From a16a51838371b8c3d2c4b444212588927b48e87d Mon Sep 17 00:00:00 2001
From: Kyotaro Horiguchi <horiguchi.kyotaro@lab.ntt.co.jp>
Date: Thu, 5 Sep 2019 21:29:32 +0900
Subject: [PATCH v8 4/4] Change policy of XLog read-buffer allocation

Page buffer in XLogReaderState was allocated by XLogReaderAllcoate but
actually it'd be the responsibility to the callers of XLogReadRecord,
which now actually reads in pages. This patch does that.
---
 src/backend/access/transam/twophase.c     | 2 ++
 src/backend/access/transam/xlog.c         | 2 ++
 src/backend/access/transam/xlogreader.c   | 3 ---
 src/backend/replication/logical/logical.c | 2 ++
 src/bin/pg_rewind/parsexlog.c             | 6 ++++++
 src/bin/pg_waldump/pg_waldump.c           | 2 ++
 6 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c
index ced11bbdae..9e80a2cdb1 100644
--- a/src/backend/access/transam/twophase.c
+++ b/src/backend/access/transam/twophase.c
@@ -1391,6 +1391,7 @@ XlogReadTwoPhaseData(XLogRecPtr lsn, char **buf, int *len)
 				(errcode(ERRCODE_OUT_OF_MEMORY),
 				 errmsg("out of memory"),
 				 errdetail("Failed while allocating a WAL reading processor.")));
+	xlogreader->readBuf = palloc(XLOG_BLCKSZ);
 
 	while (XLogReadRecord(xlogreader, lsn, &record, &errormsg) ==
 		   XLREAD_NEED_DATA)
@@ -1420,6 +1421,7 @@ XlogReadTwoPhaseData(XLogRecPtr lsn, char **buf, int *len)
 	*buf = palloc(sizeof(char) * XLogRecGetDataLen(xlogreader));
 	memcpy(*buf, XLogRecGetData(xlogreader), sizeof(char) * XLogRecGetDataLen(xlogreader));
 
+	pfree(xlogreader->readBuf);
 	XLogReaderFree(xlogreader);
 }
 
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 49e8ca486e..4cbb6de1bb 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -6349,6 +6349,7 @@ StartupXLOG(void)
 				(errcode(ERRCODE_OUT_OF_MEMORY),
 				 errmsg("out of memory"),
 				 errdetail("Failed while allocating a WAL reading processor.")));
+	xlogreader->readBuf = palloc(XLOG_BLCKSZ);
 	xlogreader->system_identifier = ControlFile->system_identifier;
 
 	/*
@@ -7721,6 +7722,7 @@ StartupXLOG(void)
 		close(readFile);
 		readFile = -1;
 	}
+	pfree(xlogreader->readBuf);
 	XLogReaderFree(xlogreader);
 
 	/*
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index 9cab82e76d..80434aed2e 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -105,7 +105,6 @@ XLogReaderAllocate(int wal_segment_size, const char *waldir)
 										  MCXT_ALLOC_NO_OOM);
 	if (!state->errormsg_buf)
 	{
-		pfree(state->readBuf);
 		pfree(state);
 		return NULL;
 	}
@@ -118,7 +117,6 @@ XLogReaderAllocate(int wal_segment_size, const char *waldir)
 	if (!allocate_recordbuf(state, 0))
 	{
 		pfree(state->errormsg_buf);
-		pfree(state->readBuf);
 		pfree(state);
 		return NULL;
 	}
@@ -142,7 +140,6 @@ XLogReaderFree(XLogReaderState *state)
 	pfree(state->errormsg_buf);
 	if (state->readRecordBuf)
 		pfree(state->readRecordBuf);
-	pfree(state->readBuf);
 	pfree(state);
 }
 
diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c
index db3e8f9dc0..99cb9bcc54 100644
--- a/src/backend/replication/logical/logical.c
+++ b/src/backend/replication/logical/logical.c
@@ -178,6 +178,7 @@ StartupDecodingContext(List *output_plugin_options,
 		ereport(ERROR,
 				(errcode(ERRCODE_OUT_OF_MEMORY),
 				 errmsg("out of memory")));
+	ctx->reader->readBuf = palloc(XLOG_BLCKSZ);
 	ctx->read_page = read_page;
 
 	ctx->reorder = ReorderBufferAllocate();
@@ -523,6 +524,7 @@ FreeDecodingContext(LogicalDecodingContext *ctx)
 
 	ReorderBufferFree(ctx->reorder);
 	FreeSnapshotBuilder(ctx->snapshot_builder);
+	pfree(ctx->reader->readBuf);
 	XLogReaderFree(ctx->reader);
 	MemoryContextDelete(ctx->context);
 }
diff --git a/src/bin/pg_rewind/parsexlog.c b/src/bin/pg_rewind/parsexlog.c
index c5e5d75a87..d0e408c0a8 100644
--- a/src/bin/pg_rewind/parsexlog.c
+++ b/src/bin/pg_rewind/parsexlog.c
@@ -60,6 +60,7 @@ extractPageMap(const char *datadir, XLogRecPtr startpoint, int tliIndex,
 	xlogreader = XLogReaderAllocate(WalSegSz, datadir);
 	if (xlogreader == NULL)
 		pg_fatal("out of memory");
+	xlogreader->readBuf = pg_malloc(XLOG_BLCKSZ);
 
 	do
 	{
@@ -92,6 +93,7 @@ extractPageMap(const char *datadir, XLogRecPtr startpoint, int tliIndex,
 
 	} while (xlogreader->ReadRecPtr != endpoint);
 
+	pg_free(xlogreader->readBuf);
 	XLogReaderFree(xlogreader);
 	if (xlogreadfd != -1)
 	{
@@ -115,6 +117,7 @@ readOneRecord(const char *datadir, XLogRecPtr ptr, int tliIndex)
 	xlogreader = XLogReaderAllocate(WalSegSz, datadir);
 	if (xlogreader == NULL)
 		pg_fatal("out of memory");
+	xlogreader->readBuf = pg_malloc(XLOG_BLCKSZ);
 
 	while (XLogReadRecord(xlogreader, ptr, &record, &errormsg) ==
 		   XLREAD_NEED_DATA)
@@ -133,6 +136,7 @@ readOneRecord(const char *datadir, XLogRecPtr ptr, int tliIndex)
 	}
 	endptr = xlogreader->EndRecPtr;
 
+	pg_free(xlogreader->readBuf);
 	XLogReaderFree(xlogreader);
 	if (xlogreadfd != -1)
 	{
@@ -174,6 +178,7 @@ findLastCheckpoint(const char *datadir, XLogRecPtr forkptr, int tliIndex,
 	xlogreader = XLogReaderAllocate(WalSegSz, datadir);
 	if (xlogreader == NULL)
 		pg_fatal("out of memory");
+	xlogreader->readBuf = pg_malloc(XLOG_BLCKSZ);
 
 	searchptr = forkptr;
 	for (;;)
@@ -222,6 +227,7 @@ findLastCheckpoint(const char *datadir, XLogRecPtr forkptr, int tliIndex,
 		searchptr = record->xl_prev;
 	}
 
+	pg_free(xlogreader->readBuf);
 	XLogReaderFree(xlogreader);
 	if (xlogreadfd != -1)
 	{
diff --git a/src/bin/pg_waldump/pg_waldump.c b/src/bin/pg_waldump/pg_waldump.c
index ee49712830..e17e66e688 100644
--- a/src/bin/pg_waldump/pg_waldump.c
+++ b/src/bin/pg_waldump/pg_waldump.c
@@ -1094,6 +1094,7 @@ main(int argc, char **argv)
 	xlogreader_state = XLogReaderAllocate(WalSegSz, waldir);
 	if (!xlogreader_state)
 		fatal_error("out of memory");
+	xlogreader_state->readBuf = palloc(XLOG_BLCKSZ);
 
 	/* first find a valid recptr to start from */
 	first_record = XLogFindNextRecord(xlogreader_state, private.startptr,
@@ -1174,6 +1175,7 @@ main(int argc, char **argv)
 					(uint32) xlogreader_state->ReadRecPtr,
 					errormsg);
 
+	pfree(xlogreader_state->readBuf);
 	XLogReaderFree(xlogreader_state);
 
 	return EXIT_SUCCESS;
-- 
2.16.3

