impossible to get here for unsupported algorithms,
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index 97165f1bb1..0f9d522087 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -41,6 +41,10 @@
 #include "lz4.h"
 #endif
 
+#ifdef USE_ZSTD
+#include "zstd.h"
+#endif
+
 static void report_invalid_record(XLogReaderState *state, const char *fmt,...)
 			pg_attribute_printf(2, 3);
 static bool allocate_recordbuf(XLogReaderState *state, uint32 reclength);
@@ -1549,6 +1553,7 @@ struct walcompression walmethods[] = {
 	{"pglz",	WAL_COMPRESSION_PGLZ},
 	{"zlib",	WAL_COMPRESSION_ZLIB},
 	{"lz4",		WAL_COMPRESSION_LZ4},
+	{"zstd",	WAL_COMPRESSION_ZSTD},
 };
 
 /*
@@ -1621,6 +1626,16 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 			break;
 #endif
 
+#ifdef USE_ZSTD
+		case WAL_COMPRESSION_ZSTD:
+			decomp_result = ZSTD_decompress(tmp.data, BLCKSZ-bkpb->hole_length,
+					ptr, bkpb->bimg_len);
+			// XXX: ZSTD_getErrorName
+			if (ZSTD_isError(decomp_result))
+				decomp_result = -1;
+			break;
+#endif
+
 		default:
 			report_invalid_record(record, "image at %X/%X is compressed with unsupported codec, block %d (%d/%s)",
 								  (uint32) (record->ReadRecPtr >> 32),
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 76f494cb9b..d372e2a817 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -213,7 +213,7 @@
 					#   open_sync
 #full_page_writes = on			# recover from partial page writes
 #wal_compression = off			# enable compression of full-page writes
-#wal_compression_method = pglz		# pglz, zlib, lz4
+#wal_compression_method = pglz		# pglz, zlib, lz4, zstd
 #wal_log_hints = off			# also do full page writes of non-critical updates
 					# (change requires restart)
 #wal_init_zero = on			# zero-fill new WAL files
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index b908fa48de..fa8146645d 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -337,6 +337,7 @@ typedef enum WalCompression
 	WAL_COMPRESSION_PGLZ,
 	WAL_COMPRESSION_ZLIB,
 	WAL_COMPRESSION_LZ4,
+	WAL_COMPRESSION_ZSTD,
 } WalCompression;
 
 extern const char *wal_compression_name(WalCompression compression);
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index 0a6422da4f..ad26393352 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -902,6 +902,9 @@
 /* Define to 1 to build with LZ4 support (--with-lz4) */
 #undef USE_LZ4
 
+/* Define to 1 if you have the `zstd' library (-lzstd). */
+#undef USE_ZSTD
+
 /* Define to select named POSIX semaphores. */
 #undef USE_NAMED_POSIX_SEMAPHORES
 
diff --git a/src/tools/msvc/Solution.pm b/src/tools/msvc/Solution.pm
index 14605371bb..fff0212087 100644
--- a/src/tools/msvc/Solution.pm
+++ b/src/tools/msvc/Solution.pm
@@ -486,6 +486,7 @@ sub GenerateFiles
 		USE_LIBXML                 => undef,
 		USE_LIBXSLT                => undef,
 		USE_LZ4                    => undef,
+		USE_ZSTD                   => $self->{options}->{zstd} ? 1 : undef,
 		USE_LDAP                   => $self->{options}->{ldap} ? 1 : undef,
 		USE_LLVM                   => undef,
 		USE_NAMED_POSIX_SEMAPHORES => undef,
-- 
2.17.0

From 9242b66ea1a4493a9100a2fbc3f243e669ee990a Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Fri, 12 Mar 2021 15:35:53 -0600
Subject: [PATCH 08/10] Default to zstd..

for CI, not for merge
---
 configure                         | 6 ++++--
 configure.ac                      | 2 +-
 src/backend/access/transam/xlog.c | 2 +-
 src/backend/utils/misc/guc.c      | 2 +-
 4 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/configure b/configure
index 81e23418b2..253f028fc4 100755
--- a/configure
+++ b/configure
@@ -1582,7 +1582,7 @@ Optional Packages:
                           use system time zone data in DIR
   --without-zlib          do not use Zlib
   --without-lz4           build without LZ4 support
-  --with-zstd             build with Zstd compression library
+  --without-zstd          build without Zstd compression library
   --with-gnu-ld           assume the C compiler uses GNU ld [default=no]
   --with-ssl=LIB          use LIB for SSL/TLS support (openssl)
   --with-openssl          obsolete spelling of --with-ssl=openssl
@@ -8740,7 +8740,9 @@ $as_echo "#define USE_ZSTD 1" >>confdefs.h
   esac
 
 else
-  with_zstd=no
+  with_zstd=yes
+
+$as_echo "#define USE_ZSTD 1" >>confdefs.h
 
 fi
 
diff --git a/configure.ac b/configure.ac
index d6f6349067..8d72710fa7 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1005,7 +1005,7 @@ fi
 # ZSTD
 #
 AC_MSG_CHECKING([whether to build with zstd support])
-PGAC_ARG_BOOL(with, zstd, no, [build with Zstd compression library],
+PGAC_ARG_BOOL(with, zstd, yes, [build without Zstd compression library],
               [AC_DEFINE([USE_ZSTD], 1, [Define to 1 to build with zstd support. (--with-zstd)])])
 AC_MSG_RESULT([$with_zstd])
 AC_SUBST(with_zstd)
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 307eee6626..92023de9f5 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -99,7 +99,7 @@ bool		EnableHotStandby = false;
 bool		fullPageWrites = true;
 bool		wal_log_hints = false;
 bool		wal_compression = false;
-int			wal_compression_method = WAL_COMPRESSION_LZ4;
+int			wal_compression_method = WAL_COMPRESSION_ZSTD;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 52f9cd0242..8031e027aa 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -4728,7 +4728,7 @@ static struct config_enum ConfigureNamesEnum[] =
 			NULL
 		},
 		&wal_compression_method,
-		WAL_COMPRESSION_LZ4, wal_compression_options,
+		WAL_COMPRESSION_ZSTD, wal_compression_options,
 		NULL, NULL, NULL
 	},
 
-- 
2.17.0

From 6172ccb12bcc85779678c439900727035b4ec3a4 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Sun, 14 Mar 2021 17:12:07 -0500
Subject: [PATCH 09/10] Add zstd compression levels

---
 src/backend/access/transam/xlog.c       |  6 +++++-
 src/backend/access/transam/xloginsert.c | 15 +++++++++++++--
 src/backend/access/transam/xlogreader.c | 12 ++++++++++++
 src/backend/utils/misc/guc.c            |  2 +-
 src/include/access/xlog_internal.h      |  4 ++++
 5 files changed, 35 insertions(+), 4 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 92023de9f5..b14c7c5929 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -99,7 +99,7 @@ bool		EnableHotStandby = false;
 bool		fullPageWrites = true;
 bool		wal_log_hints = false;
 bool		wal_compression = false;
-int			wal_compression_method = WAL_COMPRESSION_ZSTD;
+int			wal_compression_method = WAL_COMPRESSION_ZSTD_FAST_10;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
@@ -192,6 +192,10 @@ const struct config_enum_entry wal_compression_options[] = {
 #endif
 #ifdef  USE_ZSTD
 	{"zstd", WAL_COMPRESSION_ZSTD, false},
+	{"zstd-1", WAL_COMPRESSION_ZSTD_1, false},
+	{"zstd-fast-10", WAL_COMPRESSION_ZSTD_FAST_10, false},
+	{"zstd-fast-20", WAL_COMPRESSION_ZSTD_FAST_20, false},
+	{"zstd-fast-40", WAL_COMPRESSION_ZSTD_FAST_40, false},
 #endif
 	{NULL, 0, false}
 };
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
index 4591e476c6..4f11f96373 100644
--- a/src/backend/access/transam/xloginsert.c
+++ b/src/backend/access/transam/xloginsert.c
@@ -915,11 +915,22 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 
 #ifdef USE_ZSTD
 	case WAL_COMPRESSION_ZSTD:
-		len = ZSTD_compress(dest, COMPRESS_BUFSIZE, source, orig_len,
-				ZSTD_CLEVEL_DEFAULT);
+	case WAL_COMPRESSION_ZSTD_1:
+	case WAL_COMPRESSION_ZSTD_FAST_10:
+	case WAL_COMPRESSION_ZSTD_FAST_20:
+	case WAL_COMPRESSION_ZSTD_FAST_40:
+	{
+		int level = compression == WAL_COMPRESSION_ZSTD_1 ? 1 :
+			compression == WAL_COMPRESSION_ZSTD_FAST_10 ? -10 :
+			compression == WAL_COMPRESSION_ZSTD_FAST_20 ? -20 :
+			compression == WAL_COMPRESSION_ZSTD_FAST_40 ? -40 :
+			ZSTD_CLEVEL_DEFAULT;
+
+		len = ZSTD_compress(dest, COMPRESS_BUFSIZE, source, orig_len, level);
 		if (ZSTD_isError(len))
 			len = -1;
 		break;
+	}
 #endif
 
 	default:
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index 0f9d522087..0de61d3073 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -1554,6 +1554,10 @@ struct walcompression walmethods[] = {
 	{"zlib",	WAL_COMPRESSION_ZLIB},
 	{"lz4",		WAL_COMPRESSION_LZ4},
 	{"zstd",	WAL_COMPRESSION_ZSTD},
+	{"zstd-1",	WAL_COMPRESSION_ZSTD},
+	{"zstd-fast-10",WAL_COMPRESSION_ZSTD},
+	{"zstd-fast-20",WAL_COMPRESSION_ZSTD},
+	{"zstd-fast-40",WAL_COMPRESSION_ZSTD},
 };
 
 /*
@@ -1628,6 +1632,14 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 
 #ifdef USE_ZSTD
 		case WAL_COMPRESSION_ZSTD:
+		/*
+		 * There aren't actually written into the header - decompression is the
+		 * same.
+		 * case WAL_COMPRESSION_ZSTD_1:
+		 * case WAL_COMPRESSION_ZSTD_FAST_10:
+		 * case WAL_COMPRESSION_ZSTD_FAST_20:
+		 * case WAL_COMPRESSION_ZSTD_FAST_40:
+		 */
 			decomp_result = ZSTD_decompress(tmp.data, BLCKSZ-bkpb->hole_length,
 					ptr, bkpb->bimg_len);
 			// XXX: ZSTD_getErrorName
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 8031e027aa..667fc4c0c1 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -4728,7 +4728,7 @@ static struct config_enum ConfigureNamesEnum[] =
 			NULL
 		},
 		&wal_compression_method,
-		WAL_COMPRESSION_ZSTD, wal_compression_options,
+		WAL_COMPRESSION_ZSTD_FAST_10, wal_compression_options,
 		NULL, NULL, NULL
 	},
 
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index fa8146645d..a435b1a654 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -338,6 +338,10 @@ typedef enum WalCompression
 	WAL_COMPRESSION_ZLIB,
 	WAL_COMPRESSION_LZ4,
 	WAL_COMPRESSION_ZSTD,
+	WAL_COMPRESSION_ZSTD_1,
+	WAL_COMPRESSION_ZSTD_FAST_10, /* level = -10 */
+	WAL_COMPRESSION_ZSTD_FAST_20, /* level = -20 */
+	WAL_COMPRESSION_ZSTD_FAST_40, /* level = -40 */
 } WalCompression;
 
 extern const char *wal_compression_name(WalCompression compression);
-- 
2.17.0

From 5a7a38464dfe427a8eaf9f3bf054c69513a1e0d7 Mon Sep 17 00:00:00 2001
From: Andrey Borodin <amborodin@acm.org>
Date: Sat, 27 Feb 2021 09:03:50 +0500
Subject: [PATCH 01/12] Allow alternate compression methods for wal_compression

TODO: bump XLOG_PAGE_MAGIC
---
 doc/src/sgml/config.sgml                      | 17 +++++
 src/backend/Makefile                          |  2 +-
 src/backend/access/transam/xlog.c             | 10 +++
 src/backend/access/transam/xloginsert.c       | 67 ++++++++++++++++---
 src/backend/access/transam/xlogreader.c       | 64 +++++++++++++++++-
 src/backend/utils/misc/guc.c                  | 11 +++
 src/backend/utils/misc/postgresql.conf.sample |  1 +
 src/include/access/xlog.h                     |  1 +
 src/include/access/xlog_internal.h            | 16 +++++
 src/include/access/xlogrecord.h               | 11 ++-
 10 files changed, 187 insertions(+), 13 deletions(-)

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index ee4925d6d9..bed89d055d 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -3072,6 +3072,23 @@ include_dir 'conf.d'
       </listitem>
      </varlistentry>
 
+     <varlistentry id="guc-wal-compression-method" xreflabel="wal_compression_method">
+      <term><varname>wal_compressionion_method</varname> (<type>enum</type>)
+      <indexterm>
+       <primary><varname>wal_compression_method</varname> configuration parameter</primary>
+      </indexterm>
+      </term>
+      <listitem>
+       <para>
+        This parameter selects the compression method used to compress WAL when
+        <varname>wal_compression</varname> is enabled.
+        The supported methods are pglz and zlib.
+        The default value is <literal>pglz</literal>.
+        Only superusers can change this setting.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry id="guc-wal-init-zero" xreflabel="wal_init_zero">
       <term><varname>wal_init_zero</varname> (<type>boolean</type>)
       <indexterm>
diff --git a/src/backend/Makefile b/src/backend/Makefile
index 0da848b1fd..3af216ddfc 100644
--- a/src/backend/Makefile
+++ b/src/backend/Makefile
@@ -48,7 +48,7 @@ OBJS = \
 LIBS := $(filter-out -lpgport -lpgcommon, $(LIBS)) $(LDAP_LIBS_BE) $(ICU_LIBS)
 
 # The backend doesn't need everything that's in LIBS, however
-LIBS := $(filter-out -lz -lreadline -ledit -ltermcap -lncurses -lcurses, $(LIBS))
+LIBS := $(filter-out -lreadline -ledit -ltermcap -lncurses -lcurses, $(LIBS))
 
 ifeq ($(with_systemd),yes)
 LIBS += -lsystemd
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 6f8810e149..5b657ec724 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -99,6 +99,7 @@ bool		EnableHotStandby = false;
 bool		fullPageWrites = true;
 bool		wal_log_hints = false;
 bool		wal_compression = false;
+int			wal_compression_method = WAL_COMPRESSION_PGLZ;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
@@ -180,6 +181,15 @@ const struct config_enum_entry recovery_target_action_options[] = {
 	{NULL, 0, false}
 };
 
+/* Note that due to conditional compilation, offsets within the array are not static */
+const struct config_enum_entry wal_compression_options[] = {
+	{"pglz", WAL_COMPRESSION_PGLZ, false},
+#ifdef  HAVE_LIBZ
+	{"zlib", WAL_COMPRESSION_ZLIB, false},
+#endif
+	{NULL, 0, false}
+};
+
 /*
  * Statistics for current checkpoint are collected in this global struct.
  * Because only the checkpointer or a stand-alone backend can perform
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
index 7052dc245e..a93b33464f 100644
--- a/src/backend/access/transam/xloginsert.c
+++ b/src/backend/access/transam/xloginsert.c
@@ -33,8 +33,18 @@
 #include "storage/proc.h"
 #include "utils/memutils.h"
 
+#ifdef HAVE_LIBZ
+#include <zlib.h>
+/* zlib compressBound is not a macro */
+#define ZLIB_MAX_BLCKSZ		BLCKSZ + (BLCKSZ>>12) + (BLCKSZ>>14) + (BLCKSZ>>25) + 13
+#else
+#define ZLIB_MAX_BLCKSZ		0
+#endif
+
 /* Buffer size required to store a compressed version of backup block image */
-#define PGLZ_MAX_BLCKSZ PGLZ_MAX_OUTPUT(BLCKSZ)
+#define PGLZ_MAX_BLCKSZ		PGLZ_MAX_OUTPUT(BLCKSZ)
+
+#define COMPRESS_BUFSIZE	Max(PGLZ_MAX_BLCKSZ, ZLIB_MAX_BLCKSZ)
 
 /*
  * For each block reference registered with XLogRegisterBuffer, we fill in
@@ -58,7 +68,7 @@ typedef struct
 								 * backup block data in XLogRecordAssemble() */
 
 	/* buffer to store a compressed version of backup block image */
-	char		compressed_page[PGLZ_MAX_BLCKSZ];
+	char		compressed_page[COMPRESS_BUFSIZE];
 } registered_buffer;
 
 static registered_buffer *registered_buffers;
@@ -113,7 +123,8 @@ static XLogRecData *XLogRecordAssemble(RmgrId rmid, uint8 info,
 									   XLogRecPtr RedoRecPtr, bool doPageWrites,
 									   XLogRecPtr *fpw_lsn, int *num_fpi);
 static bool XLogCompressBackupBlock(char *page, uint16 hole_offset,
-									uint16 hole_length, char *dest, uint16 *dlen);
+									uint16 hole_length, char *dest,
+									uint16 *dlen, WalCompression compression);
 
 /*
  * Begin constructing a WAL record. This must be called before the
@@ -625,16 +636,26 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
 				cbimg.hole_length = 0;
 			}
 
+			bimg.bimg_info = (cbimg.hole_length == 0) ? 0 : BKPIMAGE_HAS_HOLE;
+
 			/*
 			 * Try to compress a block image if wal_compression is enabled
 			 */
 			if (wal_compression)
 			{
+				int compression;
+				/* The current compression is stored in the WAL record */
+				wal_compression_name(wal_compression_method); /* Range check */
+				compression = walmethods[wal_compression_method].walmethod;
+				Assert(compression < (1 << BKPIMAGE_COMPRESS_BITS));
+				bimg.bimg_info |=
+					compression << BKPIMAGE_COMPRESS_OFFSET_BITS;
 				is_compressed =
 					XLogCompressBackupBlock(page, bimg.hole_offset,
 											cbimg.hole_length,
 											regbuf->compressed_page,
-											&compressed_len);
+											&compressed_len,
+											wal_compression_method);
 			}
 
 			/*
@@ -652,8 +673,6 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
 			rdt_datas_last->next = &regbuf->bkp_rdatas[0];
 			rdt_datas_last = rdt_datas_last->next;
 
-			bimg.bimg_info = (cbimg.hole_length == 0) ? 0 : BKPIMAGE_HAS_HOLE;
-
 			/*
 			 * If WAL consistency checking is enabled for the resource manager
 			 * of this WAL record, a full-page image is included in the record
@@ -827,7 +846,7 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
  */
 static bool
 XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
-						char *dest, uint16 *dlen)
+						char *dest, uint16 *dlen, WalCompression compression)
 {
 	int32		orig_len = BLCKSZ - hole_length;
 	int32		len;
@@ -853,12 +872,42 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 	else
 		source = page;
 
+	switch (compression)
+	{
+	case WAL_COMPRESSION_PGLZ:
+		len = pglz_compress(source, orig_len, dest, PGLZ_strategy_default);
+		break;
+
+#ifdef HAVE_LIBZ
+	case WAL_COMPRESSION_ZLIB:
+		{
+			unsigned long	len_l = COMPRESS_BUFSIZE;
+			int ret;
+			ret = compress2((Bytef*)dest, &len_l, (Bytef*)source, orig_len, 1);
+			if (ret != Z_OK)
+				len_l = -1;
+			len = len_l;
+			break;
+		}
+#endif
+
+	default:
+		/*
+		 * It should be impossible to get here for unsupported algorithms,
+		 * which cannot be assigned if they're not enabled at compile time.
+		 */
+		ereport(ERROR,
+			(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			 errmsg("unknown compression method requested: %d(%s)",
+				 compression, wal_compression_name(compression))));
+
+	}
+
 	/*
-	 * We recheck the actual size even if pglz_compress() reports success and
+	 * We recheck the actual size even if compression reports success and
 	 * see if the number of bytes saved by compression is larger than the
 	 * length of extra data needed for the compressed version of block image.
 	 */
-	len = pglz_compress(source, orig_len, dest, PGLZ_strategy_default);
 	if (len >= 0 &&
 		len + extra_bytes < orig_len)
 	{
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index 42738eb940..0d8830fc50 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -33,6 +33,10 @@
 #include "utils/memutils.h"
 #endif
 
+#ifdef HAVE_LIBZ
+#include <zlib.h>
+#endif
+
 static void report_invalid_record(XLogReaderState *state, const char *fmt,...)
 			pg_attribute_printf(2, 3);
 static bool allocate_recordbuf(XLogReaderState *state, uint32 reclength);
@@ -1535,6 +1539,30 @@ XLogRecGetBlockData(XLogReaderState *record, uint8 block_id, Size *len)
 	}
 }
 
+/* This is a mapping indexed by wal_compression */
+// XXX: maybe this is better done as a GUC hook to assign the 1) method; and 2) level
+struct walcompression walmethods[] = {
+	{"pglz",	WAL_COMPRESSION_PGLZ},
+	{"zlib",	WAL_COMPRESSION_ZLIB},
+};
+
+/*
+ * Return a statically allocated string associated with the given compression
+ * method.
+ * This is here to be visible to frontend tools like pg_rewind.
+ */
+const char *
+wal_compression_name(WalCompression compression)
+{
+	/*
+	 * This could index into the guc array, except that it's compiled
+	 * conditionally and unsupported methods are elided.
+	 */
+	if (compression < sizeof(walmethods)/sizeof(*walmethods))
+		return walmethods[compression].name;
+	return "???";
+}
+
 /*
  * Restore a full-page image from a backup block attached to an XLOG record.
  *
@@ -1557,9 +1585,41 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 
 	if (bkpb->bimg_info & BKPIMAGE_IS_COMPRESSED)
 	{
+		int compression_method = BKPIMAGE_COMPRESSION(bkpb->bimg_info);
 		/* If a backup block image is compressed, decompress it */
-		if (pglz_decompress(ptr, bkpb->bimg_len, tmp.data,
-							BLCKSZ - bkpb->hole_length, true) < 0)
+		int32 decomp_result = -1;
+		switch (compression_method)
+		{
+		case WAL_COMPRESSION_PGLZ:
+			decomp_result = pglz_decompress(ptr, bkpb->bimg_len, tmp.data,
+							BLCKSZ - bkpb->hole_length, true);
+			break;
+
+#ifdef HAVE_LIBZ
+		case WAL_COMPRESSION_ZLIB:
+		{
+			unsigned long decomp_result_l;
+			decomp_result_l = BLCKSZ - bkpb->hole_length;
+			if (uncompress((Bytef*)tmp.data, &decomp_result_l,
+						(Bytef*)ptr, bkpb->bimg_len) == Z_OK)
+				decomp_result = decomp_result_l;
+			else
+				decomp_result = -1;
+			break;
+		}
+#endif
+
+		default:
+			report_invalid_record(record, "image at %X/%X is compressed with unsupported codec, block %d (%d/%s)",
+								  (uint32) (record->ReadRecPtr >> 32),
+								  (uint32) record->ReadRecPtr,
+								  block_id,
+								  compression_method,
+								  wal_compression_name(compression_method));
+			return false;
+		}
+
+		if (decomp_result < 0)
 		{
 			report_invalid_record(record, "invalid compressed image at %X/%X, block %d",
 								  LSN_FORMAT_ARGS(record->ReadRecPtr),
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 3b36a31a47..47d30d6cda 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -517,6 +517,7 @@ extern const struct config_enum_entry archive_mode_options[];
 extern const struct config_enum_entry recovery_target_action_options[];
 extern const struct config_enum_entry sync_method_options[];
 extern const struct config_enum_entry dynamic_shared_memory_options[];
+extern const struct config_enum_entry wal_compression_options[];
 
 /*
  * GUC option variables that are exported from this module
@@ -4760,6 +4761,16 @@ static struct config_enum ConfigureNamesEnum[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"wal_compression_method", PGC_SIGHUP, WAL_SETTINGS,
+			gettext_noop("Set the method used to compress full page images in the WAL."),
+			NULL
+		},
+		&wal_compression_method,
+		WAL_COMPRESSION_PGLZ, wal_compression_options,
+		NULL, NULL, NULL
+	},
+
 	{
 		{"dynamic_shared_memory_type", PGC_POSTMASTER, RESOURCES_MEM,
 			gettext_noop("Selects the dynamic shared memory implementation used."),
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 86425965d0..530007f55a 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -213,6 +213,7 @@
 					#   open_sync
 #full_page_writes = on			# recover from partial page writes
 #wal_compression = off			# enable compression of full-page writes
+#wal_compression_method = pglz		# pglz, zlib
 #wal_log_hints = off			# also do full page writes of non-critical updates
 					# (change requires restart)
 #wal_init_zero = on			# zero-fill new WAL files
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index 77187c12be..2f3886431a 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -117,6 +117,7 @@ extern bool EnableHotStandby;
 extern bool fullPageWrites;
 extern bool wal_log_hints;
 extern bool wal_compression;
+extern int	wal_compression_method;
 extern bool wal_init_zero;
 extern bool wal_recycle;
 extern bool *wal_consistency_checking;
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index b23e286406..b000a21557 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -324,4 +324,20 @@ extern bool InArchiveRecovery;
 extern bool StandbyMode;
 extern char *recoveryRestoreCommand;
 
+struct walcompression
+{
+	char	*name;
+	int	walmethod;	/* Compression method to be stored in WAL */
+};
+
+extern struct walcompression walmethods[];
+
+typedef enum WalCompression
+{
+	WAL_COMPRESSION_PGLZ,
+	WAL_COMPRESSION_ZLIB,
+} WalCompression;
+
+extern const char *wal_compression_name(WalCompression compression);
+
 #endif							/* XLOG_INTERNAL_H */
diff --git a/src/include/access/xlogrecord.h b/src/include/access/xlogrecord.h
index 80c92a2498..7107cf6186 100644
--- a/src/include/access/xlogrecord.h
+++ b/src/include/access/xlogrecord.h
@@ -114,7 +114,7 @@ typedef struct XLogRecordBlockHeader
  * present is (BLCKSZ - <length of "hole" bytes>).
  *
  * Additionally, when wal_compression is enabled, we will try to compress full
- * page images using the PGLZ compression algorithm, after removing the "hole".
+ * page images, after removing the "hole".
  * This can reduce the WAL volume, but at some extra cost of CPU spent
  * on the compression during WAL logging. In this case, since the "hole"
  * length cannot be calculated by subtracting the number of page image bytes
@@ -147,6 +147,15 @@ typedef struct XLogRecordBlockImageHeader
 #define BKPIMAGE_IS_COMPRESSED		0x02	/* page image is compressed */
 #define BKPIMAGE_APPLY		0x04	/* page image should be restored during
 									 * replay */
+#define BKPIMAGE_COMPRESS_METHOD1	0x08	/* bits to encode compression method */
+#define BKPIMAGE_COMPRESS_METHOD2	0x10	/* 0=pglz; 1=zlib; */
+
+/* How many bits to shift to extract compression */
+#define	BKPIMAGE_COMPRESS_OFFSET_BITS	3
+/* How many bits are for compression */
+#define	BKPIMAGE_COMPRESS_BITS		2
+/* Extract the compression from the bimg_info */
+#define	BKPIMAGE_COMPRESSION(info)	((info >> BKPIMAGE_COMPRESS_OFFSET_BITS) & ((1<<BKPIMAGE_COMPRESS_BITS) - 1))
 
 /*
  * Extra header information used when page image has "hole" and
-- 
2.17.0

From e56ace2831572babcbc6b62d66bf9f6d63aff29d Mon Sep 17 00:00:00 2001
From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Date: Mon, 8 Mar 2021 15:32:30 +0900
Subject: [PATCH 02/12] Run 011_crash_recovery.pl with wal_level=minimal

The test doesn't need that feature and pg_current_xact_id() is better
exercised by turning off the feature.

Copied from: https://www.postgresql.org/message-id/20210308.173242.463790587797836129.horikyota.ntt%40gmail.com
---
 src/test/recovery/t/011_crash_recovery.pl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/test/recovery/t/011_crash_recovery.pl b/src/test/recovery/t/011_crash_recovery.pl
index 10cd98f70a..690655dda2 100644
--- a/src/test/recovery/t/011_crash_recovery.pl
+++ b/src/test/recovery/t/011_crash_recovery.pl
@@ -11,7 +11,7 @@ use Config;
 plan tests => 3;
 
 my $node = get_new_node('primary');
-$node->init(allows_streaming => 1);
+$node->init();
 $node->start;
 
 my ($stdin, $stdout, $stderr) = ('', '', '');
-- 
2.17.0

From cbde244f9f6a804172d13870efd6327ad8c4ce4c Mon Sep 17 00:00:00 2001
From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Date: Mon, 8 Mar 2021 15:43:01 +0900
Subject: [PATCH 03/12] Make sure published XIDs are persistent

pg_xact_status() premises that XIDs obtained by
pg_current_xact_id(_if_assigned)() are persistent beyond a crash. But
XIDs are not guaranteed to go beyond WAL buffers before commit and
thus XIDs may vanish if server crashes before commit. This patch
guarantees the XID shown by the functions to be flushed out to disk.

Copied from: https://www.postgresql.org/message-id/20210308.173242.463790587797836129.horikyota.ntt%40gmail.com
---
 src/backend/access/transam/xact.c | 55 +++++++++++++++++++++++++------
 src/backend/access/transam/xlog.c |  2 +-
 src/backend/utils/adt/xid8funcs.c | 12 ++++++-
 src/include/access/xact.h         |  3 +-
 4 files changed, 59 insertions(+), 13 deletions(-)

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 6395a9b240..38e978d238 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -201,7 +201,7 @@ typedef struct TransactionStateData
 	int			prevSecContext; /* previous SecurityRestrictionContext */
 	bool		prevXactReadOnly;	/* entry-time xact r/o state */
 	bool		startedInRecovery;	/* did we start in recovery? */
-	bool		didLogXid;		/* has xid been included in WAL record? */
+	XLogRecPtr 	minLSN;			/* LSN needed to reach to record the xid */
 	int			parallelModeLevel;	/* Enter/ExitParallelMode counter */
 	bool		chain;			/* start a new block after this one */
 	bool		assigned;		/* assigned to top-level XID */
@@ -520,14 +520,46 @@ GetCurrentFullTransactionIdIfAny(void)
  *	MarkCurrentTransactionIdLoggedIfAny
  *
  * Remember that the current xid - if it is assigned - now has been wal logged.
+ *
+ * upto is the LSN up to which we need to flush WAL to ensure the current xid
+ * to be persistent. See EnsureCurrentTransactionIdLogged().
  */
 void
-MarkCurrentTransactionIdLoggedIfAny(void)
+MarkCurrentTransactionIdLoggedIfAny(XLogRecPtr upto)
 {
-	if (FullTransactionIdIsValid(CurrentTransactionState->fullTransactionId))
-		CurrentTransactionState->didLogXid = true;
+	if (FullTransactionIdIsValid(CurrentTransactionState->fullTransactionId) &&
+		XLogRecPtrIsInvalid(CurrentTransactionState->minLSN))
+		CurrentTransactionState->minLSN = upto;
 }
 
+/*
+ *	EnsureCurrentTransactionIdLogged
+ *
+ * Make sure that the current top XID is WAL-logged.
+ */
+void
+EnsureTopTransactionIdLogged(void)
+{
+	/*
+	 * We need at least one WAL record for the current top transaction to be
+	 * flushed out.  Write one if we don't have one yet.
+	 */
+	if (XLogRecPtrIsInvalid(TopTransactionStateData.minLSN))
+	{
+		xl_xact_assignment xlrec;
+
+		xlrec.xtop = XidFromFullTransactionId(XactTopFullTransactionId);
+		Assert(TransactionIdIsValid(xlrec.xtop));
+		xlrec.nsubxacts = 0;
+
+		XLogBeginInsert();
+		XLogRegisterData((char *) &xlrec, MinSizeOfXactAssignment);
+		TopTransactionStateData.minLSN =
+			XLogInsert(RM_XACT_ID, XLOG_XACT_ASSIGNMENT);
+	}
+
+	XLogFlush(TopTransactionStateData.minLSN);
+}
 
 /*
  *	GetStableLatestTransactionId
@@ -616,14 +648,14 @@ AssignTransactionId(TransactionState s)
 	 * When wal_level=logical, guarantee that a subtransaction's xid can only
 	 * be seen in the WAL stream if its toplevel xid has been logged before.
 	 * If necessary we log an xact_assignment record with fewer than
-	 * PGPROC_MAX_CACHED_SUBXIDS. Note that it is fine if didLogXid isn't set
+	 * PGPROC_MAX_CACHED_SUBXIDS. Note that it is fine if minLSN isn't set
 	 * for a transaction even though it appears in a WAL record, we just might
 	 * superfluously log something. That can happen when an xid is included
 	 * somewhere inside a wal record, but not in XLogRecord->xl_xid, like in
 	 * xl_standby_locks.
 	 */
 	if (isSubXact && XLogLogicalInfoActive() &&
-		!TopTransactionStateData.didLogXid)
+		XLogRecPtrIsInvalid(TopTransactionStateData.minLSN))
 		log_unknown_top = true;
 
 	/*
@@ -693,6 +725,7 @@ AssignTransactionId(TransactionState s)
 			log_unknown_top)
 		{
 			xl_xact_assignment xlrec;
+			XLogRecPtr		   endptr;
 
 			/*
 			 * xtop is always set by now because we recurse up transaction
@@ -707,11 +740,13 @@ AssignTransactionId(TransactionState s)
 			XLogRegisterData((char *) unreportedXids,
 							 nUnreportedXids * sizeof(TransactionId));
 
-			(void) XLogInsert(RM_XACT_ID, XLOG_XACT_ASSIGNMENT);
+			endptr = XLogInsert(RM_XACT_ID, XLOG_XACT_ASSIGNMENT);
 
 			nUnreportedXids = 0;
-			/* mark top, not current xact as having been logged */
-			TopTransactionStateData.didLogXid = true;
+
+			/* set minLSN of top, not of current xact if not yet */
+			if (XLogRecPtrIsInvalid(TopTransactionStateData.minLSN))
+				TopTransactionStateData.minLSN = endptr;
 		}
 	}
 }
@@ -2022,7 +2057,7 @@ StartTransaction(void)
 	 * initialize reported xid accounting
 	 */
 	nUnreportedXids = 0;
-	s->didLogXid = false;
+	s->minLSN = InvalidXLogRecPtr;
 
 	/*
 	 * must initialize resource-management stuff first
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 5b657ec724..8db3727502 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -1172,7 +1172,7 @@ XLogInsertRecord(XLogRecData *rdata,
 	 */
 	WALInsertLockRelease();
 
-	MarkCurrentTransactionIdLoggedIfAny();
+	MarkCurrentTransactionIdLoggedIfAny(EndPos);
 
 	END_CRIT_SECTION();
 
diff --git a/src/backend/utils/adt/xid8funcs.c b/src/backend/utils/adt/xid8funcs.c
index cc2b4ac797..992482f8c8 100644
--- a/src/backend/utils/adt/xid8funcs.c
+++ b/src/backend/utils/adt/xid8funcs.c
@@ -357,6 +357,8 @@ bad_format:
 Datum
 pg_current_xact_id(PG_FUNCTION_ARGS)
 {
+	FullTransactionId xid;
+
 	/*
 	 * Must prevent during recovery because if an xid is not assigned we try
 	 * to assign one, which would fail. Programs already rely on this function
@@ -365,7 +367,12 @@ pg_current_xact_id(PG_FUNCTION_ARGS)
 	 */
 	PreventCommandDuringRecovery("pg_current_xact_id()");
 
-	PG_RETURN_FULLTRANSACTIONID(GetTopFullTransactionId());
+	xid = GetTopFullTransactionId();
+
+	/* the XID is going to be published, make sure it is psersistent */
+	EnsureTopTransactionIdLogged();
+
+	PG_RETURN_FULLTRANSACTIONID(xid);
 }
 
 /*
@@ -380,6 +387,9 @@ pg_current_xact_id_if_assigned(PG_FUNCTION_ARGS)
 	if (!FullTransactionIdIsValid(topfxid))
 		PG_RETURN_NULL();
 
+	/* the XID is going to be published, make sure it is psersistent */
+	EnsureTopTransactionIdLogged();
+
 	PG_RETURN_FULLTRANSACTIONID(topfxid);
 }
 
diff --git a/src/include/access/xact.h b/src/include/access/xact.h
index 34cfaf542c..a61e4d6da5 100644
--- a/src/include/access/xact.h
+++ b/src/include/access/xact.h
@@ -386,7 +386,8 @@ extern FullTransactionId GetTopFullTransactionId(void);
 extern FullTransactionId GetTopFullTransactionIdIfAny(void);
 extern FullTransactionId GetCurrentFullTransactionId(void);
 extern FullTransactionId GetCurrentFullTransactionIdIfAny(void);
-extern void MarkCurrentTransactionIdLoggedIfAny(void);
+extern void MarkCurrentTransactionIdLoggedIfAny(XLogRecPtr upto);
+extern void EnsureTopTransactionIdLogged(void);
 extern bool SubTransactionIsActive(SubTransactionId subxid);
 extern CommandId GetCurrentCommandId(bool used);
 extern void SetParallelStartTimestamps(TimestampTz xact_ts, TimestampTz stmt_ts);
-- 
2.17.0

From 4573d92f93b4942e8d386adddcbfd2b369392963 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Thu, 11 Mar 2021 17:36:24 -0600
Subject: [PATCH 04/12] wal_compression_method: default to zlib..

this is meant to exercise the CIs, and not meant to be merged
---
 src/backend/access/transam/xlog.c | 2 +-
 src/backend/utils/misc/guc.c      | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 8db3727502..3ece007922 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -99,7 +99,7 @@ bool		EnableHotStandby = false;
 bool		fullPageWrites = true;
 bool		wal_log_hints = false;
 bool		wal_compression = false;
-int			wal_compression_method = WAL_COMPRESSION_PGLZ;
+int			wal_compression_method = WAL_COMPRESSION_ZLIB;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 47d30d6cda..15649bd2a7 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -1288,7 +1288,7 @@ static struct config_bool ConfigureNamesBool[] =
 			NULL
 		},
 		&wal_compression,
-		false,
+		true,
 		NULL, NULL, NULL
 	},
 
@@ -4767,7 +4767,7 @@ static struct config_enum ConfigureNamesEnum[] =
 			NULL
 		},
 		&wal_compression_method,
-		WAL_COMPRESSION_PGLZ, wal_compression_options,
+		WAL_COMPRESSION_ZLIB, wal_compression_options,
 		NULL, NULL, NULL
 	},
 
-- 
2.17.0

From ef0986c310822eeeb11032807b468958e798bb6b Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Fri, 12 Mar 2021 14:32:10 -0600
Subject: [PATCH 05/12] (re)add wal_compression_method: lz4

---
 doc/src/sgml/config.sgml                      |  3 ++-
 src/backend/access/transam/xlog.c             |  3 +++
 src/backend/access/transam/xloginsert.c       | 17 ++++++++++++++++-
 src/backend/access/transam/xlogreader.c       | 12 ++++++++++++
 src/backend/utils/misc/postgresql.conf.sample |  2 +-
 src/include/access/xlog_internal.h            |  1 +
 6 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index bed89d055d..1f21e96922 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -3082,7 +3082,8 @@ include_dir 'conf.d'
        <para>
         This parameter selects the compression method used to compress WAL when
         <varname>wal_compression</varname> is enabled.
-        The supported methods are pglz and zlib.
+        The supported methods are pglz, zlib, and (if configured when
+        <productname>PostgreSQL</productname> was built) lz4.
         The default value is <literal>pglz</literal>.
         Only superusers can change this setting.
        </para>
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 3ece007922..23f5bdc335 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -186,6 +186,9 @@ const struct config_enum_entry wal_compression_options[] = {
 	{"pglz", WAL_COMPRESSION_PGLZ, false},
 #ifdef  HAVE_LIBZ
 	{"zlib", WAL_COMPRESSION_ZLIB, false},
+#endif
+#ifdef  USE_LZ4
+	{"lz4", WAL_COMPRESSION_LZ4, false},
 #endif
 	{NULL, 0, false}
 };
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
index a93b33464f..3c15286bd8 100644
--- a/src/backend/access/transam/xloginsert.c
+++ b/src/backend/access/transam/xloginsert.c
@@ -41,10 +41,17 @@
 #define ZLIB_MAX_BLCKSZ		0
 #endif
 
+#ifdef USE_LZ4
+#include "lz4.h"
+#define	LZ4_MAX_BLCKSZ		LZ4_COMPRESSBOUND(BLCKSZ)
+#else
+#define LZ4_MAX_BLCKSZ		0
+#endif
+
 /* Buffer size required to store a compressed version of backup block image */
 #define PGLZ_MAX_BLCKSZ		PGLZ_MAX_OUTPUT(BLCKSZ)
 
-#define COMPRESS_BUFSIZE	Max(PGLZ_MAX_BLCKSZ, ZLIB_MAX_BLCKSZ)
+#define COMPRESS_BUFSIZE	Max(Max(PGLZ_MAX_BLCKSZ, ZLIB_MAX_BLCKSZ), LZ4_MAX_BLCKSZ)
 
 /*
  * For each block reference registered with XLogRegisterBuffer, we fill in
@@ -891,6 +898,14 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 		}
 #endif
 
+#ifdef USE_LZ4
+	case WAL_COMPRESSION_LZ4:
+		len = LZ4_compress_fast(source, dest, orig_len, COMPRESS_BUFSIZE, 1);
+		if (len == 0)
+			len = -1;
+		break;
+#endif
+
 	default:
 		/*
 		 * It should be impossible to get here for unsupported algorithms,
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index 0d8830fc50..97165f1bb1 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -37,6 +37,10 @@
 #include <zlib.h>
 #endif
 
+#ifdef USE_LZ4
+#include "lz4.h"
+#endif
+
 static void report_invalid_record(XLogReaderState *state, const char *fmt,...)
 			pg_attribute_printf(2, 3);
 static bool allocate_recordbuf(XLogReaderState *state, uint32 reclength);
@@ -1544,6 +1548,7 @@ XLogRecGetBlockData(XLogReaderState *record, uint8 block_id, Size *len)
 struct walcompression walmethods[] = {
 	{"pglz",	WAL_COMPRESSION_PGLZ},
 	{"zlib",	WAL_COMPRESSION_ZLIB},
+	{"lz4",		WAL_COMPRESSION_LZ4},
 };
 
 /*
@@ -1609,6 +1614,13 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 		}
 #endif
 
+#ifdef USE_LZ4
+		case WAL_COMPRESSION_LZ4:
+			decomp_result = LZ4_decompress_safe(ptr, tmp.data,
+					bkpb->bimg_len, BLCKSZ-bkpb->hole_length);
+			break;
+#endif
+
 		default:
 			report_invalid_record(record, "image at %X/%X is compressed with unsupported codec, block %d (%d/%s)",
 								  (uint32) (record->ReadRecPtr >> 32),
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 530007f55a..2a2bccbe5c 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -213,7 +213,7 @@
 					#   open_sync
 #full_page_writes = on			# recover from partial page writes
 #wal_compression = off			# enable compression of full-page writes
-#wal_compression_method = pglz		# pglz, zlib
+#wal_compression_method = pglz		# pglz, zlib, lz4
 #wal_log_hints = off			# also do full page writes of non-critical updates
 					# (change requires restart)
 #wal_init_zero = on			# zero-fill new WAL files
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index b000a21557..b908fa48de 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -336,6 +336,7 @@ typedef enum WalCompression
 {
 	WAL_COMPRESSION_PGLZ,
 	WAL_COMPRESSION_ZLIB,
+	WAL_COMPRESSION_LZ4,
 } WalCompression;
 
 extern const char *wal_compression_name(WalCompression compression);
-- 
2.17.0

From 681581da96357f1519607f09a3c57aec55d84a65 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Fri, 12 Mar 2021 14:43:53 -0600
Subject: [PATCH 06/12] add wal_compression_method: zstd

---
 configure                                     | 163 ++++++++++++++++++
 configure.ac                                  |  26 +++
 doc/src/sgml/config.sgml                      |   2 +-
 src/backend/access/transam/xlog.c             |   3 +
 src/backend/access/transam/xloginsert.c       |  18 +-
 src/backend/access/transam/xlogreader.c       |  15 ++
 src/backend/utils/misc/postgresql.conf.sample |   2 +-
 src/include/access/xlog_internal.h            |   1 +
 src/include/pg_config.h.in                    |   3 +
 src/tools/msvc/Solution.pm                    |   1 +
 10 files changed, 231 insertions(+), 3 deletions(-)

diff --git a/configure b/configure
index 6d34243dca..24824ba6c9 100755
--- a/configure
+++ b/configure
@@ -699,6 +699,9 @@ with_gnu_ld
 LD
 LDFLAGS_SL
 LDFLAGS_EX
+ZSTD_LIBS
+ZSTD_CFLAGS
+with_zstd
 LZ4_LIBS
 LZ4_CFLAGS
 with_lz4
@@ -868,6 +871,7 @@ with_libxslt
 with_system_tzdata
 with_zlib
 with_lz4
+with_zstd
 with_gnu_ld
 with_ssl
 with_openssl
@@ -897,6 +901,8 @@ XML2_CFLAGS
 XML2_LIBS
 LZ4_CFLAGS
 LZ4_LIBS
+ZSTD_CFLAGS
+ZSTD_LIBS
 LDFLAGS_EX
 LDFLAGS_SL
 PERL
@@ -1576,6 +1582,7 @@ Optional Packages:
                           use system time zone data in DIR
   --without-zlib          do not use Zlib
   --with-lz4              build with LZ4 support
+  --with-zstd             build with Zstd compression library
   --with-gnu-ld           assume the C compiler uses GNU ld [default=no]
   --with-ssl=LIB          use LIB for SSL/TLS support (openssl)
   --with-openssl          obsolete spelling of --with-ssl=openssl
@@ -1605,6 +1612,8 @@ Some influential environment variables:
   XML2_LIBS   linker flags for XML2, overriding pkg-config
   LZ4_CFLAGS  C compiler flags for LZ4, overriding pkg-config
   LZ4_LIBS    linker flags for LZ4, overriding pkg-config
+  ZSTD_CFLAGS C compiler flags for ZSTD, overriding pkg-config
+  ZSTD_LIBS   linker flags for ZSTD, overriding pkg-config
   LDFLAGS_EX  extra linker flags for linking executables only
   LDFLAGS_SL  extra linker flags for linking shared libraries only
   PERL        Perl program
@@ -8703,6 +8712,137 @@ fi
   CFLAGS="$LZ4_CFLAGS $CFLAGS"
 fi
 
+#
+# ZSTD
+#
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether to build with zstd support" >&5
+$as_echo_n "checking whether to build with zstd support... " >&6; }
+
+
+
+# Check whether --with-zstd was given.
+if test "${with_zstd+set}" = set; then :
+  withval=$with_zstd;
+  case $withval in
+    yes)
+
+$as_echo "#define USE_ZSTD 1" >>confdefs.h
+
+      ;;
+    no)
+      :
+      ;;
+    *)
+      as_fn_error $? "no argument expected for --with-zstd option" "$LINENO" 5
+      ;;
+  esac
+
+else
+  with_zstd=no
+
+fi
+
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $with_zstd" >&5
+$as_echo "$with_zstd" >&6; }
+
+
+if test "$with_zstd" = yes; then
+
+pkg_failed=no
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for libzstd" >&5
+$as_echo_n "checking for libzstd... " >&6; }
+
+if test -n "$ZSTD_CFLAGS"; then
+    pkg_cv_ZSTD_CFLAGS="$ZSTD_CFLAGS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"libzstd\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "libzstd") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_ZSTD_CFLAGS=`$PKG_CONFIG --cflags "libzstd" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+if test -n "$ZSTD_LIBS"; then
+    pkg_cv_ZSTD_LIBS="$ZSTD_LIBS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"libzstd\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "libzstd") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_ZSTD_LIBS=`$PKG_CONFIG --libs "libzstd" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+
+
+
+if test $pkg_failed = yes; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+
+if $PKG_CONFIG --atleast-pkgconfig-version 0.20; then
+        _pkg_short_errors_supported=yes
+else
+        _pkg_short_errors_supported=no
+fi
+        if test $_pkg_short_errors_supported = yes; then
+	        ZSTD_PKG_ERRORS=`$PKG_CONFIG --short-errors --print-errors --cflags --libs "libzstd" 2>&1`
+        else
+	        ZSTD_PKG_ERRORS=`$PKG_CONFIG --print-errors --cflags --libs "libzstd" 2>&1`
+        fi
+	# Put the nasty error message in config.log where it belongs
+	echo "$ZSTD_PKG_ERRORS" >&5
+
+	as_fn_error $? "Package requirements (libzstd) were not met:
+
+$ZSTD_PKG_ERRORS
+
+Consider adjusting the PKG_CONFIG_PATH environment variable if you
+installed software in a non-standard prefix.
+
+Alternatively, you may set the environment variables ZSTD_CFLAGS
+and ZSTD_LIBS to avoid the need to call pkg-config.
+See the pkg-config man page for more details." "$LINENO" 5
+elif test $pkg_failed = untried; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+	{ { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error $? "The pkg-config script could not be found or is too old.  Make sure it
+is in your PATH or set the PKG_CONFIG environment variable to the full
+path to pkg-config.
+
+Alternatively, you may set the environment variables ZSTD_CFLAGS
+and ZSTD_LIBS to avoid the need to call pkg-config.
+See the pkg-config man page for more details.
+
+To get pkg-config, see <http://pkg-config.freedesktop.org/>.
+See \`config.log' for more details" "$LINENO" 5; }
+else
+	ZSTD_CFLAGS=$pkg_cv_ZSTD_CFLAGS
+	ZSTD_LIBS=$pkg_cv_ZSTD_LIBS
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+
+fi
+  LIBS="$ZSTD_LIBS $LIBS"
+  CFLAGS="$ZSTD_CFLAGS $CFLAGS"
+fi
+
 #
 # Assignments
 #
@@ -13551,6 +13691,29 @@ done
 
 fi
 
+if test "$with_zstd" = yes; then
+  ac_save_CPPFLAGS=$CPPFLAGS
+  CPPFLAGS="$ZSTD_CFLAGS $CPPFLAGS"
+
+  # Verify we have zstd's header files
+  for ac_header in zstd.h
+do :
+  ac_fn_c_check_header_mongrel "$LINENO" "zstd.h" "ac_cv_header_zstd_h" "$ac_includes_default"
+if test "x$ac_cv_header_zstd_h" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_ZSTD_H 1
+_ACEOF
+
+else
+  as_fn_error $? "zstd.h header file is required for zstd" "$LINENO" 5
+fi
+
+done
+
+
+  CPPFLAGS=$ac_save_CPPFLAGS
+fi
+
 if test "$with_gssapi" = yes ; then
   for ac_header in gssapi/gssapi.h
 do :
diff --git a/configure.ac b/configure.ac
index e54e2fb632..5840085177 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1001,6 +1001,21 @@ if test "$with_lz4" = yes; then
   CFLAGS="$LZ4_CFLAGS $CFLAGS"
 fi
 
+#
+# ZSTD
+#
+AC_MSG_CHECKING([whether to build with zstd support])
+PGAC_ARG_BOOL(with, zstd, no, [build with Zstd compression library],
+              [AC_DEFINE([USE_ZSTD], 1, [Define to 1 to build with zstd support. (--with-zstd)])])
+AC_MSG_RESULT([$with_zstd])
+AC_SUBST(with_zstd)
+
+if test "$with_zstd" = yes; then
+  PKG_CHECK_MODULES(ZSTD, libzstd)
+  LIBS="$ZSTD_LIBS $LIBS"
+  CFLAGS="$ZSTD_CFLAGS $CFLAGS"
+fi
+
 #
 # Assignments
 #
@@ -1430,6 +1445,17 @@ if test "$with_lz4" = yes; then
        [AC_CHECK_HEADERS(lz4.h, [], [AC_MSG_ERROR([lz4.h header file is required for LZ4])])])
 fi
 
+if test "$with_zstd" = yes; then
+  ac_save_CPPFLAGS=$CPPFLAGS
+  CPPFLAGS="$ZSTD_CFLAGS $CPPFLAGS"
+
+  # Verify we have zstd's header files
+  AC_CHECK_HEADERS(zstd.h, [],
+       [AC_MSG_ERROR([zstd.h header file is required for zstd])])
+
+  CPPFLAGS=$ac_save_CPPFLAGS
+fi
+
 if test "$with_gssapi" = yes ; then
   AC_CHECK_HEADERS(gssapi/gssapi.h, [],
 	[AC_CHECK_HEADERS(gssapi.h, [], [AC_MSG_ERROR([gssapi.h header file is required for GSSAPI])])])
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 1f21e96922..429a1d44d9 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -3083,7 +3083,7 @@ include_dir 'conf.d'
         This parameter selects the compression method used to compress WAL when
         <varname>wal_compression</varname> is enabled.
         The supported methods are pglz, zlib, and (if configured when
-        <productname>PostgreSQL</productname> was built) lz4.
+        <productname>PostgreSQL</productname> was built) lz4 and zstd.
         The default value is <literal>pglz</literal>.
         Only superusers can change this setting.
        </para>
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 23f5bdc335..a745ea11f5 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -189,6 +189,9 @@ const struct config_enum_entry wal_compression_options[] = {
 #endif
 #ifdef  USE_LZ4
 	{"lz4", WAL_COMPRESSION_LZ4, false},
+#endif
+#ifdef  USE_ZSTD
+	{"zstd", WAL_COMPRESSION_ZSTD, false},
 #endif
 	{NULL, 0, false}
 };
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
index 3c15286bd8..4591e476c6 100644
--- a/src/backend/access/transam/xloginsert.c
+++ b/src/backend/access/transam/xloginsert.c
@@ -48,10 +48,17 @@
 #define LZ4_MAX_BLCKSZ		0
 #endif
 
+#ifdef USE_ZSTD
+#include "zstd.h"
+#define ZSTD_MAX_BLCKSZ		ZSTD_COMPRESSBOUND(BLCKSZ)
+#else
+#define ZSTD_MAX_BLCKSZ		0
+#endif
+
 /* Buffer size required to store a compressed version of backup block image */
 #define PGLZ_MAX_BLCKSZ		PGLZ_MAX_OUTPUT(BLCKSZ)
 
-#define COMPRESS_BUFSIZE	Max(Max(PGLZ_MAX_BLCKSZ, ZLIB_MAX_BLCKSZ), LZ4_MAX_BLCKSZ)
+#define COMPRESS_BUFSIZE	Max(Max(Max(PGLZ_MAX_BLCKSZ, ZLIB_MAX_BLCKSZ), LZ4_MAX_BLCKSZ), ZSTD_MAX_BLCKSZ)
 
 /*
  * For each block reference registered with XLogRegisterBuffer, we fill in
@@ -906,6 +913,15 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 		break;
 #endif
 
+#ifdef USE_ZSTD
+	case WAL_COMPRESSION_ZSTD:
+		len = ZSTD_compress(dest, COMPRESS_BUFSIZE, source, orig_len,
+				ZSTD_CLEVEL_DEFAULT);
+		if (ZSTD_isError(len))
+			len = -1;
+		break;
+#endif
+
 	default:
 		/*
 		 * It should be impossible to get here for unsupported algorithms,
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index 97165f1bb1..0f9d522087 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -41,6 +41,10 @@
 #include "lz4.h"
 #endif
 
+#ifdef USE_ZSTD
+#include "zstd.h"
+#endif
+
 static void report_invalid_record(XLogReaderState *state, const char *fmt,...)
 			pg_attribute_printf(2, 3);
 static bool allocate_recordbuf(XLogReaderState *state, uint32 reclength);
@@ -1549,6 +1553,7 @@ struct walcompression walmethods[] = {
 	{"pglz",	WAL_COMPRESSION_PGLZ},
 	{"zlib",	WAL_COMPRESSION_ZLIB},
 	{"lz4",		WAL_COMPRESSION_LZ4},
+	{"zstd",	WAL_COMPRESSION_ZSTD},
 };
 
 /*
@@ -1621,6 +1626,16 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 			break;
 #endif
 
+#ifdef USE_ZSTD
+		case WAL_COMPRESSION_ZSTD:
+			decomp_result = ZSTD_decompress(tmp.data, BLCKSZ-bkpb->hole_length,
+					ptr, bkpb->bimg_len);
+			// XXX: ZSTD_getErrorName
+			if (ZSTD_isError(decomp_result))
+				decomp_result = -1;
+			break;
+#endif
+
 		default:
 			report_invalid_record(record, "image at %X/%X is compressed with unsupported codec, block %d (%d/%s)",
 								  (uint32) (record->ReadRecPtr >> 32),
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 2a2bccbe5c..0fdf426dc3 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -213,7 +213,7 @@
 					#   open_sync
 #full_page_writes = on			# recover from partial page writes
 #wal_compression = off			# enable compression of full-page writes
-#wal_compression_method = pglz		# pglz, zlib, lz4
+#wal_compression_method = pglz		# pglz, zlib, lz4, zstd
 #wal_log_hints = off			# also do full page writes of non-critical updates
 					# (change requires restart)
 #wal_init_zero = on			# zero-fill new WAL files
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index b908fa48de..fa8146645d 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -337,6 +337,7 @@ typedef enum WalCompression
 	WAL_COMPRESSION_PGLZ,
 	WAL_COMPRESSION_ZLIB,
 	WAL_COMPRESSION_LZ4,
+	WAL_COMPRESSION_ZSTD,
 } WalCompression;
 
 extern const char *wal_compression_name(WalCompression compression);
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index d873c177cb..a96c580ccb 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -905,6 +905,9 @@
 /* Define to 1 to build with LZ4 support (--with-lz4) */
 #undef USE_LZ4
 
+/* Define to 1 if you have the `zstd' library (-lzstd). */
+#undef USE_ZSTD
+
 /* Define to select named POSIX semaphores. */
 #undef USE_NAMED_POSIX_SEMAPHORES
 
diff --git a/src/tools/msvc/Solution.pm b/src/tools/msvc/Solution.pm
index ea8ed4be30..094e16deda 100644
--- a/src/tools/msvc/Solution.pm
+++ b/src/tools/msvc/Solution.pm
@@ -487,6 +487,7 @@ sub GenerateFiles
 		USE_LIBXML                 => undef,
 		USE_LIBXSLT                => undef,
 		USE_LZ4                    => undef,
+		USE_ZSTD                   => $self->{options}->{zstd} ? 1 : undef,
 		USE_LDAP                   => $self->{options}->{ldap} ? 1 : undef,
 		USE_LLVM                   => undef,
 		USE_NAMED_POSIX_SEMAPHORES => undef,
-- 
2.17.0

From 0e477fdcdf25a1e59163d748df03e570684a1955 Mon Sep 17 00:00:00 2001
From: Andrey Borodin <amborodin@acm.org>
Date: Sat, 27 Feb 2021 09:03:50 +0500
Subject: [PATCH v7 1/9] Allow alternate compression methods for
 wal_compression

TODO: bump XLOG_PAGE_MAGIC
---
 doc/src/sgml/config.sgml                      | 17 +++++
 src/backend/Makefile                          |  2 +-
 src/backend/access/transam/xlog.c             | 10 +++
 src/backend/access/transam/xloginsert.c       | 67 ++++++++++++++++---
 src/backend/access/transam/xlogreader.c       | 64 +++++++++++++++++-
 src/backend/utils/misc/guc.c                  | 11 +++
 src/backend/utils/misc/postgresql.conf.sample |  1 +
 src/include/access/xlog.h                     |  1 +
 src/include/access/xlog_internal.h            | 16 +++++
 src/include/access/xlogrecord.h               | 11 ++-
 10 files changed, 187 insertions(+), 13 deletions(-)

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 7e32b0686c..70effa6345 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -3137,6 +3137,23 @@ include_dir 'conf.d'
       </listitem>
      </varlistentry>
 
+     <varlistentry id="guc-wal-compression-method" xreflabel="wal_compression_method">
+      <term><varname>wal_compressionion_method</varname> (<type>enum</type>)
+      <indexterm>
+       <primary><varname>wal_compression_method</varname> configuration parameter</primary>
+      </indexterm>
+      </term>
+      <listitem>
+       <para>
+        This parameter selects the compression method used to compress WAL when
+        <varname>wal_compression</varname> is enabled.
+        The supported methods are pglz and zlib.
+        The default value is <literal>pglz</literal>.
+        Only superusers can change this setting.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry id="guc-wal-init-zero" xreflabel="wal_init_zero">
       <term><varname>wal_init_zero</varname> (<type>boolean</type>)
       <indexterm>
diff --git a/src/backend/Makefile b/src/backend/Makefile
index 0da848b1fd..3af216ddfc 100644
--- a/src/backend/Makefile
+++ b/src/backend/Makefile
@@ -48,7 +48,7 @@ OBJS = \
 LIBS := $(filter-out -lpgport -lpgcommon, $(LIBS)) $(LDAP_LIBS_BE) $(ICU_LIBS)
 
 # The backend doesn't need everything that's in LIBS, however
-LIBS := $(filter-out -lz -lreadline -ledit -ltermcap -lncurses -lcurses, $(LIBS))
+LIBS := $(filter-out -lreadline -ledit -ltermcap -lncurses -lcurses, $(LIBS))
 
 ifeq ($(with_systemd),yes)
 LIBS += -lsystemd
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 8d163f190f..b7f8e12aea 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -99,6 +99,7 @@ bool		EnableHotStandby = false;
 bool		fullPageWrites = true;
 bool		wal_log_hints = false;
 bool		wal_compression = false;
+int			wal_compression_method = WAL_COMPRESSION_PGLZ;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
@@ -180,6 +181,15 @@ const struct config_enum_entry recovery_target_action_options[] = {
 	{NULL, 0, false}
 };
 
+/* Note that due to conditional compilation, offsets within the array are not static */
+const struct config_enum_entry wal_compression_options[] = {
+	{"pglz", WAL_COMPRESSION_PGLZ, false},
+#ifdef  HAVE_LIBZ
+	{"zlib", WAL_COMPRESSION_ZLIB, false},
+#endif
+	{NULL, 0, false}
+};
+
 /*
  * Statistics for current checkpoint are collected in this global struct.
  * Because only the checkpointer or a stand-alone backend can perform
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
index 32b4cc84e7..5ab07621d6 100644
--- a/src/backend/access/transam/xloginsert.c
+++ b/src/backend/access/transam/xloginsert.c
@@ -33,8 +33,18 @@
 #include "storage/proc.h"
 #include "utils/memutils.h"
 
+#ifdef HAVE_LIBZ
+#include <zlib.h>
+/* zlib compressBound is not a macro */
+#define ZLIB_MAX_BLCKSZ		BLCKSZ + (BLCKSZ>>12) + (BLCKSZ>>14) + (BLCKSZ>>25) + 13
+#else
+#define ZLIB_MAX_BLCKSZ		0
+#endif
+
 /* Buffer size required to store a compressed version of backup block image */
-#define PGLZ_MAX_BLCKSZ PGLZ_MAX_OUTPUT(BLCKSZ)
+#define PGLZ_MAX_BLCKSZ		PGLZ_MAX_OUTPUT(BLCKSZ)
+
+#define COMPRESS_BUFSIZE	Max(PGLZ_MAX_BLCKSZ, ZLIB_MAX_BLCKSZ)
 
 /*
  * For each block reference registered with XLogRegisterBuffer, we fill in
@@ -58,7 +68,7 @@ typedef struct
 								 * backup block data in XLogRecordAssemble() */
 
 	/* buffer to store a compressed version of backup block image */
-	char		compressed_page[PGLZ_MAX_BLCKSZ];
+	char		compressed_page[COMPRESS_BUFSIZE];
 } registered_buffer;
 
 static registered_buffer *registered_buffers;
@@ -113,7 +123,8 @@ static XLogRecData *XLogRecordAssemble(RmgrId rmid, uint8 info,
 									   XLogRecPtr RedoRecPtr, bool doPageWrites,
 									   XLogRecPtr *fpw_lsn, int *num_fpi);
 static bool XLogCompressBackupBlock(char *page, uint16 hole_offset,
-									uint16 hole_length, char *dest, uint16 *dlen);
+									uint16 hole_length, char *dest,
+									uint16 *dlen, WalCompression compression);
 
 /*
  * Begin constructing a WAL record. This must be called before the
@@ -625,16 +636,26 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
 				cbimg.hole_length = 0;
 			}
 
+			bimg.bimg_info = (cbimg.hole_length == 0) ? 0 : BKPIMAGE_HAS_HOLE;
+
 			/*
 			 * Try to compress a block image if wal_compression is enabled
 			 */
 			if (wal_compression)
 			{
+				int compression;
+				/* The current compression is stored in the WAL record */
+				wal_compression_name(wal_compression_method); /* Range check */
+				compression = walmethods[wal_compression_method].walmethod;
+				Assert(compression < (1 << BKPIMAGE_COMPRESS_BITS));
+				bimg.bimg_info |=
+					compression << BKPIMAGE_COMPRESS_OFFSET_BITS;
 				is_compressed =
 					XLogCompressBackupBlock(page, bimg.hole_offset,
 											cbimg.hole_length,
 											regbuf->compressed_page,
-											&compressed_len);
+											&compressed_len,
+											wal_compression_method);
 			}
 
 			/*
@@ -652,8 +673,6 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
 			rdt_datas_last->next = &regbuf->bkp_rdatas[0];
 			rdt_datas_last = rdt_datas_last->next;
 
-			bimg.bimg_info = (cbimg.hole_length == 0) ? 0 : BKPIMAGE_HAS_HOLE;
-
 			/*
 			 * If WAL consistency checking is enabled for the resource manager
 			 * of this WAL record, a full-page image is included in the record
@@ -827,7 +846,7 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
  */
 static bool
 XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
-						char *dest, uint16 *dlen)
+						char *dest, uint16 *dlen, WalCompression compression)
 {
 	int32		orig_len = BLCKSZ - hole_length;
 	int32		len;
@@ -853,12 +872,42 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 	else
 		source = page;
 
+	switch (compression)
+	{
+	case WAL_COMPRESSION_PGLZ:
+		len = pglz_compress(source, orig_len, dest, PGLZ_strategy_default);
+		break;
+
+#ifdef HAVE_LIBZ
+	case WAL_COMPRESSION_ZLIB:
+		{
+			unsigned long	len_l = COMPRESS_BUFSIZE;
+			int ret;
+			ret = compress2((Bytef*)dest, &len_l, (Bytef*)source, orig_len, 1);
+			if (ret != Z_OK)
+				len_l = -1;
+			len = len_l;
+			break;
+		}
+#endif
+
+	default:
+		/*
+		 * It should be impossible to get here for unsupported algorithms,
+		 * which cannot be assigned if they're not enabled at compile time.
+		 */
+		ereport(ERROR,
+			(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			 errmsg("unknown compression method requested: %d(%s)",
+				 compression, wal_compression_name(compression))));
+
+	}
+
 	/*
-	 * We recheck the actual size even if pglz_compress() reports success and
+	 * We recheck the actual size even if compression reports success and
 	 * see if the number of bytes saved by compression is larger than the
 	 * length of extra data needed for the compressed version of block image.
 	 */
-	len = pglz_compress(source, orig_len, dest, PGLZ_strategy_default);
 	if (len >= 0 &&
 		len + extra_bytes < orig_len)
 	{
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index 42738eb940..0d8830fc50 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -33,6 +33,10 @@
 #include "utils/memutils.h"
 #endif
 
+#ifdef HAVE_LIBZ
+#include <zlib.h>
+#endif
+
 static void report_invalid_record(XLogReaderState *state, const char *fmt,...)
 			pg_attribute_printf(2, 3);
 static bool allocate_recordbuf(XLogReaderState *state, uint32 reclength);
@@ -1535,6 +1539,30 @@ XLogRecGetBlockData(XLogReaderState *record, uint8 block_id, Size *len)
 	}
 }
 
+/* This is a mapping indexed by wal_compression */
+// XXX: maybe this is better done as a GUC hook to assign the 1) method; and 2) level
+struct walcompression walmethods[] = {
+	{"pglz",	WAL_COMPRESSION_PGLZ},
+	{"zlib",	WAL_COMPRESSION_ZLIB},
+};
+
+/*
+ * Return a statically allocated string associated with the given compression
+ * method.
+ * This is here to be visible to frontend tools like pg_rewind.
+ */
+const char *
+wal_compression_name(WalCompression compression)
+{
+	/*
+	 * This could index into the guc array, except that it's compiled
+	 * conditionally and unsupported methods are elided.
+	 */
+	if (compression < sizeof(walmethods)/sizeof(*walmethods))
+		return walmethods[compression].name;
+	return "???";
+}
+
 /*
  * Restore a full-page image from a backup block attached to an XLOG record.
  *
@@ -1557,9 +1585,41 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 
 	if (bkpb->bimg_info & BKPIMAGE_IS_COMPRESSED)
 	{
+		int compression_method = BKPIMAGE_COMPRESSION(bkpb->bimg_info);
 		/* If a backup block image is compressed, decompress it */
-		if (pglz_decompress(ptr, bkpb->bimg_len, tmp.data,
-							BLCKSZ - bkpb->hole_length, true) < 0)
+		int32 decomp_result = -1;
+		switch (compression_method)
+		{
+		case WAL_COMPRESSION_PGLZ:
+			decomp_result = pglz_decompress(ptr, bkpb->bimg_len, tmp.data,
+							BLCKSZ - bkpb->hole_length, true);
+			break;
+
+#ifdef HAVE_LIBZ
+		case WAL_COMPRESSION_ZLIB:
+		{
+			unsigned long decomp_result_l;
+			decomp_result_l = BLCKSZ - bkpb->hole_length;
+			if (uncompress((Bytef*)tmp.data, &decomp_result_l,
+						(Bytef*)ptr, bkpb->bimg_len) == Z_OK)
+				decomp_result = decomp_result_l;
+			else
+				decomp_result = -1;
+			break;
+		}
+#endif
+
+		default:
+			report_invalid_record(record, "image at %X/%X is compressed with unsupported codec, block %d (%d/%s)",
+								  (uint32) (record->ReadRecPtr >> 32),
+								  (uint32) record->ReadRecPtr,
+								  block_id,
+								  compression_method,
+								  wal_compression_name(compression_method));
+			return false;
+		}
+
+		if (decomp_result < 0)
 		{
 			report_invalid_record(record, "invalid compressed image at %X/%X, block %d",
 								  LSN_FORMAT_ARGS(record->ReadRecPtr),
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index ee731044b6..99932582ba 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -548,6 +548,7 @@ extern const struct config_enum_entry archive_mode_options[];
 extern const struct config_enum_entry recovery_target_action_options[];
 extern const struct config_enum_entry sync_method_options[];
 extern const struct config_enum_entry dynamic_shared_memory_options[];
+extern const struct config_enum_entry wal_compression_options[];
 
 /*
  * GUC option variables that are exported from this module
@@ -4825,6 +4826,16 @@ static struct config_enum ConfigureNamesEnum[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"wal_compression_method", PGC_SUSET, WAL_SETTINGS,
+			gettext_noop("Set the method used to compress full page images in the WAL."),
+			NULL
+		},
+		&wal_compression_method,
+		WAL_COMPRESSION_PGLZ, wal_compression_options,
+		NULL, NULL, NULL
+	},
+
 	{
 		{"dynamic_shared_memory_type", PGC_POSTMASTER, RESOURCES_MEM,
 			gettext_noop("Selects the dynamic shared memory implementation used."),
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 6e36e4c2ef..baed4d9228 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -219,6 +219,7 @@
 #wal_log_hints = off			# also do full page writes of non-critical updates
 					# (change requires restart)
 #wal_compression = off			# enable compression of full-page writes
+#wal_compression_method = pglz		# pglz, zlib
 #wal_init_zero = on			# zero-fill new WAL files
 #wal_recycle = on			# recycle WAL files
 #wal_buffers = -1			# min 32kB, -1 sets based on shared_buffers
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index 77187c12be..2f3886431a 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -117,6 +117,7 @@ extern bool EnableHotStandby;
 extern bool fullPageWrites;
 extern bool wal_log_hints;
 extern bool wal_compression;
+extern int	wal_compression_method;
 extern bool wal_init_zero;
 extern bool wal_recycle;
 extern bool *wal_consistency_checking;
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index 26a743b6b6..ceca0f7189 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -324,4 +324,20 @@ extern bool InArchiveRecovery;
 extern bool StandbyMode;
 extern char *recoveryRestoreCommand;
 
+struct walcompression
+{
+	char	*name;
+	int	walmethod;	/* Compression method to be stored in WAL */
+};
+
+extern struct walcompression walmethods[];
+
+typedef enum WalCompression
+{
+	WAL_COMPRESSION_PGLZ,
+	WAL_COMPRESSION_ZLIB,
+} WalCompression;
+
+extern const char *wal_compression_name(WalCompression compression);
+
 #endif							/* XLOG_INTERNAL_H */
diff --git a/src/include/access/xlogrecord.h b/src/include/access/xlogrecord.h
index 80c92a2498..7107cf6186 100644
--- a/src/include/access/xlogrecord.h
+++ b/src/include/access/xlogrecord.h
@@ -114,7 +114,7 @@ typedef struct XLogRecordBlockHeader
  * present is (BLCKSZ - <length of "hole" bytes>).
  *
  * Additionally, when wal_compression is enabled, we will try to compress full
- * page images using the PGLZ compression algorithm, after removing the "hole".
+ * page images, after removing the "hole".
  * This can reduce the WAL volume, but at some extra cost of CPU spent
  * on the compression during WAL logging. In this case, since the "hole"
  * length cannot be calculated by subtracting the number of page image bytes
@@ -147,6 +147,15 @@ typedef struct XLogRecordBlockImageHeader
 #define BKPIMAGE_IS_COMPRESSED		0x02	/* page image is compressed */
 #define BKPIMAGE_APPLY		0x04	/* page image should be restored during
 									 * replay */
+#define BKPIMAGE_COMPRESS_METHOD1	0x08	/* bits to encode compression method */
+#define BKPIMAGE_COMPRESS_METHOD2	0x10	/* 0=pglz; 1=zlib; */
+
+/* How many bits to shift to extract compression */
+#define	BKPIMAGE_COMPRESS_OFFSET_BITS	3
+/* How many bits are for compression */
+#define	BKPIMAGE_COMPRESS_BITS		2
+/* Extract the compression from the bimg_info */
+#define	BKPIMAGE_COMPRESSION(info)	((info >> BKPIMAGE_COMPRESS_OFFSET_BITS) & ((1<<BKPIMAGE_COMPRESS_BITS) - 1))
 
 /*
  * Extra header information used when page image has "hole" and
-- 
2.17.0

From 6be5a4076f9984851b8a59e27ae911a3098c0e8f Mon Sep 17 00:00:00 2001
From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Date: Mon, 8 Mar 2021 15:32:30 +0900
Subject: [PATCH v7 2/9] Run 011_crash_recovery.pl with wal_level=minimal

The test doesn't need that feature and pg_current_xact_id() is better
exercised by turning off the feature.

Copied from: https://www.postgresql.org/message-id/20210308.173242.463790587797836129.horikyota.ntt%40gmail.com
---
 src/test/recovery/t/011_crash_recovery.pl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/test/recovery/t/011_crash_recovery.pl b/src/test/recovery/t/011_crash_recovery.pl
index a26e99500b..2e7e3db639 100644
--- a/src/test/recovery/t/011_crash_recovery.pl
+++ b/src/test/recovery/t/011_crash_recovery.pl
@@ -14,7 +14,7 @@ use Config;
 plan tests => 3;
 
 my $node = get_new_node('primary');
-$node->init(allows_streaming => 1);
+$node->init();
 $node->start;
 
 my ($stdin, $stdout, $stderr) = ('', '', '');
-- 
2.17.0

From 49475c7919ad6d0fc6bf811c264f3d91548c57ca Mon Sep 17 00:00:00 2001
From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Date: Mon, 8 Mar 2021 15:43:01 +0900
Subject: [PATCH v7 3/9] Make sure published XIDs are persistent

pg_xact_status() premises that XIDs obtained by
pg_current_xact_id(_if_assigned)() are persistent beyond a crash. But
XIDs are not guaranteed to go beyond WAL buffers before commit and
thus XIDs may vanish if server crashes before commit. This patch
guarantees the XID shown by the functions to be flushed out to disk.

Copied from: https://www.postgresql.org/message-id/20210308.173242.463790587797836129.horikyota.ntt%40gmail.com
---
 src/backend/access/transam/xact.c | 55 +++++++++++++++++++++++++------
 src/backend/access/transam/xlog.c |  2 +-
 src/backend/utils/adt/xid8funcs.c | 12 ++++++-
 src/include/access/xact.h         |  3 +-
 4 files changed, 59 insertions(+), 13 deletions(-)

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 441445927e..da8a460722 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -201,7 +201,7 @@ typedef struct TransactionStateData
 	int			prevSecContext; /* previous SecurityRestrictionContext */
 	bool		prevXactReadOnly;	/* entry-time xact r/o state */
 	bool		startedInRecovery;	/* did we start in recovery? */
-	bool		didLogXid;		/* has xid been included in WAL record? */
+	XLogRecPtr 	minLSN;			/* LSN needed to reach to record the xid */
 	int			parallelModeLevel;	/* Enter/ExitParallelMode counter */
 	bool		chain;			/* start a new block after this one */
 	bool		assigned;		/* assigned to top-level XID */
@@ -520,14 +520,46 @@ GetCurrentFullTransactionIdIfAny(void)
  *	MarkCurrentTransactionIdLoggedIfAny
  *
  * Remember that the current xid - if it is assigned - now has been wal logged.
+ *
+ * upto is the LSN up to which we need to flush WAL to ensure the current xid
+ * to be persistent. See EnsureCurrentTransactionIdLogged().
  */
 void
-MarkCurrentTransactionIdLoggedIfAny(void)
+MarkCurrentTransactionIdLoggedIfAny(XLogRecPtr upto)
 {
-	if (FullTransactionIdIsValid(CurrentTransactionState->fullTransactionId))
-		CurrentTransactionState->didLogXid = true;
+	if (FullTransactionIdIsValid(CurrentTransactionState->fullTransactionId) &&
+		XLogRecPtrIsInvalid(CurrentTransactionState->minLSN))
+		CurrentTransactionState->minLSN = upto;
 }
 
+/*
+ *	EnsureCurrentTransactionIdLogged
+ *
+ * Make sure that the current top XID is WAL-logged.
+ */
+void
+EnsureTopTransactionIdLogged(void)
+{
+	/*
+	 * We need at least one WAL record for the current top transaction to be
+	 * flushed out.  Write one if we don't have one yet.
+	 */
+	if (XLogRecPtrIsInvalid(TopTransactionStateData.minLSN))
+	{
+		xl_xact_assignment xlrec;
+
+		xlrec.xtop = XidFromFullTransactionId(XactTopFullTransactionId);
+		Assert(TransactionIdIsValid(xlrec.xtop));
+		xlrec.nsubxacts = 0;
+
+		XLogBeginInsert();
+		XLogRegisterData((char *) &xlrec, MinSizeOfXactAssignment);
+		TopTransactionStateData.minLSN =
+			XLogInsert(RM_XACT_ID, XLOG_XACT_ASSIGNMENT);
+	}
+
+	XLogFlush(TopTransactionStateData.minLSN);
+}
 
 /*
  *	GetStableLatestTransactionId
@@ -616,14 +648,14 @@ AssignTransactionId(TransactionState s)
 	 * When wal_level=logical, guarantee that a subtransaction's xid can only
 	 * be seen in the WAL stream if its toplevel xid has been logged before.
 	 * If necessary we log an xact_assignment record with fewer than
-	 * PGPROC_MAX_CACHED_SUBXIDS. Note that it is fine if didLogXid isn't set
+	 * PGPROC_MAX_CACHED_SUBXIDS. Note that it is fine if minLSN isn't set
 	 * for a transaction even though it appears in a WAL record, we just might
 	 * superfluously log something. That can happen when an xid is included
 	 * somewhere inside a wal record, but not in XLogRecord->xl_xid, like in
 	 * xl_standby_locks.
 	 */
 	if (isSubXact && XLogLogicalInfoActive() &&
-		!TopTransactionStateData.didLogXid)
+		XLogRecPtrIsInvalid(TopTransactionStateData.minLSN))
 		log_unknown_top = true;
 
 	/*
@@ -693,6 +725,7 @@ AssignTransactionId(TransactionState s)
 			log_unknown_top)
 		{
 			xl_xact_assignment xlrec;
+			XLogRecPtr		   endptr;
 
 			/*
 			 * xtop is always set by now because we recurse up transaction
@@ -707,11 +740,13 @@ AssignTransactionId(TransactionState s)
 			XLogRegisterData((char *) unreportedXids,
 							 nUnreportedXids * sizeof(TransactionId));
 
-			(void) XLogInsert(RM_XACT_ID, XLOG_XACT_ASSIGNMENT);
+			endptr = XLogInsert(RM_XACT_ID, XLOG_XACT_ASSIGNMENT);
 
 			nUnreportedXids = 0;
-			/* mark top, not current xact as having been logged */
-			TopTransactionStateData.didLogXid = true;
+
+			/* set minLSN of top, not of current xact if not yet */
+			if (XLogRecPtrIsInvalid(TopTransactionStateData.minLSN))
+				TopTransactionStateData.minLSN = endptr;
 		}
 	}
 }
@@ -1996,7 +2031,7 @@ StartTransaction(void)
 	 * initialize reported xid accounting
 	 */
 	nUnreportedXids = 0;
-	s->didLogXid = false;
+	s->minLSN = InvalidXLogRecPtr;
 
 	/*
 	 * must initialize resource-management stuff first
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index b7f8e12aea..18dd4ff1eb 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -1172,7 +1172,7 @@ XLogInsertRecord(XLogRecData *rdata,
 	 */
 	WALInsertLockRelease();
 
-	MarkCurrentTransactionIdLoggedIfAny();
+	MarkCurrentTransactionIdLoggedIfAny(EndPos);
 
 	END_CRIT_SECTION();
 
diff --git a/src/backend/utils/adt/xid8funcs.c b/src/backend/utils/adt/xid8funcs.c
index cc2b4ac797..992482f8c8 100644
--- a/src/backend/utils/adt/xid8funcs.c
+++ b/src/backend/utils/adt/xid8funcs.c
@@ -357,6 +357,8 @@ bad_format:
 Datum
 pg_current_xact_id(PG_FUNCTION_ARGS)
 {
+	FullTransactionId xid;
+
 	/*
 	 * Must prevent during recovery because if an xid is not assigned we try
 	 * to assign one, which would fail. Programs already rely on this function
@@ -365,7 +367,12 @@ pg_current_xact_id(PG_FUNCTION_ARGS)
 	 */
 	PreventCommandDuringRecovery("pg_current_xact_id()");
 
-	PG_RETURN_FULLTRANSACTIONID(GetTopFullTransactionId());
+	xid = GetTopFullTransactionId();
+
+	/* the XID is going to be published, make sure it is psersistent */
+	EnsureTopTransactionIdLogged();
+
+	PG_RETURN_FULLTRANSACTIONID(xid);
 }
 
 /*
@@ -380,6 +387,9 @@ pg_current_xact_id_if_assigned(PG_FUNCTION_ARGS)
 	if (!FullTransactionIdIsValid(topfxid))
 		PG_RETURN_NULL();
 
+	/* the XID is going to be published, make sure it is psersistent */
+	EnsureTopTransactionIdLogged();
+
 	PG_RETURN_FULLTRANSACTIONID(topfxid);
 }
 
diff --git a/src/include/access/xact.h b/src/include/access/xact.h
index 134f6862da..593a4140df 100644
--- a/src/include/access/xact.h
+++ b/src/include/access/xact.h
@@ -386,7 +386,8 @@ extern FullTransactionId GetTopFullTransactionId(void);
 extern FullTransactionId GetTopFullTransactionIdIfAny(void);
 extern FullTransactionId GetCurrentFullTransactionId(void);
 extern FullTransactionId GetCurrentFullTransactionIdIfAny(void);
-extern void MarkCurrentTransactionIdLoggedIfAny(void);
+extern void MarkCurrentTransactionIdLoggedIfAny(XLogRecPtr upto);
+extern void EnsureTopTransactionIdLogged(void);
 extern bool SubTransactionIsActive(SubTransactionId subxid);
 extern CommandId GetCurrentCommandId(bool used);
 extern void SetParallelStartTimestamps(TimestampTz xact_ts, TimestampTz stmt_ts);
-- 
2.17.0

From ebbe58c6970498de454009f18b3493a6472faec7 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Thu, 11 Mar 2021 17:36:24 -0600
Subject: [PATCH v7 4/9] wal_compression_method: default to zlib..

this is meant to exercise the CIs, and not meant to be merged
---
 src/backend/access/transam/xlog.c | 2 +-
 src/backend/utils/misc/guc.c      | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 18dd4ff1eb..a43e04fc0b 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -99,7 +99,7 @@ bool		EnableHotStandby = false;
 bool		fullPageWrites = true;
 bool		wal_log_hints = false;
 bool		wal_compression = false;
-int			wal_compression_method = WAL_COMPRESSION_PGLZ;
+int			wal_compression_method = WAL_COMPRESSION_ZLIB;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 99932582ba..a448267ee9 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -1311,7 +1311,7 @@ static struct config_bool ConfigureNamesBool[] =
 			NULL
 		},
 		&wal_compression,
-		false,
+		true,
 		NULL, NULL, NULL
 	},
 
@@ -4832,7 +4832,7 @@ static struct config_enum ConfigureNamesEnum[] =
 			NULL
 		},
 		&wal_compression_method,
-		WAL_COMPRESSION_PGLZ, wal_compression_options,
+		WAL_COMPRESSION_ZLIB, wal_compression_options,
 		NULL, NULL, NULL
 	},
 
-- 
2.17.0

From d85bdf8e430a92ce54a8a71b83b233d724f8620e Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Fri, 12 Mar 2021 14:32:10 -0600
Subject: [PATCH v7 5/9] (re)add wal_compression_method: lz4

---
 doc/src/sgml/config.sgml                      |  3 ++-
 doc/src/sgml/install-windows.sgml             |  2 +-
 doc/src/sgml/installation.sgml                |  5 +++--
 src/backend/access/transam/xlog.c             |  3 +++
 src/backend/access/transam/xloginsert.c       | 17 ++++++++++++++++-
 src/backend/access/transam/xlogreader.c       | 12 ++++++++++++
 src/backend/utils/misc/postgresql.conf.sample |  2 +-
 src/include/access/xlog_internal.h            |  1 +
 8 files changed, 39 insertions(+), 6 deletions(-)

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 70effa6345..f2209f5df0 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -3147,7 +3147,8 @@ include_dir 'conf.d'
        <para>
         This parameter selects the compression method used to compress WAL when
         <varname>wal_compression</varname> is enabled.
-        The supported methods are pglz and zlib.
+        The supported methods are pglz, zlib, and (if configured when
+        <productname>PostgreSQL</productname> was built) lz4.
         The default value is <literal>pglz</literal>.
         Only superusers can change this setting.
        </para>
diff --git a/doc/src/sgml/install-windows.sgml b/doc/src/sgml/install-windows.sgml
index db53ee85a8..a023584722 100644
--- a/doc/src/sgml/install-windows.sgml
+++ b/doc/src/sgml/install-windows.sgml
@@ -299,7 +299,7 @@ $ENV{MSBFLAGS}="/m";
      <term><productname>LZ4</productname></term>
      <listitem><para>
       Required for supporting <productname>LZ4</productname> compression
-      method for compressing the table data. Binaries and source can be
+      method for compressing table or WAL data. Binaries and source can be
       downloaded from
       <ulink url="https://github.com/lz4/lz4/releases"></ulink>.
      </para></listitem>
diff --git a/doc/src/sgml/installation.sgml b/doc/src/sgml/installation.sgml
index 3c0aa118c7..7c8cdac25a 100644
--- a/doc/src/sgml/installation.sgml
+++ b/doc/src/sgml/installation.sgml
@@ -270,7 +270,8 @@ su - postgres
      <para>
       You need <productname>LZ4</productname>, if you want to support
       compression of data with this method; see
-      <xref linkend="guc-default-toast-compression"/>.
+      <xref linkend="guc-default-toast-compression"/> and
+      <xref linkend="guc-wal-compression-method"/>.
      </para>
     </listitem>
 
@@ -980,7 +981,7 @@ build-postgresql:
         <para>
          Build with <productname>LZ4</productname> compression support.
          This allows the use of <productname>LZ4</productname> for
-         compression of table data.
+         compression of table and WAL data.
         </para>
        </listitem>
       </varlistentry>
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index a43e04fc0b..999896487e 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -186,6 +186,9 @@ const struct config_enum_entry wal_compression_options[] = {
 	{"pglz", WAL_COMPRESSION_PGLZ, false},
 #ifdef  HAVE_LIBZ
 	{"zlib", WAL_COMPRESSION_ZLIB, false},
+#endif
+#ifdef  USE_LZ4
+	{"lz4", WAL_COMPRESSION_LZ4, false},
 #endif
 	{NULL, 0, false}
 };
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
index 5ab07621d6..30804e8cd5 100644
--- a/src/backend/access/transam/xloginsert.c
+++ b/src/backend/access/transam/xloginsert.c
@@ -41,10 +41,17 @@
 #define ZLIB_MAX_BLCKSZ		0
 #endif
 
+#ifdef USE_LZ4
+#include "lz4.h"
+#define	LZ4_MAX_BLCKSZ		LZ4_COMPRESSBOUND(BLCKSZ)
+#else
+#define LZ4_MAX_BLCKSZ		0
+#endif
+
 /* Buffer size required to store a compressed version of backup block image */
 #define PGLZ_MAX_BLCKSZ		PGLZ_MAX_OUTPUT(BLCKSZ)
 
-#define COMPRESS_BUFSIZE	Max(PGLZ_MAX_BLCKSZ, ZLIB_MAX_BLCKSZ)
+#define COMPRESS_BUFSIZE	Max(Max(PGLZ_MAX_BLCKSZ, ZLIB_MAX_BLCKSZ), LZ4_MAX_BLCKSZ)
 
 /*
  * For each block reference registered with XLogRegisterBuffer, we fill in
@@ -891,6 +898,14 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 		}
 #endif
 
+#ifdef USE_LZ4
+	case WAL_COMPRESSION_LZ4:
+		len = LZ4_compress_fast(source, dest, orig_len, COMPRESS_BUFSIZE, 1);
+		if (len == 0)
+			len = -1;
+		break;
+#endif
+
 	default:
 		/*
 		 * It should be impossible to get here for unsupported algorithms,
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index 0d8830fc50..97165f1bb1 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -37,6 +37,10 @@
 #include <zlib.h>
 #endif
 
+#ifdef USE_LZ4
+#include "lz4.h"
+#endif
+
 static void report_invalid_record(XLogReaderState *state, const char *fmt,...)
 			pg_attribute_printf(2, 3);
 static bool allocate_recordbuf(XLogReaderState *state, uint32 reclength);
@@ -1544,6 +1548,7 @@ XLogRecGetBlockData(XLogReaderState *record, uint8 block_id, Size *len)
 struct walcompression walmethods[] = {
 	{"pglz",	WAL_COMPRESSION_PGLZ},
 	{"zlib",	WAL_COMPRESSION_ZLIB},
+	{"lz4",		WAL_COMPRESSION_LZ4},
 };
 
 /*
@@ -1609,6 +1614,13 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 		}
 #endif
 
+#ifdef USE_LZ4
+		case WAL_COMPRESSION_LZ4:
+			decomp_result = LZ4_decompress_safe(ptr, tmp.data,
+					bkpb->bimg_len, BLCKSZ-bkpb->hole_length);
+			break;
+#endif
+
 		default:
 			report_invalid_record(record, "image at %X/%X is compressed with unsupported codec, block %d (%d/%s)",
 								  (uint32) (record->ReadRecPtr >> 32),
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index baed4d9228..6421ddbde8 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -219,7 +219,7 @@
 #wal_log_hints = off			# also do full page writes of non-critical updates
 					# (change requires restart)
 #wal_compression = off			# enable compression of full-page writes
-#wal_compression_method = pglz		# pglz, zlib
+#wal_compression_method = pglz		# pglz, zlib, lz4
 #wal_init_zero = on			# zero-fill new WAL files
 #wal_recycle = on			# recycle WAL files
 #wal_buffers = -1			# min 32kB, -1 sets based on shared_buffers
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index ceca0f7189..fc57ea728e 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -336,6 +336,7 @@ typedef enum WalCompression
 {
 	WAL_COMPRESSION_PGLZ,
 	WAL_COMPRESSION_ZLIB,
+	WAL_COMPRESSION_LZ4,
 } WalCompression;
 
 extern const char *wal_compression_name(WalCompression compression);
-- 
2.17.0

From 5a5b89d42aa2236f286a59d0f958e550de982b76 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Fri, 12 Mar 2021 14:43:53 -0600
Subject: [PATCH v7 6/9] add wal_compression_method: zstd

TODO: 9ca40dcd4d0cad43d95a9a253fafaa9a9ba7de24
---
 configure                                     | 217 ++++++++++++++++++
 configure.ac                                  |  33 +++
 doc/src/sgml/config.sgml                      |   2 +-
 doc/src/sgml/installation.sgml                |  19 ++
 src/backend/access/transam/xlog.c             |   3 +
 src/backend/access/transam/xloginsert.c       |  18 +-
 src/backend/access/transam/xlogreader.c       |  15 ++
 src/backend/utils/misc/postgresql.conf.sample |   2 +-
 src/include/access/xlog_internal.h            |   1 +
 src/include/pg_config.h.in                    |   3 +
 src/tools/msvc/Solution.pm                    |   1 +
 src/tools/msvc/config_default.pl              |   1 +
 12 files changed, 312 insertions(+), 3 deletions(-)

diff --git a/configure b/configure
index e9b98f442f..9d44f6acc7 100755
--- a/configure
+++ b/configure
@@ -699,6 +699,9 @@ with_gnu_ld
 LD
 LDFLAGS_SL
 LDFLAGS_EX
+ZSTD_LIBS
+ZSTD_CFLAGS
+with_zstd
 LZ4_LIBS
 LZ4_CFLAGS
 with_lz4
@@ -868,6 +871,7 @@ with_libxslt
 with_system_tzdata
 with_zlib
 with_lz4
+with_zstd
 with_gnu_ld
 with_ssl
 with_openssl
@@ -897,6 +901,8 @@ XML2_CFLAGS
 XML2_LIBS
 LZ4_CFLAGS
 LZ4_LIBS
+ZSTD_CFLAGS
+ZSTD_LIBS
 LDFLAGS_EX
 LDFLAGS_SL
 PERL
@@ -1576,6 +1582,7 @@ Optional Packages:
                           use system time zone data in DIR
   --without-zlib          do not use Zlib
   --with-lz4              build with LZ4 support
+  --with-zstd             build with Zstd compression library
   --with-gnu-ld           assume the C compiler uses GNU ld [default=no]
   --with-ssl=LIB          use LIB for SSL/TLS support (openssl)
   --with-openssl          obsolete spelling of --with-ssl=openssl
@@ -1605,6 +1612,8 @@ Some influential environment variables:
   XML2_LIBS   linker flags for XML2, overriding pkg-config
   LZ4_CFLAGS  C compiler flags for LZ4, overriding pkg-config
   LZ4_LIBS    linker flags for LZ4, overriding pkg-config
+  ZSTD_CFLAGS C compiler flags for ZSTD, overriding pkg-config
+  ZSTD_LIBS   linker flags for ZSTD, overriding pkg-config
   LDFLAGS_EX  extra linker flags for linking executables only
   LDFLAGS_SL  extra linker flags for linking shared libraries only
   PERL        Perl program
@@ -8713,6 +8722,147 @@ fi
   done
 fi
 
+#
+# ZSTD
+#
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether to build with zstd support" >&5
+$as_echo_n "checking whether to build with zstd support... " >&6; }
+
+
+
+# Check whether --with-zstd was given.
+if test "${with_zstd+set}" = set; then :
+  withval=$with_zstd;
+  case $withval in
+    yes)
+
+$as_echo "#define USE_ZSTD 1" >>confdefs.h
+
+      ;;
+    no)
+      :
+      ;;
+    *)
+      as_fn_error $? "no argument expected for --with-zstd option" "$LINENO" 5
+      ;;
+  esac
+
+else
+  with_zstd=no
+
+fi
+
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $with_zstd" >&5
+$as_echo "$with_zstd" >&6; }
+
+
+if test "$with_zstd" = yes; then
+
+pkg_failed=no
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for libzstd" >&5
+$as_echo_n "checking for libzstd... " >&6; }
+
+if test -n "$ZSTD_CFLAGS"; then
+    pkg_cv_ZSTD_CFLAGS="$ZSTD_CFLAGS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"libzstd\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "libzstd") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_ZSTD_CFLAGS=`$PKG_CONFIG --cflags "libzstd" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+if test -n "$ZSTD_LIBS"; then
+    pkg_cv_ZSTD_LIBS="$ZSTD_LIBS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"libzstd\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "libzstd") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_ZSTD_LIBS=`$PKG_CONFIG --libs "libzstd" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+
+
+
+if test $pkg_failed = yes; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+
+if $PKG_CONFIG --atleast-pkgconfig-version 0.20; then
+        _pkg_short_errors_supported=yes
+else
+        _pkg_short_errors_supported=no
+fi
+        if test $_pkg_short_errors_supported = yes; then
+	        ZSTD_PKG_ERRORS=`$PKG_CONFIG --short-errors --print-errors --cflags --libs "libzstd" 2>&1`
+        else
+	        ZSTD_PKG_ERRORS=`$PKG_CONFIG --print-errors --cflags --libs "libzstd" 2>&1`
+        fi
+	# Put the nasty error message in config.log where it belongs
+	echo "$ZSTD_PKG_ERRORS" >&5
+
+	as_fn_error $? "Package requirements (libzstd) were not met:
+
+$ZSTD_PKG_ERRORS
+
+Consider adjusting the PKG_CONFIG_PATH environment variable if you
+installed software in a non-standard prefix.
+
+Alternatively, you may set the environment variables ZSTD_CFLAGS
+and ZSTD_LIBS to avoid the need to call pkg-config.
+See the pkg-config man page for more details." "$LINENO" 5
+elif test $pkg_failed = untried; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+	{ { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error $? "The pkg-config script could not be found or is too old.  Make sure it
+is in your PATH or set the PKG_CONFIG environment variable to the full
+path to pkg-config.
+
+Alternatively, you may set the environment variables ZSTD_CFLAGS
+and ZSTD_LIBS to avoid the need to call pkg-config.
+See the pkg-config man page for more details.
+
+To get pkg-config, see <http://pkg-config.freedesktop.org/>.
+See \`config.log' for more details" "$LINENO" 5; }
+else
+	ZSTD_CFLAGS=$pkg_cv_ZSTD_CFLAGS
+	ZSTD_LIBS=$pkg_cv_ZSTD_LIBS
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+
+fi
+  # We only care about -I, -D, and -L switches;
+  # note that -lzstd will be added by AC_CHECK_LIB below.
+  for pgac_option in $ZSTD_CFLAGS; do
+    case $pgac_option in
+      -I*|-D*) CPPFLAGS="$CPPFLAGS $pgac_option";;
+    esac
+  done
+  for pgac_option in $ZSTD_LIBS; do
+    case $pgac_option in
+      -L*) LDFLAGS="$LDFLAGS $pgac_option";;
+    esac
+  done
+fi
+
 #
 # Assignments
 #
@@ -12876,6 +13026,56 @@ fi
 
 fi
 
+if test "$with_zstd" = yes ; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for ZSTD_compress in -lzstd" >&5
+$as_echo_n "checking for ZSTD_compress in -lzstd... " >&6; }
+if ${ac_cv_lib_zstd_ZSTD_compress+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ac_check_lib_save_LIBS=$LIBS
+LIBS="-lzstd  $LIBS"
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+/* Override any GCC internal prototype to avoid an error.
+   Use char because int might match the return type of a GCC
+   builtin and then its argument prototype would still apply.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+char ZSTD_compress ();
+int
+main ()
+{
+return ZSTD_compress ();
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ac_cv_lib_zstd_ZSTD_compress=yes
+else
+  ac_cv_lib_zstd_ZSTD_compress=no
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+LIBS=$ac_check_lib_save_LIBS
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_lib_zstd_ZSTD_compress" >&5
+$as_echo "$ac_cv_lib_zstd_ZSTD_compress" >&6; }
+if test "x$ac_cv_lib_zstd_ZSTD_compress" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_LIBZSTD 1
+_ACEOF
+
+  LIBS="-lzstd $LIBS"
+
+else
+  as_fn_error $? "library 'zstd' is required for ZSTD support" "$LINENO" 5
+fi
+
+fi
+
 # Note: We can test for libldap_r only after we know PTHREAD_LIBS
 if test "$with_ldap" = yes ; then
   _LIBS="$LIBS"
@@ -13598,6 +13798,23 @@ done
 
 fi
 
+if test "$with_zstd" = yes; then
+  for ac_header in zstd.h
+do :
+  ac_fn_c_check_header_mongrel "$LINENO" "zstd.h" "ac_cv_header_zstd_h" "$ac_includes_default"
+if test "x$ac_cv_header_zstd_h" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_ZSTD_H 1
+_ACEOF
+
+else
+  as_fn_error $? "zstd.h header file is required for zstd" "$LINENO" 5
+fi
+
+done
+
+fi
+
 if test "$with_gssapi" = yes ; then
   for ac_header in gssapi/gssapi.h
 do :
diff --git a/configure.ac b/configure.ac
index 3b42d8bdc9..f10c33785e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1011,6 +1011,31 @@ if test "$with_lz4" = yes; then
   done
 fi
 
+#
+# ZSTD
+#
+AC_MSG_CHECKING([whether to build with zstd support])
+PGAC_ARG_BOOL(with, zstd, no, [build with Zstd compression library],
+              [AC_DEFINE([USE_ZSTD], 1, [Define to 1 to build with zstd support. (--with-zstd)])])
+AC_MSG_RESULT([$with_zstd])
+AC_SUBST(with_zstd)
+
+if test "$with_zstd" = yes; then
+  PKG_CHECK_MODULES(ZSTD, libzstd)
+  # We only care about -I, -D, and -L switches;
+  # note that -lzstd will be added by AC_CHECK_LIB below.
+  for pgac_option in $ZSTD_CFLAGS; do
+    case $pgac_option in
+      -I*|-D*) CPPFLAGS="$CPPFLAGS $pgac_option";;
+    esac
+  done
+  for pgac_option in $ZSTD_LIBS; do
+    case $pgac_option in
+      -L*) LDFLAGS="$LDFLAGS $pgac_option";;
+    esac
+  done
+fi
+
 #
 # Assignments
 #
@@ -1285,6 +1310,10 @@ if test "$with_lz4" = yes ; then
   AC_CHECK_LIB(lz4, LZ4_compress_default, [], [AC_MSG_ERROR([library 'lz4' is required for LZ4 support])])
 fi
 
+if test "$with_zstd" = yes ; then
+  AC_CHECK_LIB(zstd, ZSTD_compress, [], [AC_MSG_ERROR([library 'zstd' is required for ZSTD support])])
+fi
+
 # Note: We can test for libldap_r only after we know PTHREAD_LIBS
 if test "$with_ldap" = yes ; then
   _LIBS="$LIBS"
@@ -1443,6 +1472,10 @@ if test "$with_lz4" = yes; then
   AC_CHECK_HEADERS(lz4.h, [], [AC_MSG_ERROR([lz4.h header file is required for LZ4])])
 fi
 
+if test "$with_zstd" = yes; then
+  AC_CHECK_HEADERS(zstd.h, [], [AC_MSG_ERROR([zstd.h header file is required for zstd])])
+fi
+
 if test "$with_gssapi" = yes ; then
   AC_CHECK_HEADERS(gssapi/gssapi.h, [],
 	[AC_CHECK_HEADERS(gssapi.h, [], [AC_MSG_ERROR([gssapi.h header file is required for GSSAPI])])])
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index f2209f5df0..da4d66ec31 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -3148,7 +3148,7 @@ include_dir 'conf.d'
         This parameter selects the compression method used to compress WAL when
         <varname>wal_compression</varname> is enabled.
         The supported methods are pglz, zlib, and (if configured when
-        <productname>PostgreSQL</productname> was built) lz4.
+        <productname>PostgreSQL</productname> was built) lz4 and zstd.
         The default value is <literal>pglz</literal>.
         Only superusers can change this setting.
        </para>
diff --git a/doc/src/sgml/installation.sgml b/doc/src/sgml/installation.sgml
index 7c8cdac25a..2e1cd2de37 100644
--- a/doc/src/sgml/installation.sgml
+++ b/doc/src/sgml/installation.sgml
@@ -275,6 +275,14 @@ su - postgres
      </para>
     </listitem>
 
+    <listitem>
+     <para>
+      The <productname>ZSTD</productname> library can be used to enable
+      compression using that method; see
+      <xref linkend="guc-wal-compression-method"/>.
+     </para>
+    </listitem>
+
     <listitem>
      <para>
       To build the <productname>PostgreSQL</productname> documentation,
@@ -986,6 +994,17 @@ build-postgresql:
        </listitem>
       </varlistentry>
 
+      <varlistentry>
+       <term><option>--with-zstd</option></term>
+       <listitem>
+        <para>
+         Build with <productname>ZSTD</productname> compression support.
+         This enables use of <productname>ZSTD</productname> for
+         compression of WAL data.
+        </para>
+       </listitem>
+      </varlistentry>
+
       <varlistentry>
        <term><option>--with-ssl=<replaceable>LIBRARY</replaceable></option>
        <indexterm>
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 999896487e..e31ce1c2a6 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -189,6 +189,9 @@ const struct config_enum_entry wal_compression_options[] = {
 #endif
 #ifdef  USE_LZ4
 	{"lz4", WAL_COMPRESSION_LZ4, false},
+#endif
+#ifdef  USE_ZSTD
+	{"zstd", WAL_COMPRESSION_ZSTD, false},
 #endif
 	{NULL, 0, false}
 };
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
index 30804e8cd5..cc7fd99a8d 100644
--- a/src/backend/access/transam/xloginsert.c
+++ b/src/backend/access/transam/xloginsert.c
@@ -48,10 +48,17 @@
 #define LZ4_MAX_BLCKSZ		0
 #endif
 
+#ifdef USE_ZSTD
+#include "zstd.h"
+#define ZSTD_MAX_BLCKSZ		ZSTD_COMPRESSBOUND(BLCKSZ)
+#else
+#define ZSTD_MAX_BLCKSZ		0
+#endif
+
 /* Buffer size required to store a compressed version of backup block image */
 #define PGLZ_MAX_BLCKSZ		PGLZ_MAX_OUTPUT(BLCKSZ)
 
-#define COMPRESS_BUFSIZE	Max(Max(PGLZ_MAX_BLCKSZ, ZLIB_MAX_BLCKSZ), LZ4_MAX_BLCKSZ)
+#define COMPRESS_BUFSIZE	Max(Max(Max(PGLZ_MAX_BLCKSZ, ZLIB_MAX_BLCKSZ), LZ4_MAX_BLCKSZ), ZSTD_MAX_BLCKSZ)
 
 /*
  * For each block reference registered with XLogRegisterBuffer, we fill in
@@ -906,6 +913,15 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 		break;
 #endif
 
+#ifdef USE_ZSTD
+	case WAL_COMPRESSION_ZSTD:
+		len = ZSTD_compress(dest, COMPRESS_BUFSIZE, source, orig_len,
+				ZSTD_CLEVEL_DEFAULT);
+		if (ZSTD_isError(len))
+			len = -1;
+		break;
+#endif
+
 	default:
 		/*
 		 * It should be impossible to get here for unsupported algorithms,
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index 97165f1bb1..0f9d522087 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -41,6 +41,10 @@
 #include "lz4.h"
 #endif
 
+#ifdef USE_ZSTD
+#include "zstd.h"
+#endif
+
 static void report_invalid_record(XLogReaderState *state, const char *fmt,...)
 			pg_attribute_printf(2, 3);
 static bool allocate_recordbuf(XLogReaderState *state, uint32 reclength);
@@ -1549,6 +1553,7 @@ struct walcompression walmethods[] = {
 	{"pglz",	WAL_COMPRESSION_PGLZ},
 	{"zlib",	WAL_COMPRESSION_ZLIB},
 	{"lz4",		WAL_COMPRESSION_LZ4},
+	{"zstd",	WAL_COMPRESSION_ZSTD},
 };
 
 /*
@@ -1621,6 +1626,16 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 			break;
 #endif
 
+#ifdef USE_ZSTD
+		case WAL_COMPRESSION_ZSTD:
+			decomp_result = ZSTD_decompress(tmp.data, BLCKSZ-bkpb->hole_length,
+					ptr, bkpb->bimg_len);
+			// XXX: ZSTD_getErrorName
+			if (ZSTD_isError(decomp_result))
+				decomp_result = -1;
+			break;
+#endif
+
 		default:
 			report_invalid_record(record, "image at %X/%X is compressed with unsupported codec, block %d (%d/%s)",
 								  (uint32) (record->ReadRecPtr >> 32),
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 6421ddbde8..5b4ef691af 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -219,7 +219,7 @@
 #wal_log_hints = off			# also do full page writes of non-critical updates
 					# (change requires restart)
 #wal_compression = off			# enable compression of full-page writes
-#wal_compression_method = pglz		# pglz, zlib, lz4
+#wal_compression_method = pglz		# pglz, zlib, lz4, zstd
 #wal_init_zero = on			# zero-fill new WAL files
 #wal_recycle = on			# recycle WAL files
 #wal_buffers = -1			# min 32kB, -1 sets based on shared_buffers
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index fc57ea728e..d70b95f69c 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -337,6 +337,7 @@ typedef enum WalCompression
 	WAL_COMPRESSION_PGLZ,
 	WAL_COMPRESSION_ZLIB,
 	WAL_COMPRESSION_LZ4,
+	WAL_COMPRESSION_ZSTD,
 } WalCompression;
 
 extern const char *wal_compression_name(WalCompression compression);
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index 783b8fc1ba..bb44ef2a9d 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -917,6 +917,9 @@
 /* Define to 1 to build with LZ4 support. (--with-lz4) */
 #undef USE_LZ4
 
+/* Define to 1 if you have the `zstd' library (-lzstd). */
+#undef USE_ZSTD
+
 /* Define to select named POSIX semaphores. */
 #undef USE_NAMED_POSIX_SEMAPHORES
 
diff --git a/src/tools/msvc/Solution.pm b/src/tools/msvc/Solution.pm
index 3c5fe5dddc..d7da5110cf 100644
--- a/src/tools/msvc/Solution.pm
+++ b/src/tools/msvc/Solution.pm
@@ -494,6 +494,7 @@ sub GenerateFiles
 		USE_LIBXML                 => undef,
 		USE_LIBXSLT                => undef,
 		USE_LZ4                    => undef,
+		USE_ZSTD                   => $self->{options}->{zstd} ? 1 : undef,
 		USE_LDAP                   => $self->{options}->{ldap} ? 1 : undef,
 		USE_LLVM                   => undef,
 		USE_NAMED_POSIX_SEMAPHORES => undef,
diff --git a/src/tools/msvc/config_default.pl b/src/tools/msvc/config_default.pl
index 460c0375d4..b8a1aac3c2 100644
--- a/src/tools/msvc/config_default.pl
+++ b/src/tools/msvc/config_default.pl
@@ -26,6 +26,7 @@ our $config = {
 	xslt      => undef,    # --with-libxslt=<path>
 	iconv     => undef,    # (not in configure, path to iconv)
 	zlib      => undef     # --with-zlib=<path>
+	zstd      => undef     # --with-zstd=<path>
 };
 
 1;
-- 
2.17.0

From e4d72530ad5c61de3ac300c379d485a30d78a755 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Fri, 12 Mar 2021 15:35:40 -0600
Subject: [PATCH v7 7/9] Default to LZ4..

this is meant to exercise in the CIs, and not meant to be merged
---
 configure                         | 6 ++++--
 configure.ac                      | 4 ++--
 src/backend/access/transam/xlog.c | 2 +-
 src/backend/utils/misc/guc.c      | 2 +-
 4 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/configure b/configure
index 9d44f6acc7..72bbd719dc 100755
--- a/configure
+++ b/configure
@@ -1581,7 +1581,7 @@ Optional Packages:
   --with-system-tzdata=DIR
                           use system time zone data in DIR
   --without-zlib          do not use Zlib
-  --with-lz4              build with LZ4 support
+  --without-lz4           build without LZ4 support
   --with-zstd             build with Zstd compression library
   --with-gnu-ld           assume the C compiler uses GNU ld [default=no]
   --with-ssl=LIB          use LIB for SSL/TLS support (openssl)
@@ -8607,7 +8607,9 @@ $as_echo "#define USE_LZ4 1" >>confdefs.h
   esac
 
 else
-  with_lz4=no
+  with_lz4=yes
+
+$as_echo "#define USE_LZ4 1" >>confdefs.h
 
 fi
 
diff --git a/configure.ac b/configure.ac
index f10c33785e..c348a3ee91 100644
--- a/configure.ac
+++ b/configure.ac
@@ -990,8 +990,8 @@ AC_SUBST(with_zlib)
 # LZ4
 #
 AC_MSG_CHECKING([whether to build with LZ4 support])
-PGAC_ARG_BOOL(with, lz4, no, [build with LZ4 support],
-              [AC_DEFINE([USE_LZ4], 1, [Define to 1 to build with LZ4 support. (--with-lz4)])])
+PGAC_ARG_BOOL(with, lz4, yes, [build without LZ4 support],
+              [AC_DEFINE([USE_LZ4], 1, [Define to 1 to build without LZ4 support. (--without-lz4)])])
 AC_MSG_RESULT([$with_lz4])
 AC_SUBST(with_lz4)
 
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index e31ce1c2a6..3ddfa8c0ee 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -99,7 +99,7 @@ bool		EnableHotStandby = false;
 bool		fullPageWrites = true;
 bool		wal_log_hints = false;
 bool		wal_compression = false;
-int			wal_compression_method = WAL_COMPRESSION_ZLIB;
+int			wal_compression_method = WAL_COMPRESSION_LZ4;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index a448267ee9..da1ed32943 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -4832,7 +4832,7 @@ static struct config_enum ConfigureNamesEnum[] =
 			NULL
 		},
 		&wal_compression_method,
-		WAL_COMPRESSION_ZLIB, wal_compression_options,
+		WAL_COMPRESSION_LZ4, wal_compression_options,
 		NULL, NULL, NULL
 	},
 
-- 
2.17.0

From d5cb40623911967af5dee561a884ae641ea4638e Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Fri, 12 Mar 2021 15:35:53 -0600
Subject: [PATCH v7 8/9] Default to zstd..

for CI, not for merge
---
 configure                         | 6 ++++--
 configure.ac                      | 2 +-
 src/backend/access/transam/xlog.c | 2 +-
 src/backend/utils/misc/guc.c      | 2 +-
 4 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/configure b/configure
index 72bbd719dc..b445db933e 100755
--- a/configure
+++ b/configure
@@ -1582,7 +1582,7 @@ Optional Packages:
                           use system time zone data in DIR
   --without-zlib          do not use Zlib
   --without-lz4           build without LZ4 support
-  --with-zstd             build with Zstd compression library
+  --without-zstd          build without Zstd compression library
   --with-gnu-ld           assume the C compiler uses GNU ld [default=no]
   --with-ssl=LIB          use LIB for SSL/TLS support (openssl)
   --with-openssl          obsolete spelling of --with-ssl=openssl
@@ -8750,7 +8750,9 @@ $as_echo "#define USE_ZSTD 1" >>confdefs.h
   esac
 
 else
-  with_zstd=no
+  with_zstd=yes
+
+$as_echo "#define USE_ZSTD 1" >>confdefs.h
 
 fi
 
diff --git a/configure.ac b/configure.ac
index c348a3ee91..f8ee35ebfd 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1015,7 +1015,7 @@ fi
 # ZSTD
 #
 AC_MSG_CHECKING([whether to build with zstd support])
-PGAC_ARG_BOOL(with, zstd, no, [build with Zstd compression library],
+PGAC_ARG_BOOL(with, zstd, yes, [build without Zstd compression library],
               [AC_DEFINE([USE_ZSTD], 1, [Define to 1 to build with zstd support. (--with-zstd)])])
 AC_MSG_RESULT([$with_zstd])
 AC_SUBST(with_zstd)
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 3ddfa8c0ee..33aa35e783 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -99,7 +99,7 @@ bool		EnableHotStandby = false;
 bool		fullPageWrites = true;
 bool		wal_log_hints = false;
 bool		wal_compression = false;
-int			wal_compression_method = WAL_COMPRESSION_LZ4;
+int			wal_compression_method = WAL_COMPRESSION_ZSTD;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index da1ed32943..dab7084fea 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -4832,7 +4832,7 @@ static struct config_enum ConfigureNamesEnum[] =
 			NULL
 		},
 		&wal_compression_method,
-		WAL_COMPRESSION_LZ4, wal_compression_options,
+		WAL_COMPRESSION_ZSTD, wal_compression_options,
 		NULL, NULL, NULL
 	},
 
-- 
2.17.0

From 07a9ee6809ac9da3627652391bad2a20852f6c06 Mon Sep 17 00:00:00 2001
From: Andrey Borodin <amborodin@acm.org>
Date: Sat, 27 Feb 2021 09:03:50 +0500
Subject: [PATCH v8 1/9] Allow alternate compression methods for
 wal_compression

TODO: bump XLOG_PAGE_MAGIC
---
 doc/src/sgml/config.sgml                      |  9 +-
 doc/src/sgml/installation.sgml                |  4 +-
 src/backend/Makefile                          |  2 +-
 src/backend/access/transam/xlog.c             |  2 +-
 src/backend/access/transam/xloginsert.c       | 65 +++++++++++--
 src/backend/access/transam/xlogreader.c       | 97 ++++++++++++++++---
 src/backend/utils/misc/guc.c                  | 21 ++--
 src/backend/utils/misc/postgresql.conf.sample |  2 +-
 src/bin/pg_waldump/pg_waldump.c               | 13 ++-
 src/include/access/xlog.h                     |  2 +-
 src/include/access/xlog_internal.h            | 10 ++
 src/include/access/xlogrecord.h               | 15 ++-
 12 files changed, 194 insertions(+), 48 deletions(-)

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 7e32b0686c..218a98cfc6 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -3113,23 +3113,26 @@ include_dir 'conf.d'
      </varlistentry>
 
      <varlistentry id="guc-wal-compression" xreflabel="wal_compression">
-      <term><varname>wal_compression</varname> (<type>boolean</type>)
+      <term><varname>wal_compression</varname> (<type>enum</type>)
       <indexterm>
        <primary><varname>wal_compression</varname> configuration parameter</primary>
       </indexterm>
       </term>
       <listitem>
        <para>
-        When this parameter is <literal>on</literal>, the <productname>PostgreSQL</productname>
+        This parameter enables compression of WAL using the specified 
+        compression method.
+        When enabled, the <productname>PostgreSQL</productname>
         server compresses full page images written to WAL when
         <xref linkend="guc-full-page-writes"/> is on or during a base backup.
         A compressed page image will be decompressed during WAL replay.
+        The supported methods are pglz and zlib.
         The default value is <literal>off</literal>.
         Only superusers can change this setting.
        </para>
 
        <para>
-        Turning this parameter on can reduce the WAL volume without
+        Enabling compression can reduce the WAL volume without
         increasing the risk of unrecoverable data corruption,
         but at the cost of some extra CPU spent on the compression during
         WAL logging and on the decompression during WAL replay.
diff --git a/doc/src/sgml/installation.sgml b/doc/src/sgml/installation.sgml
index 3c0aa118c7..073d5089f7 100644
--- a/doc/src/sgml/installation.sgml
+++ b/doc/src/sgml/installation.sgml
@@ -147,7 +147,7 @@ su - postgres
       specify the <option>--without-zlib</option> option to
       <filename>configure</filename>. Using this option disables
       support for compressed archives in <application>pg_dump</application> and
-      <application>pg_restore</application>.
+      <application>pg_restore</application>, and compressed WAL.
      </para>
     </listitem>
    </itemizedlist>
@@ -1236,7 +1236,7 @@ build-postgresql:
          Prevents use of the <application>Zlib</application> library.
          This disables
          support for compressed archives in <application>pg_dump</application>
-         and <application>pg_restore</application>.
+         and <application>pg_restore</application> and compressed WAL.
         </para>
        </listitem>
       </varlistentry>
diff --git a/src/backend/Makefile b/src/backend/Makefile
index 0da848b1fd..3af216ddfc 100644
--- a/src/backend/Makefile
+++ b/src/backend/Makefile
@@ -48,7 +48,7 @@ OBJS = \
 LIBS := $(filter-out -lpgport -lpgcommon, $(LIBS)) $(LDAP_LIBS_BE) $(ICU_LIBS)
 
 # The backend doesn't need everything that's in LIBS, however
-LIBS := $(filter-out -lz -lreadline -ledit -ltermcap -lncurses -lcurses, $(LIBS))
+LIBS := $(filter-out -lreadline -ledit -ltermcap -lncurses -lcurses, $(LIBS))
 
 ifeq ($(with_systemd),yes)
 LIBS += -lsystemd
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 441a9124cd..64094e7175 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -98,7 +98,7 @@ char	   *XLogArchiveCommand = NULL;
 bool		EnableHotStandby = false;
 bool		fullPageWrites = true;
 bool		wal_log_hints = false;
-bool		wal_compression = false;
+int		wal_compression = WAL_COMPRESSION_NONE;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
index 32b4cc84e7..4f81f19c49 100644
--- a/src/backend/access/transam/xloginsert.c
+++ b/src/backend/access/transam/xloginsert.c
@@ -33,8 +33,18 @@
 #include "storage/proc.h"
 #include "utils/memutils.h"
 
+#ifdef HAVE_LIBZ
+#include <zlib.h>
+/* zlib compressBound is not a macro */
+#define ZLIB_MAX_BLCKSZ		BLCKSZ + (BLCKSZ>>12) + (BLCKSZ>>14) + (BLCKSZ>>25) + 13
+#else
+#define ZLIB_MAX_BLCKSZ		0
+#endif
+
 /* Buffer size required to store a compressed version of backup block image */
-#define PGLZ_MAX_BLCKSZ PGLZ_MAX_OUTPUT(BLCKSZ)
+#define PGLZ_MAX_BLCKSZ		PGLZ_MAX_OUTPUT(BLCKSZ)
+
+#define COMPRESS_BUFSIZE	Max(PGLZ_MAX_BLCKSZ, ZLIB_MAX_BLCKSZ)
 
 /*
  * For each block reference registered with XLogRegisterBuffer, we fill in
@@ -58,7 +68,7 @@ typedef struct
 								 * backup block data in XLogRecordAssemble() */
 
 	/* buffer to store a compressed version of backup block image */
-	char		compressed_page[PGLZ_MAX_BLCKSZ];
+	char		compressed_page[COMPRESS_BUFSIZE];
 } registered_buffer;
 
 static registered_buffer *registered_buffers;
@@ -113,7 +123,8 @@ static XLogRecData *XLogRecordAssemble(RmgrId rmid, uint8 info,
 									   XLogRecPtr RedoRecPtr, bool doPageWrites,
 									   XLogRecPtr *fpw_lsn, int *num_fpi);
 static bool XLogCompressBackupBlock(char *page, uint16 hole_offset,
-									uint16 hole_length, char *dest, uint16 *dlen);
+									uint16 hole_length, char *dest,
+									uint16 *dlen, WalCompression compression);
 
 /*
  * Begin constructing a WAL record. This must be called before the
@@ -628,13 +639,14 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
 			/*
 			 * Try to compress a block image if wal_compression is enabled
 			 */
-			if (wal_compression)
+			if (wal_compression != WAL_COMPRESSION_NONE)
 			{
 				is_compressed =
 					XLogCompressBackupBlock(page, bimg.hole_offset,
 											cbimg.hole_length,
 											regbuf->compressed_page,
-											&compressed_len);
+											&compressed_len,
+											wal_compression);
 			}
 
 			/*
@@ -665,8 +677,13 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
 
 			if (is_compressed)
 			{
+				/* The current compression is stored in the WAL record */
+				wal_compression_name(wal_compression); /* Range check */
+				Assert(wal_compression < (1 << BKPIMAGE_COMPRESS_BITS));
+
 				bimg.length = compressed_len;
-				bimg.bimg_info |= BKPIMAGE_IS_COMPRESSED;
+				bimg.bimg_info |=
+					wal_compression << BKPIMAGE_COMPRESS_OFFSET_BITS;
 
 				rdt_datas_last->data = regbuf->compressed_page;
 				rdt_datas_last->len = compressed_len;
@@ -827,7 +844,7 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
  */
 static bool
 XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
-						char *dest, uint16 *dlen)
+						char *dest, uint16 *dlen, WalCompression compression)
 {
 	int32		orig_len = BLCKSZ - hole_length;
 	int32		len;
@@ -853,12 +870,42 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 	else
 		source = page;
 
+	switch (compression)
+	{
+	case WAL_COMPRESSION_PGLZ:
+		len = pglz_compress(source, orig_len, dest, PGLZ_strategy_default);
+		break;
+
+#ifdef HAVE_LIBZ
+	case WAL_COMPRESSION_ZLIB:
+		{
+			unsigned long	len_l = COMPRESS_BUFSIZE;
+			int ret;
+			ret = compress2((Bytef*)dest, &len_l, (Bytef*)source, orig_len, 1);
+			if (ret != Z_OK)
+				len_l = -1;
+			len = len_l;
+			break;
+		}
+#endif
+
+	default:
+		/*
+		 * It should be impossible to get here for unsupported algorithms,
+		 * which cannot be assigned if they're not enabled at compile time.
+		 */
+		ereport(ERROR,
+			(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			 errmsg("unknown compression method requested: %d/%s",
+				 compression, wal_compression_name(compression))));
+
+	}
+
 	/*
-	 * We recheck the actual size even if pglz_compress() reports success and
+	 * We recheck the actual size even if compression reports success and
 	 * see if the number of bytes saved by compression is larger than the
 	 * length of extra data needed for the compressed version of block image.
 	 */
-	len = pglz_compress(source, orig_len, dest, PGLZ_strategy_default);
 	if (len >= 0 &&
 		len + extra_bytes < orig_len)
 	{
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index 42738eb940..822b2612cd 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -26,6 +26,7 @@
 #include "catalog/pg_control.h"
 #include "common/pg_lzcompress.h"
 #include "replication/origin.h"
+#include "utils/guc.h"
 
 #ifndef FRONTEND
 #include "miscadmin.h"
@@ -33,6 +34,10 @@
 #include "utils/memutils.h"
 #endif
 
+#ifdef HAVE_LIBZ
+#include <zlib.h>
+#endif
+
 static void report_invalid_record(XLogReaderState *state, const char *fmt,...)
 			pg_attribute_printf(2, 3);
 static bool allocate_recordbuf(XLogReaderState *state, uint32 reclength);
@@ -50,6 +55,27 @@ static void WALOpenSegmentInit(WALOpenSegment *seg, WALSegmentContext *segcxt,
 /* size of the buffer allocated for error message. */
 #define MAX_ERRORMSG_LEN 1000
 
+/*
+ * Accept the likely variants for none and pglz, for compatibility with old
+ * server versions where wal_compression was a boolean.
+ */
+const struct config_enum_entry wal_compression_options[] = {
+	{"off", WAL_COMPRESSION_NONE, false},
+	{"none", WAL_COMPRESSION_NONE, false},
+	{"false", WAL_COMPRESSION_NONE, true},
+	{"no", WAL_COMPRESSION_NONE, true},
+	{"0", WAL_COMPRESSION_NONE, true},
+	{"pglz", WAL_COMPRESSION_PGLZ, false},
+	{"true", WAL_COMPRESSION_PGLZ, true},
+	{"yes", WAL_COMPRESSION_PGLZ, true},
+	{"on", WAL_COMPRESSION_PGLZ, true},
+	{"1", WAL_COMPRESSION_PGLZ, true},
+#ifdef  HAVE_LIBZ
+	{"zlib", WAL_COMPRESSION_ZLIB, false},
+#endif
+	{NULL, 0, false}
+};
+
 /*
  * Construct a string in state->errormsg_buf explaining what's wrong with
  * the current record being read.
@@ -1290,7 +1316,7 @@ DecodeXLogRecord(XLogReaderState *state, XLogRecord *record, char **errormsg)
 
 				blk->apply_image = ((blk->bimg_info & BKPIMAGE_APPLY) != 0);
 
-				if (blk->bimg_info & BKPIMAGE_IS_COMPRESSED)
+				if (BKPIMAGE_IS_COMPRESSED(blk->bimg_info))
 				{
 					if (blk->bimg_info & BKPIMAGE_HAS_HOLE)
 						COPY_HEADER_FIELD(&blk->hole_length, sizeof(uint16));
@@ -1335,29 +1361,28 @@ DecodeXLogRecord(XLogReaderState *state, XLogRecord *record, char **errormsg)
 				}
 
 				/*
-				 * cross-check that bimg_len < BLCKSZ if the IS_COMPRESSED
-				 * flag is set.
+				 * cross-check that bimg_len < BLCKSZ if it's compressed
 				 */
-				if ((blk->bimg_info & BKPIMAGE_IS_COMPRESSED) &&
+				if (BKPIMAGE_IS_COMPRESSED(blk->bimg_info) &&
 					blk->bimg_len == BLCKSZ)
 				{
 					report_invalid_record(state,
-										  "BKPIMAGE_IS_COMPRESSED set, but block image length %u at %X/%X",
+										  "BKPIMAGE_IS_COMPRESSED, but block image length %u at %X/%X",
 										  (unsigned int) blk->bimg_len,
 										  LSN_FORMAT_ARGS(state->ReadRecPtr));
 					goto err;
 				}
 
 				/*
-				 * cross-check that bimg_len = BLCKSZ if neither HAS_HOLE nor
-				 * IS_COMPRESSED flag is set.
+				 * cross-check that bimg_len = BLCKSZ if neither HAS_HOLE is
+				 * set nor IS_COMPRESSED().
 				 */
 				if (!(blk->bimg_info & BKPIMAGE_HAS_HOLE) &&
-					!(blk->bimg_info & BKPIMAGE_IS_COMPRESSED) &&
+					!BKPIMAGE_IS_COMPRESSED(blk->bimg_info) &&
 					blk->bimg_len != BLCKSZ)
 				{
 					report_invalid_record(state,
-										  "neither BKPIMAGE_HAS_HOLE nor BKPIMAGE_IS_COMPRESSED set, but block image length is %u at %X/%X",
+										  "neither BKPIMAGE_HAS_HOLE nor BKPIMAGE_IS_COMPRESSED, but block image length is %u at %X/%X",
 										  (unsigned int) blk->data_len,
 										  LSN_FORMAT_ARGS(state->ReadRecPtr));
 					goto err;
@@ -1535,6 +1560,22 @@ XLogRecGetBlockData(XLogReaderState *record, uint8 block_id, Size *len)
 	}
 }
 
+/*
+ * Return a statically allocated string associated with the given compression
+ * method.
+ */
+const char *
+wal_compression_name(WalCompression compression)
+{
+	for (int i=0; wal_compression_options[i].name != NULL; ++i)
+	{
+		if (wal_compression_options[i].val == compression)
+			return wal_compression_options[i].name;
+	}
+
+	return "???";
+}
+
 /*
  * Restore a full-page image from a backup block attached to an XLOG record.
  *
@@ -1555,11 +1596,43 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 	bkpb = &record->blocks[block_id];
 	ptr = bkpb->bkp_image;
 
-	if (bkpb->bimg_info & BKPIMAGE_IS_COMPRESSED)
+	if (BKPIMAGE_IS_COMPRESSED(bkpb->bimg_info))
 	{
+		int compression_method = BKPIMAGE_COMPRESSION(bkpb->bimg_info);
 		/* If a backup block image is compressed, decompress it */
-		if (pglz_decompress(ptr, bkpb->bimg_len, tmp.data,
-							BLCKSZ - bkpb->hole_length, true) < 0)
+		int32 decomp_result = -1;
+		switch (compression_method)
+		{
+		case WAL_COMPRESSION_PGLZ:
+			decomp_result = pglz_decompress(ptr, bkpb->bimg_len, tmp.data,
+							BLCKSZ - bkpb->hole_length, true);
+			break;
+
+#ifdef HAVE_LIBZ
+		case WAL_COMPRESSION_ZLIB:
+		{
+			unsigned long decomp_result_l;
+			decomp_result_l = BLCKSZ - bkpb->hole_length;
+			if (uncompress((Bytef*)tmp.data, &decomp_result_l,
+						(Bytef*)ptr, bkpb->bimg_len) == Z_OK)
+				decomp_result = decomp_result_l;
+			else
+				decomp_result = -1;
+			break;
+		}
+#endif
+
+		default:
+			report_invalid_record(record, "image at %X/%X is compressed with unsupported codec, block %d (%d/%s)",
+								  (uint32) (record->ReadRecPtr >> 32),
+								  (uint32) record->ReadRecPtr,
+								  block_id,
+								  compression_method,
+								  wal_compression_name(compression_method));
+			return false;
+		}
+
+		if (decomp_result < 0)
 		{
 			report_invalid_record(record, "invalid compressed image at %X/%X, block %d",
 								  LSN_FORMAT_ARGS(record->ReadRecPtr),
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index ee731044b6..8860deda2a 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -548,6 +548,7 @@ extern const struct config_enum_entry archive_mode_options[];
 extern const struct config_enum_entry recovery_target_action_options[];
 extern const struct config_enum_entry sync_method_options[];
 extern const struct config_enum_entry dynamic_shared_memory_options[];
+extern const struct config_enum_entry wal_compression_options[];
 
 /*
  * GUC option variables that are exported from this module
@@ -1304,16 +1305,6 @@ static struct config_bool ConfigureNamesBool[] =
 		NULL, NULL, NULL
 	},
 
-	{
-		{"wal_compression", PGC_SUSET, WAL_SETTINGS,
-			gettext_noop("Compresses full-page writes written in WAL file."),
-			NULL
-		},
-		&wal_compression,
-		false,
-		NULL, NULL, NULL
-	},
-
 	{
 		{"wal_init_zero", PGC_SUSET, WAL_SETTINGS,
 			gettext_noop("Writes zeroes to new WAL files before first use."),
@@ -4825,6 +4816,16 @@ static struct config_enum ConfigureNamesEnum[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"wal_compression", PGC_SUSET, WAL_SETTINGS,
+			gettext_noop("Set the method used to compress full page images in the WAL."),
+			NULL
+		},
+		&wal_compression,
+		WAL_COMPRESSION_NONE, wal_compression_options,
+		NULL, NULL, NULL
+	},
+
 	{
 		{"dynamic_shared_memory_type", PGC_POSTMASTER, RESOURCES_MEM,
 			gettext_noop("Selects the dynamic shared memory implementation used."),
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 6e36e4c2ef..3991d35afd 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -218,7 +218,7 @@
 #full_page_writes = on			# recover from partial page writes
 #wal_log_hints = off			# also do full page writes of non-critical updates
 					# (change requires restart)
-#wal_compression = off			# enable compression of full-page writes
+#wal_compression = off			# enable compression of full-page writes: off, pglz, zlib
 #wal_init_zero = on			# zero-fill new WAL files
 #wal_recycle = on			# recycle WAL files
 #wal_buffers = -1			# min 32kB, -1 sets based on shared_buffers
diff --git a/src/bin/pg_waldump/pg_waldump.c b/src/bin/pg_waldump/pg_waldump.c
index f8b8afe4a7..1cd71ac2f7 100644
--- a/src/bin/pg_waldump/pg_waldump.c
+++ b/src/bin/pg_waldump/pg_waldump.c
@@ -537,18 +537,21 @@ XLogDumpDisplayRecord(XLogDumpConfig *config, XLogReaderState *record)
 				   blk);
 			if (XLogRecHasBlockImage(record, block_id))
 			{
-				if (record->blocks[block_id].bimg_info &
-					BKPIMAGE_IS_COMPRESSED)
+				if (BKPIMAGE_IS_COMPRESSED(record->blocks[block_id].bimg_info))
 				{
+					int compression = BKPIMAGE_COMPRESSION(
+							record->blocks[block_id].bimg_info);
+
 					printf(" (FPW%s); hole: offset: %u, length: %u, "
-						   "compression saved: %u",
+						   "compression method %d/%s, saved: %u",
 						   XLogRecBlockImageApply(record, block_id) ?
 						   "" : " for WAL verification",
 						   record->blocks[block_id].hole_offset,
 						   record->blocks[block_id].hole_length,
+						   compression, wal_compression_name(compression),
 						   BLCKSZ -
-						   record->blocks[block_id].hole_length -
-						   record->blocks[block_id].bimg_len);
+							   record->blocks[block_id].hole_length -
+							   record->blocks[block_id].bimg_len);
 				}
 				else
 				{
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index 77187c12be..e8b2c53784 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -116,7 +116,7 @@ extern char *XLogArchiveCommand;
 extern bool EnableHotStandby;
 extern bool fullPageWrites;
 extern bool wal_log_hints;
-extern bool wal_compression;
+extern int wal_compression;
 extern bool wal_init_zero;
 extern bool wal_recycle;
 extern bool *wal_consistency_checking;
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index 26a743b6b6..8b740af66d 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -324,4 +324,14 @@ extern bool InArchiveRecovery;
 extern bool StandbyMode;
 extern char *recoveryRestoreCommand;
 
+/* These are the compression IDs written into bimg_info */
+typedef enum WalCompression
+{
+	WAL_COMPRESSION_NONE,
+	WAL_COMPRESSION_PGLZ,
+	WAL_COMPRESSION_ZLIB,
+} WalCompression;
+
+extern const char *wal_compression_name(WalCompression compression);
+
 #endif							/* XLOG_INTERNAL_H */
diff --git a/src/include/access/xlogrecord.h b/src/include/access/xlogrecord.h
index 80c92a2498..2a60c0fb92 100644
--- a/src/include/access/xlogrecord.h
+++ b/src/include/access/xlogrecord.h
@@ -114,7 +114,7 @@ typedef struct XLogRecordBlockHeader
  * present is (BLCKSZ - <length of "hole" bytes>).
  *
  * Additionally, when wal_compression is enabled, we will try to compress full
- * page images using the PGLZ compression algorithm, after removing the "hole".
+ * page images, after removing the "hole".
  * This can reduce the WAL volume, but at some extra cost of CPU spent
  * on the compression during WAL logging. In this case, since the "hole"
  * length cannot be calculated by subtracting the number of page image bytes
@@ -144,9 +144,18 @@ typedef struct XLogRecordBlockImageHeader
 
 /* Information stored in bimg_info */
 #define BKPIMAGE_HAS_HOLE		0x01	/* page image has "hole" */
-#define BKPIMAGE_IS_COMPRESSED		0x02	/* page image is compressed */
-#define BKPIMAGE_APPLY		0x04	/* page image should be restored during
+#define	BKPIMAGE_APPLY		0x02	/* page image should be restored during
 									 * replay */
+#define BKPIMAGE_COMPRESS_METHOD1	0x04	/* bits to encode compression method */
+#define BKPIMAGE_COMPRESS_METHOD2	0x08	/* 0=none, 1=pglz, 2=zlib */
+
+/* How many bits to shift to extract compression */
+#define	BKPIMAGE_COMPRESS_OFFSET_BITS	2
+/* How many bits are for compression */
+#define	BKPIMAGE_COMPRESS_BITS			2
+/* Extract the compression from the bimg_info */
+#define	BKPIMAGE_COMPRESSION(info)		((info >> BKPIMAGE_COMPRESS_OFFSET_BITS) & ((1<<BKPIMAGE_COMPRESS_BITS) - 1))
+#define	BKPIMAGE_IS_COMPRESSED(info)	(BKPIMAGE_COMPRESSION(info) != 0)
 
 /*
  * Extra header information used when page image has "hole" and
-- 
2.17.0

From 01c937b9a6847a03d0cbb9c857f11419c6fcb89a Mon Sep 17 00:00:00 2001
From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Date: Mon, 8 Mar 2021 15:32:30 +0900
Subject: [PATCH v8 2/9] Run 011_crash_recovery.pl with wal_level=minimal

The test doesn't need that feature and pg_current_xact_id() is better
exercised by turning off the feature.

Copied from: https://www.postgresql.org/message-id/20210308.173242.463790587797836129.horikyota.ntt%40gmail.com
---
 src/test/recovery/t/011_crash_recovery.pl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/test/recovery/t/011_crash_recovery.pl b/src/test/recovery/t/011_crash_recovery.pl
index a26e99500b..2e7e3db639 100644
--- a/src/test/recovery/t/011_crash_recovery.pl
+++ b/src/test/recovery/t/011_crash_recovery.pl
@@ -14,7 +14,7 @@ use Config;
 plan tests => 3;
 
 my $node = get_new_node('primary');
-$node->init(allows_streaming => 1);
+$node->init();
 $node->start;
 
 my ($stdin, $stdout, $stderr) = ('', '', '');
-- 
2.17.0

From 9e55bcf6da1d6ffda8d652f5c15060d3b0fa5c35 Mon Sep 17 00:00:00 2001
From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Date: Mon, 8 Mar 2021 15:43:01 +0900
Subject: [PATCH v8 3/9] Make sure published XIDs are persistent

pg_xact_status() premises that XIDs obtained by
pg_current_xact_id(_if_assigned)() are persistent beyond a crash. But
XIDs are not guaranteed to go beyond WAL buffers before commit and
thus XIDs may vanish if server crashes before commit. This patch
guarantees the XID shown by the functions to be flushed out to disk.

Copied from: https://www.postgresql.org/message-id/20210308.173242.463790587797836129.horikyota.ntt%40gmail.com
---
 src/backend/access/transam/xact.c | 55 +++++++++++++++++++++++++------
 src/backend/access/transam/xlog.c |  2 +-
 src/backend/utils/adt/xid8funcs.c | 12 ++++++-
 src/include/access/xact.h         |  3 +-
 4 files changed, 59 insertions(+), 13 deletions(-)

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 441445927e..da8a460722 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -201,7 +201,7 @@ typedef struct TransactionStateData
 	int			prevSecContext; /* previous SecurityRestrictionContext */
 	bool		prevXactReadOnly;	/* entry-time xact r/o state */
 	bool		startedInRecovery;	/* did we start in recovery? */
-	bool		didLogXid;		/* has xid been included in WAL record? */
+	XLogRecPtr 	minLSN;			/* LSN needed to reach to record the xid */
 	int			parallelModeLevel;	/* Enter/ExitParallelMode counter */
 	bool		chain;			/* start a new block after this one */
 	bool		assigned;		/* assigned to top-level XID */
@@ -520,14 +520,46 @@ GetCurrentFullTransactionIdIfAny(void)
  *	MarkCurrentTransactionIdLoggedIfAny
  *
  * Remember that the current xid - if it is assigned - now has been wal logged.
+ *
+ * upto is the LSN up to which we need to flush WAL to ensure the current xid
+ * to be persistent. See EnsureCurrentTransactionIdLogged().
  */
 void
-MarkCurrentTransactionIdLoggedIfAny(void)
+MarkCurrentTransactionIdLoggedIfAny(XLogRecPtr upto)
 {
-	if (FullTransactionIdIsValid(CurrentTransactionState->fullTransactionId))
-		CurrentTransactionState->didLogXid = true;
+	if (FullTransactionIdIsValid(CurrentTransactionState->fullTransactionId) &&
+		XLogRecPtrIsInvalid(CurrentTransactionState->minLSN))
+		CurrentTransactionState->minLSN = upto;
 }
 
+/*
+ *	EnsureCurrentTransactionIdLogged
+ *
+ * Make sure that the current top XID is WAL-logged.
+ */
+void
+EnsureTopTransactionIdLogged(void)
+{
+	/*
+	 * We need at least one WAL record for the current top transaction to be
+	 * flushed out.  Write one if we don't have one yet.
+	 */
+	if (XLogRecPtrIsInvalid(TopTransactionStateData.minLSN))
+	{
+		xl_xact_assignment xlrec;
+
+		xlrec.xtop = XidFromFullTransactionId(XactTopFullTransactionId);
+		Assert(TransactionIdIsValid(xlrec.xtop));
+		xlrec.nsubxacts = 0;
+
+		XLogBeginInsert();
+		XLogRegisterData((char *) &xlrec, MinSizeOfXactAssignment);
+		TopTransactionStateData.minLSN =
+			XLogInsert(RM_XACT_ID, XLOG_XACT_ASSIGNMENT);
+	}
+
+	XLogFlush(TopTransactionStateData.minLSN);
+}
 
 /*
  *	GetStableLatestTransactionId
@@ -616,14 +648,14 @@ AssignTransactionId(TransactionState s)
 	 * When wal_level=logical, guarantee that a subtransaction's xid can only
 	 * be seen in the WAL stream if its toplevel xid has been logged before.
 	 * If necessary we log an xact_assignment record with fewer than
-	 * PGPROC_MAX_CACHED_SUBXIDS. Note that it is fine if didLogXid isn't set
+	 * PGPROC_MAX_CACHED_SUBXIDS. Note that it is fine if minLSN isn't set
 	 * for a transaction even though it appears in a WAL record, we just might
 	 * superfluously log something. That can happen when an xid is included
 	 * somewhere inside a wal record, but not in XLogRecord->xl_xid, like in
 	 * xl_standby_locks.
 	 */
 	if (isSubXact && XLogLogicalInfoActive() &&
-		!TopTransactionStateData.didLogXid)
+		XLogRecPtrIsInvalid(TopTransactionStateData.minLSN))
 		log_unknown_top = true;
 
 	/*
@@ -693,6 +725,7 @@ AssignTransactionId(TransactionState s)
 			log_unknown_top)
 		{
 			xl_xact_assignment xlrec;
+			XLogRecPtr		   endptr;
 
 			/*
 			 * xtop is always set by now because we recurse up transaction
@@ -707,11 +740,13 @@ AssignTransactionId(TransactionState s)
 			XLogRegisterData((char *) unreportedXids,
 							 nUnreportedXids * sizeof(TransactionId));
 
-			(void) XLogInsert(RM_XACT_ID, XLOG_XACT_ASSIGNMENT);
+			endptr = XLogInsert(RM_XACT_ID, XLOG_XACT_ASSIGNMENT);
 
 			nUnreportedXids = 0;
-			/* mark top, not current xact as having been logged */
-			TopTransactionStateData.didLogXid = true;
+
+			/* set minLSN of top, not of current xact if not yet */
+			if (XLogRecPtrIsInvalid(TopTransactionStateData.minLSN))
+				TopTransactionStateData.minLSN = endptr;
 		}
 	}
 }
@@ -1996,7 +2031,7 @@ StartTransaction(void)
 	 * initialize reported xid accounting
 	 */
 	nUnreportedXids = 0;
-	s->didLogXid = false;
+	s->minLSN = InvalidXLogRecPtr;
 
 	/*
 	 * must initialize resource-management stuff first
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 64094e7175..18d8743715 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -1162,7 +1162,7 @@ XLogInsertRecord(XLogRecData *rdata,
 	 */
 	WALInsertLockRelease();
 
-	MarkCurrentTransactionIdLoggedIfAny();
+	MarkCurrentTransactionIdLoggedIfAny(EndPos);
 
 	END_CRIT_SECTION();
 
diff --git a/src/backend/utils/adt/xid8funcs.c b/src/backend/utils/adt/xid8funcs.c
index cc2b4ac797..992482f8c8 100644
--- a/src/backend/utils/adt/xid8funcs.c
+++ b/src/backend/utils/adt/xid8funcs.c
@@ -357,6 +357,8 @@ bad_format:
 Datum
 pg_current_xact_id(PG_FUNCTION_ARGS)
 {
+	FullTransactionId xid;
+
 	/*
 	 * Must prevent during recovery because if an xid is not assigned we try
 	 * to assign one, which would fail. Programs already rely on this function
@@ -365,7 +367,12 @@ pg_current_xact_id(PG_FUNCTION_ARGS)
 	 */
 	PreventCommandDuringRecovery("pg_current_xact_id()");
 
-	PG_RETURN_FULLTRANSACTIONID(GetTopFullTransactionId());
+	xid = GetTopFullTransactionId();
+
+	/* the XID is going to be published, make sure it is psersistent */
+	EnsureTopTransactionIdLogged();
+
+	PG_RETURN_FULLTRANSACTIONID(xid);
 }
 
 /*
@@ -380,6 +387,9 @@ pg_current_xact_id_if_assigned(PG_FUNCTION_ARGS)
 	if (!FullTransactionIdIsValid(topfxid))
 		PG_RETURN_NULL();
 
+	/* the XID is going to be published, make sure it is psersistent */
+	EnsureTopTransactionIdLogged();
+
 	PG_RETURN_FULLTRANSACTIONID(topfxid);
 }
 
diff --git a/src/include/access/xact.h b/src/include/access/xact.h
index 134f6862da..593a4140df 100644
--- a/src/include/access/xact.h
+++ b/src/include/access/xact.h
@@ -386,7 +386,8 @@ extern FullTransactionId GetTopFullTransactionId(void);
 extern FullTransactionId GetTopFullTransactionIdIfAny(void);
 extern FullTransactionId GetCurrentFullTransactionId(void);
 extern FullTransactionId GetCurrentFullTransactionIdIfAny(void);
-extern void MarkCurrentTransactionIdLoggedIfAny(void);
+extern void MarkCurrentTransactionIdLoggedIfAny(XLogRecPtr upto);
+extern void EnsureTopTransactionIdLogged(void);
 extern bool SubTransactionIsActive(SubTransactionId subxid);
 extern CommandId GetCurrentCommandId(bool used);
 extern void SetParallelStartTimestamps(TimestampTz xact_ts, TimestampTz stmt_ts);
-- 
2.17.0

From d002f2c66fea54e04bc8c75ccf39eb1bf3c0b5a8 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Thu, 11 Mar 2021 17:36:24 -0600
Subject: [PATCH v8 4/9] wal_compression_method: default to zlib..

this is meant to exercise the CIs, and not meant to be merged
---
 src/backend/access/transam/xlog.c | 2 +-
 src/backend/utils/misc/guc.c      | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 18d8743715..bbac9ac882 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -98,7 +98,7 @@ char	   *XLogArchiveCommand = NULL;
 bool		EnableHotStandby = false;
 bool		fullPageWrites = true;
 bool		wal_log_hints = false;
-int		wal_compression = WAL_COMPRESSION_NONE;
+int		wal_compression = WAL_COMPRESSION_ZLIB;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 8860deda2a..f1d73c8b61 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -4822,7 +4822,7 @@ static struct config_enum ConfigureNamesEnum[] =
 			NULL
 		},
 		&wal_compression,
-		WAL_COMPRESSION_NONE, wal_compression_options,
+		WAL_COMPRESSION_ZLIB, wal_compression_options,
 		NULL, NULL, NULL
 	},
 
-- 
2.17.0

From cfbf78b2fa5f478b4699f881c9e9d6cfb627b976 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Mon, 24 May 2021 23:32:30 -0500
Subject: [PATCH v8 5/9] (re)add wal_compression_method: lz4

---
 doc/src/sgml/config.sgml                      |  3 ++-
 doc/src/sgml/install-windows.sgml             |  2 +-
 doc/src/sgml/installation.sgml                |  5 +++--
 src/backend/access/transam/xloginsert.c       | 17 ++++++++++++++++-
 src/backend/access/transam/xlogreader.c       | 14 ++++++++++++++
 src/backend/utils/misc/postgresql.conf.sample |  2 +-
 src/include/access/xlog_internal.h            |  1 +
 src/include/access/xlogrecord.h               |  2 +-
 8 files changed, 39 insertions(+), 7 deletions(-)

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 218a98cfc6..352b31fa81 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -3126,7 +3126,8 @@ include_dir 'conf.d'
         server compresses full page images written to WAL when
         <xref linkend="guc-full-page-writes"/> is on or during a base backup.
         A compressed page image will be decompressed during WAL replay.
-        The supported methods are pglz and zlib.
+        The supported methods are pglz, zlib, and (if configured when
+        <productname>PostgreSQL</productname> was built) lz4.
         The default value is <literal>off</literal>.
         Only superusers can change this setting.
        </para>
diff --git a/doc/src/sgml/install-windows.sgml b/doc/src/sgml/install-windows.sgml
index db53ee85a8..a023584722 100644
--- a/doc/src/sgml/install-windows.sgml
+++ b/doc/src/sgml/install-windows.sgml
@@ -299,7 +299,7 @@ $ENV{MSBFLAGS}="/m";
      <term><productname>LZ4</productname></term>
      <listitem><para>
       Required for supporting <productname>LZ4</productname> compression
-      method for compressing the table data. Binaries and source can be
+      method for compressing table or WAL data. Binaries and source can be
       downloaded from
       <ulink url="https://github.com/lz4/lz4/releases"></ulink>.
      </para></listitem>
diff --git a/doc/src/sgml/installation.sgml b/doc/src/sgml/installation.sgml
index 073d5089f7..c7673a4dc8 100644
--- a/doc/src/sgml/installation.sgml
+++ b/doc/src/sgml/installation.sgml
@@ -270,7 +270,8 @@ su - postgres
      <para>
       You need <productname>LZ4</productname>, if you want to support
       compression of data with this method; see
-      <xref linkend="guc-default-toast-compression"/>.
+      <xref linkend="guc-default-toast-compression"/> and
+      <xref linkend="guc-wal-compression"/>.
      </para>
     </listitem>
 
@@ -980,7 +981,7 @@ build-postgresql:
         <para>
          Build with <productname>LZ4</productname> compression support.
          This allows the use of <productname>LZ4</productname> for
-         compression of table data.
+         compression of table and WAL data.
         </para>
        </listitem>
       </varlistentry>
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
index 4f81f19c49..a8794a941a 100644
--- a/src/backend/access/transam/xloginsert.c
+++ b/src/backend/access/transam/xloginsert.c
@@ -41,10 +41,17 @@
 #define ZLIB_MAX_BLCKSZ		0
 #endif
 
+#ifdef USE_LZ4
+#include "lz4.h"
+#define	LZ4_MAX_BLCKSZ		LZ4_COMPRESSBOUND(BLCKSZ)
+#else
+#define LZ4_MAX_BLCKSZ		0
+#endif
+
 /* Buffer size required to store a compressed version of backup block image */
 #define PGLZ_MAX_BLCKSZ		PGLZ_MAX_OUTPUT(BLCKSZ)
 
-#define COMPRESS_BUFSIZE	Max(PGLZ_MAX_BLCKSZ, ZLIB_MAX_BLCKSZ)
+#define COMPRESS_BUFSIZE	Max(Max(PGLZ_MAX_BLCKSZ, ZLIB_MAX_BLCKSZ), LZ4_MAX_BLCKSZ)
 
 /*
  * For each block reference registered with XLogRegisterBuffer, we fill in
@@ -889,6 +896,14 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 		}
 #endif
 
+#ifdef USE_LZ4
+	case WAL_COMPRESSION_LZ4:
+		len = LZ4_compress_fast(source, dest, orig_len, COMPRESS_BUFSIZE, 1);
+		if (len == 0)
+			len = -1;
+		break;
+#endif
+
 	default:
 		/*
 		 * It should be impossible to get here for unsupported algorithms,
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index 822b2612cd..753b38e58a 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -38,6 +38,10 @@
 #include <zlib.h>
 #endif
 
+#ifdef USE_LZ4
+#include "lz4.h"
+#endif
+
 static void report_invalid_record(XLogReaderState *state, const char *fmt,...)
 			pg_attribute_printf(2, 3);
 static bool allocate_recordbuf(XLogReaderState *state, uint32 reclength);
@@ -72,6 +76,9 @@ const struct config_enum_entry wal_compression_options[] = {
 	{"1", WAL_COMPRESSION_PGLZ, true},
 #ifdef  HAVE_LIBZ
 	{"zlib", WAL_COMPRESSION_ZLIB, false},
+#endif
+#ifdef  USE_LZ4
+	{"lz4", WAL_COMPRESSION_LZ4, false},
 #endif
 	{NULL, 0, false}
 };
@@ -1622,6 +1629,13 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 		}
 #endif
 
+#ifdef USE_LZ4
+		case WAL_COMPRESSION_LZ4:
+			decomp_result = LZ4_decompress_safe(ptr, tmp.data,
+					bkpb->bimg_len, BLCKSZ-bkpb->hole_length);
+			break;
+#endif
+
 		default:
 			report_invalid_record(record, "image at %X/%X is compressed with unsupported codec, block %d (%d/%s)",
 								  (uint32) (record->ReadRecPtr >> 32),
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 3991d35afd..dbf3155502 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -218,7 +218,7 @@
 #full_page_writes = on			# recover from partial page writes
 #wal_log_hints = off			# also do full page writes of non-critical updates
 					# (change requires restart)
-#wal_compression = off			# enable compression of full-page writes: off, pglz, zlib
+#wal_compression = off			# enable compression of full-page writes: off, pglz, zlib, lz4
 #wal_init_zero = on			# zero-fill new WAL files
 #wal_recycle = on			# recycle WAL files
 #wal_buffers = -1			# min 32kB, -1 sets based on shared_buffers
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index 8b740af66d..0287592cd4 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -330,6 +330,7 @@ typedef enum WalCompression
 	WAL_COMPRESSION_NONE,
 	WAL_COMPRESSION_PGLZ,
 	WAL_COMPRESSION_ZLIB,
+	WAL_COMPRESSION_LZ4,
 } WalCompression;
 
 extern const char *wal_compression_name(WalCompression compression);
diff --git a/src/include/access/xlogrecord.h b/src/include/access/xlogrecord.h
index 2a60c0fb92..abb42b364d 100644
--- a/src/include/access/xlogrecord.h
+++ b/src/include/access/xlogrecord.h
@@ -147,7 +147,7 @@ typedef struct XLogRecordBlockImageHeader
 #define	BKPIMAGE_APPLY		0x02	/* page image should be restored during
 									 * replay */
 #define BKPIMAGE_COMPRESS_METHOD1	0x04	/* bits to encode compression method */
-#define BKPIMAGE_COMPRESS_METHOD2	0x08	/* 0=none, 1=pglz, 2=zlib */
+#define BKPIMAGE_COMPRESS_METHOD2	0x08	/* 0=none, 1=pglz, 2=zlib, 3=lz4 */
 
 /* How many bits to shift to extract compression */
 #define	BKPIMAGE_COMPRESS_OFFSET_BITS	2
-- 
2.17.0

From 11ff52f20a3079e60186eab6c749b30ba3f5fe87 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Fri, 12 Mar 2021 15:35:40 -0600
Subject: [PATCH v8 6/9] Default to LZ4..

this is meant to exercise in the CIs, and not meant to be merged
---
 configure                         | 6 ++++--
 configure.ac                      | 4 ++--
 src/backend/access/transam/xlog.c | 2 +-
 src/backend/utils/misc/guc.c      | 2 +-
 4 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/configure b/configure
index e9b98f442f..7038b0727c 100755
--- a/configure
+++ b/configure
@@ -1575,7 +1575,7 @@ Optional Packages:
   --with-system-tzdata=DIR
                           use system time zone data in DIR
   --without-zlib          do not use Zlib
-  --with-lz4              build with LZ4 support
+  --without-lz4           build without LZ4 support
   --with-gnu-ld           assume the C compiler uses GNU ld [default=no]
   --with-ssl=LIB          use LIB for SSL/TLS support (openssl)
   --with-openssl          obsolete spelling of --with-ssl=openssl
@@ -8598,7 +8598,9 @@ $as_echo "#define USE_LZ4 1" >>confdefs.h
   esac
 
 else
-  with_lz4=no
+  with_lz4=yes
+
+$as_echo "#define USE_LZ4 1" >>confdefs.h
 
 fi
 
diff --git a/configure.ac b/configure.ac
index 3b42d8bdc9..cb0261f179 100644
--- a/configure.ac
+++ b/configure.ac
@@ -990,8 +990,8 @@ AC_SUBST(with_zlib)
 # LZ4
 #
 AC_MSG_CHECKING([whether to build with LZ4 support])
-PGAC_ARG_BOOL(with, lz4, no, [build with LZ4 support],
-              [AC_DEFINE([USE_LZ4], 1, [Define to 1 to build with LZ4 support. (--with-lz4)])])
+PGAC_ARG_BOOL(with, lz4, yes, [build without LZ4 support],
+              [AC_DEFINE([USE_LZ4], 1, [Define to 1 to build without LZ4 support. (--without-lz4)])])
 AC_MSG_RESULT([$with_lz4])
 AC_SUBST(with_lz4)
 
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index bbac9ac882..75fbf11229 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -98,7 +98,7 @@ char	   *XLogArchiveCommand = NULL;
 bool		EnableHotStandby = false;
 bool		fullPageWrites = true;
 bool		wal_log_hints = false;
-int		wal_compression = WAL_COMPRESSION_ZLIB;
+int		wal_compression = WAL_COMPRESSION_LZ4;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index f1d73c8b61..89ae829719 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -4822,7 +4822,7 @@ static struct config_enum ConfigureNamesEnum[] =
 			NULL
 		},
 		&wal_compression,
-		WAL_COMPRESSION_ZLIB, wal_compression_options,
+		WAL_COMPRESSION_LZ4, wal_compression_options,
 		NULL, NULL, NULL
 	},
 
-- 
2.17.0

From d006044bdd6272fa4e37890b8e634b0b2a179dff Mon Sep 17 00:00:00 2001
From: Andrey Borodin <amborodin@acm.org>
Date: Sat, 27 Feb 2021 09:03:50 +0500
Subject: [PATCH v9 1/9] Allow alternate compression methods for
 wal_compression

TODO: bump XLOG_PAGE_MAGIC
---
 doc/src/sgml/config.sgml                      |  9 +-
 doc/src/sgml/installation.sgml                |  4 +-
 src/backend/Makefile                          |  2 +-
 src/backend/access/transam/xlog.c             | 14 ++-
 src/backend/access/transam/xloginsert.c       | 65 ++++++++++--
 src/backend/access/transam/xlogreader.c       | 99 ++++++++++++++++---
 src/backend/utils/misc/guc.c                  | 21 ++--
 src/backend/utils/misc/postgresql.conf.sample |  2 +-
 src/bin/pg_waldump/pg_waldump.c               | 13 ++-
 src/include/access/xlog.h                     |  2 +-
 src/include/access/xlog_internal.h            | 10 ++
 src/include/access/xlogrecord.h               | 15 ++-
 12 files changed, 207 insertions(+), 49 deletions(-)

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index aa3e178240..1df56d8034 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -3127,23 +3127,26 @@ include_dir 'conf.d'
      </varlistentry>
 
      <varlistentry id="guc-wal-compression" xreflabel="wal_compression">
-      <term><varname>wal_compression</varname> (<type>boolean</type>)
+      <term><varname>wal_compression</varname> (<type>enum</type>)
       <indexterm>
        <primary><varname>wal_compression</varname> configuration parameter</primary>
       </indexterm>
       </term>
       <listitem>
        <para>
-        When this parameter is <literal>on</literal>, the <productname>PostgreSQL</productname>
+        This parameter enables compression of WAL using the specified 
+        compression method.
+        When enabled, the <productname>PostgreSQL</productname>
         server compresses full page images written to WAL when
         <xref linkend="guc-full-page-writes"/> is on or during a base backup.
         A compressed page image will be decompressed during WAL replay.
+        The supported methods are pglz and zlib.
         The default value is <literal>off</literal>.
         Only superusers can change this setting.
        </para>
 
        <para>
-        Turning this parameter on can reduce the WAL volume without
+        Enabling compression can reduce the WAL volume without
         increasing the risk of unrecoverable data corruption,
         but at the cost of some extra CPU spent on the compression during
         WAL logging and on the decompression during WAL replay.
diff --git a/doc/src/sgml/installation.sgml b/doc/src/sgml/installation.sgml
index 3c0aa118c7..073d5089f7 100644
--- a/doc/src/sgml/installation.sgml
+++ b/doc/src/sgml/installation.sgml
@@ -147,7 +147,7 @@ su - postgres
       specify the <option>--without-zlib</option> option to
       <filename>configure</filename>. Using this option disables
       support for compressed archives in <application>pg_dump</application> and
-      <application>pg_restore</application>.
+      <application>pg_restore</application>, and compressed WAL.
      </para>
     </listitem>
    </itemizedlist>
@@ -1236,7 +1236,7 @@ build-postgresql:
          Prevents use of the <application>Zlib</application> library.
          This disables
          support for compressed archives in <application>pg_dump</application>
-         and <application>pg_restore</application>.
+         and <application>pg_restore</application> and compressed WAL.
         </para>
        </listitem>
       </varlistentry>
diff --git a/src/backend/Makefile b/src/backend/Makefile
index 0da848b1fd..3af216ddfc 100644
--- a/src/backend/Makefile
+++ b/src/backend/Makefile
@@ -48,7 +48,7 @@ OBJS = \
 LIBS := $(filter-out -lpgport -lpgcommon, $(LIBS)) $(LDAP_LIBS_BE) $(ICU_LIBS)
 
 # The backend doesn't need everything that's in LIBS, however
-LIBS := $(filter-out -lz -lreadline -ledit -ltermcap -lncurses -lcurses, $(LIBS))
+LIBS := $(filter-out -lreadline -ledit -ltermcap -lncurses -lcurses, $(LIBS))
 
 ifeq ($(with_systemd),yes)
 LIBS += -lsystemd
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 17eeff0720..1ccc51575a 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -98,7 +98,7 @@ char	   *XLogArchiveCommand = NULL;
 bool		EnableHotStandby = false;
 bool		fullPageWrites = true;
 bool		wal_log_hints = false;
-bool		wal_compression = false;
+int		wal_compression = WAL_COMPRESSION_NONE;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
@@ -10470,7 +10470,17 @@ xlog_block_info(StringInfo buf, XLogReaderState *record)
 							 rnode.spcNode, rnode.dbNode, rnode.relNode,
 							 blk);
 		if (XLogRecHasBlockImage(record, block_id))
-			appendStringInfoString(buf, " FPW");
+		{
+			int compression =
+				BKPIMAGE_IS_COMPRESSED(record->blocks[block_id].bimg_info) ?
+				BKPIMAGE_COMPRESSION(record->blocks[block_id].bimg_info) : -1;
+			if (compression == -1)
+				appendStringInfoString(buf, " FPW");
+			else
+				appendStringInfo(buf, " FPW, compression method %d/%s",
+					compression, wal_compression_name(compression));
+		}
+
 	}
 }
 
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
index 32b4cc84e7..4f81f19c49 100644
--- a/src/backend/access/transam/xloginsert.c
+++ b/src/backend/access/transam/xloginsert.c
@@ -33,8 +33,18 @@
 #include "storage/proc.h"
 #include "utils/memutils.h"
 
+#ifdef HAVE_LIBZ
+#include <zlib.h>
+/* zlib compressBound is not a macro */
+#define ZLIB_MAX_BLCKSZ		BLCKSZ + (BLCKSZ>>12) + (BLCKSZ>>14) + (BLCKSZ>>25) + 13
+#else
+#define ZLIB_MAX_BLCKSZ		0
+#endif
+
 /* Buffer size required to store a compressed version of backup block image */
-#define PGLZ_MAX_BLCKSZ PGLZ_MAX_OUTPUT(BLCKSZ)
+#define PGLZ_MAX_BLCKSZ		PGLZ_MAX_OUTPUT(BLCKSZ)
+
+#define COMPRESS_BUFSIZE	Max(PGLZ_MAX_BLCKSZ, ZLIB_MAX_BLCKSZ)
 
 /*
  * For each block reference registered with XLogRegisterBuffer, we fill in
@@ -58,7 +68,7 @@ typedef struct
 								 * backup block data in XLogRecordAssemble() */
 
 	/* buffer to store a compressed version of backup block image */
-	char		compressed_page[PGLZ_MAX_BLCKSZ];
+	char		compressed_page[COMPRESS_BUFSIZE];
 } registered_buffer;
 
 static registered_buffer *registered_buffers;
@@ -113,7 +123,8 @@ static XLogRecData *XLogRecordAssemble(RmgrId rmid, uint8 info,
 									   XLogRecPtr RedoRecPtr, bool doPageWrites,
 									   XLogRecPtr *fpw_lsn, int *num_fpi);
 static bool XLogCompressBackupBlock(char *page, uint16 hole_offset,
-									uint16 hole_length, char *dest, uint16 *dlen);
+									uint16 hole_length, char *dest,
+									uint16 *dlen, WalCompression compression);
 
 /*
  * Begin constructing a WAL record. This must be called before the
@@ -628,13 +639,14 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
 			/*
 			 * Try to compress a block image if wal_compression is enabled
 			 */
-			if (wal_compression)
+			if (wal_compression != WAL_COMPRESSION_NONE)
 			{
 				is_compressed =
 					XLogCompressBackupBlock(page, bimg.hole_offset,
 											cbimg.hole_length,
 											regbuf->compressed_page,
-											&compressed_len);
+											&compressed_len,
+											wal_compression);
 			}
 
 			/*
@@ -665,8 +677,13 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
 
 			if (is_compressed)
 			{
+				/* The current compression is stored in the WAL record */
+				wal_compression_name(wal_compression); /* Range check */
+				Assert(wal_compression < (1 << BKPIMAGE_COMPRESS_BITS));
+
 				bimg.length = compressed_len;
-				bimg.bimg_info |= BKPIMAGE_IS_COMPRESSED;
+				bimg.bimg_info |=
+					wal_compression << BKPIMAGE_COMPRESS_OFFSET_BITS;
 
 				rdt_datas_last->data = regbuf->compressed_page;
 				rdt_datas_last->len = compressed_len;
@@ -827,7 +844,7 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
  */
 static bool
 XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
-						char *dest, uint16 *dlen)
+						char *dest, uint16 *dlen, WalCompression compression)
 {
 	int32		orig_len = BLCKSZ - hole_length;
 	int32		len;
@@ -853,12 +870,42 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 	else
 		source = page;
 
+	switch (compression)
+	{
+	case WAL_COMPRESSION_PGLZ:
+		len = pglz_compress(source, orig_len, dest, PGLZ_strategy_default);
+		break;
+
+#ifdef HAVE_LIBZ
+	case WAL_COMPRESSION_ZLIB:
+		{
+			unsigned long	len_l = COMPRESS_BUFSIZE;
+			int ret;
+			ret = compress2((Bytef*)dest, &len_l, (Bytef*)source, orig_len, 1);
+			if (ret != Z_OK)
+				len_l = -1;
+			len = len_l;
+			break;
+		}
+#endif
+
+	default:
+		/*
+		 * It should be impossible to get here for unsupported algorithms,
+		 * which cannot be assigned if they're not enabled at compile time.
+		 */
+		ereport(ERROR,
+			(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			 errmsg("unknown compression method requested: %d/%s",
+				 compression, wal_compression_name(compression))));
+
+	}
+
 	/*
-	 * We recheck the actual size even if pglz_compress() reports success and
+	 * We recheck the actual size even if compression reports success and
 	 * see if the number of bytes saved by compression is larger than the
 	 * length of extra data needed for the compressed version of block image.
 	 */
-	len = pglz_compress(source, orig_len, dest, PGLZ_strategy_default);
 	if (len >= 0 &&
 		len + extra_bytes < orig_len)
 	{
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index 42738eb940..3a922caaeb 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -26,6 +26,7 @@
 #include "catalog/pg_control.h"
 #include "common/pg_lzcompress.h"
 #include "replication/origin.h"
+#include "utils/guc.h"
 
 #ifndef FRONTEND
 #include "miscadmin.h"
@@ -33,6 +34,10 @@
 #include "utils/memutils.h"
 #endif
 
+#ifdef HAVE_LIBZ
+#include <zlib.h>
+#endif
+
 static void report_invalid_record(XLogReaderState *state, const char *fmt,...)
 			pg_attribute_printf(2, 3);
 static bool allocate_recordbuf(XLogReaderState *state, uint32 reclength);
@@ -50,6 +55,29 @@ static void WALOpenSegmentInit(WALOpenSegment *seg, WALSegmentContext *segcxt,
 /* size of the buffer allocated for error message. */
 #define MAX_ERRORMSG_LEN 1000
 
+/*
+ * Accept the likely variants for none and pglz, for compatibility with old
+ * server versions where wal_compression was a boolean.
+ */
+const struct config_enum_entry wal_compression_options[] = {
+	{"off", WAL_COMPRESSION_NONE, false},
+	{"none", WAL_COMPRESSION_NONE, false},
+	{"false", WAL_COMPRESSION_NONE, true},
+	{"no", WAL_COMPRESSION_NONE, true},
+	{"0", WAL_COMPRESSION_NONE, true},
+	{"pglz", WAL_COMPRESSION_PGLZ, false},
+	{"true", WAL_COMPRESSION_PGLZ, true},
+	{"yes", WAL_COMPRESSION_PGLZ, true},
+	{"on", WAL_COMPRESSION_PGLZ, true},
+	{"1", WAL_COMPRESSION_PGLZ, true},
+
+#ifdef  HAVE_LIBZ
+	{"zlib", WAL_COMPRESSION_ZLIB, false},
+#endif
+
+	{NULL, 0, false}
+};
+
 /*
  * Construct a string in state->errormsg_buf explaining what's wrong with
  * the current record being read.
@@ -1290,7 +1318,7 @@ DecodeXLogRecord(XLogReaderState *state, XLogRecord *record, char **errormsg)
 
 				blk->apply_image = ((blk->bimg_info & BKPIMAGE_APPLY) != 0);
 
-				if (blk->bimg_info & BKPIMAGE_IS_COMPRESSED)
+				if (BKPIMAGE_IS_COMPRESSED(blk->bimg_info))
 				{
 					if (blk->bimg_info & BKPIMAGE_HAS_HOLE)
 						COPY_HEADER_FIELD(&blk->hole_length, sizeof(uint16));
@@ -1335,29 +1363,28 @@ DecodeXLogRecord(XLogReaderState *state, XLogRecord *record, char **errormsg)
 				}
 
 				/*
-				 * cross-check that bimg_len < BLCKSZ if the IS_COMPRESSED
-				 * flag is set.
+				 * cross-check that bimg_len < BLCKSZ if it's compressed
 				 */
-				if ((blk->bimg_info & BKPIMAGE_IS_COMPRESSED) &&
+				if (BKPIMAGE_IS_COMPRESSED(blk->bimg_info) &&
 					blk->bimg_len == BLCKSZ)
 				{
 					report_invalid_record(state,
-										  "BKPIMAGE_IS_COMPRESSED set, but block image length %u at %X/%X",
+										  "BKPIMAGE_IS_COMPRESSED, but block image length %u at %X/%X",
 										  (unsigned int) blk->bimg_len,
 										  LSN_FORMAT_ARGS(state->ReadRecPtr));
 					goto err;
 				}
 
 				/*
-				 * cross-check that bimg_len = BLCKSZ if neither HAS_HOLE nor
-				 * IS_COMPRESSED flag is set.
+				 * cross-check that bimg_len = BLCKSZ if neither HAS_HOLE is
+				 * set nor IS_COMPRESSED().
 				 */
 				if (!(blk->bimg_info & BKPIMAGE_HAS_HOLE) &&
-					!(blk->bimg_info & BKPIMAGE_IS_COMPRESSED) &&
+					!BKPIMAGE_IS_COMPRESSED(blk->bimg_info) &&
 					blk->bimg_len != BLCKSZ)
 				{
 					report_invalid_record(state,
-										  "neither BKPIMAGE_HAS_HOLE nor BKPIMAGE_IS_COMPRESSED set, but block image length is %u at %X/%X",
+										  "neither BKPIMAGE_HAS_HOLE nor BKPIMAGE_IS_COMPRESSED, but block image length is %u at %X/%X",
 										  (unsigned int) blk->data_len,
 										  LSN_FORMAT_ARGS(state->ReadRecPtr));
 					goto err;
@@ -1535,6 +1562,22 @@ XLogRecGetBlockData(XLogReaderState *record, uint8 block_id, Size *len)
 	}
 }
 
+/*
+ * Return a statically allocated string associated with the given compression
+ * method.
+ */
+const char *
+wal_compression_name(WalCompression compression)
+{
+	for (int i=0; wal_compression_options[i].name != NULL; ++i)
+	{
+		if (wal_compression_options[i].val == compression)
+			return wal_compression_options[i].name;
+	}
+
+	return "???";
+}
+
 /*
  * Restore a full-page image from a backup block attached to an XLOG record.
  *
@@ -1555,11 +1598,43 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 	bkpb = &record->blocks[block_id];
 	ptr = bkpb->bkp_image;
 
-	if (bkpb->bimg_info & BKPIMAGE_IS_COMPRESSED)
+	if (BKPIMAGE_IS_COMPRESSED(bkpb->bimg_info))
 	{
+		int compression_method = BKPIMAGE_COMPRESSION(bkpb->bimg_info);
 		/* If a backup block image is compressed, decompress it */
-		if (pglz_decompress(ptr, bkpb->bimg_len, tmp.data,
-							BLCKSZ - bkpb->hole_length, true) < 0)
+		int32 decomp_result = -1;
+		switch (compression_method)
+		{
+		case WAL_COMPRESSION_PGLZ:
+			decomp_result = pglz_decompress(ptr, bkpb->bimg_len, tmp.data,
+							BLCKSZ - bkpb->hole_length, true);
+			break;
+
+#ifdef HAVE_LIBZ
+		case WAL_COMPRESSION_ZLIB:
+		{
+			unsigned long decomp_result_l;
+			decomp_result_l = BLCKSZ - bkpb->hole_length;
+			if (uncompress((Bytef*)tmp.data, &decomp_result_l,
+						(Bytef*)ptr, bkpb->bimg_len) == Z_OK)
+				decomp_result = decomp_result_l;
+			else
+				decomp_result = -1;
+			break;
+		}
+#endif
+
+		default:
+			report_invalid_record(record, "image at %X/%X is compressed with unsupported codec, block %d (%d/%s)",
+								  (uint32) (record->ReadRecPtr >> 32),
+								  (uint32) record->ReadRecPtr,
+								  block_id,
+								  compression_method,
+								  wal_compression_name(compression_method));
+			return false;
+		}
+
+		if (decomp_result < 0)
 		{
 			report_invalid_record(record, "invalid compressed image at %X/%X, block %d",
 								  LSN_FORMAT_ARGS(record->ReadRecPtr),
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 68b62d523d..ce1149bed5 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -548,6 +548,7 @@ extern const struct config_enum_entry archive_mode_options[];
 extern const struct config_enum_entry recovery_target_action_options[];
 extern const struct config_enum_entry sync_method_options[];
 extern const struct config_enum_entry dynamic_shared_memory_options[];
+extern const struct config_enum_entry wal_compression_options[];
 
 /*
  * GUC option variables that are exported from this module
@@ -1304,16 +1305,6 @@ static struct config_bool ConfigureNamesBool[] =
 		NULL, NULL, NULL
 	},
 
-	{
-		{"wal_compression", PGC_SUSET, WAL_SETTINGS,
-			gettext_noop("Compresses full-page writes written in WAL file."),
-			NULL
-		},
-		&wal_compression,
-		false,
-		NULL, NULL, NULL
-	},
-
 	{
 		{"wal_init_zero", PGC_SUSET, WAL_SETTINGS,
 			gettext_noop("Writes zeroes to new WAL files before first use."),
@@ -4825,6 +4816,16 @@ static struct config_enum ConfigureNamesEnum[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"wal_compression", PGC_SUSET, WAL_SETTINGS,
+			gettext_noop("Set the method used to compress full page images in the WAL."),
+			NULL
+		},
+		&wal_compression,
+		WAL_COMPRESSION_NONE, wal_compression_options,
+		NULL, NULL, NULL
+	},
+
 	{
 		{"dynamic_shared_memory_type", PGC_POSTMASTER, RESOURCES_MEM,
 			gettext_noop("Selects the dynamic shared memory implementation used."),
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index ddbb6dc2be..61786c6e07 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -218,7 +218,7 @@
 #full_page_writes = on			# recover from partial page writes
 #wal_log_hints = off			# also do full page writes of non-critical updates
 					# (change requires restart)
-#wal_compression = off			# enable compression of full-page writes
+#wal_compression = off			# enable compression of full-page writes: off, pglz, zlib
 #wal_init_zero = on			# zero-fill new WAL files
 #wal_recycle = on			# recycle WAL files
 #wal_buffers = -1			# min 32kB, -1 sets based on shared_buffers
diff --git a/src/bin/pg_waldump/pg_waldump.c b/src/bin/pg_waldump/pg_waldump.c
index f8b8afe4a7..1cd71ac2f7 100644
--- a/src/bin/pg_waldump/pg_waldump.c
+++ b/src/bin/pg_waldump/pg_waldump.c
@@ -537,18 +537,21 @@ XLogDumpDisplayRecord(XLogDumpConfig *config, XLogReaderState *record)
 				   blk);
 			if (XLogRecHasBlockImage(record, block_id))
 			{
-				if (record->blocks[block_id].bimg_info &
-					BKPIMAGE_IS_COMPRESSED)
+				if (BKPIMAGE_IS_COMPRESSED(record->blocks[block_id].bimg_info))
 				{
+					int compression = BKPIMAGE_COMPRESSION(
+							record->blocks[block_id].bimg_info);
+
 					printf(" (FPW%s); hole: offset: %u, length: %u, "
-						   "compression saved: %u",
+						   "compression method %d/%s, saved: %u",
 						   XLogRecBlockImageApply(record, block_id) ?
 						   "" : " for WAL verification",
 						   record->blocks[block_id].hole_offset,
 						   record->blocks[block_id].hole_length,
+						   compression, wal_compression_name(compression),
 						   BLCKSZ -
-						   record->blocks[block_id].hole_length -
-						   record->blocks[block_id].bimg_len);
+							   record->blocks[block_id].hole_length -
+							   record->blocks[block_id].bimg_len);
 				}
 				else
 				{
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index 77187c12be..e8b2c53784 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -116,7 +116,7 @@ extern char *XLogArchiveCommand;
 extern bool EnableHotStandby;
 extern bool fullPageWrites;
 extern bool wal_log_hints;
-extern bool wal_compression;
+extern int wal_compression;
 extern bool wal_init_zero;
 extern bool wal_recycle;
 extern bool *wal_consistency_checking;
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index 26a743b6b6..8b740af66d 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -324,4 +324,14 @@ extern bool InArchiveRecovery;
 extern bool StandbyMode;
 extern char *recoveryRestoreCommand;
 
+/* These are the compression IDs written into bimg_info */
+typedef enum WalCompression
+{
+	WAL_COMPRESSION_NONE,
+	WAL_COMPRESSION_PGLZ,
+	WAL_COMPRESSION_ZLIB,
+} WalCompression;
+
+extern const char *wal_compression_name(WalCompression compression);
+
 #endif							/* XLOG_INTERNAL_H */
diff --git a/src/include/access/xlogrecord.h b/src/include/access/xlogrecord.h
index 80c92a2498..2a60c0fb92 100644
--- a/src/include/access/xlogrecord.h
+++ b/src/include/access/xlogrecord.h
@@ -114,7 +114,7 @@ typedef struct XLogRecordBlockHeader
  * present is (BLCKSZ - <length of "hole" bytes>).
  *
  * Additionally, when wal_compression is enabled, we will try to compress full
- * page images using the PGLZ compression algorithm, after removing the "hole".
+ * page images, after removing the "hole".
  * This can reduce the WAL volume, but at some extra cost of CPU spent
  * on the compression during WAL logging. In this case, since the "hole"
  * length cannot be calculated by subtracting the number of page image bytes
@@ -144,9 +144,18 @@ typedef struct XLogRecordBlockImageHeader
 
 /* Information stored in bimg_info */
 #define BKPIMAGE_HAS_HOLE		0x01	/* page image has "hole" */
-#define BKPIMAGE_IS_COMPRESSED		0x02	/* page image is compressed */
-#define BKPIMAGE_APPLY		0x04	/* page image should be restored during
+#define	BKPIMAGE_APPLY		0x02	/* page image should be restored during
 									 * replay */
+#define BKPIMAGE_COMPRESS_METHOD1	0x04	/* bits to encode compression method */
+#define BKPIMAGE_COMPRESS_METHOD2	0x08	/* 0=none, 1=pglz, 2=zlib */
+
+/* How many bits to shift to extract compression */
+#define	BKPIMAGE_COMPRESS_OFFSET_BITS	2
+/* How many bits are for compression */
+#define	BKPIMAGE_COMPRESS_BITS			2
+/* Extract the compression from the bimg_info */
+#define	BKPIMAGE_COMPRESSION(info)		((info >> BKPIMAGE_COMPRESS_OFFSET_BITS) & ((1<<BKPIMAGE_COMPRESS_BITS) - 1))
+#define	BKPIMAGE_IS_COMPRESSED(info)	(BKPIMAGE_COMPRESSION(info) != 0)
 
 /*
  * Extra header information used when page image has "hole" and
-- 
2.17.0

From dc75a78fd4b8f4b036b9d06b1b8d48aab84ccd5c Mon Sep 17 00:00:00 2001
From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Date: Mon, 8 Mar 2021 15:32:30 +0900
Subject: [PATCH v9 2/9] Run 011_crash_recovery.pl with wal_level=minimal

The test doesn't need that feature and pg_current_xact_id() is better
exercised by turning off the feature.

Copied from: https://www.postgresql.org/message-id/20210308.173242.463790587797836129.horikyota.ntt%40gmail.com
---
 src/test/recovery/t/011_crash_recovery.pl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/test/recovery/t/011_crash_recovery.pl b/src/test/recovery/t/011_crash_recovery.pl
index a26e99500b..2e7e3db639 100644
--- a/src/test/recovery/t/011_crash_recovery.pl
+++ b/src/test/recovery/t/011_crash_recovery.pl
@@ -14,7 +14,7 @@ use Config;
 plan tests => 3;
 
 my $node = get_new_node('primary');
-$node->init(allows_streaming => 1);
+$node->init();
 $node->start;
 
 my ($stdin, $stdout, $stderr) = ('', '', '');
-- 
2.17.0

From db62efed575e3f1a30a84ae8e525915afe3c7a94 Mon Sep 17 00:00:00 2001
From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Date: Mon, 8 Mar 2021 15:43:01 +0900
Subject: [PATCH v9 3/9] Make sure published XIDs are persistent

pg_xact_status() premises that XIDs obtained by
pg_current_xact_id(_if_assigned)() are persistent beyond a crash. But
XIDs are not guaranteed to go beyond WAL buffers before commit and
thus XIDs may vanish if server crashes before commit. This patch
guarantees the XID shown by the functions to be flushed out to disk.

Copied from: https://www.postgresql.org/message-id/20210308.173242.463790587797836129.horikyota.ntt%40gmail.com
---
 src/backend/access/transam/xact.c | 55 +++++++++++++++++++++++++------
 src/backend/access/transam/xlog.c |  2 +-
 src/backend/utils/adt/xid8funcs.c | 12 ++++++-
 src/include/access/xact.h         |  3 +-
 4 files changed, 59 insertions(+), 13 deletions(-)

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 441445927e..da8a460722 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -201,7 +201,7 @@ typedef struct TransactionStateData
 	int			prevSecContext; /* previous SecurityRestrictionContext */
 	bool		prevXactReadOnly;	/* entry-time xact r/o state */
 	bool		startedInRecovery;	/* did we start in recovery? */
-	bool		didLogXid;		/* has xid been included in WAL record? */
+	XLogRecPtr 	minLSN;			/* LSN needed to reach to record the xid */
 	int			parallelModeLevel;	/* Enter/ExitParallelMode counter */
 	bool		chain;			/* start a new block after this one */
 	bool		assigned;		/* assigned to top-level XID */
@@ -520,14 +520,46 @@ GetCurrentFullTransactionIdIfAny(void)
  *	MarkCurrentTransactionIdLoggedIfAny
  *
  * Remember that the current xid - if it is assigned - now has been wal logged.
+ *
+ * upto is the LSN up to which we need to flush WAL to ensure the current xid
+ * to be persistent. See EnsureCurrentTransactionIdLogged().
  */
 void
-MarkCurrentTransactionIdLoggedIfAny(void)
+MarkCurrentTransactionIdLoggedIfAny(XLogRecPtr upto)
 {
-	if (FullTransactionIdIsValid(CurrentTransactionState->fullTransactionId))
-		CurrentTransactionState->didLogXid = true;
+	if (FullTransactionIdIsValid(CurrentTransactionState->fullTransactionId) &&
+		XLogRecPtrIsInvalid(CurrentTransactionState->minLSN))
+		CurrentTransactionState->minLSN = upto;
 }
 
+/*
+ *	EnsureCurrentTransactionIdLogged
+ *
+ * Make sure that the current top XID is WAL-logged.
+ */
+void
+EnsureTopTransactionIdLogged(void)
+{
+	/*
+	 * We need at least one WAL record for the current top transaction to be
+	 * flushed out.  Write one if we don't have one yet.
+	 */
+	if (XLogRecPtrIsInvalid(TopTransactionStateData.minLSN))
+	{
+		xl_xact_assignment xlrec;
+
+		xlrec.xtop = XidFromFullTransactionId(XactTopFullTransactionId);
+		Assert(TransactionIdIsValid(xlrec.xtop));
+		xlrec.nsubxacts = 0;
+
+		XLogBeginInsert();
+		XLogRegisterData((char *) &xlrec, MinSizeOfXactAssignment);
+		TopTransactionStateData.minLSN =
+			XLogInsert(RM_XACT_ID, XLOG_XACT_ASSIGNMENT);
+	}
+
+	XLogFlush(TopTransactionStateData.minLSN);
+}
 
 /*
  *	GetStableLatestTransactionId
@@ -616,14 +648,14 @@ AssignTransactionId(TransactionState s)
 	 * When wal_level=logical, guarantee that a subtransaction's xid can only
 	 * be seen in the WAL stream if its toplevel xid has been logged before.
 	 * If necessary we log an xact_assignment record with fewer than
-	 * PGPROC_MAX_CACHED_SUBXIDS. Note that it is fine if didLogXid isn't set
+	 * PGPROC_MAX_CACHED_SUBXIDS. Note that it is fine if minLSN isn't set
 	 * for a transaction even though it appears in a WAL record, we just might
 	 * superfluously log something. That can happen when an xid is included
 	 * somewhere inside a wal record, but not in XLogRecord->xl_xid, like in
 	 * xl_standby_locks.
 	 */
 	if (isSubXact && XLogLogicalInfoActive() &&
-		!TopTransactionStateData.didLogXid)
+		XLogRecPtrIsInvalid(TopTransactionStateData.minLSN))
 		log_unknown_top = true;
 
 	/*
@@ -693,6 +725,7 @@ AssignTransactionId(TransactionState s)
 			log_unknown_top)
 		{
 			xl_xact_assignment xlrec;
+			XLogRecPtr		   endptr;
 
 			/*
 			 * xtop is always set by now because we recurse up transaction
@@ -707,11 +740,13 @@ AssignTransactionId(TransactionState s)
 			XLogRegisterData((char *) unreportedXids,
 							 nUnreportedXids * sizeof(TransactionId));
 
-			(void) XLogInsert(RM_XACT_ID, XLOG_XACT_ASSIGNMENT);
+			endptr = XLogInsert(RM_XACT_ID, XLOG_XACT_ASSIGNMENT);
 
 			nUnreportedXids = 0;
-			/* mark top, not current xact as having been logged */
-			TopTransactionStateData.didLogXid = true;
+
+			/* set minLSN of top, not of current xact if not yet */
+			if (XLogRecPtrIsInvalid(TopTransactionStateData.minLSN))
+				TopTransactionStateData.minLSN = endptr;
 		}
 	}
 }
@@ -1996,7 +2031,7 @@ StartTransaction(void)
 	 * initialize reported xid accounting
 	 */
 	nUnreportedXids = 0;
-	s->didLogXid = false;
+	s->minLSN = InvalidXLogRecPtr;
 
 	/*
 	 * must initialize resource-management stuff first
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 1ccc51575a..f7909aa1d7 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -1162,7 +1162,7 @@ XLogInsertRecord(XLogRecData *rdata,
 	 */
 	WALInsertLockRelease();
 
-	MarkCurrentTransactionIdLoggedIfAny();
+	MarkCurrentTransactionIdLoggedIfAny(EndPos);
 
 	END_CRIT_SECTION();
 
diff --git a/src/backend/utils/adt/xid8funcs.c b/src/backend/utils/adt/xid8funcs.c
index cc2b4ac797..992482f8c8 100644
--- a/src/backend/utils/adt/xid8funcs.c
+++ b/src/backend/utils/adt/xid8funcs.c
@@ -357,6 +357,8 @@ bad_format:
 Datum
 pg_current_xact_id(PG_FUNCTION_ARGS)
 {
+	FullTransactionId xid;
+
 	/*
 	 * Must prevent during recovery because if an xid is not assigned we try
 	 * to assign one, which would fail. Programs already rely on this function
@@ -365,7 +367,12 @@ pg_current_xact_id(PG_FUNCTION_ARGS)
 	 */
 	PreventCommandDuringRecovery("pg_current_xact_id()");
 
-	PG_RETURN_FULLTRANSACTIONID(GetTopFullTransactionId());
+	xid = GetTopFullTransactionId();
+
+	/* the XID is going to be published, make sure it is psersistent */
+	EnsureTopTransactionIdLogged();
+
+	PG_RETURN_FULLTRANSACTIONID(xid);
 }
 
 /*
@@ -380,6 +387,9 @@ pg_current_xact_id_if_assigned(PG_FUNCTION_ARGS)
 	if (!FullTransactionIdIsValid(topfxid))
 		PG_RETURN_NULL();
 
+	/* the XID is going to be published, make sure it is psersistent */
+	EnsureTopTransactionIdLogged();
+
 	PG_RETURN_FULLTRANSACTIONID(topfxid);
 }
 
diff --git a/src/include/access/xact.h b/src/include/access/xact.h
index 134f6862da..593a4140df 100644
--- a/src/include/access/xact.h
+++ b/src/include/access/xact.h
@@ -386,7 +386,8 @@ extern FullTransactionId GetTopFullTransactionId(void);
 extern FullTransactionId GetTopFullTransactionIdIfAny(void);
 extern FullTransactionId GetCurrentFullTransactionId(void);
 extern FullTransactionId GetCurrentFullTransactionIdIfAny(void);
-extern void MarkCurrentTransactionIdLoggedIfAny(void);
+extern void MarkCurrentTransactionIdLoggedIfAny(XLogRecPtr upto);
+extern void EnsureTopTransactionIdLogged(void);
 extern bool SubTransactionIsActive(SubTransactionId subxid);
 extern CommandId GetCurrentCommandId(bool used);
 extern void SetParallelStartTimestamps(TimestampTz xact_ts, TimestampTz stmt_ts);
-- 
2.17.0

From 2a899bbbbca7d18ce79258001de910a1715bed3a Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Thu, 11 Mar 2021 17:36:24 -0600
Subject: [PATCH v9 4/9] wal_compression_method: default to zlib..

this is meant to exercise the CIs, and not meant to be merged
---
 src/backend/access/transam/xlog.c | 2 +-
 src/backend/utils/misc/guc.c      | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index f7909aa1d7..3254c42243 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -98,7 +98,7 @@ char	   *XLogArchiveCommand = NULL;
 bool		EnableHotStandby = false;
 bool		fullPageWrites = true;
 bool		wal_log_hints = false;
-int		wal_compression = WAL_COMPRESSION_NONE;
+int		wal_compression = WAL_COMPRESSION_ZLIB;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index ce1149bed5..14a2203225 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -4822,7 +4822,7 @@ static struct config_enum ConfigureNamesEnum[] =
 			NULL
 		},
 		&wal_compression,
-		WAL_COMPRESSION_NONE, wal_compression_options,
+		WAL_COMPRESSION_ZLIB, wal_compression_options,
 		NULL, NULL, NULL
 	},
 
-- 
2.17.0

From d953ea3a2cf103bf0650c80ad5855bed87204f81 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Mon, 24 May 2021 23:32:30 -0500
Subject: [PATCH v9 5/9] (re)add wal_compression_method: lz4

---
 doc/src/sgml/config.sgml                      |  3 ++-
 doc/src/sgml/install-windows.sgml             |  2 +-
 doc/src/sgml/installation.sgml                |  5 +++--
 src/backend/access/transam/xloginsert.c       | 17 ++++++++++++++++-
 src/backend/access/transam/xlogreader.c       | 15 +++++++++++++++
 src/backend/utils/misc/postgresql.conf.sample |  2 +-
 src/include/access/xlog_internal.h            |  1 +
 src/include/access/xlogrecord.h               |  2 +-
 8 files changed, 40 insertions(+), 7 deletions(-)

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 1df56d8034..df5ff70d91 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -3140,7 +3140,8 @@ include_dir 'conf.d'
         server compresses full page images written to WAL when
         <xref linkend="guc-full-page-writes"/> is on or during a base backup.
         A compressed page image will be decompressed during WAL replay.
-        The supported methods are pglz and zlib.
+        The supported methods are pglz, zlib, and (if configured when
+        <productname>PostgreSQL</productname> was built) lz4.
         The default value is <literal>off</literal>.
         Only superusers can change this setting.
        </para>
diff --git a/doc/src/sgml/install-windows.sgml b/doc/src/sgml/install-windows.sgml
index 312edc6f7a..ba794b8c93 100644
--- a/doc/src/sgml/install-windows.sgml
+++ b/doc/src/sgml/install-windows.sgml
@@ -299,7 +299,7 @@ $ENV{MSBFLAGS}="/m";
      <term><productname>LZ4</productname></term>
      <listitem><para>
       Required for supporting <productname>LZ4</productname> compression
-      method for compressing the table data. Binaries and source can be
+      method for compressing table or WAL data. Binaries and source can be
       downloaded from
       <ulink url="https://github.com/lz4/lz4/releases"></ulink>.
      </para></listitem>
diff --git a/doc/src/sgml/installation.sgml b/doc/src/sgml/installation.sgml
index 073d5089f7..c7673a4dc8 100644
--- a/doc/src/sgml/installation.sgml
+++ b/doc/src/sgml/installation.sgml
@@ -270,7 +270,8 @@ su - postgres
      <para>
       You need <productname>LZ4</productname>, if you want to support
       compression of data with this method; see
-      <xref linkend="guc-default-toast-compression"/>.
+      <xref linkend="guc-default-toast-compression"/> and
+      <xref linkend="guc-wal-compression"/>.
      </para>
     </listitem>
 
@@ -980,7 +981,7 @@ build-postgresql:
         <para>
          Build with <productname>LZ4</productname> compression support.
          This allows the use of <productname>LZ4</productname> for
-         compression of table data.
+         compression of table and WAL data.
         </para>
        </listitem>
       </varlistentry>
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
index 4f81f19c49..a8794a941a 100644
--- a/src/backend/access/transam/xloginsert.c
+++ b/src/backend/access/transam/xloginsert.c
@@ -41,10 +41,17 @@
 #define ZLIB_MAX_BLCKSZ		0
 #endif
 
+#ifdef USE_LZ4
+#include "lz4.h"
+#define	LZ4_MAX_BLCKSZ		LZ4_COMPRESSBOUND(BLCKSZ)
+#else
+#define LZ4_MAX_BLCKSZ		0
+#endif
+
 /* Buffer size required to store a compressed version of backup block image */
 #define PGLZ_MAX_BLCKSZ		PGLZ_MAX_OUTPUT(BLCKSZ)
 
-#define COMPRESS_BUFSIZE	Max(PGLZ_MAX_BLCKSZ, ZLIB_MAX_BLCKSZ)
+#define COMPRESS_BUFSIZE	Max(Max(PGLZ_MAX_BLCKSZ, ZLIB_MAX_BLCKSZ), LZ4_MAX_BLCKSZ)
 
 /*
  * For each block reference registered with XLogRegisterBuffer, we fill in
@@ -889,6 +896,14 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 		}
 #endif
 
+#ifdef USE_LZ4
+	case WAL_COMPRESSION_LZ4:
+		len = LZ4_compress_fast(source, dest, orig_len, COMPRESS_BUFSIZE, 1);
+		if (len == 0)
+			len = -1;
+		break;
+#endif
+
 	default:
 		/*
 		 * It should be impossible to get here for unsupported algorithms,
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index 3a922caaeb..e44817fece 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -38,6 +38,10 @@
 #include <zlib.h>
 #endif
 
+#ifdef USE_LZ4
+#include "lz4.h"
+#endif
+
 static void report_invalid_record(XLogReaderState *state, const char *fmt,...)
 			pg_attribute_printf(2, 3);
 static bool allocate_recordbuf(XLogReaderState *state, uint32 reclength);
@@ -75,6 +79,10 @@ const struct config_enum_entry wal_compression_options[] = {
 	{"zlib", WAL_COMPRESSION_ZLIB, false},
 #endif
 
+#ifdef  USE_LZ4
+	{"lz4", WAL_COMPRESSION_LZ4, false},
+#endif
+
 	{NULL, 0, false}
 };
 
@@ -1624,6 +1632,13 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 		}
 #endif
 
+#ifdef USE_LZ4
+		case WAL_COMPRESSION_LZ4:
+			decomp_result = LZ4_decompress_safe(ptr, tmp.data,
+					bkpb->bimg_len, BLCKSZ-bkpb->hole_length);
+			break;
+#endif
+
 		default:
 			report_invalid_record(record, "image at %X/%X is compressed with unsupported codec, block %d (%d/%s)",
 								  (uint32) (record->ReadRecPtr >> 32),
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 61786c6e07..728acef953 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -218,7 +218,7 @@
 #full_page_writes = on			# recover from partial page writes
 #wal_log_hints = off			# also do full page writes of non-critical updates
 					# (change requires restart)
-#wal_compression = off			# enable compression of full-page writes: off, pglz, zlib
+#wal_compression = off			# enable compression of full-page writes: off, pglz, zlib, lz4
 #wal_init_zero = on			# zero-fill new WAL files
 #wal_recycle = on			# recycle WAL files
 #wal_buffers = -1			# min 32kB, -1 sets based on shared_buffers
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index 8b740af66d..0287592cd4 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -330,6 +330,7 @@ typedef enum WalCompression
 	WAL_COMPRESSION_NONE,
 	WAL_COMPRESSION_PGLZ,
 	WAL_COMPRESSION_ZLIB,
+	WAL_COMPRESSION_LZ4,
 } WalCompression;
 
 extern const char *wal_compression_name(WalCompression compression);
diff --git a/src/include/access/xlogrecord.h b/src/include/access/xlogrecord.h
index 2a60c0fb92..abb42b364d 100644
--- a/src/include/access/xlogrecord.h
+++ b/src/include/access/xlogrecord.h
@@ -147,7 +147,7 @@ typedef struct XLogRecordBlockImageHeader
 #define	BKPIMAGE_APPLY		0x02	/* page image should be restored during
 									 * replay */
 #define BKPIMAGE_COMPRESS_METHOD1	0x04	/* bits to encode compression method */
-#define BKPIMAGE_COMPRESS_METHOD2	0x08	/* 0=none, 1=pglz, 2=zlib */
+#define BKPIMAGE_COMPRESS_METHOD2	0x08	/* 0=none, 1=pglz, 2=zlib, 3=lz4 */
 
 /* How many bits to shift to extract compression */
 #define	BKPIMAGE_COMPRESS_OFFSET_BITS	2
-- 
2.17.0

From 20924767e23ba489c27599e91eb80fc8935d603d Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Fri, 12 Mar 2021 15:35:40 -0600
Subject: [PATCH v9 6/9] Default to LZ4..

this is meant to exercise in the CIs, and not meant to be merged
---
 configure                         | 6 ++++--
 configure.ac                      | 4 ++--
 src/backend/access/transam/xlog.c | 2 +-
 src/backend/utils/misc/guc.c      | 2 +-
 4 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/configure b/configure
index e9b98f442f..7038b0727c 100755
--- a/configure
+++ b/configure
@@ -1575,7 +1575,7 @@ Optional Packages:
   --with-system-tzdata=DIR
                           use system time zone data in DIR
   --without-zlib          do not use Zlib
-  --with-lz4              build with LZ4 support
+  --without-lz4           build without LZ4 support
   --with-gnu-ld           assume the C compiler uses GNU ld [default=no]
   --with-ssl=LIB          use LIB for SSL/TLS support (openssl)
   --with-openssl          obsolete spelling of --with-ssl=openssl
@@ -8598,7 +8598,9 @@ $as_echo "#define USE_LZ4 1" >>confdefs.h
   esac
 
 else
-  with_lz4=no
+  with_lz4=yes
+
+$as_echo "#define USE_LZ4 1" >>confdefs.h
 
 fi
 
diff --git a/configure.ac b/configure.ac
index 3b42d8bdc9..cb0261f179 100644
--- a/configure.ac
+++ b/configure.ac
@@ -990,8 +990,8 @@ AC_SUBST(with_zlib)
 # LZ4
 #
 AC_MSG_CHECKING([whether to build with LZ4 support])
-PGAC_ARG_BOOL(with, lz4, no, [build with LZ4 support],
-              [AC_DEFINE([USE_LZ4], 1, [Define to 1 to build with LZ4 support. (--with-lz4)])])
+PGAC_ARG_BOOL(with, lz4, yes, [build without LZ4 support],
+              [AC_DEFINE([USE_LZ4], 1, [Define to 1 to build without LZ4 support. (--without-lz4)])])
 AC_MSG_RESULT([$with_lz4])
 AC_SUBST(with_lz4)
 
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 3254c42243..f2b0af6360 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -98,7 +98,7 @@ char	   *XLogArchiveCommand = NULL;
 bool		EnableHotStandby = false;
 bool		fullPageWrites = true;
 bool		wal_log_hints = false;
-int		wal_compression = WAL_COMPRESSION_ZLIB;
+int		wal_compression = WAL_COMPRESSION_LZ4;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 14a2203225..0ad62e4d1f 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -4822,7 +4822,7 @@ static struct config_enum ConfigureNamesEnum[] =
 			NULL
 		},
 		&wal_compression,
-		WAL_COMPRESSION_ZLIB, wal_compression_options,
+		WAL_COMPRESSION_LZ4, wal_compression_options,
 		NULL, NULL, NULL
 	},
 
-- 
2.17.0

From e25090646f6a0ca619bb9faaa7ff6a330c277b0f Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Fri, 12 Mar 2021 14:43:53 -0600
Subject: [PATCH v9 7/9] add wal_compression_method: zstd

TODO: 9ca40dcd4d0cad43d95a9a253fafaa9a9ba7de24
---
 configure                                     | 217 ++++++++++++++++++
 configure.ac                                  |  33 +++
 doc/src/sgml/config.sgml                      |   2 +-
 doc/src/sgml/installation.sgml                |  19 ++
 src/backend/access/transam/xloginsert.c       |  18 +-
 src/backend/access/transam/xlogreader.c       |  18 ++
 src/backend/utils/misc/postgresql.conf.sample |   2 +-
 src/include/access/xlog_internal.h            |   1 +
 src/include/access/xlogrecord.h               |   5 +-
 src/include/pg_config.h.in                    |   3 +
 src/tools/msvc/Solution.pm                    |   1 +
 src/tools/msvc/config_default.pl              |   1 +
 12 files changed, 315 insertions(+), 5 deletions(-)

diff --git a/configure b/configure
index 7038b0727c..72bbd719dc 100755
--- a/configure
+++ b/configure
@@ -699,6 +699,9 @@ with_gnu_ld
 LD
 LDFLAGS_SL
 LDFLAGS_EX
+ZSTD_LIBS
+ZSTD_CFLAGS
+with_zstd
 LZ4_LIBS
 LZ4_CFLAGS
 with_lz4
@@ -868,6 +871,7 @@ with_libxslt
 with_system_tzdata
 with_zlib
 with_lz4
+with_zstd
 with_gnu_ld
 with_ssl
 with_openssl
@@ -897,6 +901,8 @@ XML2_CFLAGS
 XML2_LIBS
 LZ4_CFLAGS
 LZ4_LIBS
+ZSTD_CFLAGS
+ZSTD_LIBS
 LDFLAGS_EX
 LDFLAGS_SL
 PERL
@@ -1576,6 +1582,7 @@ Optional Packages:
                           use system time zone data in DIR
   --without-zlib          do not use Zlib
   --without-lz4           build without LZ4 support
+  --with-zstd             build with Zstd compression library
   --with-gnu-ld           assume the C compiler uses GNU ld [default=no]
   --with-ssl=LIB          use LIB for SSL/TLS support (openssl)
   --with-openssl          obsolete spelling of --with-ssl=openssl
@@ -1605,6 +1612,8 @@ Some influential environment variables:
   XML2_LIBS   linker flags for XML2, overriding pkg-config
   LZ4_CFLAGS  C compiler flags for LZ4, overriding pkg-config
   LZ4_LIBS    linker flags for LZ4, overriding pkg-config
+  ZSTD_CFLAGS C compiler flags for ZSTD, overriding pkg-config
+  ZSTD_LIBS   linker flags for ZSTD, overriding pkg-config
   LDFLAGS_EX  extra linker flags for linking executables only
   LDFLAGS_SL  extra linker flags for linking shared libraries only
   PERL        Perl program
@@ -8715,6 +8724,147 @@ fi
   done
 fi
 
+#
+# ZSTD
+#
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether to build with zstd support" >&5
+$as_echo_n "checking whether to build with zstd support... " >&6; }
+
+
+
+# Check whether --with-zstd was given.
+if test "${with_zstd+set}" = set; then :
+  withval=$with_zstd;
+  case $withval in
+    yes)
+
+$as_echo "#define USE_ZSTD 1" >>confdefs.h
+
+      ;;
+    no)
+      :
+      ;;
+    *)
+      as_fn_error $? "no argument expected for --with-zstd option" "$LINENO" 5
+      ;;
+  esac
+
+else
+  with_zstd=no
+
+fi
+
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $with_zstd" >&5
+$as_echo "$with_zstd" >&6; }
+
+
+if test "$with_zstd" = yes; then
+
+pkg_failed=no
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for libzstd" >&5
+$as_echo_n "checking for libzstd... " >&6; }
+
+if test -n "$ZSTD_CFLAGS"; then
+    pkg_cv_ZSTD_CFLAGS="$ZSTD_CFLAGS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"libzstd\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "libzstd") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_ZSTD_CFLAGS=`$PKG_CONFIG --cflags "libzstd" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+if test -n "$ZSTD_LIBS"; then
+    pkg_cv_ZSTD_LIBS="$ZSTD_LIBS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"libzstd\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "libzstd") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_ZSTD_LIBS=`$PKG_CONFIG --libs "libzstd" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+
+
+
+if test $pkg_failed = yes; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+
+if $PKG_CONFIG --atleast-pkgconfig-version 0.20; then
+        _pkg_short_errors_supported=yes
+else
+        _pkg_short_errors_supported=no
+fi
+        if test $_pkg_short_errors_supported = yes; then
+	        ZSTD_PKG_ERRORS=`$PKG_CONFIG --short-errors --print-errors --cflags --libs "libzstd" 2>&1`
+        else
+	        ZSTD_PKG_ERRORS=`$PKG_CONFIG --print-errors --cflags --libs "libzstd" 2>&1`
+        fi
+	# Put the nasty error message in config.log where it belongs
+	echo "$ZSTD_PKG_ERRORS" >&5
+
+	as_fn_error $? "Package requirements (libzstd) were not met:
+
+$ZSTD_PKG_ERRORS
+
+Consider adjusting the PKG_CONFIG_PATH environment variable if you
+installed software in a non-standard prefix.
+
+Alternatively, you may set the environment variables ZSTD_CFLAGS
+and ZSTD_LIBS to avoid the need to call pkg-config.
+See the pkg-config man page for more details." "$LINENO" 5
+elif test $pkg_failed = untried; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+	{ { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error $? "The pkg-config script could not be found or is too old.  Make sure it
+is in your PATH or set the PKG_CONFIG environment variable to the full
+path to pkg-config.
+
+Alternatively, you may set the environment variables ZSTD_CFLAGS
+and ZSTD_LIBS to avoid the need to call pkg-config.
+See the pkg-config man page for more details.
+
+To get pkg-config, see <http://pkg-config.freedesktop.org/>.
+See \`config.log' for more details" "$LINENO" 5; }
+else
+	ZSTD_CFLAGS=$pkg_cv_ZSTD_CFLAGS
+	ZSTD_LIBS=$pkg_cv_ZSTD_LIBS
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+
+fi
+  # We only care about -I, -D, and -L switches;
+  # note that -lzstd will be added by AC_CHECK_LIB below.
+  for pgac_option in $ZSTD_CFLAGS; do
+    case $pgac_option in
+      -I*|-D*) CPPFLAGS="$CPPFLAGS $pgac_option";;
+    esac
+  done
+  for pgac_option in $ZSTD_LIBS; do
+    case $pgac_option in
+      -L*) LDFLAGS="$LDFLAGS $pgac_option";;
+    esac
+  done
+fi
+
 #
 # Assignments
 #
@@ -12878,6 +13028,56 @@ fi
 
 fi
 
+if test "$with_zstd" = yes ; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for ZSTD_compress in -lzstd" >&5
+$as_echo_n "checking for ZSTD_compress in -lzstd... " >&6; }
+if ${ac_cv_lib_zstd_ZSTD_compress+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ac_check_lib_save_LIBS=$LIBS
+LIBS="-lzstd  $LIBS"
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+/* Override any GCC internal prototype to avoid an error.
+   Use char because int might match the return type of a GCC
+   builtin and then its argument prototype would still apply.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+char ZSTD_compress ();
+int
+main ()
+{
+return ZSTD_compress ();
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ac_cv_lib_zstd_ZSTD_compress=yes
+else
+  ac_cv_lib_zstd_ZSTD_compress=no
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+LIBS=$ac_check_lib_save_LIBS
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_lib_zstd_ZSTD_compress" >&5
+$as_echo "$ac_cv_lib_zstd_ZSTD_compress" >&6; }
+if test "x$ac_cv_lib_zstd_ZSTD_compress" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_LIBZSTD 1
+_ACEOF
+
+  LIBS="-lzstd $LIBS"
+
+else
+  as_fn_error $? "library 'zstd' is required for ZSTD support" "$LINENO" 5
+fi
+
+fi
+
 # Note: We can test for libldap_r only after we know PTHREAD_LIBS
 if test "$with_ldap" = yes ; then
   _LIBS="$LIBS"
@@ -13600,6 +13800,23 @@ done
 
 fi
 
+if test "$with_zstd" = yes; then
+  for ac_header in zstd.h
+do :
+  ac_fn_c_check_header_mongrel "$LINENO" "zstd.h" "ac_cv_header_zstd_h" "$ac_includes_default"
+if test "x$ac_cv_header_zstd_h" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_ZSTD_H 1
+_ACEOF
+
+else
+  as_fn_error $? "zstd.h header file is required for zstd" "$LINENO" 5
+fi
+
+done
+
+fi
+
 if test "$with_gssapi" = yes ; then
   for ac_header in gssapi/gssapi.h
 do :
diff --git a/configure.ac b/configure.ac
index cb0261f179..c348a3ee91 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1011,6 +1011,31 @@ if test "$with_lz4" = yes; then
   done
 fi
 
+#
+# ZSTD
+#
+AC_MSG_CHECKING([whether to build with zstd support])
+PGAC_ARG_BOOL(with, zstd, no, [build with Zstd compression library],
+              [AC_DEFINE([USE_ZSTD], 1, [Define to 1 to build with zstd support. (--with-zstd)])])
+AC_MSG_RESULT([$with_zstd])
+AC_SUBST(with_zstd)
+
+if test "$with_zstd" = yes; then
+  PKG_CHECK_MODULES(ZSTD, libzstd)
+  # We only care about -I, -D, and -L switches;
+  # note that -lzstd will be added by AC_CHECK_LIB below.
+  for pgac_option in $ZSTD_CFLAGS; do
+    case $pgac_option in
+      -I*|-D*) CPPFLAGS="$CPPFLAGS $pgac_option";;
+    esac
+  done
+  for pgac_option in $ZSTD_LIBS; do
+    case $pgac_option in
+      -L*) LDFLAGS="$LDFLAGS $pgac_option";;
+    esac
+  done
+fi
+
 #
 # Assignments
 #
@@ -1285,6 +1310,10 @@ if test "$with_lz4" = yes ; then
   AC_CHECK_LIB(lz4, LZ4_compress_default, [], [AC_MSG_ERROR([library 'lz4' is required for LZ4 support])])
 fi
 
+if test "$with_zstd" = yes ; then
+  AC_CHECK_LIB(zstd, ZSTD_compress, [], [AC_MSG_ERROR([library 'zstd' is required for ZSTD support])])
+fi
+
 # Note: We can test for libldap_r only after we know PTHREAD_LIBS
 if test "$with_ldap" = yes ; then
   _LIBS="$LIBS"
@@ -1443,6 +1472,10 @@ if test "$with_lz4" = yes; then
   AC_CHECK_HEADERS(lz4.h, [], [AC_MSG_ERROR([lz4.h header file is required for LZ4])])
 fi
 
+if test "$with_zstd" = yes; then
+  AC_CHECK_HEADERS(zstd.h, [], [AC_MSG_ERROR([zstd.h header file is required for zstd])])
+fi
+
 if test "$with_gssapi" = yes ; then
   AC_CHECK_HEADERS(gssapi/gssapi.h, [],
 	[AC_CHECK_HEADERS(gssapi.h, [], [AC_MSG_ERROR([gssapi.h header file is required for GSSAPI])])])
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index df5ff70d91..ee4c44fb7f 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -3141,7 +3141,7 @@ include_dir 'conf.d'
         <xref linkend="guc-full-page-writes"/> is on or during a base backup.
         A compressed page image will be decompressed during WAL replay.
         The supported methods are pglz, zlib, and (if configured when
-        <productname>PostgreSQL</productname> was built) lz4.
+        <productname>PostgreSQL</productname> was built) lz4 and zstd.
         The default value is <literal>off</literal>.
         Only superusers can change this setting.
        </para>
diff --git a/doc/src/sgml/installation.sgml b/doc/src/sgml/installation.sgml
index c7673a4dc8..3e985bbd05 100644
--- a/doc/src/sgml/installation.sgml
+++ b/doc/src/sgml/installation.sgml
@@ -275,6 +275,14 @@ su - postgres
      </para>
     </listitem>
 
+    <listitem>
+     <para>
+      The <productname>ZSTD</productname> library can be used to enable
+      compression using that method; see
+      <xref linkend="guc-wal-compression"/>.
+     </para>
+    </listitem>
+
     <listitem>
      <para>
       To build the <productname>PostgreSQL</productname> documentation,
@@ -986,6 +994,17 @@ build-postgresql:
        </listitem>
       </varlistentry>
 
+      <varlistentry>
+       <term><option>--with-zstd</option></term>
+       <listitem>
+        <para>
+         Build with <productname>ZSTD</productname> compression support.
+         This enables use of <productname>ZSTD</productname> for
+         compression of WAL data.
+        </para>
+       </listitem>
+      </varlistentry>
+
       <varlistentry>
        <term><option>--with-ssl=<replaceable>LIBRARY</replaceable></option>
        <indexterm>
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
index a8794a941a..96f497d5d6 100644
--- a/src/backend/access/transam/xloginsert.c
+++ b/src/backend/access/transam/xloginsert.c
@@ -48,10 +48,17 @@
 #define LZ4_MAX_BLCKSZ		0
 #endif
 
+#ifdef USE_ZSTD
+#include "zstd.h"
+#define ZSTD_MAX_BLCKSZ		ZSTD_COMPRESSBOUND(BLCKSZ)
+#else
+#define ZSTD_MAX_BLCKSZ		0
+#endif
+
 /* Buffer size required to store a compressed version of backup block image */
 #define PGLZ_MAX_BLCKSZ		PGLZ_MAX_OUTPUT(BLCKSZ)
 
-#define COMPRESS_BUFSIZE	Max(Max(PGLZ_MAX_BLCKSZ, ZLIB_MAX_BLCKSZ), LZ4_MAX_BLCKSZ)
+#define COMPRESS_BUFSIZE	Max(Max(Max(PGLZ_MAX_BLCKSZ, ZLIB_MAX_BLCKSZ), LZ4_MAX_BLCKSZ), ZSTD_MAX_BLCKSZ)
 
 /*
  * For each block reference registered with XLogRegisterBuffer, we fill in
@@ -904,6 +911,15 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 		break;
 #endif
 
+#ifdef USE_ZSTD
+	case WAL_COMPRESSION_ZSTD:
+		len = ZSTD_compress(dest, COMPRESS_BUFSIZE, source, orig_len,
+				ZSTD_CLEVEL_DEFAULT);
+		if (ZSTD_isError(len))
+			len = -1;
+		break;
+#endif
+
 	default:
 		/*
 		 * It should be impossible to get here for unsupported algorithms,
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index e44817fece..1b13d1f660 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -42,6 +42,10 @@
 #include "lz4.h"
 #endif
 
+#ifdef USE_ZSTD
+#include "zstd.h"
+#endif
+
 static void report_invalid_record(XLogReaderState *state, const char *fmt,...)
 			pg_attribute_printf(2, 3);
 static bool allocate_recordbuf(XLogReaderState *state, uint32 reclength);
@@ -83,6 +87,10 @@ const struct config_enum_entry wal_compression_options[] = {
 	{"lz4", WAL_COMPRESSION_LZ4, false},
 #endif
 
+#ifdef  USE_ZSTD
+	{"zstd", WAL_COMPRESSION_ZSTD, false},
+#endif
+
 	{NULL, 0, false}
 };
 
@@ -1639,6 +1647,16 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 			break;
 #endif
 
+#ifdef USE_ZSTD
+		case WAL_COMPRESSION_ZSTD:
+			decomp_result = ZSTD_decompress(tmp.data, BLCKSZ-bkpb->hole_length,
+					ptr, bkpb->bimg_len);
+			// XXX: ZSTD_getErrorName
+			if (ZSTD_isError(decomp_result))
+				decomp_result = -1;
+			break;
+#endif
+
 		default:
 			report_invalid_record(record, "image at %X/%X is compressed with unsupported codec, block %d (%d/%s)",
 								  (uint32) (record->ReadRecPtr >> 32),
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 728acef953..818b26faad 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -218,7 +218,7 @@
 #full_page_writes = on			# recover from partial page writes
 #wal_log_hints = off			# also do full page writes of non-critical updates
 					# (change requires restart)
-#wal_compression = off			# enable compression of full-page writes: off, pglz, zlib, lz4
+#wal_compression = off			# enable compression of full-page writes: off, pglz, zlib, lz4, zstd
 #wal_init_zero = on			# zero-fill new WAL files
 #wal_recycle = on			# recycle WAL files
 #wal_buffers = -1			# min 32kB, -1 sets based on shared_buffers
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index 0287592cd4..1da965a708 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -331,6 +331,7 @@ typedef enum WalCompression
 	WAL_COMPRESSION_PGLZ,
 	WAL_COMPRESSION_ZLIB,
 	WAL_COMPRESSION_LZ4,
+	WAL_COMPRESSION_ZSTD,
 } WalCompression;
 
 extern const char *wal_compression_name(WalCompression compression);
diff --git a/src/include/access/xlogrecord.h b/src/include/access/xlogrecord.h
index abb42b364d..84ffb17596 100644
--- a/src/include/access/xlogrecord.h
+++ b/src/include/access/xlogrecord.h
@@ -147,12 +147,13 @@ typedef struct XLogRecordBlockImageHeader
 #define	BKPIMAGE_APPLY		0x02	/* page image should be restored during
 									 * replay */
 #define BKPIMAGE_COMPRESS_METHOD1	0x04	/* bits to encode compression method */
-#define BKPIMAGE_COMPRESS_METHOD2	0x08	/* 0=none, 1=pglz, 2=zlib, 3=lz4 */
+#define BKPIMAGE_COMPRESS_METHOD2	0x08	/* 0=none, 1=pglz, 2=zlib, 3=lz4, 4=zstd */
+#define BKPIMAGE_COMPRESS_METHOD3	0x10
 
 /* How many bits to shift to extract compression */
 #define	BKPIMAGE_COMPRESS_OFFSET_BITS	2
 /* How many bits are for compression */
-#define	BKPIMAGE_COMPRESS_BITS			2
+#define	BKPIMAGE_COMPRESS_BITS			3
 /* Extract the compression from the bimg_info */
 #define	BKPIMAGE_COMPRESSION(info)		((info >> BKPIMAGE_COMPRESS_OFFSET_BITS) & ((1<<BKPIMAGE_COMPRESS_BITS) - 1))
 #define	BKPIMAGE_IS_COMPRESSED(info)	(BKPIMAGE_COMPRESSION(info) != 0)
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index 783b8fc1ba..bb44ef2a9d 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -917,6 +917,9 @@
 /* Define to 1 to build with LZ4 support. (--with-lz4) */
 #undef USE_LZ4
 
+/* Define to 1 if you have the `zstd' library (-lzstd). */
+#undef USE_ZSTD
+
 /* Define to select named POSIX semaphores. */
 #undef USE_NAMED_POSIX_SEMAPHORES
 
diff --git a/src/tools/msvc/Solution.pm b/src/tools/msvc/Solution.pm
index a7b8f720b5..28ff10f09f 100644
--- a/src/tools/msvc/Solution.pm
+++ b/src/tools/msvc/Solution.pm
@@ -494,6 +494,7 @@ sub GenerateFiles
 		USE_LIBXML                 => undef,
 		USE_LIBXSLT                => undef,
 		USE_LZ4                    => undef,
+		USE_ZSTD                   => $self->{options}->{zstd} ? 1 : undef,
 		USE_LDAP                   => $self->{options}->{ldap} ? 1 : undef,
 		USE_LLVM                   => undef,
 		USE_NAMED_POSIX_SEMAPHORES => undef,
diff --git a/src/tools/msvc/config_default.pl b/src/tools/msvc/config_default.pl
index 460c0375d4..b8a1aac3c2 100644
--- a/src/tools/msvc/config_default.pl
+++ b/src/tools/msvc/config_default.pl
@@ -26,6 +26,7 @@ our $config = {
 	xslt      => undef,    # --with-libxslt=<path>
 	iconv     => undef,    # (not in configure, path to iconv)
 	zlib      => undef     # --with-zlib=<path>
+	zstd      => undef     # --with-zstd=<path>
 };
 
 1;
-- 
2.17.0

From 3929203166e8fadcd33dbd46ffdf7522e1bf0151 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Fri, 12 Mar 2021 15:35:53 -0600
Subject: [PATCH v9 8/9] Default to zstd..

for CI, not for merge
---
 configure                         | 6 ++++--
 configure.ac                      | 2 +-
 src/backend/access/transam/xlog.c | 2 +-
 src/backend/utils/misc/guc.c      | 2 +-
 4 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/configure b/configure
index 72bbd719dc..b445db933e 100755
--- a/configure
+++ b/configure
@@ -1582,7 +1582,7 @@ Optional Packages:
                           use system time zone data in DIR
   --without-zlib          do not use Zlib
   --without-lz4           build without LZ4 support
-  --with-zstd             build with Zstd compression library
+  --without-zstd          build without Zstd compression library
   --with-gnu-ld           assume the C compiler uses GNU ld [default=no]
   --with-ssl=LIB          use LIB for SSL/TLS support (openssl)
   --with-openssl          obsolete spelling of --with-ssl=openssl
@@ -8750,7 +8750,9 @@ $as_echo "#define USE_ZSTD 1" >>confdefs.h
   esac
 
 else
-  with_zstd=no
+  with_zstd=yes
+
+$as_echo "#define USE_ZSTD 1" >>confdefs.h
 
 fi
 
diff --git a/configure.ac b/configure.ac
index c348a3ee91..f8ee35ebfd 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1015,7 +1015,7 @@ fi
 # ZSTD
 #
 AC_MSG_CHECKING([whether to build with zstd support])
-PGAC_ARG_BOOL(with, zstd, no, [build with Zstd compression library],
+PGAC_ARG_BOOL(with, zstd, yes, [build without Zstd compression library],
               [AC_DEFINE([USE_ZSTD], 1, [Define to 1 to build with zstd support. (--with-zstd)])])
 AC_MSG_RESULT([$with_zstd])
 AC_SUBST(with_zstd)
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index f2b0af6360..599381337e 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -98,7 +98,7 @@ char	   *XLogArchiveCommand = NULL;
 bool		EnableHotStandby = false;
 bool		fullPageWrites = true;
 bool		wal_log_hints = false;
-int		wal_compression = WAL_COMPRESSION_LZ4;
+int		wal_compression = WAL_COMPRESSION_ZSTD;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 0ad62e4d1f..f37251a27f 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -4822,7 +4822,7 @@ static struct config_enum ConfigureNamesEnum[] =
 			NULL
 		},
 		&wal_compression,
-		WAL_COMPRESSION_LZ4, wal_compression_options,
+		WAL_COMPRESSION_ZSTD, wal_compression_options,
 		NULL, NULL, NULL
 	},
 
-- 
2.17.0

From ecee845d049e8a7e939fe3b7bc9807ecc1b0a2c7 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Sun, 14 Mar 2021 17:12:07 -0500
Subject: [PATCH v9 9/9] Use GUC hooks to support compression 'level'

---
 src/backend/access/transam/xlog.c       |  19 +++-
 src/backend/access/transam/xloginsert.c |   7 +-
 src/backend/access/transam/xlogreader.c | 120 ++++++++++++++++++++----
 src/backend/utils/misc/guc.c            |  20 ++--
 src/include/access/xlog.h               |  10 +-
 src/include/access/xlogreader.h         |   2 +
 6 files changed, 144 insertions(+), 34 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 599381337e..4ec688a612 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -98,7 +98,9 @@ char	   *XLogArchiveCommand = NULL;
 bool		EnableHotStandby = false;
 bool		fullPageWrites = true;
 bool		wal_log_hints = false;
-int		wal_compression = WAL_COMPRESSION_ZSTD;
+char		*wal_compression_string = ""; /* Overwritten by GUC */
+int			wal_compression = WAL_COMPRESSION_ZSTD;
+int			wal_compression_level = 1;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
@@ -10603,6 +10605,21 @@ assign_xlog_sync_method(int new_sync_method, void *extra)
 	}
 }
 
+bool
+check_wal_compression(char **newval, void **extra, GucSource source)
+{
+	int tmp;
+	return get_compression_level(*newval, &tmp) != -1;
+}
+
+/* Parse the GUC into integers for wal_compression and wal_compression_level */
+void
+assign_wal_compression(const char *newval, void *extra)
+{
+	wal_compression = get_compression_level(newval, &wal_compression_level);
+	Assert(wal_compression >= 0);
+}
+
 
 /*
  * Issue appropriate kind of fsync (if any) for an XLOG output file.
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
index 96f497d5d6..16dab2e5a6 100644
--- a/src/backend/access/transam/xloginsert.c
+++ b/src/backend/access/transam/xloginsert.c
@@ -895,7 +895,7 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 		{
 			unsigned long	len_l = COMPRESS_BUFSIZE;
 			int ret;
-			ret = compress2((Bytef*)dest, &len_l, (Bytef*)source, orig_len, 1);
+			ret = compress2((Bytef*)dest, &len_l, (Bytef*)source, orig_len, wal_compression_level);
 			if (ret != Z_OK)
 				len_l = -1;
 			len = len_l;
@@ -905,7 +905,7 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 
 #ifdef USE_LZ4
 	case WAL_COMPRESSION_LZ4:
-		len = LZ4_compress_fast(source, dest, orig_len, COMPRESS_BUFSIZE, 1);
+		len = LZ4_compress_fast(source, dest, orig_len, COMPRESS_BUFSIZE, wal_compression_level);
 		if (len == 0)
 			len = -1;
 		break;
@@ -913,8 +913,7 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 
 #ifdef USE_ZSTD
 	case WAL_COMPRESSION_ZSTD:
-		len = ZSTD_compress(dest, COMPRESS_BUFSIZE, source, orig_len,
-				ZSTD_CLEVEL_DEFAULT);
+		len = ZSTD_compress(dest, COMPRESS_BUFSIZE, source, orig_len, wal_compression_level);
 		if (ZSTD_isError(len))
 			len = -1;
 		break;
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index 1b13d1f660..a33f13b6cd 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -26,6 +26,7 @@
 #include "catalog/pg_control.h"
 #include "common/pg_lzcompress.h"
 #include "replication/origin.h"
+#include "utils/builtins.h"
 #include "utils/guc.h"
 
 #ifndef FRONTEND
@@ -63,35 +64,41 @@ static void WALOpenSegmentInit(WALOpenSegment *seg, WALSegmentContext *segcxt,
 /* size of the buffer allocated for error message. */
 #define MAX_ERRORMSG_LEN 1000
 
-/*
- * Accept the likely variants for none and pglz, for compatibility with old
- * server versions where wal_compression was a boolean.
- */
-const struct config_enum_entry wal_compression_options[] = {
+static const struct {
+	char *name;
+	enum WalCompression compress_id; /* The internal ID (which includes the compression level) */
+	bool has_level; /* If it accepts a numeric "level" */
+	int min_level, dfl_level, max_level;
+} wal_compression_options[] = {
+	/*
+	 * Accept the likely variants for none and pglz, for compatibility with old
+	 * server versions where wal_compression was a boolean.
+	 */
 	{"off", WAL_COMPRESSION_NONE, false},
 	{"none", WAL_COMPRESSION_NONE, false},
-	{"false", WAL_COMPRESSION_NONE, true},
-	{"no", WAL_COMPRESSION_NONE, true},
-	{"0", WAL_COMPRESSION_NONE, true},
+	{"false", WAL_COMPRESSION_NONE, false},
+	{"no", WAL_COMPRESSION_NONE, false},
+	{"0", WAL_COMPRESSION_NONE, false},
+
 	{"pglz", WAL_COMPRESSION_PGLZ, false},
-	{"true", WAL_COMPRESSION_PGLZ, true},
-	{"yes", WAL_COMPRESSION_PGLZ, true},
-	{"on", WAL_COMPRESSION_PGLZ, true},
-	{"1", WAL_COMPRESSION_PGLZ, true},
+	{"true", WAL_COMPRESSION_PGLZ, false},
+	{"yes", WAL_COMPRESSION_PGLZ, false},
+	{"on", WAL_COMPRESSION_PGLZ, false},
+	{"1", WAL_COMPRESSION_PGLZ, false},
 
 #ifdef  HAVE_LIBZ
-	{"zlib", WAL_COMPRESSION_ZLIB, false},
+	{"zlib", WAL_COMPRESSION_ZLIB, true, 0, 1, 9},
 #endif
 
 #ifdef  USE_LZ4
-	{"lz4", WAL_COMPRESSION_LZ4, false},
+	{"lz4", WAL_COMPRESSION_LZ4, true, 1, 1, 65537},
 #endif
 
 #ifdef  USE_ZSTD
-	{"zstd", WAL_COMPRESSION_ZSTD, false},
+	{"zstd-fast", WAL_COMPRESSION_ZSTD, true, -50, -10, -1 }, /* Must be before zstd... */
+	{"zstd", WAL_COMPRESSION_ZSTD, true, -50, ZSTD_CLEVEL_DEFAULT, 10},
 #endif
 
-	{NULL, 0, false}
 };
 
 /*
@@ -1578,6 +1585,83 @@ XLogRecGetBlockData(XLogReaderState *record, uint8 block_id, Size *len)
 	}
 }
 
+/*
+ * Return the wal compression ID, or -1 if the input is
+ * invalid/unrecognized/unsupported.
+ * The compression level is stored in *level.
+ */
+int
+get_compression_level(const char *in, int *level)
+{
+	for (int idx=0; idx < lengthof(wal_compression_options); ++idx)
+	{
+		int len;
+		int tmp;
+		char *end;
+
+		if (strcmp(in, wal_compression_options[idx].name) == 0)
+		{
+			/* it has no -level suffix */
+			*level = wal_compression_options[idx].dfl_level;
+			return wal_compression_options[idx].compress_id;
+		}
+
+		len = strlen(wal_compression_options[idx].name);
+		if (strncmp(in, wal_compression_options[idx].name, len) != 0)
+			continue;
+		if (in[len] != '-')
+			continue;
+
+		/* it has a -level suffix, but level is not allowed */
+		if (!wal_compression_options[idx].has_level)
+		{
+#ifndef FRONTEND
+			GUC_check_errdetail("Compression method does not accept a compression level");
+#endif
+			return -1;
+		}
+
+		in += len + 1;
+		len = strlen(in);
+		errno = 0;
+		tmp = strtol(in, &end, 0);
+		if (end != in+len || end == in ||
+				(errno != 0 && tmp == 0) ||
+				(errno == ERANGE && (tmp == LONG_MIN || tmp == LONG_MAX)))
+		{
+#ifndef FRONTEND
+			GUC_check_errdetail("Could not parse compression level: %s", in);
+#endif
+			return -1;
+		}
+
+		/*
+		 * For convenience, allow specification of zstd-fast-N, which is
+		 * interpretted as a negative compression level.
+		 */
+		if (strncmp(wal_compression_options[idx].name, "zstd-fast", 9) == 0 &&
+				tmp > 0)
+				tmp = -tmp;
+
+		if (tmp < wal_compression_options[idx].min_level ||
+				tmp > wal_compression_options[idx].max_level)
+		{
+#ifndef FRONTEND
+			GUC_check_errdetail("Compression level is outside of allowed range: %d...%d",
+					wal_compression_options[idx].min_level,
+					wal_compression_options[idx].max_level);
+#endif
+			return -1;
+		}
+
+		*level = tmp;
+		return wal_compression_options[idx].compress_id;
+	}
+
+	return -1;
+}
+
+
 /*
  * Return a statically allocated string associated with the given compression
  * method.
@@ -1585,9 +1669,9 @@ XLogRecGetBlockData(XLogReaderState *record, uint8 block_id, Size *len)
 const char *
 wal_compression_name(WalCompression compression)
 {
-	for (int i=0; wal_compression_options[i].name != NULL; ++i)
+	for (int i=0; i < lengthof(wal_compression_options); ++i)
 	{
-		if (wal_compression_options[i].val == compression)
+		if (wal_compression_options[i].compress_id == compression)
 			return wal_compression_options[i].name;
 	}
 
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index f37251a27f..29cb12c8a5 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -4556,6 +4556,16 @@ static struct config_string ConfigureNamesString[] =
 		check_wal_consistency_checking, assign_wal_consistency_checking, NULL
 	},
 
+	{
+		{"wal_compression", PGC_SUSET, WAL_SETTINGS,
+			gettext_noop("Set the method used to compress full page images in the WAL."),
+			NULL
+		},
+		&wal_compression_string,
+		"zstd",
+		check_wal_compression, assign_wal_compression, NULL
+	},
+
 	{
 		{"jit_provider", PGC_POSTMASTER, CLIENT_CONN_PRELOAD,
 			gettext_noop("JIT provider to use."),
@@ -4816,16 +4826,6 @@ static struct config_enum ConfigureNamesEnum[] =
 		NULL, NULL, NULL
 	},
 
-	{
-		{"wal_compression", PGC_SUSET, WAL_SETTINGS,
-			gettext_noop("Set the method used to compress full page images in the WAL."),
-			NULL
-		},
-		&wal_compression,
-		WAL_COMPRESSION_ZSTD, wal_compression_options,
-		NULL, NULL, NULL
-	},
-
 	{
 		{"dynamic_shared_memory_type", PGC_POSTMASTER, RESOURCES_MEM,
 			gettext_noop("Selects the dynamic shared memory implementation used."),
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index e8b2c53784..7a05838d0b 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -19,6 +19,7 @@
 #include "lib/stringinfo.h"
 #include "nodes/pg_list.h"
 #include "storage/fd.h"
+#include "utils/guc.h"
 
 
 /* Sync methods */
@@ -116,7 +117,6 @@ extern char *XLogArchiveCommand;
 extern bool EnableHotStandby;
 extern bool fullPageWrites;
 extern bool wal_log_hints;
-extern int wal_compression;
 extern bool wal_init_zero;
 extern bool wal_recycle;
 extern bool *wal_consistency_checking;
@@ -143,6 +143,9 @@ extern char *PromoteTriggerFile;
 extern RecoveryTargetTimeLineGoal recoveryTargetTimeLineGoal;
 extern TimeLineID recoveryTargetTLIRequested;
 extern TimeLineID recoveryTargetTLI;
+extern char *wal_compression_string;
+extern int wal_compression;
+extern int wal_compression_level;
 
 extern int	CheckPointSegments;
 
@@ -361,6 +364,11 @@ extern void XLogRequestWalReceiverReply(void);
 extern void assign_max_wal_size(int newval, void *extra);
 extern void assign_checkpoint_completion_target(double newval, void *extra);
 
+/* GUC */
+extern bool check_wal_compression(char **newval, void **extra, GucSource source);
+extern void assign_wal_compression(const char *newval, void *extra);
+
+
 /*
  * Routines to start, stop, and get status of a base backup.
  */
diff --git a/src/include/access/xlogreader.h b/src/include/access/xlogreader.h
index 21d200d3df..b4d0ab4517 100644
--- a/src/include/access/xlogreader.h
+++ b/src/include/access/xlogreader.h
@@ -327,4 +327,6 @@ extern bool XLogRecGetBlockTag(XLogReaderState *record, uint8 block_id,
 							   RelFileNode *rnode, ForkNumber *forknum,
 							   BlockNumber *blknum);
 
+extern int get_compression_level(const char *in, int *level);
+
 #endif							/* XLOGREADER_H */
-- 
2.17.0

From d20de46ee91b753a82378960cc51b1f9e527507f Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Wed, 16 Jun 2021 14:19:16 +0900
Subject: [PATCH v10 1/2] Add more options for wal_compression

---
 src/include/access/xlog.h                     |  28 ++-
 src/include/access/xlogrecord.h               |  17 +-
 src/include/pg_config.h.in                    |   9 +
 src/backend/Makefile                          |   2 +-
 src/backend/access/transam/xlog.c             |   3 +-
 src/backend/access/transam/xloginsert.c       | 114 ++++++++-
 src/backend/access/transam/xlogreader.c       |  98 +++++++-
 src/backend/utils/misc/guc.c                  |  52 ++++-
 src/backend/utils/misc/postgresql.conf.sample |   8 +-
 src/bin/pg_waldump/pg_waldump.c               |  20 +-
 doc/src/sgml/config.sgml                      |  37 ++-
 doc/src/sgml/install-windows.sgml             |   2 +-
 doc/src/sgml/installation.sgml                |  28 ++-
 configure                                     | 217 ++++++++++++++++++
 configure.ac                                  |  33 +++
 src/tools/msvc/Solution.pm                    |   2 +
 src/tools/msvc/config_default.pl              |   1 +
 17 files changed, 622 insertions(+), 49 deletions(-)

diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index 77187c12be..e7953572d0 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -116,7 +116,8 @@ extern char *XLogArchiveCommand;
 extern bool EnableHotStandby;
 extern bool fullPageWrites;
 extern bool wal_log_hints;
-extern bool wal_compression;
+extern int	wal_compression;
+extern int	wal_compression_level;
 extern bool wal_init_zero;
 extern bool wal_recycle;
 extern bool *wal_consistency_checking;
@@ -167,6 +168,31 @@ typedef enum WalLevel
 	WAL_LEVEL_LOGICAL
 } WalLevel;
 
+/* WAL compressions */
+typedef enum WalCompression
+{
+	WAL_COMPRESSION_NONE = 0,
+	WAL_COMPRESSION_PGLZ,
+	WAL_COMPRESSION_ZLIB,
+	WAL_COMPRESSION_LZ4,
+	WAL_COMPRESSION_ZSTD,
+} WalCompression;
+
+/*---------
+ * Compression methods supported for wal_compression have different
+ * ideas of what a compression level is, though they all use an integer
+ * to measure it:
+ * - ZLIB ranks from 0 to 9, with a default at 1.
+ * - LZ4 ranks from 1 to 65537, with a default at 1.
+ * - ZSTD ranks from -50 to 10, with a default at ZSTD_CLEVEL_DEFAULT.
+ *
+ * This default value is chosen so as it does not map with supported
+ * ranges for any of the supported methods listed above.  When set to
+ * this value, the default compression level is used for each method.
+ *---------
+ */
+#define WAL_COMPRESSION_LEVEL_DEFAULT -10000
+
 /* Recovery states */
 typedef enum RecoveryState
 {
diff --git a/src/include/access/xlogrecord.h b/src/include/access/xlogrecord.h
index 80c92a2498..cba42c10e7 100644
--- a/src/include/access/xlogrecord.h
+++ b/src/include/access/xlogrecord.h
@@ -114,8 +114,8 @@ typedef struct XLogRecordBlockHeader
  * present is (BLCKSZ - <length of "hole" bytes>).
  *
  * Additionally, when wal_compression is enabled, we will try to compress full
- * page images using the PGLZ compression algorithm, after removing the "hole".
- * This can reduce the WAL volume, but at some extra cost of CPU spent
+ * page images using one of the supported algorithms, after removing the
+ * "hole". This can reduce the WAL volume, but at some extra cost of CPU spent
  * on the compression during WAL logging. In this case, since the "hole"
  * length cannot be calculated by subtracting the number of page image bytes
  * from BLCKSZ, basically it needs to be stored as an extra information.
@@ -144,9 +144,16 @@ typedef struct XLogRecordBlockImageHeader
 
 /* Information stored in bimg_info */
 #define BKPIMAGE_HAS_HOLE		0x01	/* page image has "hole" */
-#define BKPIMAGE_IS_COMPRESSED		0x02	/* page image is compressed */
-#define BKPIMAGE_APPLY		0x04	/* page image should be restored during
-									 * replay */
+#define BKPIMAGE_APPLY			0x02	/* page image should be restored
+										 * during replay */
+/* compression methods supported */
+#define BKPIMAGE_COMPRESS_PGLZ	0x04
+#define BKPIMAGE_COMPRESS_ZLIB	0x08
+#define BKPIMAGE_COMPRESS_LZ4	0x10
+#define BKPIMAGE_COMPRESS_ZSTD	0x20
+#define	BKPIMAGE_IS_COMPRESSED(info) \
+	((info & (BKPIMAGE_COMPRESS_PGLZ | BKPIMAGE_COMPRESS_ZLIB | \
+			  BKPIMAGE_COMPRESS_LZ4 | BKPIMAGE_COMPRESS_ZSTD)) != 0)
 
 /*
  * Extra header information used when page image has "hole" and
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index 783b8fc1ba..1951d88ac9 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -355,6 +355,9 @@
 /* Define to 1 if you have the `z' library (-lz). */
 #undef HAVE_LIBZ
 
+/* Define to 1 if you have the `zstd' library (-lzstd). */
+#undef HAVE_LIBZSTD
+
 /* Define to 1 if you have the `link' function. */
 #undef HAVE_LINK
 
@@ -722,6 +725,9 @@
 /* Define to 1 if the assembler supports X86_64's POPCNTQ instruction. */
 #undef HAVE_X86_64_POPCNTQ
 
+/* Define to 1 if you have the <zstd.h> header file. */
+#undef HAVE_ZSTD_H
+
 /* Define to 1 if the system has the type `_Bool'. */
 #undef HAVE__BOOL
 
@@ -953,6 +959,9 @@
 /* Define to select Win32-style shared memory. */
 #undef USE_WIN32_SHARED_MEMORY
 
+/* Define to 1 to build with zstd support. (--with-zstd) */
+#undef USE_ZSTD
+
 /* Define to 1 if `wcstombs_l' requires <xlocale.h>. */
 #undef WCSTOMBS_L_IN_XLOCALE
 
diff --git a/src/backend/Makefile b/src/backend/Makefile
index 0da848b1fd..3af216ddfc 100644
--- a/src/backend/Makefile
+++ b/src/backend/Makefile
@@ -48,7 +48,7 @@ OBJS = \
 LIBS := $(filter-out -lpgport -lpgcommon, $(LIBS)) $(LDAP_LIBS_BE) $(ICU_LIBS)
 
 # The backend doesn't need everything that's in LIBS, however
-LIBS := $(filter-out -lz -lreadline -ledit -ltermcap -lncurses -lcurses, $(LIBS))
+LIBS := $(filter-out -lreadline -ledit -ltermcap -lncurses -lcurses, $(LIBS))
 
 ifeq ($(with_systemd),yes)
 LIBS += -lsystemd
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 17eeff0720..21349e011c 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -98,7 +98,8 @@ char	   *XLogArchiveCommand = NULL;
 bool		EnableHotStandby = false;
 bool		fullPageWrites = true;
 bool		wal_log_hints = false;
-bool		wal_compression = false;
+int			wal_compression = WAL_COMPRESSION_NONE;
+int			wal_compression_level = -1;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
index 32b4cc84e7..b2ca1acc0d 100644
--- a/src/backend/access/transam/xloginsert.c
+++ b/src/backend/access/transam/xloginsert.c
@@ -33,8 +33,33 @@
 #include "storage/proc.h"
 #include "utils/memutils.h"
 
+/* XXX: this needs to be heavily cleaned up */
+#ifdef HAVE_LIBZ
+#include <zlib.h>
+/* zlib compressBound is not a macro */
+#define ZLIB_MAX_BLCKSZ		BLCKSZ + (BLCKSZ>>12) + (BLCKSZ>>14) + (BLCKSZ>>25) + 13
+#else
+#define ZLIB_MAX_BLCKSZ		0
+#endif
+
+#ifdef USE_LZ4
+#include <lz4.h>
+#define	LZ4_MAX_BLCKSZ		LZ4_COMPRESSBOUND(BLCKSZ)
+#else
+#define LZ4_MAX_BLCKSZ		0
+#endif
+
+#ifdef USE_ZSTD
+#include <zstd.h>
+#define ZSTD_MAX_BLCKSZ		ZSTD_COMPRESSBOUND(BLCKSZ)
+#else
+#define ZSTD_MAX_BLCKSZ		0
+#endif
+
 /* Buffer size required to store a compressed version of backup block image */
-#define PGLZ_MAX_BLCKSZ PGLZ_MAX_OUTPUT(BLCKSZ)
+#define PGLZ_MAX_BLCKSZ		PGLZ_MAX_OUTPUT(BLCKSZ)
+
+#define COMPRESS_BUFSIZE	Max(Max(Max(PGLZ_MAX_BLCKSZ, ZLIB_MAX_BLCKSZ), LZ4_MAX_BLCKSZ), ZSTD_MAX_BLCKSZ)
 
 /*
  * For each block reference registered with XLogRegisterBuffer, we fill in
@@ -58,7 +83,7 @@ typedef struct
 								 * backup block data in XLogRecordAssemble() */
 
 	/* buffer to store a compressed version of backup block image */
-	char		compressed_page[PGLZ_MAX_BLCKSZ];
+	char		compressed_page[COMPRESS_BUFSIZE];
 } registered_buffer;
 
 static registered_buffer *registered_buffers;
@@ -628,7 +653,7 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
 			/*
 			 * Try to compress a block image if wal_compression is enabled
 			 */
-			if (wal_compression)
+			if (wal_compression != WAL_COMPRESSION_NONE)
 			{
 				is_compressed =
 					XLogCompressBackupBlock(page, bimg.hole_offset,
@@ -665,8 +690,39 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
 
 			if (is_compressed)
 			{
+				/* The current compression is stored in the WAL record */
 				bimg.length = compressed_len;
-				bimg.bimg_info |= BKPIMAGE_IS_COMPRESSED;
+
+				/* Append the compression method used */
+				switch (wal_compression)
+				{
+					case WAL_COMPRESSION_PGLZ:
+						bimg.bimg_info |= BKPIMAGE_COMPRESS_PGLZ;
+						break;
+					case WAL_COMPRESSION_ZLIB:
+#ifdef HAVE_LIBZ
+						bimg.bimg_info |= BKPIMAGE_COMPRESS_ZLIB;
+#else
+						elog(ERROR, "ZLIB is not supported by this build");
+#endif
+						break;
+					case WAL_COMPRESSION_LZ4:
+#ifdef USE_LZ4
+						bimg.bimg_info |= BKPIMAGE_COMPRESS_LZ4;
+#else
+						elog(ERROR, "LZ4 is not supported by this build");
+#endif
+						break;
+					case WAL_COMPRESSION_ZSTD:
+#ifdef USE_ZSTD
+						bimg.bimg_info |= BKPIMAGE_COMPRESS_ZSTD;
+#else
+						elog(ERROR, "ZSTD is not supported by this build");
+#endif
+						break;
+					default:
+						elog(ERROR, "unsupported WAL compression method specified");
+				}
 
 				rdt_datas_last->data = regbuf->compressed_page;
 				rdt_datas_last->len = compressed_len;
@@ -853,12 +909,58 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 	else
 		source = page;
 
+	switch (wal_compression)
+	{
+		case WAL_COMPRESSION_PGLZ:
+			len = pglz_compress(source, orig_len, dest, PGLZ_strategy_default);
+			break;
+
+#ifdef HAVE_LIBZ
+		case WAL_COMPRESSION_ZLIB:
+			{
+				unsigned long	len_l = COMPRESS_BUFSIZE;
+				int				ret;
+
+				ret = compress2((Bytef *) dest, &len_l, (Bytef *)
+								source, orig_len,
+								wal_compression_level == WAL_COMPRESSION_LEVEL_DEFAULT ?
+								1 : wal_compression_level);
+				if (ret != Z_OK)
+					len_l = -1;
+				len = len_l;
+				break;
+			}
+#endif
+
+#ifdef USE_LZ4
+		case WAL_COMPRESSION_LZ4:
+			len = LZ4_compress_fast(source, dest, orig_len, COMPRESS_BUFSIZE,
+									wal_compression_level == WAL_COMPRESSION_LEVEL_DEFAULT ?
+									1 : wal_compression_level);
+			if (len == 0)
+				len = -1;
+			break;
+#endif
+
+#ifdef USE_ZSTD
+		case WAL_COMPRESSION_ZSTD:
+			len = ZSTD_compress(dest, COMPRESS_BUFSIZE, source, orig_len,
+								wal_compression_level == WAL_COMPRESSION_LEVEL_DEFAULT ?
+								ZSTD_CLEVEL_DEFAULT : wal_compression_level);
+			if (ZSTD_isError(len))
+				len = -1;
+			break;
+#endif
+
+		default:
+			elog(ERROR, "unsupported WAL compression method specified");
+	}
+
 	/*
-	 * We recheck the actual size even if pglz_compress() reports success and
+	 * We recheck the actual size even if compression reports success and
 	 * see if the number of bytes saved by compression is larger than the
 	 * length of extra data needed for the compressed version of block image.
 	 */
-	len = pglz_compress(source, orig_len, dest, PGLZ_strategy_default);
 	if (len >= 0 &&
 		len + extra_bytes < orig_len)
 	{
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index 42738eb940..f9dc0ee910 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -18,6 +18,15 @@
 #include "postgres.h"
 
 #include <unistd.h>
+#ifdef HAVE_LIBZ
+#include <zlib.h>
+#endif
+#ifdef USE_LZ4
+#include <lz4.h>
+#endif
+#ifdef USE_ZSTD
+#include <zstd.h>
+#endif
 
 #include "access/transam.h"
 #include "access/xlog_internal.h"
@@ -1290,7 +1299,7 @@ DecodeXLogRecord(XLogReaderState *state, XLogRecord *record, char **errormsg)
 
 				blk->apply_image = ((blk->bimg_info & BKPIMAGE_APPLY) != 0);
 
-				if (blk->bimg_info & BKPIMAGE_IS_COMPRESSED)
+				if (BKPIMAGE_IS_COMPRESSED(blk->bimg_info))
 				{
 					if (blk->bimg_info & BKPIMAGE_HAS_HOLE)
 						COPY_HEADER_FIELD(&blk->hole_length, sizeof(uint16));
@@ -1335,29 +1344,28 @@ DecodeXLogRecord(XLogReaderState *state, XLogRecord *record, char **errormsg)
 				}
 
 				/*
-				 * cross-check that bimg_len < BLCKSZ if the IS_COMPRESSED
-				 * flag is set.
+				 * cross-check that bimg_len < BLCKSZ if it's compressed
 				 */
-				if ((blk->bimg_info & BKPIMAGE_IS_COMPRESSED) &&
+				if (BKPIMAGE_IS_COMPRESSED(blk->bimg_info) &&
 					blk->bimg_len == BLCKSZ)
 				{
 					report_invalid_record(state,
-										  "BKPIMAGE_IS_COMPRESSED set, but block image length %u at %X/%X",
+										  "BKPIMAGE_IS_COMPRESSED, but block image length %u at %X/%X",
 										  (unsigned int) blk->bimg_len,
 										  LSN_FORMAT_ARGS(state->ReadRecPtr));
 					goto err;
 				}
 
 				/*
-				 * cross-check that bimg_len = BLCKSZ if neither HAS_HOLE nor
-				 * IS_COMPRESSED flag is set.
+				 * cross-check that bimg_len = BLCKSZ if neither HAS_HOLE is
+				 * set nor IS_COMPRESSED().
 				 */
 				if (!(blk->bimg_info & BKPIMAGE_HAS_HOLE) &&
-					!(blk->bimg_info & BKPIMAGE_IS_COMPRESSED) &&
+					!BKPIMAGE_IS_COMPRESSED(blk->bimg_info) &&
 					blk->bimg_len != BLCKSZ)
 				{
 					report_invalid_record(state,
-										  "neither BKPIMAGE_HAS_HOLE nor BKPIMAGE_IS_COMPRESSED set, but block image length is %u at %X/%X",
+										  "neither BKPIMAGE_HAS_HOLE nor BKPIMAGE_IS_COMPRESSED, but block image length is %u at %X/%X",
 										  (unsigned int) blk->data_len,
 										  LSN_FORMAT_ARGS(state->ReadRecPtr));
 					goto err;
@@ -1555,17 +1563,83 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 	bkpb = &record->blocks[block_id];
 	ptr = bkpb->bkp_image;
 
-	if (bkpb->bimg_info & BKPIMAGE_IS_COMPRESSED)
+	if (BKPIMAGE_IS_COMPRESSED(bkpb->bimg_info))
 	{
 		/* If a backup block image is compressed, decompress it */
-		if (pglz_decompress(ptr, bkpb->bimg_len, tmp.data,
-							BLCKSZ - bkpb->hole_length, true) < 0)
+		int32 decomp_result = -1;
+
+		if ((bkpb->bimg_info & BKPIMAGE_COMPRESS_PGLZ) != 0)
+		{
+			decomp_result = pglz_decompress(ptr, bkpb->bimg_len, tmp.data,
+							BLCKSZ - bkpb->hole_length, true);
+		}
+		else if ((bkpb->bimg_info & BKPIMAGE_COMPRESS_ZLIB) != 0)
+		{
+#ifdef HAVE_LIBZ
+			unsigned long decomp_result_l;
+
+			decomp_result_l = BLCKSZ - bkpb->hole_length;
+			if (uncompress((Bytef*) tmp.data, &decomp_result_l,
+						   (Bytef*) ptr, bkpb->bimg_len) == Z_OK)
+				decomp_result = decomp_result_l;
+			else
+				decomp_result = -1;
+#else
+			report_invalid_record(record, "image at %X/%X compressed with %s not supported, block %d",
+								  (uint32) (record->ReadRecPtr >> 32),
+								  (uint32) record->ReadRecPtr,
+								  "zlib",
+								  block_id);
+#endif
+		}
+		else if ((bkpb->bimg_info & BKPIMAGE_COMPRESS_LZ4) != 0)
+		{
+#ifdef USE_LZ4
+			decomp_result = LZ4_decompress_safe(ptr, tmp.data,
+					bkpb->bimg_len, BLCKSZ-bkpb->hole_length);
+#else
+			report_invalid_record(record, "image at %X/%X compressed with %s not supported, block %d",
+								  (uint32) (record->ReadRecPtr >> 32),
+								  (uint32) record->ReadRecPtr,
+								  "lz4",
+								  block_id);
+#endif
+		}
+		else if ((bkpb->bimg_info & BKPIMAGE_COMPRESS_ZSTD) != 0)
+		{
+#ifdef USE_ZSTD
+			decomp_result = ZSTD_decompress(tmp.data, BLCKSZ-bkpb->hole_length,
+					ptr, bkpb->bimg_len);
+			/*
+			 * XXX: ZSTD_getErrorName (I need to study those APIs more,
+			 * perhaps).
+			 */
+			if (ZSTD_isError(decomp_result))
+				decomp_result = -1;
+#else
+			report_invalid_record(record, "image at %X/%X compressed with %s not supported, block %d",
+								  (uint32) (record->ReadRecPtr >> 32),
+								  (uint32) record->ReadRecPtr,
+								  "zstd",
+								  block_id);
+#endif
+		}
+		else
+		{
+			report_invalid_record(record, "image at %X/%X is compressed with unknown method, block %d",
+								  (uint32) (record->ReadRecPtr >> 32),
+								  (uint32) record->ReadRecPtr,
+								  block_id);
+		}
+
+		if (decomp_result < 0)
 		{
 			report_invalid_record(record, "invalid compressed image at %X/%X, block %d",
 								  LSN_FORMAT_ARGS(record->ReadRecPtr),
 								  block_id);
 			return false;
 		}
+
 		ptr = tmp.data;
 	}
 
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 68b62d523d..1ea332a27f 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -540,6 +540,28 @@ static struct config_enum_entry default_toast_compression_options[] = {
 	{NULL, 0, false}
 };
 
+static const struct config_enum_entry wal_compression_options[] = {
+	{"pglz", WAL_COMPRESSION_PGLZ, false},
+#ifdef HAVE_LIBZ
+	{"zlib", WAL_COMPRESSION_ZLIB, false},
+#endif
+#ifdef USE_LZ4
+	{"lz4", WAL_COMPRESSION_LZ4, false},
+#endif
+#ifdef USE_ZSTD
+	{"zstd", WAL_COMPRESSION_ZSTD, false},
+#endif
+	{"on", WAL_COMPRESSION_PGLZ, false},
+	{"off", WAL_COMPRESSION_NONE, false},
+	{"true", WAL_COMPRESSION_PGLZ, true},
+	{"false", WAL_COMPRESSION_NONE, true},
+	{"yes", WAL_COMPRESSION_PGLZ, true},
+	{"no", WAL_COMPRESSION_NONE, true},
+	{"1", WAL_COMPRESSION_PGLZ, true},
+	{"0", WAL_COMPRESSION_NONE, true},
+	{NULL, 0, false}
+};
+
 /*
  * Options for enum values stored in other modules
  */
@@ -1304,16 +1326,6 @@ static struct config_bool ConfigureNamesBool[] =
 		NULL, NULL, NULL
 	},
 
-	{
-		{"wal_compression", PGC_SUSET, WAL_SETTINGS,
-			gettext_noop("Compresses full-page writes written in WAL file."),
-			NULL
-		},
-		&wal_compression,
-		false,
-		NULL, NULL, NULL
-	},
-
 	{
 		{"wal_init_zero", PGC_SUSET, WAL_SETTINGS,
 			gettext_noop("Writes zeroes to new WAL files before first use."),
@@ -2261,6 +2273,16 @@ static struct config_int ConfigureNamesInt[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"wal_compression_level", PGC_SUSET, CONN_AUTH_SETTINGS,
+			gettext_noop("Sets the compression level used with wal_compression."),
+			NULL
+		},
+		&wal_compression_level,
+		WAL_COMPRESSION_LEVEL_DEFAULT, INT_MIN, INT_MAX,
+		NULL, NULL, NULL
+	},
+
 	{
 		{"wal_receiver_status_interval", PGC_SIGHUP, REPLICATION_STANDBY,
 			gettext_noop("Sets the maximum interval between WAL receiver status reports to the sending server."),
@@ -4815,6 +4837,16 @@ static struct config_enum ConfigureNamesEnum[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"wal_compression", PGC_SUSET, WAL_SETTINGS,
+			gettext_noop("Set the method used to compress full page images in the WAL."),
+			NULL
+		},
+		&wal_compression,
+		WAL_COMPRESSION_NONE, wal_compression_options,
+		NULL, NULL, NULL
+	},
+
 	{
 		{"wal_level", PGC_POSTMASTER, WAL_SETTINGS,
 			gettext_noop("Sets the level of information written to the WAL."),
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index ddbb6dc2be..50c7c90fab 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -218,7 +218,13 @@
 #full_page_writes = on			# recover from partial page writes
 #wal_log_hints = off			# also do full page writes of non-critical updates
 					# (change requires restart)
-#wal_compression = off			# enable compression of full-page writes
+#wal_compression = off			# enables compression of full-page writes;
+					# off, pglz, zlib, lz4, zstd, or on
+#wal_compression_level = -10000		# compression level applied with
+					# wal_compression. Depends on the
+					# compression algorithm used. -10000
+					# implies to use the default of each
+					# algorithm.
 #wal_init_zero = on			# zero-fill new WAL files
 #wal_recycle = on			# recycle WAL files
 #wal_buffers = -1			# min 32kB, -1 sets based on shared_buffers
diff --git a/src/bin/pg_waldump/pg_waldump.c b/src/bin/pg_waldump/pg_waldump.c
index f8b8afe4a7..7e94cf31e8 100644
--- a/src/bin/pg_waldump/pg_waldump.c
+++ b/src/bin/pg_waldump/pg_waldump.c
@@ -537,18 +537,30 @@ XLogDumpDisplayRecord(XLogDumpConfig *config, XLogReaderState *record)
 				   blk);
 			if (XLogRecHasBlockImage(record, block_id))
 			{
-				if (record->blocks[block_id].bimg_info &
-					BKPIMAGE_IS_COMPRESSED)
+				uint8	bimg_info = record->blocks[block_id].bimg_info;
+
+				if (BKPIMAGE_IS_COMPRESSED(bimg_info))
 				{
+					const char *method = "???";
+					if ((bimg_info & BKPIMAGE_COMPRESS_PGLZ) != 0)
+						method = "pglz";
+					else if ((bimg_info & BKPIMAGE_COMPRESS_ZLIB) != 0)
+						method = "zlib";
+					else if ((bimg_info & BKPIMAGE_COMPRESS_LZ4) != 0)
+						method = "lz4";
+					else if ((bimg_info & BKPIMAGE_COMPRESS_ZSTD) != 0)
+						method = "zstd";
+
 					printf(" (FPW%s); hole: offset: %u, length: %u, "
-						   "compression saved: %u",
+						   "compression saved: %u, method: %s",
 						   XLogRecBlockImageApply(record, block_id) ?
 						   "" : " for WAL verification",
 						   record->blocks[block_id].hole_offset,
 						   record->blocks[block_id].hole_length,
 						   BLCKSZ -
 						   record->blocks[block_id].hole_length -
-						   record->blocks[block_id].bimg_len);
+						   record->blocks[block_id].bimg_len,
+						   method);
 				}
 				else
 				{
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index aa3e178240..f6322ed425 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -3127,23 +3127,32 @@ include_dir 'conf.d'
      </varlistentry>
 
      <varlistentry id="guc-wal-compression" xreflabel="wal_compression">
-      <term><varname>wal_compression</varname> (<type>boolean</type>)
+      <term><varname>wal_compression</varname> (<type>enum</type>)
       <indexterm>
        <primary><varname>wal_compression</varname> configuration parameter</primary>
       </indexterm>
       </term>
       <listitem>
        <para>
-        When this parameter is <literal>on</literal>, the <productname>PostgreSQL</productname>
+        This parameter enables compression of WAL using the specified 
+        compression method.
+        When enabled, the <productname>PostgreSQL</productname>
         server compresses full page images written to WAL when
         <xref linkend="guc-full-page-writes"/> is on or during a base backup.
         A compressed page image will be decompressed during WAL replay.
+        The supported methods are pglz, <literal>zlib</literal> 
+        (if <productname>PostgreSQL</productname> was not built with
+        <option>--without-zlib</option>), <literal>lz4</literal>
+        (if <productname>PostgreSQL</productname> was compiled with
+        <option>--with-lz4</option>) and <literal>zstd</literal>
+        (if <productname>PostgreSQL</productname> was compiled with
+        <option>--with-zstd</option>).
         The default value is <literal>off</literal>.
         Only superusers can change this setting.
        </para>
 
        <para>
-        Turning this parameter on can reduce the WAL volume without
+        Enabling compression can reduce the WAL volume without
         increasing the risk of unrecoverable data corruption,
         but at the cost of some extra CPU spent on the compression during
         WAL logging and on the decompression during WAL replay.
@@ -3151,6 +3160,28 @@ include_dir 'conf.d'
       </listitem>
      </varlistentry>
 
+     <varlistentry id="guc-wal-compression-level" xreflabel="wal_compression_level">
+      <term><varname>wal_compression_level</varname> (<type>enum</type>)
+      <indexterm>
+       <primary><varname>wal_compression_level</varname> configuration parameter</primary>
+      </indexterm>
+      </term>
+      <listitem>
+       <para>
+        If set, controls the level of compression used with
+        <varname>wal_compression</varname>. The range of levels supported
+        depends on the compression method used. The default is
+        <literal>-10000</literal>, to use the default level compression
+        recommended by a given method. There should be no need to change
+        this parameter, except for users experienced with compression
+        algorithms.
+       </para>
+       <para>
+        Only superusers can change this setting.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry id="guc-wal-init-zero" xreflabel="wal_init_zero">
       <term><varname>wal_init_zero</varname> (<type>boolean</type>)
       <indexterm>
diff --git a/doc/src/sgml/install-windows.sgml b/doc/src/sgml/install-windows.sgml
index 312edc6f7a..ba794b8c93 100644
--- a/doc/src/sgml/install-windows.sgml
+++ b/doc/src/sgml/install-windows.sgml
@@ -299,7 +299,7 @@ $ENV{MSBFLAGS}="/m";
      <term><productname>LZ4</productname></term>
      <listitem><para>
       Required for supporting <productname>LZ4</productname> compression
-      method for compressing the table data. Binaries and source can be
+      method for compressing table or WAL data. Binaries and source can be
       downloaded from
       <ulink url="https://github.com/lz4/lz4/releases"></ulink>.
      </para></listitem>
diff --git a/doc/src/sgml/installation.sgml b/doc/src/sgml/installation.sgml
index 3c0aa118c7..3e985bbd05 100644
--- a/doc/src/sgml/installation.sgml
+++ b/doc/src/sgml/installation.sgml
@@ -147,7 +147,7 @@ su - postgres
       specify the <option>--without-zlib</option> option to
       <filename>configure</filename>. Using this option disables
       support for compressed archives in <application>pg_dump</application> and
-      <application>pg_restore</application>.
+      <application>pg_restore</application>, and compressed WAL.
      </para>
     </listitem>
    </itemizedlist>
@@ -270,7 +270,16 @@ su - postgres
      <para>
       You need <productname>LZ4</productname>, if you want to support
       compression of data with this method; see
-      <xref linkend="guc-default-toast-compression"/>.
+      <xref linkend="guc-default-toast-compression"/> and
+      <xref linkend="guc-wal-compression"/>.
+     </para>
+    </listitem>
+
+    <listitem>
+     <para>
+      The <productname>ZSTD</productname> library can be used to enable
+      compression using that method; see
+      <xref linkend="guc-wal-compression"/>.
      </para>
     </listitem>
 
@@ -980,7 +989,18 @@ build-postgresql:
         <para>
          Build with <productname>LZ4</productname> compression support.
          This allows the use of <productname>LZ4</productname> for
-         compression of table data.
+         compression of table and WAL data.
+        </para>
+       </listitem>
+      </varlistentry>
+
+      <varlistentry>
+       <term><option>--with-zstd</option></term>
+       <listitem>
+        <para>
+         Build with <productname>ZSTD</productname> compression support.
+         This enables use of <productname>ZSTD</productname> for
+         compression of WAL data.
         </para>
        </listitem>
       </varlistentry>
@@ -1236,7 +1256,7 @@ build-postgresql:
          Prevents use of the <application>Zlib</application> library.
          This disables
          support for compressed archives in <application>pg_dump</application>
-         and <application>pg_restore</application>.
+         and <application>pg_restore</application> and compressed WAL.
         </para>
        </listitem>
       </varlistentry>
diff --git a/configure b/configure
index e9b98f442f..5317911100 100755
--- a/configure
+++ b/configure
@@ -699,6 +699,9 @@ with_gnu_ld
 LD
 LDFLAGS_SL
 LDFLAGS_EX
+ZSTD_LIBS
+ZSTD_CFLAGS
+with_zstd
 LZ4_LIBS
 LZ4_CFLAGS
 with_lz4
@@ -868,6 +871,7 @@ with_libxslt
 with_system_tzdata
 with_zlib
 with_lz4
+with_zstd
 with_gnu_ld
 with_ssl
 with_openssl
@@ -897,6 +901,8 @@ XML2_CFLAGS
 XML2_LIBS
 LZ4_CFLAGS
 LZ4_LIBS
+ZSTD_CFLAGS
+ZSTD_LIBS
 LDFLAGS_EX
 LDFLAGS_SL
 PERL
@@ -1576,6 +1582,7 @@ Optional Packages:
                           use system time zone data in DIR
   --without-zlib          do not use Zlib
   --with-lz4              build with LZ4 support
+  --with-zstd             build without Zstd compression library
   --with-gnu-ld           assume the C compiler uses GNU ld [default=no]
   --with-ssl=LIB          use LIB for SSL/TLS support (openssl)
   --with-openssl          obsolete spelling of --with-ssl=openssl
@@ -1605,6 +1612,8 @@ Some influential environment variables:
   XML2_LIBS   linker flags for XML2, overriding pkg-config
   LZ4_CFLAGS  C compiler flags for LZ4, overriding pkg-config
   LZ4_LIBS    linker flags for LZ4, overriding pkg-config
+  ZSTD_CFLAGS C compiler flags for ZSTD, overriding pkg-config
+  ZSTD_LIBS   linker flags for ZSTD, overriding pkg-config
   LDFLAGS_EX  extra linker flags for linking executables only
   LDFLAGS_SL  extra linker flags for linking shared libraries only
   PERL        Perl program
@@ -8713,6 +8722,147 @@ fi
   done
 fi
 
+#
+# ZSTD
+#
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether to build with zstd support" >&5
+$as_echo_n "checking whether to build with zstd support... " >&6; }
+
+
+
+# Check whether --with-zstd was given.
+if test "${with_zstd+set}" = set; then :
+  withval=$with_zstd;
+  case $withval in
+    yes)
+
+$as_echo "#define USE_ZSTD 1" >>confdefs.h
+
+      ;;
+    no)
+      :
+      ;;
+    *)
+      as_fn_error $? "no argument expected for --with-zstd option" "$LINENO" 5
+      ;;
+  esac
+
+else
+  with_zstd=no
+
+fi
+
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $with_zstd" >&5
+$as_echo "$with_zstd" >&6; }
+
+
+if test "$with_zstd" = yes; then
+
+pkg_failed=no
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for libzstd" >&5
+$as_echo_n "checking for libzstd... " >&6; }
+
+if test -n "$ZSTD_CFLAGS"; then
+    pkg_cv_ZSTD_CFLAGS="$ZSTD_CFLAGS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"libzstd\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "libzstd") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_ZSTD_CFLAGS=`$PKG_CONFIG --cflags "libzstd" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+if test -n "$ZSTD_LIBS"; then
+    pkg_cv_ZSTD_LIBS="$ZSTD_LIBS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"libzstd\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "libzstd") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_ZSTD_LIBS=`$PKG_CONFIG --libs "libzstd" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+
+
+
+if test $pkg_failed = yes; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+
+if $PKG_CONFIG --atleast-pkgconfig-version 0.20; then
+        _pkg_short_errors_supported=yes
+else
+        _pkg_short_errors_supported=no
+fi
+        if test $_pkg_short_errors_supported = yes; then
+	        ZSTD_PKG_ERRORS=`$PKG_CONFIG --short-errors --print-errors --cflags --libs "libzstd" 2>&1`
+        else
+	        ZSTD_PKG_ERRORS=`$PKG_CONFIG --print-errors --cflags --libs "libzstd" 2>&1`
+        fi
+	# Put the nasty error message in config.log where it belongs
+	echo "$ZSTD_PKG_ERRORS" >&5
+
+	as_fn_error $? "Package requirements (libzstd) were not met:
+
+$ZSTD_PKG_ERRORS
+
+Consider adjusting the PKG_CONFIG_PATH environment variable if you
+installed software in a non-standard prefix.
+
+Alternatively, you may set the environment variables ZSTD_CFLAGS
+and ZSTD_LIBS to avoid the need to call pkg-config.
+See the pkg-config man page for more details." "$LINENO" 5
+elif test $pkg_failed = untried; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+	{ { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error $? "The pkg-config script could not be found or is too old.  Make sure it
+is in your PATH or set the PKG_CONFIG environment variable to the full
+path to pkg-config.
+
+Alternatively, you may set the environment variables ZSTD_CFLAGS
+and ZSTD_LIBS to avoid the need to call pkg-config.
+See the pkg-config man page for more details.
+
+To get pkg-config, see <http://pkg-config.freedesktop.org/>.
+See \`config.log' for more details" "$LINENO" 5; }
+else
+	ZSTD_CFLAGS=$pkg_cv_ZSTD_CFLAGS
+	ZSTD_LIBS=$pkg_cv_ZSTD_LIBS
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+
+fi
+  # We only care about -I, -D, and -L switches;
+  # note that -lzstd will be added by AC_CHECK_LIB below.
+  for pgac_option in $ZSTD_CFLAGS; do
+    case $pgac_option in
+      -I*|-D*) CPPFLAGS="$CPPFLAGS $pgac_option";;
+    esac
+  done
+  for pgac_option in $ZSTD_LIBS; do
+    case $pgac_option in
+      -L*) LDFLAGS="$LDFLAGS $pgac_option";;
+    esac
+  done
+fi
+
 #
 # Assignments
 #
@@ -12876,6 +13026,56 @@ fi
 
 fi
 
+if test "$with_zstd" = yes ; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for ZSTD_compress in -lzstd" >&5
+$as_echo_n "checking for ZSTD_compress in -lzstd... " >&6; }
+if ${ac_cv_lib_zstd_ZSTD_compress+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ac_check_lib_save_LIBS=$LIBS
+LIBS="-lzstd  $LIBS"
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+/* Override any GCC internal prototype to avoid an error.
+   Use char because int might match the return type of a GCC
+   builtin and then its argument prototype would still apply.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+char ZSTD_compress ();
+int
+main ()
+{
+return ZSTD_compress ();
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ac_cv_lib_zstd_ZSTD_compress=yes
+else
+  ac_cv_lib_zstd_ZSTD_compress=no
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+LIBS=$ac_check_lib_save_LIBS
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_lib_zstd_ZSTD_compress" >&5
+$as_echo "$ac_cv_lib_zstd_ZSTD_compress" >&6; }
+if test "x$ac_cv_lib_zstd_ZSTD_compress" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_LIBZSTD 1
+_ACEOF
+
+  LIBS="-lzstd $LIBS"
+
+else
+  as_fn_error $? "library 'zstd' is required for ZSTD support" "$LINENO" 5
+fi
+
+fi
+
 # Note: We can test for libldap_r only after we know PTHREAD_LIBS
 if test "$with_ldap" = yes ; then
   _LIBS="$LIBS"
@@ -13598,6 +13798,23 @@ done
 
 fi
 
+if test "$with_zstd" = yes; then
+  for ac_header in zstd.h
+do :
+  ac_fn_c_check_header_mongrel "$LINENO" "zstd.h" "ac_cv_header_zstd_h" "$ac_includes_default"
+if test "x$ac_cv_header_zstd_h" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_ZSTD_H 1
+_ACEOF
+
+else
+  as_fn_error $? "zstd.h header file is required for zstd" "$LINENO" 5
+fi
+
+done
+
+fi
+
 if test "$with_gssapi" = yes ; then
   for ac_header in gssapi/gssapi.h
 do :
diff --git a/configure.ac b/configure.ac
index 3b42d8bdc9..56aa15b8e1 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1011,6 +1011,31 @@ if test "$with_lz4" = yes; then
   done
 fi
 
+#
+# ZSTD
+#
+AC_MSG_CHECKING([whether to build with zstd support])
+PGAC_ARG_BOOL(with, zstd, no, [build without Zstd compression library],
+              [AC_DEFINE([USE_ZSTD], 1, [Define to 1 to build with zstd support. (--with-zstd)])])
+AC_MSG_RESULT([$with_zstd])
+AC_SUBST(with_zstd)
+
+if test "$with_zstd" = yes; then
+  PKG_CHECK_MODULES(ZSTD, libzstd)
+  # We only care about -I, -D, and -L switches;
+  # note that -lzstd will be added by AC_CHECK_LIB below.
+  for pgac_option in $ZSTD_CFLAGS; do
+    case $pgac_option in
+      -I*|-D*) CPPFLAGS="$CPPFLAGS $pgac_option";;
+    esac
+  done
+  for pgac_option in $ZSTD_LIBS; do
+    case $pgac_option in
+      -L*) LDFLAGS="$LDFLAGS $pgac_option";;
+    esac
+  done
+fi
+
 #
 # Assignments
 #
@@ -1285,6 +1310,10 @@ if test "$with_lz4" = yes ; then
   AC_CHECK_LIB(lz4, LZ4_compress_default, [], [AC_MSG_ERROR([library 'lz4' is required for LZ4 support])])
 fi
 
+if test "$with_zstd" = yes ; then
+  AC_CHECK_LIB(zstd, ZSTD_compress, [], [AC_MSG_ERROR([library 'zstd' is required for ZSTD support])])
+fi
+
 # Note: We can test for libldap_r only after we know PTHREAD_LIBS
 if test "$with_ldap" = yes ; then
   _LIBS="$LIBS"
@@ -1443,6 +1472,10 @@ if test "$with_lz4" = yes; then
   AC_CHECK_HEADERS(lz4.h, [], [AC_MSG_ERROR([lz4.h header file is required for LZ4])])
 fi
 
+if test "$with_zstd" = yes; then
+  AC_CHECK_HEADERS(zstd.h, [], [AC_MSG_ERROR([zstd.h header file is required for zstd])])
+fi
+
 if test "$with_gssapi" = yes ; then
   AC_CHECK_HEADERS(gssapi/gssapi.h, [],
 	[AC_CHECK_HEADERS(gssapi.h, [], [AC_MSG_ERROR([gssapi.h header file is required for GSSAPI])])])
diff --git a/src/tools/msvc/Solution.pm b/src/tools/msvc/Solution.pm
index a7b8f720b5..133de6fba6 100644
--- a/src/tools/msvc/Solution.pm
+++ b/src/tools/msvc/Solution.pm
@@ -494,6 +494,8 @@ sub GenerateFiles
 		USE_LIBXML                 => undef,
 		USE_LIBXSLT                => undef,
 		USE_LZ4                    => undef,
+		# XXX; support for zstd is still required here.
+		USE_ZSTD                   => $self->{options}->{zstd} ? 1 : undef,
 		USE_LDAP                   => $self->{options}->{ldap} ? 1 : undef,
 		USE_LLVM                   => undef,
 		USE_NAMED_POSIX_SEMAPHORES => undef,
diff --git a/src/tools/msvc/config_default.pl b/src/tools/msvc/config_default.pl
index 460c0375d4..b8a1aac3c2 100644
--- a/src/tools/msvc/config_default.pl
+++ b/src/tools/msvc/config_default.pl
@@ -26,6 +26,7 @@ our $config = {
 	xslt      => undef,    # --with-libxslt=<path>
 	iconv     => undef,    # (not in configure, path to iconv)
 	zlib      => undef     # --with-zlib=<path>
+	zstd      => undef     # --with-zstd=<path>
 };
 
 1;
-- 
2.32.0

From 51a7b458db74c1c285688ab9991fe590c9c97357 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Wed, 16 Jun 2021 14:49:22 +0900
Subject: [PATCH v10 2/2] Add tweak to test CPU usage within a session, for
 wal_compression

---
 src/backend/tcop/postgres.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 8cea10c901..2d7affe115 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -178,6 +178,10 @@ static bool RecoveryConflictPending = false;
 static bool RecoveryConflictRetryable = true;
 static ProcSignalReason RecoveryConflictReason;
 
+/* Amount of user and system time used, tracked at start */
+static struct timeval user_time;
+static struct timeval system_time;
+
 /* reused buffer to pass to SendRowDescriptionMessage() */
 static MemoryContext row_description_context = NULL;
 static StringInfoData row_description_buf;
@@ -3937,6 +3941,12 @@ PostgresMain(int argc, char *argv[],
 	volatile bool send_ready_for_query = true;
 	bool		idle_in_transaction_timeout_enabled = false;
 	bool		idle_session_timeout_enabled = false;
+	struct rusage r;
+
+	/* Get start usage for reference point */
+	getrusage(RUSAGE_SELF, &r);
+	memcpy((char *) &user_time, (char *) &r.ru_utime, sizeof(user_time));
+	memcpy((char *) &system_time, (char *) &r.ru_stime, sizeof(system_time));
 
 	/* Initialize startup process environment if necessary. */
 	if (!IsUnderPostmaster)
@@ -4683,6 +4693,14 @@ PostgresMain(int argc, char *argv[],
 
 			case 'X':
 
+				/* Get stop status of process and log comparison with start */
+				getrusage(RUSAGE_SELF, &r);
+				elog(LOG,"user diff: %ld.%06ld, system diff: %ld.%06ld",
+					 (long) (r.ru_utime.tv_sec - user_time.tv_sec),
+					 (long) (r.ru_utime.tv_usec - user_time.tv_usec),
+					 (long) (r.ru_stime.tv_sec - system_time.tv_sec),
+					 (long) (r.ru_stime.tv_usec - system_time.tv_usec));
+
 				/*
 				 * Reset whereToSendOutput to prevent ereport from attempting
 				 * to send any more messages to client.
-- 
2.32.0

From db0f45172bc7d2fa7b62d83dea521fe3f90358d3 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Thu, 17 Jun 2021 15:33:56 +0900
Subject: [PATCH v11 1/2] Add wal_compression=lz4

---
 src/include/access/xlog.h                     | 10 ++-
 src/include/access/xlogrecord.h               | 16 +++--
 src/backend/access/transam/xlog.c             |  2 +-
 src/backend/access/transam/xloginsert.c       | 63 ++++++++++++++++---
 src/backend/access/transam/xlogreader.c       | 56 +++++++++++++----
 src/backend/utils/misc/guc.c                  | 36 ++++++++---
 src/backend/utils/misc/postgresql.conf.sample |  3 +-
 src/bin/pg_waldump/pg_waldump.c               | 16 +++--
 doc/src/sgml/config.sgml                      | 11 +++-
 doc/src/sgml/install-windows.sgml             |  2 +-
 doc/src/sgml/installation.sgml                |  5 +-
 doc/src/sgml/standalone-profile.xsl           |  4 ++
 12 files changed, 176 insertions(+), 48 deletions(-)

diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index 77187c12be..a41847b982 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -116,7 +116,7 @@ extern char *XLogArchiveCommand;
 extern bool EnableHotStandby;
 extern bool fullPageWrites;
 extern bool wal_log_hints;
-extern bool wal_compression;
+extern int	wal_compression;
 extern bool wal_init_zero;
 extern bool wal_recycle;
 extern bool *wal_consistency_checking;
@@ -167,6 +167,14 @@ typedef enum WalLevel
 	WAL_LEVEL_LOGICAL
 } WalLevel;
 
+/* Compression algorithms for WAL */
+typedef enum WalCompression
+{
+	WAL_COMPRESSION_NONE = 0,
+	WAL_COMPRESSION_PGLZ,
+	WAL_COMPRESSION_LZ4
+} WalCompression;
+
 /* Recovery states */
 typedef enum RecoveryState
 {
diff --git a/src/include/access/xlogrecord.h b/src/include/access/xlogrecord.h
index 80c92a2498..e06ee92a5e 100644
--- a/src/include/access/xlogrecord.h
+++ b/src/include/access/xlogrecord.h
@@ -114,8 +114,8 @@ typedef struct XLogRecordBlockHeader
  * present is (BLCKSZ - <length of "hole" bytes>).
  *
  * Additionally, when wal_compression is enabled, we will try to compress full
- * page images using the PGLZ compression algorithm, after removing the "hole".
- * This can reduce the WAL volume, but at some extra cost of CPU spent
+ * page images using one of the supported algorithms, after removing the
+ * "hole". This can reduce the WAL volume, but at some extra cost of CPU spent
  * on the compression during WAL logging. In this case, since the "hole"
  * length cannot be calculated by subtracting the number of page image bytes
  * from BLCKSZ, basically it needs to be stored as an extra information.
@@ -134,7 +134,7 @@ typedef struct XLogRecordBlockImageHeader
 	uint8		bimg_info;		/* flag bits, see below */
 
 	/*
-	 * If BKPIMAGE_HAS_HOLE and BKPIMAGE_IS_COMPRESSED, an
+	 * If BKPIMAGE_HAS_HOLE and BKPIMAGE_COMPRESSED(), an
 	 * XLogRecordBlockCompressHeader struct follows.
 	 */
 } XLogRecordBlockImageHeader;
@@ -144,9 +144,13 @@ typedef struct XLogRecordBlockImageHeader
 
 /* Information stored in bimg_info */
 #define BKPIMAGE_HAS_HOLE		0x01	/* page image has "hole" */
-#define BKPIMAGE_IS_COMPRESSED		0x02	/* page image is compressed */
-#define BKPIMAGE_APPLY		0x04	/* page image should be restored during
-									 * replay */
+#define BKPIMAGE_APPLY			0x02	/* page image should be restored
+										 * during replay */
+/* compression methods supported */
+#define BKPIMAGE_COMPRESS_PGLZ	0x04
+#define BKPIMAGE_COMPRESS_LZ4	0x08
+#define	BKPIMAGE_COMPRESSED(info) \
+	((info & (BKPIMAGE_COMPRESS_PGLZ | BKPIMAGE_COMPRESS_LZ4)) != 0)
 
 /*
  * Extra header information used when page image has "hole" and
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 1b3a3d9bea..eea0f2b179 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -98,7 +98,7 @@ char	   *XLogArchiveCommand = NULL;
 bool		EnableHotStandby = false;
 bool		fullPageWrites = true;
 bool		wal_log_hints = false;
-bool		wal_compression = false;
+int			wal_compression = WAL_COMPRESSION_NONE;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
 bool		wal_init_zero = true;
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
index 32b4cc84e7..dd49550823 100644
--- a/src/backend/access/transam/xloginsert.c
+++ b/src/backend/access/transam/xloginsert.c
@@ -33,8 +33,20 @@
 #include "storage/proc.h"
 #include "utils/memutils.h"
 
-/* Buffer size required to store a compressed version of backup block image */
-#define PGLZ_MAX_BLCKSZ PGLZ_MAX_OUTPUT(BLCKSZ)
+/*
+ * Guess the maximum buffer size required to store a compressed version of
+ * backup block image.
+ */
+#ifdef USE_LZ4
+#include <lz4.h>
+#define	LZ4_MAX_BLCKSZ		LZ4_COMPRESSBOUND(BLCKSZ)
+#else
+#define LZ4_MAX_BLCKSZ		0
+#endif
+
+#define PGLZ_MAX_BLCKSZ		PGLZ_MAX_OUTPUT(BLCKSZ)
+
+#define COMPRESS_BUFSIZE	Max(PGLZ_MAX_BLCKSZ, LZ4_MAX_BLCKSZ)
 
 /*
  * For each block reference registered with XLogRegisterBuffer, we fill in
@@ -58,7 +70,7 @@ typedef struct
 								 * backup block data in XLogRecordAssemble() */
 
 	/* buffer to store a compressed version of backup block image */
-	char		compressed_page[PGLZ_MAX_BLCKSZ];
+	char		compressed_page[COMPRESS_BUFSIZE];
 } registered_buffer;
 
 static registered_buffer *registered_buffers;
@@ -628,7 +640,7 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
 			/*
 			 * Try to compress a block image if wal_compression is enabled
 			 */
-			if (wal_compression)
+			if (wal_compression != WAL_COMPRESSION_NONE)
 			{
 				is_compressed =
 					XLogCompressBackupBlock(page, bimg.hole_offset,
@@ -665,8 +677,27 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
 
 			if (is_compressed)
 			{
+				/* The current compression is stored in the WAL record */
 				bimg.length = compressed_len;
-				bimg.bimg_info |= BKPIMAGE_IS_COMPRESSED;
+
+				/* Append the compression method used */
+				switch (wal_compression)
+				{
+					case WAL_COMPRESSION_PGLZ:
+						bimg.bimg_info |= BKPIMAGE_COMPRESS_PGLZ;
+						break;
+
+					case WAL_COMPRESSION_LZ4:
+#ifdef USE_LZ4
+						bimg.bimg_info |= BKPIMAGE_COMPRESS_LZ4;
+#else
+						elog(ERROR, "LZ4 is not supported by this build");
+#endif
+						break;
+
+					default:
+						elog(ERROR, "unsupported WAL compression method specified");
+				}
 
 				rdt_datas_last->data = regbuf->compressed_page;
 				rdt_datas_last->len = compressed_len;
@@ -853,12 +884,30 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 	else
 		source = page;
 
+	switch (wal_compression)
+	{
+		case WAL_COMPRESSION_PGLZ:
+			len = pglz_compress(source, orig_len, dest, PGLZ_strategy_default);
+			break;
+
+#ifdef USE_LZ4
+		case WAL_COMPRESSION_LZ4:
+			len = LZ4_compress_fast(source, dest, orig_len,
+									COMPRESS_BUFSIZE, 1);
+			if (len <= 0)
+				len = -1;	/* failure */
+			break;
+#endif
+
+		default:
+			elog(ERROR, "unsupported WAL compression method specified");
+	}
+
 	/*
-	 * We recheck the actual size even if pglz_compress() reports success and
+	 * We recheck the actual size even if compression reports success and
 	 * see if the number of bytes saved by compression is larger than the
 	 * length of extra data needed for the compressed version of block image.
 	 */
-	len = pglz_compress(source, orig_len, dest, PGLZ_strategy_default);
 	if (len >= 0 &&
 		len + extra_bytes < orig_len)
 	{
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index 42738eb940..a5feaa7da3 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -18,6 +18,9 @@
 #include "postgres.h"
 
 #include <unistd.h>
+#ifdef USE_LZ4
+#include <lz4.h>
+#endif
 
 #include "access/transam.h"
 #include "access/xlog_internal.h"
@@ -1290,7 +1293,7 @@ DecodeXLogRecord(XLogReaderState *state, XLogRecord *record, char **errormsg)
 
 				blk->apply_image = ((blk->bimg_info & BKPIMAGE_APPLY) != 0);
 
-				if (blk->bimg_info & BKPIMAGE_IS_COMPRESSED)
+				if (BKPIMAGE_COMPRESSED(blk->bimg_info))
 				{
 					if (blk->bimg_info & BKPIMAGE_HAS_HOLE)
 						COPY_HEADER_FIELD(&blk->hole_length, sizeof(uint16));
@@ -1335,29 +1338,28 @@ DecodeXLogRecord(XLogReaderState *state, XLogRecord *record, char **errormsg)
 				}
 
 				/*
-				 * cross-check that bimg_len < BLCKSZ if the IS_COMPRESSED
-				 * flag is set.
+				 * Cross-check that bimg_len < BLCKSZ if it is compressed.
 				 */
-				if ((blk->bimg_info & BKPIMAGE_IS_COMPRESSED) &&
+				if (BKPIMAGE_COMPRESSED(blk->bimg_info) &&
 					blk->bimg_len == BLCKSZ)
 				{
 					report_invalid_record(state,
-										  "BKPIMAGE_IS_COMPRESSED set, but block image length %u at %X/%X",
+										  "BKPIMAGE_COMPRESSED, but block image length %u at %X/%X",
 										  (unsigned int) blk->bimg_len,
 										  LSN_FORMAT_ARGS(state->ReadRecPtr));
 					goto err;
 				}
 
 				/*
-				 * cross-check that bimg_len = BLCKSZ if neither HAS_HOLE nor
-				 * IS_COMPRESSED flag is set.
+				 * cross-check that bimg_len = BLCKSZ if neither HAS_HOLE is
+				 * set nor IS_COMPRESSED().
 				 */
 				if (!(blk->bimg_info & BKPIMAGE_HAS_HOLE) &&
-					!(blk->bimg_info & BKPIMAGE_IS_COMPRESSED) &&
+					!BKPIMAGE_COMPRESSED(blk->bimg_info) &&
 					blk->bimg_len != BLCKSZ)
 				{
 					report_invalid_record(state,
-										  "neither BKPIMAGE_HAS_HOLE nor BKPIMAGE_IS_COMPRESSED set, but block image length is %u at %X/%X",
+										  "neither BKPIMAGE_HAS_HOLE nor BKPIMAGE_COMPRESSED, but block image length is %u at %X/%X",
 										  (unsigned int) blk->data_len,
 										  LSN_FORMAT_ARGS(state->ReadRecPtr));
 					goto err;
@@ -1555,17 +1557,47 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 	bkpb = &record->blocks[block_id];
 	ptr = bkpb->bkp_image;
 
-	if (bkpb->bimg_info & BKPIMAGE_IS_COMPRESSED)
+	if (BKPIMAGE_COMPRESSED(bkpb->bimg_info))
 	{
 		/* If a backup block image is compressed, decompress it */
-		if (pglz_decompress(ptr, bkpb->bimg_len, tmp.data,
-							BLCKSZ - bkpb->hole_length, true) < 0)
+		bool	decomp_success = true;
+
+		if ((bkpb->bimg_info & BKPIMAGE_COMPRESS_PGLZ) != 0)
+		{
+			if (pglz_decompress(ptr, bkpb->bimg_len, tmp.data,
+								BLCKSZ - bkpb->hole_length, true) < 0)
+				decomp_success = false;
+		}
+		else if ((bkpb->bimg_info & BKPIMAGE_COMPRESS_LZ4) != 0)
+		{
+#ifdef USE_LZ4
+			if (LZ4_decompress_safe(ptr, tmp.data,
+									bkpb->bimg_len, BLCKSZ-bkpb->hole_length) <= 0)
+				decomp_success = false;
+#else
+			report_invalid_record(record, "image at %X/%X compressed with %s not supported, block %d",
+								  (uint32) (record->ReadRecPtr >> 32),
+								  (uint32) record->ReadRecPtr,
+								  "lz4",
+								  block_id);
+#endif
+		}
+		else
+		{
+			report_invalid_record(record, "image at %X/%X is compressed with unknown method, block %d",
+								  (uint32) (record->ReadRecPtr >> 32),
+								  (uint32) record->ReadRecPtr,
+								  block_id);
+		}
+
+		if (!decomp_success)
 		{
 			report_invalid_record(record, "invalid compressed image at %X/%X, block %d",
 								  LSN_FORMAT_ARGS(record->ReadRecPtr),
 								  block_id);
 			return false;
 		}
+
 		ptr = tmp.data;
 	}
 
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 68b62d523d..748893b624 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -540,6 +540,22 @@ static struct config_enum_entry default_toast_compression_options[] = {
 	{NULL, 0, false}
 };
 
+static const struct config_enum_entry wal_compression_options[] = {
+	{"pglz", WAL_COMPRESSION_PGLZ, false},
+#ifdef USE_LZ4
+	{"lz4", WAL_COMPRESSION_LZ4, false},
+#endif
+	{"on", WAL_COMPRESSION_PGLZ, false},
+	{"off", WAL_COMPRESSION_NONE, false},
+	{"true", WAL_COMPRESSION_PGLZ, true},
+	{"false", WAL_COMPRESSION_NONE, true},
+	{"yes", WAL_COMPRESSION_PGLZ, true},
+	{"no", WAL_COMPRESSION_NONE, true},
+	{"1", WAL_COMPRESSION_PGLZ, true},
+	{"0", WAL_COMPRESSION_NONE, true},
+	{NULL, 0, false}
+};
+
 /*
  * Options for enum values stored in other modules
  */
@@ -1304,16 +1320,6 @@ static struct config_bool ConfigureNamesBool[] =
 		NULL, NULL, NULL
 	},
 
-	{
-		{"wal_compression", PGC_SUSET, WAL_SETTINGS,
-			gettext_noop("Compresses full-page writes written in WAL file."),
-			NULL
-		},
-		&wal_compression,
-		false,
-		NULL, NULL, NULL
-	},
-
 	{
 		{"wal_init_zero", PGC_SUSET, WAL_SETTINGS,
 			gettext_noop("Writes zeroes to new WAL files before first use."),
@@ -4815,6 +4821,16 @@ static struct config_enum ConfigureNamesEnum[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"wal_compression", PGC_SUSET, WAL_SETTINGS,
+			gettext_noop("Set the method used to compress full page images in WAL files."),
+			NULL
+		},
+		&wal_compression,
+		WAL_COMPRESSION_NONE, wal_compression_options,
+		NULL, NULL, NULL
+	},
+
 	{
 		{"wal_level", PGC_POSTMASTER, WAL_SETTINGS,
 			gettext_noop("Sets the level of information written to the WAL."),
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index ddbb6dc2be..e0c5766b18 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -218,7 +218,8 @@
 #full_page_writes = on			# recover from partial page writes
 #wal_log_hints = off			# also do full page writes of non-critical updates
 					# (change requires restart)
-#wal_compression = off			# enable compression of full-page writes
+#wal_compression = off			# enables compression of full-page writes;
+					# off, pglz, lz4, or on
 #wal_init_zero = on			# zero-fill new WAL files
 #wal_recycle = on			# recycle WAL files
 #wal_buffers = -1			# min 32kB, -1 sets based on shared_buffers
diff --git a/src/bin/pg_waldump/pg_waldump.c b/src/bin/pg_waldump/pg_waldump.c
index f8b8afe4a7..ceeb91b694 100644
--- a/src/bin/pg_waldump/pg_waldump.c
+++ b/src/bin/pg_waldump/pg_waldump.c
@@ -537,18 +537,26 @@ XLogDumpDisplayRecord(XLogDumpConfig *config, XLogReaderState *record)
 				   blk);
 			if (XLogRecHasBlockImage(record, block_id))
 			{
-				if (record->blocks[block_id].bimg_info &
-					BKPIMAGE_IS_COMPRESSED)
+				uint8	bimg_info = record->blocks[block_id].bimg_info;
+
+				if (BKPIMAGE_COMPRESSED(bimg_info))
 				{
+					const char *method = "???";
+					if ((bimg_info & BKPIMAGE_COMPRESS_PGLZ) != 0)
+						method = "pglz";
+					else if ((bimg_info & BKPIMAGE_COMPRESS_LZ4) != 0)
+						method = "lz4";
+
 					printf(" (FPW%s); hole: offset: %u, length: %u, "
-						   "compression saved: %u",
+						   "compression saved: %u, method: %s",
 						   XLogRecBlockImageApply(record, block_id) ?
 						   "" : " for WAL verification",
 						   record->blocks[block_id].hole_offset,
 						   record->blocks[block_id].hole_length,
 						   BLCKSZ -
 						   record->blocks[block_id].hole_length -
-						   record->blocks[block_id].bimg_len);
+						   record->blocks[block_id].bimg_len,
+						   method);
 				}
 				else
 				{
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index aa3e178240..b238f41315 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -3127,23 +3127,28 @@ include_dir 'conf.d'
      </varlistentry>
 
      <varlistentry id="guc-wal-compression" xreflabel="wal_compression">
-      <term><varname>wal_compression</varname> (<type>boolean</type>)
+      <term><varname>wal_compression</varname> (<type>enum</type>)
       <indexterm>
        <primary><varname>wal_compression</varname> configuration parameter</primary>
       </indexterm>
       </term>
       <listitem>
        <para>
-        When this parameter is <literal>on</literal>, the <productname>PostgreSQL</productname>
+        This parameter enables compression of WAL using the specified 
+        compression method.
+        When enabled, the <productname>PostgreSQL</productname>
         server compresses full page images written to WAL when
         <xref linkend="guc-full-page-writes"/> is on or during a base backup.
         A compressed page image will be decompressed during WAL replay.
+        The supported methods are pglz and <literal>lz4</literal>
+        (if <productname>PostgreSQL</productname> was compiled with
+        <option>--with-lz4</option>).
         The default value is <literal>off</literal>.
         Only superusers can change this setting.
        </para>
 
        <para>
-        Turning this parameter on can reduce the WAL volume without
+        Enabling compression can reduce the WAL volume without
         increasing the risk of unrecoverable data corruption,
         but at the cost of some extra CPU spent on the compression during
         WAL logging and on the decompression during WAL replay.
diff --git a/doc/src/sgml/install-windows.sgml b/doc/src/sgml/install-windows.sgml
index 312edc6f7a..ba794b8c93 100644
--- a/doc/src/sgml/install-windows.sgml
+++ b/doc/src/sgml/install-windows.sgml
@@ -299,7 +299,7 @@ $ENV{MSBFLAGS}="/m";
      <term><productname>LZ4</productname></term>
      <listitem><para>
       Required for supporting <productname>LZ4</productname> compression
-      method for compressing the table data. Binaries and source can be
+      method for compressing table or WAL data. Binaries and source can be
       downloaded from
       <ulink url="https://github.com/lz4/lz4/releases"></ulink>.
      </para></listitem>
diff --git a/doc/src/sgml/installation.sgml b/doc/src/sgml/installation.sgml
index 3c0aa118c7..61d0bc8c43 100644
--- a/doc/src/sgml/installation.sgml
+++ b/doc/src/sgml/installation.sgml
@@ -270,7 +270,8 @@ su - postgres
      <para>
       You need <productname>LZ4</productname>, if you want to support
       compression of data with this method; see
-      <xref linkend="guc-default-toast-compression"/>.
+      <xref linkend="guc-default-toast-compression"/> and
+      <xref linkend="guc-wal-compression"/>.
      </para>
     </listitem>
 
@@ -980,7 +981,7 @@ build-postgresql:
         <para>
          Build with <productname>LZ4</productname> compression support.
          This allows the use of <productname>LZ4</productname> for
-         compression of table data.
+         compression of table and WAL data.
         </para>
        </listitem>
       </varlistentry>
diff --git a/doc/src/sgml/standalone-profile.xsl b/doc/src/sgml/standalone-profile.xsl
index 8bdf58632c..d748076a05 100644
--- a/doc/src/sgml/standalone-profile.xsl
+++ b/doc/src/sgml/standalone-profile.xsl
@@ -52,6 +52,10 @@ variant without links and references to the main documentation.
   <xsl:text>the configuration parameter default_toast_compression</xsl:text>
 </xsl:template>
 
+<xsl:template match="xref[@linkend='guc-wal-compression']">
+  <xsl:text>the configuration parameter wal_compression</xsl:text>
+</xsl:template>
+
 <xsl:template match="xref[@linkend='install-windows']">
   <xsl:text>the documentation</xsl:text>
 </xsl:template>
-- 
2.32.0

From e242dc434d5bd83f6f6617650263473e0e61ac9c Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Thu, 17 Jun 2021 15:35:58 +0900
Subject: [PATCH v11 2/2] Add wal_compression=zstd

This is still a WIP patch, that requires checks with its APIs and
adjustments with the Windows builds.
---
 src/include/access/xlog.h                     |   3 +-
 src/include/access/xlogrecord.h               |   4 +-
 src/include/pg_config.h.in                    |   9 +
 src/backend/access/transam/xloginsert.c       |  31 ++-
 src/backend/access/transam/xlogreader.c       |  20 ++
 src/backend/utils/misc/guc.c                  |   3 +
 src/backend/utils/misc/postgresql.conf.sample |   2 +-
 src/bin/pg_waldump/pg_waldump.c               |   2 +
 doc/src/sgml/config.sgml                      |   6 +-
 doc/src/sgml/installation.sgml                |  19 ++
 configure                                     | 217 ++++++++++++++++++
 configure.ac                                  |  33 +++
 src/tools/msvc/Solution.pm                    |   2 +
 src/tools/msvc/config_default.pl              |   3 +-
 14 files changed, 343 insertions(+), 11 deletions(-)

diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index a41847b982..e4f64374ae 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -172,7 +172,8 @@ typedef enum WalCompression
 {
 	WAL_COMPRESSION_NONE = 0,
 	WAL_COMPRESSION_PGLZ,
-	WAL_COMPRESSION_LZ4
+	WAL_COMPRESSION_LZ4,
+	WAL_COMPRESSION_ZSTD,
 } WalCompression;
 
 /* Recovery states */
diff --git a/src/include/access/xlogrecord.h b/src/include/access/xlogrecord.h
index e06ee92a5e..895970cd36 100644
--- a/src/include/access/xlogrecord.h
+++ b/src/include/access/xlogrecord.h
@@ -149,8 +149,10 @@ typedef struct XLogRecordBlockImageHeader
 /* compression methods supported */
 #define BKPIMAGE_COMPRESS_PGLZ	0x04
 #define BKPIMAGE_COMPRESS_LZ4	0x08
+#define BKPIMAGE_COMPRESS_ZSTD	0x10
 #define	BKPIMAGE_COMPRESSED(info) \
-	((info & (BKPIMAGE_COMPRESS_PGLZ | BKPIMAGE_COMPRESS_LZ4)) != 0)
+	((info & (BKPIMAGE_COMPRESS_PGLZ | BKPIMAGE_COMPRESS_LZ4 | \
+			  BKPIMAGE_COMPRESS_ZSTD)) != 0)
 
 /*
  * Extra header information used when page image has "hole" and
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index 783b8fc1ba..1951d88ac9 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -355,6 +355,9 @@
 /* Define to 1 if you have the `z' library (-lz). */
 #undef HAVE_LIBZ
 
+/* Define to 1 if you have the `zstd' library (-lzstd). */
+#undef HAVE_LIBZSTD
+
 /* Define to 1 if you have the `link' function. */
 #undef HAVE_LINK
 
@@ -722,6 +725,9 @@
 /* Define to 1 if the assembler supports X86_64's POPCNTQ instruction. */
 #undef HAVE_X86_64_POPCNTQ
 
+/* Define to 1 if you have the <zstd.h> header file. */
+#undef HAVE_ZSTD_H
+
 /* Define to 1 if the system has the type `_Bool'. */
 #undef HAVE__BOOL
 
@@ -953,6 +959,9 @@
 /* Define to select Win32-style shared memory. */
 #undef USE_WIN32_SHARED_MEMORY
 
+/* Define to 1 to build with zstd support. (--with-zstd) */
+#undef USE_ZSTD
+
 /* Define to 1 if `wcstombs_l' requires <xlocale.h>. */
 #undef WCSTOMBS_L_IN_XLOCALE
 
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
index dd49550823..c78d78f6bf 100644
--- a/src/backend/access/transam/xloginsert.c
+++ b/src/backend/access/transam/xloginsert.c
@@ -33,10 +33,6 @@
 #include "storage/proc.h"
 #include "utils/memutils.h"
 
-/*
- * Guess the maximum buffer size required to store a compressed version of
- * backup block image.
- */
 #ifdef USE_LZ4
 #include <lz4.h>
 #define	LZ4_MAX_BLCKSZ		LZ4_COMPRESSBOUND(BLCKSZ)
@@ -44,9 +40,17 @@
 #define LZ4_MAX_BLCKSZ		0
 #endif
 
+#ifdef USE_ZSTD
+#include <zstd.h>
+#define ZSTD_MAX_BLCKSZ		ZSTD_COMPRESSBOUND(BLCKSZ)
+#else
+#define ZSTD_MAX_BLCKSZ		0
+#endif
+
+/* Buffer size required to store a compressed version of backup block image */
 #define PGLZ_MAX_BLCKSZ		PGLZ_MAX_OUTPUT(BLCKSZ)
 
-#define COMPRESS_BUFSIZE	Max(PGLZ_MAX_BLCKSZ, LZ4_MAX_BLCKSZ)
+#define COMPRESS_BUFSIZE	Max(Max(PGLZ_MAX_BLCKSZ, LZ4_MAX_BLCKSZ), ZSTD_MAX_BLCKSZ)
 
 /*
  * For each block reference registered with XLogRegisterBuffer, we fill in
@@ -695,6 +699,14 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
 #endif
 						break;
 
+					case WAL_COMPRESSION_ZSTD:
+#ifdef USE_ZSTD
+						bimg.bimg_info |= BKPIMAGE_COMPRESS_ZSTD;
+#else
+						elog(ERROR, "ZSTD is not supported by this build");
+#endif
+						break;
+
 					default:
 						elog(ERROR, "unsupported WAL compression method specified");
 				}
@@ -899,6 +911,15 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 			break;
 #endif
 
+#ifdef USE_ZSTD
+		case WAL_COMPRESSION_ZSTD:
+			len = ZSTD_compress(dest, COMPRESS_BUFSIZE, source, orig_len,
+								ZSTD_CLEVEL_DEFAULT);
+			if (ZSTD_isError(len))
+				len = -1;
+			break;
+#endif
+
 		default:
 			elog(ERROR, "unsupported WAL compression method specified");
 	}
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index a5feaa7da3..65921e2f56 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -21,6 +21,9 @@
 #ifdef USE_LZ4
 #include <lz4.h>
 #endif
+#ifdef USE_ZSTD
+#include <zstd.h>
+#endif
 
 #include "access/transam.h"
 #include "access/xlog_internal.h"
@@ -1580,6 +1583,23 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 								  (uint32) record->ReadRecPtr,
 								  "lz4",
 								  block_id);
+#endif
+		}
+		else if ((bkpb->bimg_info & BKPIMAGE_COMPRESS_ZSTD) != 0)
+		{
+#ifdef USE_ZSTD
+			size_t decomp_result = ZSTD_decompress(tmp.data,
+												   BLCKSZ-bkpb->hole_length,
+												   ptr, bkpb->bimg_len);
+
+			if (ZSTD_isError(decomp_result))
+				decomp_success = false;
+#else
+			report_invalid_record(record, "image at %X/%X compressed with %s not supported, block %d",
+								  (uint32) (record->ReadRecPtr >> 32),
+								  (uint32) record->ReadRecPtr,
+								  "zstd",
+								  block_id);
 #endif
 		}
 		else
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 748893b624..afe411255d 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -544,6 +544,9 @@ static const struct config_enum_entry wal_compression_options[] = {
 	{"pglz", WAL_COMPRESSION_PGLZ, false},
 #ifdef USE_LZ4
 	{"lz4", WAL_COMPRESSION_LZ4, false},
+#endif
+#ifdef USE_ZSTD
+	{"zstd", WAL_COMPRESSION_ZSTD, false},
 #endif
 	{"on", WAL_COMPRESSION_PGLZ, false},
 	{"off", WAL_COMPRESSION_NONE, false},
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index e0c5766b18..1f3086a341 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -219,7 +219,7 @@
 #wal_log_hints = off			# also do full page writes of non-critical updates
 					# (change requires restart)
 #wal_compression = off			# enables compression of full-page writes;
-					# off, pglz, lz4, or on
+					# off, pglz, lz4, zstd, or on
 #wal_init_zero = on			# zero-fill new WAL files
 #wal_recycle = on			# recycle WAL files
 #wal_buffers = -1			# min 32kB, -1 sets based on shared_buffers
diff --git a/src/bin/pg_waldump/pg_waldump.c b/src/bin/pg_waldump/pg_waldump.c
index ceeb91b694..f75df00dd1 100644
--- a/src/bin/pg_waldump/pg_waldump.c
+++ b/src/bin/pg_waldump/pg_waldump.c
@@ -546,6 +546,8 @@ XLogDumpDisplayRecord(XLogDumpConfig *config, XLogReaderState *record)
 						method = "pglz";
 					else if ((bimg_info & BKPIMAGE_COMPRESS_LZ4) != 0)
 						method = "lz4";
+					else if ((bimg_info & BKPIMAGE_COMPRESS_ZSTD) != 0)
+						method = "zstd";
 
 					printf(" (FPW%s); hole: offset: %u, length: %u, "
 						   "compression saved: %u, method: %s",
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index b238f41315..be73b11028 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -3140,9 +3140,11 @@ include_dir 'conf.d'
         server compresses full page images written to WAL when
         <xref linkend="guc-full-page-writes"/> is on or during a base backup.
         A compressed page image will be decompressed during WAL replay.
-        The supported methods are pglz and <literal>lz4</literal>
+        The supported methods are pglz, <literal>lz4</literal>
         (if <productname>PostgreSQL</productname> was compiled with
-        <option>--with-lz4</option>).
+        <option>--with-lz4</option>) and <literal>zstd</literal>
+        (if <productname>PostgreSQL</productname> was compiled with
+        <option>--with-zstd</option>).
         The default value is <literal>off</literal>.
         Only superusers can change this setting.
        </para>
diff --git a/doc/src/sgml/installation.sgml b/doc/src/sgml/installation.sgml
index 61d0bc8c43..5b024a7bb1 100644
--- a/doc/src/sgml/installation.sgml
+++ b/doc/src/sgml/installation.sgml
@@ -275,6 +275,14 @@ su - postgres
      </para>
     </listitem>
 
+    <listitem>
+     <para>
+      The <productname>ZSTD</productname> library can be used to enable
+      compression using that method; see
+      <xref linkend="guc-wal-compression"/>.
+     </para>
+    </listitem>
+
     <listitem>
      <para>
       To build the <productname>PostgreSQL</productname> documentation,
@@ -986,6 +994,17 @@ build-postgresql:
        </listitem>
       </varlistentry>
 
+      <varlistentry>
+       <term><option>--with-zstd</option></term>
+       <listitem>
+        <para>
+         Build with <productname>ZSTD</productname> compression support.
+         This enables use of <productname>ZSTD</productname> for
+         compression of WAL data.
+        </para>
+       </listitem>
+      </varlistentry>
+
       <varlistentry>
        <term><option>--with-ssl=<replaceable>LIBRARY</replaceable></option>
        <indexterm>
diff --git a/configure b/configure
index e9b98f442f..5317911100 100755
--- a/configure
+++ b/configure
@@ -699,6 +699,9 @@ with_gnu_ld
 LD
 LDFLAGS_SL
 LDFLAGS_EX
+ZSTD_LIBS
+ZSTD_CFLAGS
+with_zstd
 LZ4_LIBS
 LZ4_CFLAGS
 with_lz4
@@ -868,6 +871,7 @@ with_libxslt
 with_system_tzdata
 with_zlib
 with_lz4
+with_zstd
 with_gnu_ld
 with_ssl
 with_openssl
@@ -897,6 +901,8 @@ XML2_CFLAGS
 XML2_LIBS
 LZ4_CFLAGS
 LZ4_LIBS
+ZSTD_CFLAGS
+ZSTD_LIBS
 LDFLAGS_EX
 LDFLAGS_SL
 PERL
@@ -1576,6 +1582,7 @@ Optional Packages:
                           use system time zone data in DIR
   --without-zlib          do not use Zlib
   --with-lz4              build with LZ4 support
+  --with-zstd             build without Zstd compression library
   --with-gnu-ld           assume the C compiler uses GNU ld [default=no]
   --with-ssl=LIB          use LIB for SSL/TLS support (openssl)
   --with-openssl          obsolete spelling of --with-ssl=openssl
@@ -1605,6 +1612,8 @@ Some influential environment variables:
   XML2_LIBS   linker flags for XML2, overriding pkg-config
   LZ4_CFLAGS  C compiler flags for LZ4, overriding pkg-config
   LZ4_LIBS    linker flags for LZ4, overriding pkg-config
+  ZSTD_CFLAGS C compiler flags for ZSTD, overriding pkg-config
+  ZSTD_LIBS   linker flags for ZSTD, overriding pkg-config
   LDFLAGS_EX  extra linker flags for linking executables only
   LDFLAGS_SL  extra linker flags for linking shared libraries only
   PERL        Perl program
@@ -8713,6 +8722,147 @@ fi
   done
 fi
 
+#
+# ZSTD
+#
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether to build with zstd support" >&5
+$as_echo_n "checking whether to build with zstd support... " >&6; }
+
+
+
+# Check whether --with-zstd was given.
+if test "${with_zstd+set}" = set; then :
+  withval=$with_zstd;
+  case $withval in
+    yes)
+
+$as_echo "#define USE_ZSTD 1" >>confdefs.h
+
+      ;;
+    no)
+      :
+      ;;
+    *)
+      as_fn_error $? "no argument expected for --with-zstd option" "$LINENO" 5
+      ;;
+  esac
+
+else
+  with_zstd=no
+
+fi
+
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $with_zstd" >&5
+$as_echo "$with_zstd" >&6; }
+
+
+if test "$with_zstd" = yes; then
+
+pkg_failed=no
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for libzstd" >&5
+$as_echo_n "checking for libzstd... " >&6; }
+
+if test -n "$ZSTD_CFLAGS"; then
+    pkg_cv_ZSTD_CFLAGS="$ZSTD_CFLAGS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"libzstd\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "libzstd") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_ZSTD_CFLAGS=`$PKG_CONFIG --cflags "libzstd" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+if test -n "$ZSTD_LIBS"; then
+    pkg_cv_ZSTD_LIBS="$ZSTD_LIBS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"libzstd\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "libzstd") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_ZSTD_LIBS=`$PKG_CONFIG --libs "libzstd" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+
+
+
+if test $pkg_failed = yes; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+
+if $PKG_CONFIG --atleast-pkgconfig-version 0.20; then
+        _pkg_short_errors_supported=yes
+else
+        _pkg_short_errors_supported=no
+fi
+        if test $_pkg_short_errors_supported = yes; then
+	        ZSTD_PKG_ERRORS=`$PKG_CONFIG --short-errors --print-errors --cflags --libs "libzstd" 2>&1`
+        else
+	        ZSTD_PKG_ERRORS=`$PKG_CONFIG --print-errors --cflags --libs "libzstd" 2>&1`
+        fi
+	# Put the nasty error message in config.log where it belongs
+	echo "$ZSTD_PKG_ERRORS" >&5
+
+	as_fn_error $? "Package requirements (libzstd) were not met:
+
+$ZSTD_PKG_ERRORS
+
+Consider adjusting the PKG_CONFIG_PATH environment variable if you
+installed software in a non-standard prefix.
+
+Alternatively, you may set the environment variables ZSTD_CFLAGS
+and ZSTD_LIBS to avoid the need to call pkg-config.
+See the pkg-config man page for more details." "$LINENO" 5
+elif test $pkg_failed = untried; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+	{ { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error $? "The pkg-config script could not be found or is too old.  Make sure it
+is in your PATH or set the PKG_CONFIG environment variable to the full
+path to pkg-config.
+
+Alternatively, you may set the environment variables ZSTD_CFLAGS
+and ZSTD_LIBS to avoid the need to call pkg-config.
+See the pkg-config man page for more details.
+
+To get pkg-config, see <http://pkg-config.freedesktop.org/>.
+See \`config.log' for more details" "$LINENO" 5; }
+else
+	ZSTD_CFLAGS=$pkg_cv_ZSTD_CFLAGS
+	ZSTD_LIBS=$pkg_cv_ZSTD_LIBS
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+
+fi
+  # We only care about -I, -D, and -L switches;
+  # note that -lzstd will be added by AC_CHECK_LIB below.
+  for pgac_option in $ZSTD_CFLAGS; do
+    case $pgac_option in
+      -I*|-D*) CPPFLAGS="$CPPFLAGS $pgac_option";;
+    esac
+  done
+  for pgac_option in $ZSTD_LIBS; do
+    case $pgac_option in
+      -L*) LDFLAGS="$LDFLAGS $pgac_option";;
+    esac
+  done
+fi
+
 #
 # Assignments
 #
@@ -12876,6 +13026,56 @@ fi
 
 fi
 
+if test "$with_zstd" = yes ; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for ZSTD_compress in -lzstd" >&5
+$as_echo_n "checking for ZSTD_compress in -lzstd... " >&6; }
+if ${ac_cv_lib_zstd_ZSTD_compress+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ac_check_lib_save_LIBS=$LIBS
+LIBS="-lzstd  $LIBS"
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+/* Override any GCC internal prototype to avoid an error.
+   Use char because int might match the return type of a GCC
+   builtin and then its argument prototype would still apply.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+char ZSTD_compress ();
+int
+main ()
+{
+return ZSTD_compress ();
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ac_cv_lib_zstd_ZSTD_compress=yes
+else
+  ac_cv_lib_zstd_ZSTD_compress=no
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+LIBS=$ac_check_lib_save_LIBS
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_lib_zstd_ZSTD_compress" >&5
+$as_echo "$ac_cv_lib_zstd_ZSTD_compress" >&6; }
+if test "x$ac_cv_lib_zstd_ZSTD_compress" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_LIBZSTD 1
+_ACEOF
+
+  LIBS="-lzstd $LIBS"
+
+else
+  as_fn_error $? "library 'zstd' is required for ZSTD support" "$LINENO" 5
+fi
+
+fi
+
 # Note: We can test for libldap_r only after we know PTHREAD_LIBS
 if test "$with_ldap" = yes ; then
   _LIBS="$LIBS"
@@ -13598,6 +13798,23 @@ done
 
 fi
 
+if test "$with_zstd" = yes; then
+  for ac_header in zstd.h
+do :
+  ac_fn_c_check_header_mongrel "$LINENO" "zstd.h" "ac_cv_header_zstd_h" "$ac_includes_default"
+if test "x$ac_cv_header_zstd_h" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_ZSTD_H 1
+_ACEOF
+
+else
+  as_fn_error $? "zstd.h header file is required for zstd" "$LINENO" 5
+fi
+
+done
+
+fi
+
 if test "$with_gssapi" = yes ; then
   for ac_header in gssapi/gssapi.h
 do :
diff --git a/configure.ac b/configure.ac
index 3b42d8bdc9..56aa15b8e1 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1011,6 +1011,31 @@ if test "$with_lz4" = yes; then
   done
 fi
 
+#
+# ZSTD
+#
+AC_MSG_CHECKING([whether to build with zstd support])
+PGAC_ARG_BOOL(with, zstd, no, [build without Zstd compression library],
+              [AC_DEFINE([USE_ZSTD], 1, [Define to 1 to build with zstd support. (--with-zstd)])])
+AC_MSG_RESULT([$with_zstd])
+AC_SUBST(with_zstd)
+
+if test "$with_zstd" = yes; then
+  PKG_CHECK_MODULES(ZSTD, libzstd)
+  # We only care about -I, -D, and -L switches;
+  # note that -lzstd will be added by AC_CHECK_LIB below.
+  for pgac_option in $ZSTD_CFLAGS; do
+    case $pgac_option in
+      -I*|-D*) CPPFLAGS="$CPPFLAGS $pgac_option";;
+    esac
+  done
+  for pgac_option in $ZSTD_LIBS; do
+    case $pgac_option in
+      -L*) LDFLAGS="$LDFLAGS $pgac_option";;
+    esac
+  done
+fi
+
 #
 # Assignments
 #
@@ -1285,6 +1310,10 @@ if test "$with_lz4" = yes ; then
   AC_CHECK_LIB(lz4, LZ4_compress_default, [], [AC_MSG_ERROR([library 'lz4' is required for LZ4 support])])
 fi
 
+if test "$with_zstd" = yes ; then
+  AC_CHECK_LIB(zstd, ZSTD_compress, [], [AC_MSG_ERROR([library 'zstd' is required for ZSTD support])])
+fi
+
 # Note: We can test for libldap_r only after we know PTHREAD_LIBS
 if test "$with_ldap" = yes ; then
   _LIBS="$LIBS"
@@ -1443,6 +1472,10 @@ if test "$with_lz4" = yes; then
   AC_CHECK_HEADERS(lz4.h, [], [AC_MSG_ERROR([lz4.h header file is required for LZ4])])
 fi
 
+if test "$with_zstd" = yes; then
+  AC_CHECK_HEADERS(zstd.h, [], [AC_MSG_ERROR([zstd.h header file is required for zstd])])
+fi
+
 if test "$with_gssapi" = yes ; then
   AC_CHECK_HEADERS(gssapi/gssapi.h, [],
 	[AC_CHECK_HEADERS(gssapi.h, [], [AC_MSG_ERROR([gssapi.h header file is required for GSSAPI])])])
diff --git a/src/tools/msvc/Solution.pm b/src/tools/msvc/Solution.pm
index a7b8f720b5..133de6fba6 100644
--- a/src/tools/msvc/Solution.pm
+++ b/src/tools/msvc/Solution.pm
@@ -494,6 +494,8 @@ sub GenerateFiles
 		USE_LIBXML                 => undef,
 		USE_LIBXSLT                => undef,
 		USE_LZ4                    => undef,
+		# XXX; support for zstd is still required here.
+		USE_ZSTD                   => $self->{options}->{zstd} ? 1 : undef,
 		USE_LDAP                   => $self->{options}->{ldap} ? 1 : undef,
 		USE_LLVM                   => undef,
 		USE_NAMED_POSIX_SEMAPHORES => undef,
diff --git a/src/tools/msvc/config_default.pl b/src/tools/msvc/config_default.pl
index 460c0375d4..a7512651b3 100644
--- a/src/tools/msvc/config_default.pl
+++ b/src/tools/msvc/config_default.pl
@@ -25,7 +25,8 @@ our $config = {
 	xml       => undef,    # --with-libxml=<path>
 	xslt      => undef,    # --with-libxslt=<path>
 	iconv     => undef,    # (not in configure, path to iconv)
-	zlib      => undef     # --with-zlib=<path>
+	zlib      => undef,    # --with-zlib=<path>
+	zstd      => undef     # --with-zstd=<path>
 };
 
 1;
-- 
2.32.0

From f529a6908d4a502dc0615d149335033c5a82bc41 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Tue, 29 Jun 2021 12:37:04 +0900
Subject: [PATCH v12] Add wal_compression=zstd

This is still a WIP patch, that requires checks with its APIs and
adjustments with the Windows builds.
---
 src/include/access/xlog.h                     |   3 +-
 src/include/access/xlogrecord.h               |   4 +-
 src/include/pg_config.h.in                    |   9 +
 src/backend/access/transam/xloginsert.c       |  29 ++-
 src/backend/access/transam/xlogreader.c       |  21 ++
 src/backend/utils/misc/guc.c                  |   3 +
 src/backend/utils/misc/postgresql.conf.sample |   2 +-
 src/bin/pg_waldump/pg_waldump.c               |   2 +
 doc/src/sgml/config.sgml                      |   6 +-
 doc/src/sgml/installation.sgml                |  19 ++
 configure                                     | 217 ++++++++++++++++++
 configure.ac                                  |  33 +++
 src/tools/msvc/Solution.pm                    |   2 +
 src/tools/msvc/config_default.pl              |   3 +-
 14 files changed, 346 insertions(+), 7 deletions(-)

diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index ccfcf43d62..02126886a1 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -172,7 +172,8 @@ typedef enum WalCompression
 {
 	WAL_COMPRESSION_NONE = 0,
 	WAL_COMPRESSION_PGLZ,
-	WAL_COMPRESSION_LZ4
+	WAL_COMPRESSION_LZ4,
+	WAL_COMPRESSION_ZSTD
 } WalCompression;
 
 /* Recovery states */
diff --git a/src/include/access/xlogrecord.h b/src/include/access/xlogrecord.h
index e06ee92a5e..895970cd36 100644
--- a/src/include/access/xlogrecord.h
+++ b/src/include/access/xlogrecord.h
@@ -149,8 +149,10 @@ typedef struct XLogRecordBlockImageHeader
 /* compression methods supported */
 #define BKPIMAGE_COMPRESS_PGLZ	0x04
 #define BKPIMAGE_COMPRESS_LZ4	0x08
+#define BKPIMAGE_COMPRESS_ZSTD	0x10
 #define	BKPIMAGE_COMPRESSED(info) \
-	((info & (BKPIMAGE_COMPRESS_PGLZ | BKPIMAGE_COMPRESS_LZ4)) != 0)
+	((info & (BKPIMAGE_COMPRESS_PGLZ | BKPIMAGE_COMPRESS_LZ4 | \
+			  BKPIMAGE_COMPRESS_ZSTD)) != 0)
 
 /*
  * Extra header information used when page image has "hole" and
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index 783b8fc1ba..1951d88ac9 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -355,6 +355,9 @@
 /* Define to 1 if you have the `z' library (-lz). */
 #undef HAVE_LIBZ
 
+/* Define to 1 if you have the `zstd' library (-lzstd). */
+#undef HAVE_LIBZSTD
+
 /* Define to 1 if you have the `link' function. */
 #undef HAVE_LINK
 
@@ -722,6 +725,9 @@
 /* Define to 1 if the assembler supports X86_64's POPCNTQ instruction. */
 #undef HAVE_X86_64_POPCNTQ
 
+/* Define to 1 if you have the <zstd.h> header file. */
+#undef HAVE_ZSTD_H
+
 /* Define to 1 if the system has the type `_Bool'. */
 #undef HAVE__BOOL
 
@@ -953,6 +959,9 @@
 /* Define to select Win32-style shared memory. */
 #undef USE_WIN32_SHARED_MEMORY
 
+/* Define to 1 to build with zstd support. (--with-zstd) */
+#undef USE_ZSTD
+
 /* Define to 1 if `wcstombs_l' requires <xlocale.h>. */
 #undef WCSTOMBS_L_IN_XLOCALE
 
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
index 3d2c9c3e8c..525b73fbb0 100644
--- a/src/backend/access/transam/xloginsert.c
+++ b/src/backend/access/transam/xloginsert.c
@@ -44,9 +44,17 @@
 #define LZ4_MAX_BLCKSZ		0
 #endif
 
+#ifdef USE_ZSTD
+#include <zstd.h>
+#define ZSTD_MAX_BLCKSZ		ZSTD_COMPRESSBOUND(BLCKSZ)
+#else
+#define ZSTD_MAX_BLCKSZ		0
+#endif
+
+/* Buffer size required to store a compressed version of backup block image */
 #define PGLZ_MAX_BLCKSZ		PGLZ_MAX_OUTPUT(BLCKSZ)
 
-#define COMPRESS_BUFSIZE	Max(PGLZ_MAX_BLCKSZ, LZ4_MAX_BLCKSZ)
+#define COMPRESS_BUFSIZE	Max(Max(PGLZ_MAX_BLCKSZ, LZ4_MAX_BLCKSZ), ZSTD_MAX_BLCKSZ)
 
 /*
  * For each block reference registered with XLogRegisterBuffer, we fill in
@@ -695,6 +703,14 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
 #endif
 						break;
 
+					case WAL_COMPRESSION_ZSTD:
+#ifdef USE_ZSTD
+						bimg.bimg_info |= BKPIMAGE_COMPRESS_ZSTD;
+#else
+						elog(ERROR, "ZSTD is not supported by this build");
+#endif
+						break;
+
 					case WAL_COMPRESSION_NONE:
 						Assert(false);	/* cannot happen */
 						break;
@@ -903,6 +919,17 @@ XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
 #endif
 			break;
 
+		case WAL_COMPRESSION_ZSTD:
+#ifdef USE_ZSTD
+			len = ZSTD_compress(dest, COMPRESS_BUFSIZE, source, orig_len,
+								ZSTD_CLEVEL_DEFAULT);
+			if (ZSTD_isError(len))
+				len = -1;
+#else
+			elog(ERROR, "ZSTD is not supported by this build");
+#endif
+			break;
+
 		case WAL_COMPRESSION_NONE:
 			Assert(false);		/* cannot happen */
 			break;
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index 9a2cdf888e..ca1df891c6 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -21,6 +21,9 @@
 #ifdef USE_LZ4
 #include <lz4.h>
 #endif
+#ifdef USE_ZSTD
+#include <zstd.h>
+#endif
 
 #include "access/transam.h"
 #include "access/xlog_internal.h"
@@ -1581,6 +1584,24 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 								  "LZ4",
 								  block_id);
 			return false;
+#endif
+		}
+		else if ((bkpb->bimg_info & BKPIMAGE_COMPRESS_ZSTD) != 0)
+		{
+#ifdef USE_ZSTD
+			size_t decomp_result = ZSTD_decompress(tmp.data,
+												   BLCKSZ-bkpb->hole_length,
+												   ptr, bkpb->bimg_len);
+
+			if (ZSTD_isError(decomp_result))
+				decomp_success = false;
+#else
+			report_invalid_record(record, "image at %X/%X compressed with %s not supported by build, block %d",
+								  (uint32) (record->ReadRecPtr >> 32),
+								  (uint32) record->ReadRecPtr,
+								  "zstd",
+								  block_id);
+			return false;
 #endif
 		}
 		else
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 480e8cd199..807f84abc4 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -544,6 +544,9 @@ static const struct config_enum_entry wal_compression_options[] = {
 	{"pglz", WAL_COMPRESSION_PGLZ, false},
 #ifdef USE_LZ4
 	{"lz4", WAL_COMPRESSION_LZ4, false},
+#endif
+#ifdef USE_ZSTD
+	{"zstd", WAL_COMPRESSION_ZSTD, false},
 #endif
 	{"on", WAL_COMPRESSION_PGLZ, false},
 	{"off", WAL_COMPRESSION_NONE, false},
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index b696abfe54..1401e40ffd 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -219,7 +219,7 @@
 #wal_log_hints = off			# also do full page writes of non-critical updates
 					# (change requires restart)
 #wal_compression = off			# enables compression of full-page writes;
-					# off, pglz, lz4, or on
+					# off, pglz, lz4, zstd, or on
 #wal_init_zero = on			# zero-fill new WAL files
 #wal_recycle = on			# recycle WAL files
 #wal_buffers = -1			# min 32kB, -1 sets based on shared_buffers
diff --git a/src/bin/pg_waldump/pg_waldump.c b/src/bin/pg_waldump/pg_waldump.c
index d83847b276..c9f85a6a91 100644
--- a/src/bin/pg_waldump/pg_waldump.c
+++ b/src/bin/pg_waldump/pg_waldump.c
@@ -547,6 +547,8 @@ XLogDumpDisplayRecord(XLogDumpConfig *config, XLogReaderState *record)
 						method = "pglz";
 					else if ((bimg_info & BKPIMAGE_COMPRESS_LZ4) != 0)
 						method = "lz4";
+					else if ((bimg_info & BKPIMAGE_COMPRESS_ZSTD) != 0)
+						method = "zstd";
 					else
 						method = "unknown";
 
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 6098f6b020..7a69ae7470 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -3141,9 +3141,11 @@ include_dir 'conf.d'
         server compresses full page images written to WAL when
         <xref linkend="guc-full-page-writes"/> is on or during a base backup.
         A compressed page image will be decompressed during WAL replay.
-        The supported methods are <literal>pglz</literal> and
+        The supported methods are <literal>pglz</literal>,
         <literal>lz4</literal> (if <productname>PostgreSQL</productname> was
-        compiled with <option>--with-lz4</option>). The default value is
+        compiled with <option>--with-lz4</option>) and
+        <literal>zstd</literal> (if <productname>PostgreSQL</productname> was
+        compiled with <option>--with-zstd</option>. The default value is
         <literal>off</literal>. Only superusers can change this setting.
        </para>
 
diff --git a/doc/src/sgml/installation.sgml b/doc/src/sgml/installation.sgml
index 61d0bc8c43..5b024a7bb1 100644
--- a/doc/src/sgml/installation.sgml
+++ b/doc/src/sgml/installation.sgml
@@ -275,6 +275,14 @@ su - postgres
      </para>
     </listitem>
 
+    <listitem>
+     <para>
+      The <productname>ZSTD</productname> library can be used to enable
+      compression using that method; see
+      <xref linkend="guc-wal-compression"/>.
+     </para>
+    </listitem>
+
     <listitem>
      <para>
       To build the <productname>PostgreSQL</productname> documentation,
@@ -986,6 +994,17 @@ build-postgresql:
        </listitem>
       </varlistentry>
 
+      <varlistentry>
+       <term><option>--with-zstd</option></term>
+       <listitem>
+        <para>
+         Build with <productname>ZSTD</productname> compression support.
+         This enables use of <productname>ZSTD</productname> for
+         compression of WAL data.
+        </para>
+       </listitem>
+      </varlistentry>
+
       <varlistentry>
        <term><option>--with-ssl=<replaceable>LIBRARY</replaceable></option>
        <indexterm>
diff --git a/configure b/configure
index e468def49e..66d8095811 100755
--- a/configure
+++ b/configure
@@ -699,6 +699,9 @@ with_gnu_ld
 LD
 LDFLAGS_SL
 LDFLAGS_EX
+ZSTD_LIBS
+ZSTD_CFLAGS
+with_zstd
 LZ4_LIBS
 LZ4_CFLAGS
 with_lz4
@@ -868,6 +871,7 @@ with_libxslt
 with_system_tzdata
 with_zlib
 with_lz4
+with_zstd
 with_gnu_ld
 with_ssl
 with_openssl
@@ -897,6 +901,8 @@ XML2_CFLAGS
 XML2_LIBS
 LZ4_CFLAGS
 LZ4_LIBS
+ZSTD_CFLAGS
+ZSTD_LIBS
 LDFLAGS_EX
 LDFLAGS_SL
 PERL
@@ -1576,6 +1582,7 @@ Optional Packages:
                           use system time zone data in DIR
   --without-zlib          do not use Zlib
   --with-lz4              build with LZ4 support
+  --with-zstd             build without Zstd compression library
   --with-gnu-ld           assume the C compiler uses GNU ld [default=no]
   --with-ssl=LIB          use LIB for SSL/TLS support (openssl)
   --with-openssl          obsolete spelling of --with-ssl=openssl
@@ -1605,6 +1612,8 @@ Some influential environment variables:
   XML2_LIBS   linker flags for XML2, overriding pkg-config
   LZ4_CFLAGS  C compiler flags for LZ4, overriding pkg-config
   LZ4_LIBS    linker flags for LZ4, overriding pkg-config
+  ZSTD_CFLAGS C compiler flags for ZSTD, overriding pkg-config
+  ZSTD_LIBS   linker flags for ZSTD, overriding pkg-config
   LDFLAGS_EX  extra linker flags for linking executables only
   LDFLAGS_SL  extra linker flags for linking shared libraries only
   PERL        Perl program
@@ -8713,6 +8722,147 @@ fi
   done
 fi
 
+#
+# ZSTD
+#
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether to build with zstd support" >&5
+$as_echo_n "checking whether to build with zstd support... " >&6; }
+
+
+
+# Check whether --with-zstd was given.
+if test "${with_zstd+set}" = set; then :
+  withval=$with_zstd;
+  case $withval in
+    yes)
+
+$as_echo "#define USE_ZSTD 1" >>confdefs.h
+
+      ;;
+    no)
+      :
+      ;;
+    *)
+      as_fn_error $? "no argument expected for --with-zstd option" "$LINENO" 5
+      ;;
+  esac
+
+else
+  with_zstd=no
+
+fi
+
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $with_zstd" >&5
+$as_echo "$with_zstd" >&6; }
+
+
+if test "$with_zstd" = yes; then
+
+pkg_failed=no
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for libzstd" >&5
+$as_echo_n "checking for libzstd... " >&6; }
+
+if test -n "$ZSTD_CFLAGS"; then
+    pkg_cv_ZSTD_CFLAGS="$ZSTD_CFLAGS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"libzstd\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "libzstd") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_ZSTD_CFLAGS=`$PKG_CONFIG --cflags "libzstd" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+if test -n "$ZSTD_LIBS"; then
+    pkg_cv_ZSTD_LIBS="$ZSTD_LIBS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"libzstd\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "libzstd") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_ZSTD_LIBS=`$PKG_CONFIG --libs "libzstd" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+
+
+
+if test $pkg_failed = yes; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+
+if $PKG_CONFIG --atleast-pkgconfig-version 0.20; then
+        _pkg_short_errors_supported=yes
+else
+        _pkg_short_errors_supported=no
+fi
+        if test $_pkg_short_errors_supported = yes; then
+	        ZSTD_PKG_ERRORS=`$PKG_CONFIG --short-errors --print-errors --cflags --libs "libzstd" 2>&1`
+        else
+	        ZSTD_PKG_ERRORS=`$PKG_CONFIG --print-errors --cflags --libs "libzstd" 2>&1`
+        fi
+	# Put the nasty error message in config.log where it belongs
+	echo "$ZSTD_PKG_ERRORS" >&5
+
+	as_fn_error $? "Package requirements (libzstd) were not met:
+
+$ZSTD_PKG_ERRORS
+
+Consider adjusting the PKG_CONFIG_PATH environment variable if you
+installed software in a non-standard prefix.
+
+Alternatively, you may set the environment variables ZSTD_CFLAGS
+and ZSTD_LIBS to avoid the need to call pkg-config.
+See the pkg-config man page for more details." "$LINENO" 5
+elif test $pkg_failed = untried; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+	{ { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error $? "The pkg-config script could not be found or is too old.  Make sure it
+is in your PATH or set the PKG_CONFIG environment variable to the full
+path to pkg-config.
+
+Alternatively, you may set the environment variables ZSTD_CFLAGS
+and ZSTD_LIBS to avoid the need to call pkg-config.
+See the pkg-config man page for more details.
+
+To get pkg-config, see <http://pkg-config.freedesktop.org/>.
+See \`config.log' for more details" "$LINENO" 5; }
+else
+	ZSTD_CFLAGS=$pkg_cv_ZSTD_CFLAGS
+	ZSTD_LIBS=$pkg_cv_ZSTD_LIBS
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+
+fi
+  # We only care about -I, -D, and -L switches;
+  # note that -lzstd will be added by AC_CHECK_LIB below.
+  for pgac_option in $ZSTD_CFLAGS; do
+    case $pgac_option in
+      -I*|-D*) CPPFLAGS="$CPPFLAGS $pgac_option";;
+    esac
+  done
+  for pgac_option in $ZSTD_LIBS; do
+    case $pgac_option in
+      -L*) LDFLAGS="$LDFLAGS $pgac_option";;
+    esac
+  done
+fi
+
 #
 # Assignments
 #
@@ -12876,6 +13026,56 @@ fi
 
 fi
 
+if test "$with_zstd" = yes ; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for ZSTD_compress in -lzstd" >&5
+$as_echo_n "checking for ZSTD_compress in -lzstd... " >&6; }
+if ${ac_cv_lib_zstd_ZSTD_compress+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ac_check_lib_save_LIBS=$LIBS
+LIBS="-lzstd  $LIBS"
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+/* Override any GCC internal prototype to avoid an error.
+   Use char because int might match the return type of a GCC
+   builtin and then its argument prototype would still apply.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+char ZSTD_compress ();
+int
+main ()
+{
+return ZSTD_compress ();
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ac_cv_lib_zstd_ZSTD_compress=yes
+else
+  ac_cv_lib_zstd_ZSTD_compress=no
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+LIBS=$ac_check_lib_save_LIBS
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_lib_zstd_ZSTD_compress" >&5
+$as_echo "$ac_cv_lib_zstd_ZSTD_compress" >&6; }
+if test "x$ac_cv_lib_zstd_ZSTD_compress" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_LIBZSTD 1
+_ACEOF
+
+  LIBS="-lzstd $LIBS"
+
+else
+  as_fn_error $? "library 'zstd' is required for ZSTD support" "$LINENO" 5
+fi
+
+fi
+
 # Note: We can test for libldap_r only after we know PTHREAD_LIBS
 if test "$with_ldap" = yes ; then
   _LIBS="$LIBS"
@@ -13598,6 +13798,23 @@ done
 
 fi
 
+if test "$with_zstd" = yes; then
+  for ac_header in zstd.h
+do :
+  ac_fn_c_check_header_mongrel "$LINENO" "zstd.h" "ac_cv_header_zstd_h" "$ac_includes_default"
+if test "x$ac_cv_header_zstd_h" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_ZSTD_H 1
+_ACEOF
+
+else
+  as_fn_error $? "zstd.h header file is required for zstd" "$LINENO" 5
+fi
+
+done
+
+fi
+
 if test "$with_gssapi" = yes ; then
   for ac_header in gssapi/gssapi.h
 do :
diff --git a/configure.ac b/configure.ac
index 39666f9727..c29200b1e4 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1011,6 +1011,31 @@ if test "$with_lz4" = yes; then
   done
 fi
 
+#
+# ZSTD
+#
+AC_MSG_CHECKING([whether to build with zstd support])
+PGAC_ARG_BOOL(with, zstd, no, [build without Zstd compression library],
+              [AC_DEFINE([USE_ZSTD], 1, [Define to 1 to build with zstd support. (--with-zstd)])])
+AC_MSG_RESULT([$with_zstd])
+AC_SUBST(with_zstd)
+
+if test "$with_zstd" = yes; then
+  PKG_CHECK_MODULES(ZSTD, libzstd)
+  # We only care about -I, -D, and -L switches;
+  # note that -lzstd will be added by AC_CHECK_LIB below.
+  for pgac_option in $ZSTD_CFLAGS; do
+    case $pgac_option in
+      -I*|-D*) CPPFLAGS="$CPPFLAGS $pgac_option";;
+    esac
+  done
+  for pgac_option in $ZSTD_LIBS; do
+    case $pgac_option in
+      -L*) LDFLAGS="$LDFLAGS $pgac_option";;
+    esac
+  done
+fi
+
 #
 # Assignments
 #
@@ -1285,6 +1310,10 @@ if test "$with_lz4" = yes ; then
   AC_CHECK_LIB(lz4, LZ4_compress_default, [], [AC_MSG_ERROR([library 'lz4' is required for LZ4 support])])
 fi
 
+if test "$with_zstd" = yes ; then
+  AC_CHECK_LIB(zstd, ZSTD_compress, [], [AC_MSG_ERROR([library 'zstd' is required for ZSTD support])])
+fi
+
 # Note: We can test for libldap_r only after we know PTHREAD_LIBS
 if test "$with_ldap" = yes ; then
   _LIBS="$LIBS"
@@ -1443,6 +1472,10 @@ if test "$with_lz4" = yes; then
   AC_CHECK_HEADERS(lz4.h, [], [AC_MSG_ERROR([lz4.h header file is required for LZ4])])
 fi
 
+if test "$with_zstd" = yes; then
+  AC_CHECK_HEADERS(zstd.h, [], [AC_MSG_ERROR([zstd.h header file is required for zstd])])
+fi
+
 if test "$with_gssapi" = yes ; then
   AC_CHECK_HEADERS(gssapi/gssapi.h, [],
 	[AC_CHECK_HEADERS(gssapi.h, [], [AC_MSG_ERROR([gssapi.h header file is required for GSSAPI])])])
diff --git a/src/tools/msvc/Solution.pm b/src/tools/msvc/Solution.pm
index fcb43b0ca0..0a9ce1e0d4 100644
--- a/src/tools/msvc/Solution.pm
+++ b/src/tools/msvc/Solution.pm
@@ -494,6 +494,8 @@ sub GenerateFiles
 		USE_LIBXML                 => undef,
 		USE_LIBXSLT                => undef,
 		USE_LZ4                    => undef,
+		# XXX; support for zstd is still required here.
+		USE_ZSTD                   => $self->{options}->{zstd} ? 1 : undef,
 		USE_LDAP                   => $self->{options}->{ldap} ? 1 : undef,
 		USE_LLVM                   => undef,
 		USE_NAMED_POSIX_SEMAPHORES => undef,
diff --git a/src/tools/msvc/config_default.pl b/src/tools/msvc/config_default.pl
index 460c0375d4..a7512651b3 100644
--- a/src/tools/msvc/config_default.pl
+++ b/src/tools/msvc/config_default.pl
@@ -25,7 +25,8 @@ our $config = {
 	xml       => undef,    # --with-libxml=<path>
 	xslt      => undef,    # --with-libxslt=<path>
 	iconv     => undef,    # (not in configure, path to iconv)
-	zlib      => undef     # --with-zlib=<path>
+	zlib      => undef,    # --with-zlib=<path>
+	zstd      => undef     # --with-zstd=<path>
 };
 
 1;
-- 
2.32.0

From ce76fbaa0c0c9126a8b233891b9b32001b07129b Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Sat, 19 Feb 2022 11:35:53 -0600
Subject: [PATCH] xlog_block_info: show compression method

---
 src/backend/access/transam/xlogrecovery.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/src/backend/access/transam/xlogrecovery.c b/src/backend/access/transam/xlogrecovery.c
index 4ad145dd167..75a72b47f78 100644
--- a/src/backend/access/transam/xlogrecovery.c
+++ b/src/backend/access/transam/xlogrecovery.c
@@ -2238,7 +2238,20 @@ xlog_block_info(StringInfo buf, XLogReaderState *record)
 							 rlocator.relNumber,
 							 blk);
 		if (XLogRecHasBlockImage(record, block_id))
-			appendStringInfoString(buf, " FPW");
+		{
+			if (!BKPIMAGE_COMPRESSED(record->blocks[block_id].bimg_info))
+				appendStringInfoString(buf, " FPW");
+			else
+			{
+				uint8 info = record->blocks[block_id].bimg_info;
+				char *compression =
+					(BKPIMAGE_COMPRESS_PGLZ & info) ? "pglz" :
+					(BKPIMAGE_COMPRESS_LZ4 & info) ? "lz4" :
+					(BKPIMAGE_COMPRESS_ZSTD & info) ? "zstd" : "unknown";
+
+				appendStringInfo(buf, " FPW, compression method: %s", compression);
+			}
+		}
 	}
 }
 
-- 
2.17.1

From d413109bcb6c239023effc64ead945ad594008a6 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Wed, 7 Sep 2022 15:25:50 +0900
Subject: [PATCH] Provide more context for errors of RestoreBlockImage()

---
 src/backend/access/transam/xlogreader.c   | 22 +++++++++++++++++-----
 src/backend/access/transam/xlogrecovery.c |  4 +++-
 src/backend/access/transam/xlogutils.c    |  4 +++-
 3 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index cdcacc7803..94cbeba459 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -2021,7 +2021,8 @@ XLogRecGetBlockData(XLogReaderState *record, uint8 block_id, Size *len)
 /*
  * Restore a full-page image from a backup block attached to an XLOG record.
  *
- * Returns true if a full-page image is restored.
+ * Returns true if a full-page image is restored, and false on failure with
+ * an error to be consumed by the caller.
  */
 bool
 RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
@@ -2032,9 +2033,20 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 
 	if (block_id > record->record->max_block_id ||
 		!record->record->blocks[block_id].in_use)
+	{
+		report_invalid_record(record,
+							  "could not restore image at %X/%X with invalid block %d specified",
+							  LSN_FORMAT_ARGS(record->ReadRecPtr),
+							  block_id);
 		return false;
+	}
 	if (!record->record->blocks[block_id].has_image)
+	{
+		report_invalid_record(record, "could not restore image at %X/%X with invalid state, block %d",
+							  LSN_FORMAT_ARGS(record->ReadRecPtr),
+							  block_id);
 		return false;
+	}
 
 	bkpb = &record->record->blocks[block_id];
 	ptr = bkpb->bkp_image;
@@ -2057,7 +2069,7 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 									bkpb->bimg_len, BLCKSZ - bkpb->hole_length) <= 0)
 				decomp_success = false;
 #else
-			report_invalid_record(record, "image at %X/%X compressed with %s not supported by build, block %d",
+			report_invalid_record(record, "could not restore image at %X/%X compressed with %s not supported by build, block %d",
 								  LSN_FORMAT_ARGS(record->ReadRecPtr),
 								  "LZ4",
 								  block_id);
@@ -2074,7 +2086,7 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 			if (ZSTD_isError(decomp_result))
 				decomp_success = false;
 #else
-			report_invalid_record(record, "image at %X/%X compressed with %s not supported by build, block %d",
+			report_invalid_record(record, "could not restore image at %X/%X compressed with %s not supported by build, block %d",
 								  LSN_FORMAT_ARGS(record->ReadRecPtr),
 								  "zstd",
 								  block_id);
@@ -2083,7 +2095,7 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 		}
 		else
 		{
-			report_invalid_record(record, "image at %X/%X compressed with unknown method, block %d",
+			report_invalid_record(record, "could not restore image at %X/%X compressed with unknown method, block %d",
 								  LSN_FORMAT_ARGS(record->ReadRecPtr),
 								  block_id);
 			return false;
@@ -2091,7 +2103,7 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 
 		if (!decomp_success)
 		{
-			report_invalid_record(record, "invalid compressed image at %X/%X, block %d",
+			report_invalid_record(record, "could not decompress image at %X/%X, block %d",
 								  LSN_FORMAT_ARGS(record->ReadRecPtr),
 								  block_id);
 			return false;
diff --git a/src/backend/access/transam/xlogrecovery.c b/src/backend/access/transam/xlogrecovery.c
index ae2af5ae3d..9a80084a68 100644
--- a/src/backend/access/transam/xlogrecovery.c
+++ b/src/backend/access/transam/xlogrecovery.c
@@ -2412,7 +2412,9 @@ verifyBackupPageConsistency(XLogReaderState *record)
 		 * can be directly applied on it.
 		 */
 		if (!RestoreBlockImage(record, block_id, primary_image_masked))
-			elog(ERROR, "failed to restore block image");
+			ereport(ERROR,
+					(errcode(ERRCODE_INTERNAL_ERROR),
+					 errmsg_internal("%s", record->errormsg_buf)));
 
 		/*
 		 * If masking function is defined, mask both the primary and replay
diff --git a/src/backend/access/transam/xlogutils.c b/src/backend/access/transam/xlogutils.c
index 0cda22597f..e60951a5fc 100644
--- a/src/backend/access/transam/xlogutils.c
+++ b/src/backend/access/transam/xlogutils.c
@@ -393,7 +393,9 @@ XLogReadBufferForRedoExtended(XLogReaderState *record,
 									  prefetch_buffer);
 		page = BufferGetPage(*buf);
 		if (!RestoreBlockImage(record, block_id, page))
-			elog(ERROR, "failed to restore block image");
+			ereport(ERROR,
+					(errcode(ERRCODE_INTERNAL_ERROR),
+					 errmsg_internal("%s", record->errormsg_buf)));
 
 		/*
 		 * The page may be uninitialized. If so, we can't set the LSN because
-- 
2.37.2