Database-level collation version tracking

From 718942496eb0fa19ab092e3c74af42149f86f756 Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <peter@eisentraut.org>
Date: Tue, 1 Feb 2022 16:09:30 +0100
Subject: [PATCH v2] Database-level collation version tracking

This adds to database objects the same version tracking that collation
objects have.  There is a new pg_database column datcollversion that
stores the version, a new function
pg_database_collation_actual_version() to get the version from the
operating system, and a new subcommand ALTER DATABASE ... REFRESH
COLLATION VERSION.

This was not originally added together with pg_collation.collversion,
since originally version tracking was only supported for ICU, and ICU
on a database-level is not currently supported.  But we now have
version tracking for glibc (since PG13), FreeBSD (since PG14), and
Windows (since PG13), so this is useful to have now.
---
 doc/src/sgml/catalogs.sgml            |  11 ++
 doc/src/sgml/func.sgml                |  18 ++++
 doc/src/sgml/ref/alter_collation.sgml |   3 +-
 doc/src/sgml/ref/alter_database.sgml  |  12 +++
 src/backend/commands/dbcommands.c     | 146 ++++++++++++++++++++++++--
 src/backend/parser/gram.y             |   6 ++
 src/backend/tcop/utility.c            |  14 +--
 src/backend/utils/init/postinit.c     |  33 ++++++
 src/bin/initdb/initdb.c               |  12 +++
 src/bin/pg_dump/pg_dump.c             |  20 ++++
 src/bin/psql/tab-complete.c           |   2 +-
 src/include/catalog/pg_database.h     |   3 +
 src/include/catalog/pg_proc.dat       |   5 +
 src/include/commands/dbcommands.h     |   1 +
 src/include/nodes/nodes.h             |   1 +
 src/include/nodes/parsenodes.h        |   6 ++
 16 files changed, 279 insertions(+), 14 deletions(-)

diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index 879d2dbce0..5a1627a394 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -3043,6 +3043,17 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
       </para></entry>
      </row>
 
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>datcollversion</structfield> <type>text</type>
+      </para>
+      <para>
+       Provider-specific version of the collation.  This is recorded when the
+       database is created and then checked when it is used, to detect
+       changes in the collation definition that could lead to data corruption.
+      </para></entry>
+     </row>
+
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>datacl</structfield> <type>aclitem[]</type>
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 8754f2f89b..49644666bc 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -27061,6 +27061,24 @@ postgres=# SELECT * FROM pg_walfile_name_offset(pg_stop_backup());
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_database_collation_actual_version</primary>
+        </indexterm>
+        <function>pg_database_collation_actual_version</function> ( <type>oid</type> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Returns the actual version of the database's collation as it is currently
+        installed in the operating system.  If this is different from the
+        value in
+        <structname>pg_database</structname>.<structfield>datcollversion</structfield>,
+        then objects depending on the collation might need to be rebuilt.  See
+        also <xref linkend="sql-alterdatabase"/>.
+       </para></entry>
+      </row>
+
       <row>
        <entry role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/doc/src/sgml/ref/alter_collation.sgml b/doc/src/sgml/ref/alter_collation.sgml
index 892c466565..a8c831d728 100644
--- a/doc/src/sgml/ref/alter_collation.sgml
+++ b/doc/src/sgml/ref/alter_collation.sgml
@@ -151,7 +151,8 @@ HINT:  Rebuild all objects affected by this collation and run ALTER COLLATION pg
    </para>
   </note>
   <para>
-   Currently, there is no version tracking for the database default collation.
+   For the database default collation, there is an analogous command
+   <literal>ALTER DATABASE ... REFRESH COLLATION VERSION</literal>.
   </para>
 
   <para>
diff --git a/doc/src/sgml/ref/alter_database.sgml b/doc/src/sgml/ref/alter_database.sgml
index 81e37536a3..89ed261b4c 100644
--- a/doc/src/sgml/ref/alter_database.sgml
+++ b/doc/src/sgml/ref/alter_database.sgml
@@ -35,6 +35,8 @@ ALTER DATABASE <replaceable class="parameter">name</replaceable> OWNER TO { <rep
 
 ALTER DATABASE <replaceable class="parameter">name</replaceable> SET TABLESPACE <replaceable class="parameter">new_tablespace</replaceable>
 
+ALTER DATABASE <replaceable class="parameter">name</replaceable> REFRESH COLLATION VERSION
+
 ALTER DATABASE <replaceable class="parameter">name</replaceable> SET <replaceable>configuration_parameter</replaceable> { TO | = } { <replaceable>value</replaceable> | DEFAULT }
 ALTER DATABASE <replaceable class="parameter">name</replaceable> SET <replaceable>configuration_parameter</replaceable> FROM CURRENT
 ALTER DATABASE <replaceable class="parameter">name</replaceable> RESET <replaceable>configuration_parameter</replaceable>
@@ -171,6 +173,16 @@ ALTER DATABASE <replaceable class="parameter">name</replaceable> RESET ALL
     </listitem>
    </varlistentry>
 
+   <varlistentry>
+    <term><literal>REFRESH COLLATION VERSION</literal></term>
+    <listitem>
+     <para>
+      Update the database collation version.  See <xref
+      linkend="sql-altercollation-notes"/> for background.
+     </para>
+    </listitem>
+   </varlistentry>
+
      <varlistentry>
       <term><replaceable>configuration_parameter</replaceable></term>
       <term><replaceable>value</replaceable></term>
diff --git a/src/backend/commands/dbcommands.c b/src/backend/commands/dbcommands.c
index e673138cbd..78010f2198 100644
--- a/src/backend/commands/dbcommands.c
+++ b/src/backend/commands/dbcommands.c
@@ -36,6 +36,7 @@
 #include "catalog/indexing.h"
 #include "catalog/objectaccess.h"
 #include "catalog/pg_authid.h"
+#include "catalog/pg_collation.h"
 #include "catalog/pg_database.h"
 #include "catalog/pg_db_role_setting.h"
 #include "catalog/pg_subscription.h"
@@ -85,7 +86,8 @@ static bool get_db_info(const char *name, LOCKMODE lockmode,
 						Oid *dbIdP, Oid *ownerIdP,
 						int *encodingP, bool *dbIsTemplateP, bool *dbAllowConnP,
 						TransactionId *dbFrozenXidP, MultiXactId *dbMinMultiP,
-						Oid *dbTablespace, char **dbCollate, char **dbCtype);
+						Oid *dbTablespace, char **dbCollate, char **dbCtype,
+						char **dbCollversion);
 static bool have_createdb_privilege(void);
 static void remove_dbtablespaces(Oid db_id);
 static bool check_db_file_conflict(Oid db_id);
@@ -105,6 +107,7 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 	int			src_encoding = -1;
 	char	   *src_collate = NULL;
 	char	   *src_ctype = NULL;
+	char	   *src_collversion = NULL;
 	bool		src_istemplate;
 	bool		src_allowconn;
 	TransactionId src_frozenxid = InvalidTransactionId;
@@ -128,6 +131,7 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 	DefElem    *distemplate = NULL;
 	DefElem    *dallowconnections = NULL;
 	DefElem    *dconnlimit = NULL;
+	DefElem	   *dcollversion = NULL;
 	char	   *dbname = stmt->dbname;
 	char	   *dbowner = NULL;
 	const char *dbtemplate = NULL;
@@ -138,6 +142,7 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 	bool		dbistemplate = false;
 	bool		dballowconnections = true;
 	int			dbconnlimit = -1;
+	char	   *dbcollversion = NULL;
 	int			notherbackends;
 	int			npreparedxacts;
 	createdb_failure_params fparms;
@@ -207,6 +212,12 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 				errorConflictingDefElem(defel, pstate);
 			dconnlimit = defel;
 		}
+		else if (strcmp(defel->defname, "collation_version") == 0)
+		{
+			if (dcollversion)
+				errorConflictingDefElem(defel, pstate);
+			dcollversion = defel;
+		}
 		else if (strcmp(defel->defname, "location") == 0)
 		{
 			ereport(WARNING,
@@ -305,6 +316,8 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 					 errmsg("invalid connection limit: %d", dbconnlimit)));
 	}
+	if (dcollversion)
+		dbcollversion = defGetString(dcollversion);
 
 	/* obtain OID of proposed owner */
 	if (dbowner)
@@ -342,7 +355,7 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 					 &src_dboid, &src_owner, &src_encoding,
 					 &src_istemplate, &src_allowconn,
 					 &src_frozenxid, &src_minmxid, &src_deftablespace,
-					 &src_collate, &src_ctype))
+					 &src_collate, &src_ctype, &src_collversion))
 		ereport(ERROR,
 				(errcode(ERRCODE_UNDEFINED_DATABASE),
 				 errmsg("template database \"%s\" does not exist",
@@ -368,6 +381,8 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 		dbcollate = src_collate;
 	if (dbctype == NULL)
 		dbctype = src_ctype;
+	if (dbcollversion == NULL)
+		dbcollversion = src_collversion;
 
 	/* Some encodings are client only */
 	if (!PG_VALID_BE_ENCODING(encoding))
@@ -424,6 +439,14 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 					 errhint("Use the same LC_CTYPE as in the template database, or use template0 as template.")));
 	}
 
+	/*
+	 * Normally, we copy the collation version from the template database.
+	 * This last resort only applies if the template database does not have a
+	 * collation version, which is normally only the case for template0.
+	 */
+	if (!dbcollversion)
+		dbcollversion = get_collation_actual_version(COLLPROVIDER_LIBC, dbcollate);
+
 	/* Resolve default tablespace for new database */
 	if (dtablespacename && dtablespacename->arg)
 	{
@@ -578,6 +601,10 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 	new_record[Anum_pg_database_dattablespace - 1] = ObjectIdGetDatum(dst_deftablespace);
 	new_record[Anum_pg_database_datcollate - 1] = CStringGetTextDatum(dbcollate);
 	new_record[Anum_pg_database_datctype - 1] = CStringGetTextDatum(dbctype);
+	if (dbcollversion)
+		new_record[Anum_pg_database_datcollversion - 1] = CStringGetTextDatum(dbcollversion);
+	else
+		new_record_nulls[Anum_pg_database_datcollversion - 1] = true;
 
 	/*
 	 * We deliberately set datacl to default (NULL), rather than copying it
@@ -844,7 +871,7 @@ dropdb(const char *dbname, bool missing_ok, bool force)
 	pgdbrel = table_open(DatabaseRelationId, RowExclusiveLock);
 
 	if (!get_db_info(dbname, AccessExclusiveLock, &db_id, NULL, NULL,
-					 &db_istemplate, NULL, NULL, NULL, NULL, NULL, NULL))
+					 &db_istemplate, NULL, NULL, NULL, NULL, NULL, NULL, NULL))
 	{
 		if (!missing_ok)
 		{
@@ -1043,7 +1070,7 @@ RenameDatabase(const char *oldname, const char *newname)
 	rel = table_open(DatabaseRelationId, RowExclusiveLock);
 
 	if (!get_db_info(oldname, AccessExclusiveLock, &db_id, NULL, NULL,
-					 NULL, NULL, NULL, NULL, NULL, NULL, NULL))
+					 NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL))
 		ereport(ERROR,
 				(errcode(ERRCODE_UNDEFINED_DATABASE),
 				 errmsg("database \"%s\" does not exist", oldname)));
@@ -1156,7 +1183,7 @@ movedb(const char *dbname, const char *tblspcname)
 	pgdbrel = table_open(DatabaseRelationId, RowExclusiveLock);
 
 	if (!get_db_info(dbname, AccessExclusiveLock, &db_id, NULL, NULL,
-					 NULL, NULL, NULL, NULL, &src_tblspcoid, NULL, NULL))
+					 NULL, NULL, NULL, NULL, &src_tblspcoid, NULL, NULL, NULL))
 		ereport(ERROR,
 				(errcode(ERRCODE_UNDEFINED_DATABASE),
 				 errmsg("database \"%s\" does not exist", dbname)));
@@ -1643,6 +1670,76 @@ AlterDatabase(ParseState *pstate, AlterDatabaseStmt *stmt, bool isTopLevel)
 }
 
 
+/*
+ * ALTER DATABASE name REFRESH COLLATION VERSION
+ */
+Oid
+AlterDatabaseRefreshColl(AlterDatabaseRefreshCollStmt *stmt)
+{
+	Relation	rel;
+	Oid			dboid;
+	HeapTuple	tup;
+	Datum		datum;
+	bool		isnull;
+	char	   *oldversion;
+	char	   *newversion;
+
+	rel = table_open(DatabaseRelationId, RowExclusiveLock);
+	dboid = get_database_oid(stmt->dbname, false);
+
+	if (!pg_database_ownercheck(dboid, GetUserId()))
+		aclcheck_error(ACLCHECK_NOT_OWNER, OBJECT_DATABASE,
+					   stmt->dbname);
+
+	tup = SearchSysCacheCopy1(DATABASEOID, ObjectIdGetDatum(dboid));
+	if (!HeapTupleIsValid(tup))
+		elog(ERROR, "cache lookup failed for database %u", dboid);
+
+	datum = SysCacheGetAttr(DATABASEOID, tup, Anum_pg_database_datcollversion, &isnull);
+	oldversion = isnull ? NULL : TextDatumGetCString(datum);
+
+	datum = SysCacheGetAttr(DATABASEOID, tup, Anum_pg_database_datcollate, &isnull);
+	Assert(!isnull);
+	newversion = get_collation_actual_version(COLLPROVIDER_LIBC, TextDatumGetCString(datum));
+
+	/* cannot change from NULL to non-NULL or vice versa */
+	if ((!oldversion && newversion) || (oldversion && !newversion))
+		elog(ERROR, "invalid collation version change");
+	else if (oldversion && newversion && strcmp(newversion, oldversion) != 0)
+	{
+		bool		nulls[Natts_pg_database];
+		bool		replaces[Natts_pg_database];
+		Datum		values[Natts_pg_database];
+
+		ereport(NOTICE,
+				(errmsg("changing version from %s to %s",
+						oldversion, newversion)));
+
+		memset(values, 0, sizeof(values));
+		memset(nulls, false, sizeof(nulls));
+		memset(replaces, false, sizeof(replaces));
+
+		values[Anum_pg_database_datcollversion - 1] = CStringGetTextDatum(newversion);
+		replaces[Anum_pg_database_datcollversion - 1] = true;
+
+		tup = heap_modify_tuple(tup, RelationGetDescr(rel),
+								values, nulls, replaces);
+	}
+	else
+		ereport(NOTICE,
+				(errmsg("version has not changed")));
+
+	CatalogTupleUpdate(rel, &tup->t_self, tup);
+
+	InvokeObjectPostAlterHook(DatabaseRelationId, dboid, 0);
+
+	heap_freetuple(tup);
+	table_close(rel, NoLock);
+
+	return dboid;
+}
+
+
 /*
  * ALTER DATABASE name SET ...
  */
@@ -1785,6 +1882,34 @@ AlterDatabaseOwner(const char *dbname, Oid newOwnerId)
 }
 
 
+Datum
+pg_database_collation_actual_version(PG_FUNCTION_ARGS)
+{
+	Oid			dbid = PG_GETARG_OID(0);
+	HeapTuple	tp;
+	Datum		datum;
+	bool		isnull;
+	char	   *version;
+
+	tp = SearchSysCache1(DATABASEOID, ObjectIdGetDatum(dbid));
+	if (!HeapTupleIsValid(tp))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("database with OID %u does not exist", dbid)));
+
+	datum = SysCacheGetAttr(DATABASEOID, tp, Anum_pg_database_datcollate, &isnull);
+	Assert(!isnull);
+	version = get_collation_actual_version(COLLPROVIDER_LIBC, TextDatumGetCString(datum));
+
+	ReleaseSysCache(tp);
+
+	if (version)
+		PG_RETURN_TEXT_P(cstring_to_text(version));
+	else
+		PG_RETURN_NULL();
+}
+
+
 /*
  * Helper functions
  */
@@ -1800,7 +1925,8 @@ get_db_info(const char *name, LOCKMODE lockmode,
 			Oid *dbIdP, Oid *ownerIdP,
 			int *encodingP, bool *dbIsTemplateP, bool *dbAllowConnP,
 			TransactionId *dbFrozenXidP, MultiXactId *dbMinMultiP,
-			Oid *dbTablespace, char **dbCollate, char **dbCtype)
+			Oid *dbTablespace, char **dbCollate, char **dbCtype,
+			char **dbCollversion)
 {
 	bool		result = false;
 	Relation	relation;
@@ -1905,6 +2031,14 @@ get_db_info(const char *name, LOCKMODE lockmode,
 					Assert(!isnull);
 					*dbCtype = TextDatumGetCString(datum);
 				}
+				if (dbCollversion)
+				{
+					datum = SysCacheGetAttr(DATABASEOID, tuple, Anum_pg_database_datcollversion, &isnull);
+					if (isnull)
+						*dbCollversion = NULL;
+					else
+						*dbCollversion = TextDatumGetCString(datum);
+				}
 				ReleaseSysCache(tuple);
 				result = true;
 				break;
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index c4f3242506..92f93cfc72 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -10465,6 +10465,12 @@ AlterDatabaseStmt:
 														(Node *)makeString($6), @6));
 					$$ = (Node *)n;
 				 }
+			| ALTER DATABASE name REFRESH COLLATION VERSION_P
+				 {
+					AlterDatabaseRefreshCollStmt *n = makeNode(AlterDatabaseRefreshCollStmt);
+					n->dbname = $3;
+					$$ = (Node *)n;
+				 }
 		;
 
 AlterDatabaseSetStmt:
diff --git a/src/backend/tcop/utility.c b/src/backend/tcop/utility.c
index 83e4e37c78..3780c6e812 100644
--- a/src/backend/tcop/utility.c
+++ b/src/backend/tcop/utility.c
@@ -136,6 +136,7 @@ ClassifyUtilityCommandAsReadOnly(Node *parsetree)
 	switch (nodeTag(parsetree))
 	{
 		case T_AlterCollationStmt:
+		case T_AlterDatabaseRefreshCollStmt:
 		case T_AlterDatabaseSetStmt:
 		case T_AlterDatabaseStmt:
 		case T_AlterDefaultPrivilegesStmt:
@@ -779,6 +780,11 @@ standard_ProcessUtility(PlannedStmt *pstmt,
 			AlterDatabase(pstate, (AlterDatabaseStmt *) parsetree, isTopLevel);
 			break;
 
+		case T_AlterDatabaseRefreshCollStmt:
+			/* no event triggers for global objects */
+			AlterDatabaseRefreshColl((AlterDatabaseRefreshCollStmt *) parsetree);
+			break;
+
 		case T_AlterDatabaseSetStmt:
 			/* no event triggers for global objects */
 			AlterDatabaseSet((AlterDatabaseSetStmt *) parsetree);
@@ -2801,9 +2807,7 @@ CreateCommandTag(Node *parsetree)
 			break;
 
 		case T_AlterDatabaseStmt:
-			tag = CMDTAG_ALTER_DATABASE;
-			break;
-
+		case T_AlterDatabaseRefreshCollStmt:
 		case T_AlterDatabaseSetStmt:
 			tag = CMDTAG_ALTER_DATABASE;
 			break;
@@ -3444,9 +3448,7 @@ GetCommandLogLevel(Node *parsetree)
 			break;
 
 		case T_AlterDatabaseStmt:
-			lev = LOGSTMT_DDL;
-			break;
-
+		case T_AlterDatabaseRefreshCollStmt:
 		case T_AlterDatabaseSetStmt:
 			lev = LOGSTMT_DDL;
 			break;
diff --git a/src/backend/utils/init/postinit.c b/src/backend/utils/init/postinit.c
index 5b9ed2f6f5..228bb63f97 100644
--- a/src/backend/utils/init/postinit.c
+++ b/src/backend/utils/init/postinit.c
@@ -31,6 +31,7 @@
 #include "catalog/catalog.h"
 #include "catalog/namespace.h"
 #include "catalog/pg_authid.h"
+#include "catalog/pg_collation.h"
 #include "catalog/pg_database.h"
 #include "catalog/pg_db_role_setting.h"
 #include "catalog/pg_tablespace.h"
@@ -414,6 +415,38 @@ CheckMyDatabase(const char *name, bool am_superuser, bool override_allow_connect
 						   " which is not recognized by setlocale().", ctype),
 				 errhint("Recreate the database with another locale or install the missing locale.")));
 
+	/*
+	 * Check collation version.  See similar code in
+	 * pg_newlocale_from_collation().
+	 */
+	datum = SysCacheGetAttr(DATABASEOID, tup, Anum_pg_database_datcollversion,
+							&isnull);
+	if (!isnull)
+	{
+		char	   *actual_versionstr;
+		char	   *collversionstr;
+
+		collversionstr = TextDatumGetCString(datum);
+
+		actual_versionstr = get_collation_actual_version(COLLPROVIDER_LIBC, collate);
+		if (!actual_versionstr)
+			ereport(ERROR,
+					(errmsg("database \"%s\" has no actual collation version, but a version was specified",
+							name)));
+
+		if (strcmp(actual_versionstr, collversionstr) != 0)
+			ereport(WARNING,
+					(errmsg("database \"%s\" has a collation version mismatch",
+							name),
+					 errdetail("The database was created using collation version %s, "
+							   "but the operating system provides version %s.",
+							   collversionstr, actual_versionstr),
+					 errhint("Rebuild all objects affected by collation in this database and run "
+							 "ALTER DATABASE %s REFRESH COLLATION VERSION, "
+							 "or build PostgreSQL with the right library version.",
+							 quote_identifier(name))));
+	}
+
 	/* Make the locale settings visible as GUC variables, too */
 	SetConfigOption("lc_collate", collate, PGC_INTERNAL, PGC_S_OVERRIDE);
 	SetConfigOption("lc_ctype", ctype, PGC_INTERNAL, PGC_S_OVERRIDE);
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index d78e8e67b8..6e70d1b724 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -1857,6 +1857,18 @@ make_template0(FILE *cmdfd)
 		"CREATE DATABASE template0 IS_TEMPLATE = true ALLOW_CONNECTIONS = false OID = "
 		CppAsString2(Template0ObjectId) ";\n\n",
 
+		/*
+		 * template0 shouldn't have any collation-dependent objects, so unset
+		 * the collation version.  This avoids warnings when making a new
+		 * database from it.
+		 */
+		"UPDATE pg_database SET datcollversion = NULL WHERE datname = 'template0';\n\n",
+
+		/*
+		 * While we are here, do set the collation version on template1.
+		 */
+		"UPDATE pg_database SET datcollversion = pg_database_collation_actual_version(oid) WHERE datname = 'template1';\n\n",
+
 		/*
 		 * Explicitly revoke public create-schema and create-temp-table
 		 * privileges in template1 and template0; else the latter would be on
diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index 3499c0a4d5..7df576961e 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -2761,6 +2761,7 @@ dumpDatabase(Archive *fout)
 				i_acldefault,
 				i_datistemplate,
 				i_datconnlimit,
+				i_datcollversion,
 				i_tablespace;
 	CatalogId	dbCatId;
 	DumpId		dbDumpId;
@@ -2792,6 +2793,10 @@ dumpDatabase(Archive *fout)
 		appendPQExpBuffer(dbQry, "datminmxid, ");
 	else
 		appendPQExpBuffer(dbQry, "0 AS datminmxid, ");
+	if (fout->remoteVersion >= 150000)
+		appendPQExpBuffer(dbQry, "datcollversion, ");
+	else
+		appendPQExpBuffer(dbQry, "NULL AS datcollversion, ");
 	appendPQExpBuffer(dbQry,
 					  "(SELECT spcname FROM pg_tablespace t WHERE t.oid = dattablespace) AS tablespace, "
 					  "shobj_description(oid, 'pg_database') AS description "
@@ -2813,6 +2818,7 @@ dumpDatabase(Archive *fout)
 	i_acldefault = PQfnumber(res, "acldefault");
 	i_datistemplate = PQfnumber(res, "datistemplate");
 	i_datconnlimit = PQfnumber(res, "datconnlimit");
+	i_datcollversion = PQfnumber(res, "datcollversion");
 	i_tablespace = PQfnumber(res, "tablespace");
 
 	dbCatId.tableoid = atooid(PQgetvalue(res, 0, i_tableoid));
@@ -2871,6 +2877,20 @@ dumpDatabase(Archive *fout)
 			appendStringLiteralAH(creaQry, ctype, fout);
 		}
 	}
+	/*
+	 * For binary upgrade, carry over the collation version.  For normal
+	 * dump/restore, omit the version, so that it is computed upon restore.
+	 */
+	if (dopt->binary_upgrade)
+	{
+		if (!PQgetisnull(res, 0, i_datcollversion))
+		{
+			appendPQExpBufferStr(creaQry, " COLLATION_VERSION = ");
+			appendStringLiteralAH(creaQry,
+								  PQgetvalue(res, 0, i_datcollversion),
+								  fout);
+		}
+	}
 
 	/*
 	 * Note: looking at dopt->outputNoTablespaces here is completely the wrong
diff --git a/src/bin/psql/tab-complete.c b/src/bin/psql/tab-complete.c
index d1e421bc0f..d8ea142856 100644
--- a/src/bin/psql/tab-complete.c
+++ b/src/bin/psql/tab-complete.c
@@ -1839,7 +1839,7 @@ psql_completion(const char *text, int start, int end)
 
 	/* ALTER DATABASE <name> */
 	else if (Matches("ALTER", "DATABASE", MatchAny))
-		COMPLETE_WITH("RESET", "SET", "OWNER TO", "RENAME TO",
+		COMPLETE_WITH("RESET", "SET", "OWNER TO", "REFRESH COLLATION VERSION", "RENAME TO",
 					  "IS_TEMPLATE", "ALLOW_CONNECTIONS",
 					  "CONNECTION LIMIT");
 
diff --git a/src/include/catalog/pg_database.h b/src/include/catalog/pg_database.h
index 90b43a4ecc..76adbd4aad 100644
--- a/src/include/catalog/pg_database.h
+++ b/src/include/catalog/pg_database.h
@@ -65,6 +65,9 @@ CATALOG(pg_database,1262,DatabaseRelationId) BKI_SHARED_RELATION BKI_ROWTYPE_OID
 	/* LC_CTYPE setting */
 	text		datctype BKI_FORCE_NOT_NULL;
 
+	/* provider-dependent version of collation data */
+	text		datcollversion BKI_DEFAULT(_null_);
+
 	/* access permissions */
 	aclitem		datacl[1];
 #endif
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 7024dbe10a..2f45c764e2 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -11615,6 +11615,11 @@
   proname => 'pg_collation_actual_version', procost => '100',
   provolatile => 'v', prorettype => 'text', proargtypes => 'oid',
   prosrc => 'pg_collation_actual_version' },
+{ oid => '9167',
+  descr => 'get actual version of database collation from operating system',
+  proname => 'pg_database_collation_actual_version', procost => '100',
+  provolatile => 'v', prorettype => 'text', proargtypes => 'oid',
+  prosrc => 'pg_database_collation_actual_version' },
 
 # system management/monitoring related functions
 { oid => '3353', descr => 'list files in the log directory',
diff --git a/src/include/commands/dbcommands.h b/src/include/commands/dbcommands.h
index b1e8b5eb96..7faf6bf41c 100644
--- a/src/include/commands/dbcommands.h
+++ b/src/include/commands/dbcommands.h
@@ -24,6 +24,7 @@ extern void dropdb(const char *dbname, bool missing_ok, bool force);
 extern void DropDatabase(ParseState *pstate, DropdbStmt *stmt);
 extern ObjectAddress RenameDatabase(const char *oldname, const char *newname);
 extern Oid	AlterDatabase(ParseState *pstate, AlterDatabaseStmt *stmt, bool isTopLevel);
+extern Oid	AlterDatabaseRefreshColl(AlterDatabaseRefreshCollStmt *stmt);
 extern Oid	AlterDatabaseSet(AlterDatabaseSetStmt *stmt);
 extern ObjectAddress AlterDatabaseOwner(const char *dbname, Oid newOwnerId);
 
diff --git a/src/include/nodes/nodes.h b/src/include/nodes/nodes.h
index da35f2c272..5d075f0c34 100644
--- a/src/include/nodes/nodes.h
+++ b/src/include/nodes/nodes.h
@@ -370,6 +370,7 @@ typedef enum NodeTag
 	T_CheckPointStmt,
 	T_CreateSchemaStmt,
 	T_AlterDatabaseStmt,
+	T_AlterDatabaseRefreshCollStmt,
 	T_AlterDatabaseSetStmt,
 	T_AlterRoleSetStmt,
 	T_CreateConversionStmt,
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 37fcc4c9b5..34218b718c 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -3308,6 +3308,12 @@ typedef struct AlterDatabaseStmt
 	List	   *options;		/* List of DefElem nodes */
 } AlterDatabaseStmt;
 
+typedef struct AlterDatabaseRefreshCollStmt
+{
+	NodeTag		type;
+	char	   *dbname;
+} AlterDatabaseRefreshCollStmt;
+
 typedef struct AlterDatabaseSetStmt
 {
 	NodeTag		type;
-- 
2.33.1

From c50f4561932f5ff23715a0fb6e3e9554ce395f16 Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <peter@eisentraut.org>
Date: Mon, 7 Feb 2022 16:32:19 +0100
Subject: [PATCH v3] Database-level collation version tracking

This adds to database objects the same version tracking that collation
objects have.  There is a new pg_database column datcollversion that
stores the version, a new function
pg_database_collation_actual_version() to get the version from the
operating system, and a new subcommand ALTER DATABASE ... REFRESH
COLLATION VERSION.

This was not originally added together with pg_collation.collversion,
since originally version tracking was only supported for ICU, and ICU
on a database-level is not currently supported.  But we now have
version tracking for glibc (since PG13), FreeBSD (since PG14), and
Windows (since PG13), so this is useful to have now.

Discussion: https://www.postgresql.org/message-id/flat/f0ff3190-29a3-5b39-a179-fa32eee57db6%40enterprisedb.com

XXX catversion bump
---
 doc/src/sgml/catalogs.sgml            |  11 ++
 doc/src/sgml/func.sgml                |  18 ++++
 doc/src/sgml/ref/alter_collation.sgml |   3 +-
 doc/src/sgml/ref/alter_database.sgml  |  12 +++
 doc/src/sgml/ref/create_database.sgml |  21 ++++
 src/backend/commands/dbcommands.c     | 146 ++++++++++++++++++++++++--
 src/backend/parser/gram.y             |   6 ++
 src/backend/tcop/utility.c            |  14 +--
 src/backend/utils/init/postinit.c     |  33 ++++++
 src/bin/initdb/initdb.c               |  12 +++
 src/bin/pg_dump/pg_dump.c             |  20 ++++
 src/bin/psql/tab-complete.c           |   2 +-
 src/include/catalog/pg_database.h     |   3 +
 src/include/catalog/pg_proc.dat       |   5 +
 src/include/commands/dbcommands.h     |   1 +
 src/include/nodes/nodes.h             |   1 +
 src/include/nodes/parsenodes.h        |   6 ++
 17 files changed, 300 insertions(+), 14 deletions(-)

diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index 879d2dbce0..5a1627a394 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -3043,6 +3043,17 @@ <title><structname>pg_database</structname> Columns</title>
       </para></entry>
      </row>
 
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>datcollversion</structfield> <type>text</type>
+      </para>
+      <para>
+       Provider-specific version of the collation.  This is recorded when the
+       database is created and then checked when it is used, to detect
+       changes in the collation definition that could lead to data corruption.
+      </para></entry>
+     </row>
+
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>datacl</structfield> <type>aclitem[]</type>
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 8754f2f89b..49644666bc 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -27061,6 +27061,24 @@ <title>Collation Management Functions</title>
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_database_collation_actual_version</primary>
+        </indexterm>
+        <function>pg_database_collation_actual_version</function> ( <type>oid</type> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Returns the actual version of the database's collation as it is currently
+        installed in the operating system.  If this is different from the
+        value in
+        <structname>pg_database</structname>.<structfield>datcollversion</structfield>,
+        then objects depending on the collation might need to be rebuilt.  See
+        also <xref linkend="sql-alterdatabase"/>.
+       </para></entry>
+      </row>
+
       <row>
        <entry role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/doc/src/sgml/ref/alter_collation.sgml b/doc/src/sgml/ref/alter_collation.sgml
index 892c466565..a8c831d728 100644
--- a/doc/src/sgml/ref/alter_collation.sgml
+++ b/doc/src/sgml/ref/alter_collation.sgml
@@ -151,7 +151,8 @@ <title>Notes</title>
    </para>
   </note>
   <para>
-   Currently, there is no version tracking for the database default collation.
+   For the database default collation, there is an analogous command
+   <literal>ALTER DATABASE ... REFRESH COLLATION VERSION</literal>.
   </para>
 
   <para>
diff --git a/doc/src/sgml/ref/alter_database.sgml b/doc/src/sgml/ref/alter_database.sgml
index 81e37536a3..89ed261b4c 100644
--- a/doc/src/sgml/ref/alter_database.sgml
+++ b/doc/src/sgml/ref/alter_database.sgml
@@ -35,6 +35,8 @@
 
 ALTER DATABASE <replaceable class="parameter">name</replaceable> SET TABLESPACE <replaceable class="parameter">new_tablespace</replaceable>
 
+ALTER DATABASE <replaceable class="parameter">name</replaceable> REFRESH COLLATION VERSION
+
 ALTER DATABASE <replaceable class="parameter">name</replaceable> SET <replaceable>configuration_parameter</replaceable> { TO | = } { <replaceable>value</replaceable> | DEFAULT }
 ALTER DATABASE <replaceable class="parameter">name</replaceable> SET <replaceable>configuration_parameter</replaceable> FROM CURRENT
 ALTER DATABASE <replaceable class="parameter">name</replaceable> RESET <replaceable>configuration_parameter</replaceable>
@@ -171,6 +173,16 @@ <title>Parameters</title>
     </listitem>
    </varlistentry>
 
+   <varlistentry>
+    <term><literal>REFRESH COLLATION VERSION</literal></term>
+    <listitem>
+     <para>
+      Update the database collation version.  See <xref
+      linkend="sql-altercollation-notes"/> for background.
+     </para>
+    </listitem>
+   </varlistentry>
+
      <varlistentry>
       <term><replaceable>configuration_parameter</replaceable></term>
       <term><replaceable>value</replaceable></term>
diff --git a/doc/src/sgml/ref/create_database.sgml b/doc/src/sgml/ref/create_database.sgml
index f22e28dc81..f70d0c75b4 100644
--- a/doc/src/sgml/ref/create_database.sgml
+++ b/doc/src/sgml/ref/create_database.sgml
@@ -28,6 +28,7 @@
            [ LOCALE [=] <replaceable class="parameter">locale</replaceable> ]
            [ LC_COLLATE [=] <replaceable class="parameter">lc_collate</replaceable> ]
            [ LC_CTYPE [=] <replaceable class="parameter">lc_ctype</replaceable> ]
+           [ COLLATION_VERSION = <replaceable>collation_version</replaceable> ]
            [ TABLESPACE [=] <replaceable class="parameter">tablespace_name</replaceable> ]
            [ ALLOW_CONNECTIONS [=] <replaceable class="parameter">allowconn</replaceable> ]
            [ CONNECTION LIMIT [=] <replaceable class="parameter">connlimit</replaceable> ]
@@ -158,6 +159,26 @@ <title>Parameters</title>
        </para>
       </listitem>
      </varlistentry>
+
+     <varlistentry>
+      <term><replaceable>collation_version</replaceable></term>
+
+      <listitem>
+       <para>
+        Specifies the collation version string to store with the database.
+        Normally, this should be omitted, which will cause the version to be
+        computed from the actual version of the database collation as provided
+        by the operating system.  This option is intended to be used by
+        <command>pg_upgrade</command> for copying the version from an existing
+        installation.
+       </para>
+
+       <para>
+        See also <xref linkend="sql-alterdatabase"/> for how to handle
+        database collation version mismatches.
+       </para>
+     </listitem>
+    </varlistentry>
      <varlistentry>
       <term><replaceable class="parameter">tablespace_name</replaceable></term>
       <listitem>
diff --git a/src/backend/commands/dbcommands.c b/src/backend/commands/dbcommands.c
index e673138cbd..78010f2198 100644
--- a/src/backend/commands/dbcommands.c
+++ b/src/backend/commands/dbcommands.c
@@ -36,6 +36,7 @@
 #include "catalog/indexing.h"
 #include "catalog/objectaccess.h"
 #include "catalog/pg_authid.h"
+#include "catalog/pg_collation.h"
 #include "catalog/pg_database.h"
 #include "catalog/pg_db_role_setting.h"
 #include "catalog/pg_subscription.h"
@@ -85,7 +86,8 @@ static bool get_db_info(const char *name, LOCKMODE lockmode,
 						Oid *dbIdP, Oid *ownerIdP,
 						int *encodingP, bool *dbIsTemplateP, bool *dbAllowConnP,
 						TransactionId *dbFrozenXidP, MultiXactId *dbMinMultiP,
-						Oid *dbTablespace, char **dbCollate, char **dbCtype);
+						Oid *dbTablespace, char **dbCollate, char **dbCtype,
+						char **dbCollversion);
 static bool have_createdb_privilege(void);
 static void remove_dbtablespaces(Oid db_id);
 static bool check_db_file_conflict(Oid db_id);
@@ -105,6 +107,7 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 	int			src_encoding = -1;
 	char	   *src_collate = NULL;
 	char	   *src_ctype = NULL;
+	char	   *src_collversion = NULL;
 	bool		src_istemplate;
 	bool		src_allowconn;
 	TransactionId src_frozenxid = InvalidTransactionId;
@@ -128,6 +131,7 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 	DefElem    *distemplate = NULL;
 	DefElem    *dallowconnections = NULL;
 	DefElem    *dconnlimit = NULL;
+	DefElem	   *dcollversion = NULL;
 	char	   *dbname = stmt->dbname;
 	char	   *dbowner = NULL;
 	const char *dbtemplate = NULL;
@@ -138,6 +142,7 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 	bool		dbistemplate = false;
 	bool		dballowconnections = true;
 	int			dbconnlimit = -1;
+	char	   *dbcollversion = NULL;
 	int			notherbackends;
 	int			npreparedxacts;
 	createdb_failure_params fparms;
@@ -207,6 +212,12 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 				errorConflictingDefElem(defel, pstate);
 			dconnlimit = defel;
 		}
+		else if (strcmp(defel->defname, "collation_version") == 0)
+		{
+			if (dcollversion)
+				errorConflictingDefElem(defel, pstate);
+			dcollversion = defel;
+		}
 		else if (strcmp(defel->defname, "location") == 0)
 		{
 			ereport(WARNING,
@@ -305,6 +316,8 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 					 errmsg("invalid connection limit: %d", dbconnlimit)));
 	}
+	if (dcollversion)
+		dbcollversion = defGetString(dcollversion);
 
 	/* obtain OID of proposed owner */
 	if (dbowner)
@@ -342,7 +355,7 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 					 &src_dboid, &src_owner, &src_encoding,
 					 &src_istemplate, &src_allowconn,
 					 &src_frozenxid, &src_minmxid, &src_deftablespace,
-					 &src_collate, &src_ctype))
+					 &src_collate, &src_ctype, &src_collversion))
 		ereport(ERROR,
 				(errcode(ERRCODE_UNDEFINED_DATABASE),
 				 errmsg("template database \"%s\" does not exist",
@@ -368,6 +381,8 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 		dbcollate = src_collate;
 	if (dbctype == NULL)
 		dbctype = src_ctype;
+	if (dbcollversion == NULL)
+		dbcollversion = src_collversion;
 
 	/* Some encodings are client only */
 	if (!PG_VALID_BE_ENCODING(encoding))
@@ -424,6 +439,14 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 					 errhint("Use the same LC_CTYPE as in the template database, or use template0 as template.")));
 	}
 
+	/*
+	 * Normally, we copy the collation version from the template database.
+	 * This last resort only applies if the template database does not have a
+	 * collation version, which is normally only the case for template0.
+	 */
+	if (!dbcollversion)
+		dbcollversion = get_collation_actual_version(COLLPROVIDER_LIBC, dbcollate);
+
 	/* Resolve default tablespace for new database */
 	if (dtablespacename && dtablespacename->arg)
 	{
@@ -578,6 +601,10 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 	new_record[Anum_pg_database_dattablespace - 1] = ObjectIdGetDatum(dst_deftablespace);
 	new_record[Anum_pg_database_datcollate - 1] = CStringGetTextDatum(dbcollate);
 	new_record[Anum_pg_database_datctype - 1] = CStringGetTextDatum(dbctype);
+	if (dbcollversion)
+		new_record[Anum_pg_database_datcollversion - 1] = CStringGetTextDatum(dbcollversion);
+	else
+		new_record_nulls[Anum_pg_database_datcollversion - 1] = true;
 
 	/*
 	 * We deliberately set datacl to default (NULL), rather than copying it
@@ -844,7 +871,7 @@ dropdb(const char *dbname, bool missing_ok, bool force)
 	pgdbrel = table_open(DatabaseRelationId, RowExclusiveLock);
 
 	if (!get_db_info(dbname, AccessExclusiveLock, &db_id, NULL, NULL,
-					 &db_istemplate, NULL, NULL, NULL, NULL, NULL, NULL))
+					 &db_istemplate, NULL, NULL, NULL, NULL, NULL, NULL, NULL))
 	{
 		if (!missing_ok)
 		{
@@ -1043,7 +1070,7 @@ RenameDatabase(const char *oldname, const char *newname)
 	rel = table_open(DatabaseRelationId, RowExclusiveLock);
 
 	if (!get_db_info(oldname, AccessExclusiveLock, &db_id, NULL, NULL,
-					 NULL, NULL, NULL, NULL, NULL, NULL, NULL))
+					 NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL))
 		ereport(ERROR,
 				(errcode(ERRCODE_UNDEFINED_DATABASE),
 				 errmsg("database \"%s\" does not exist", oldname)));
@@ -1156,7 +1183,7 @@ movedb(const char *dbname, const char *tblspcname)
 	pgdbrel = table_open(DatabaseRelationId, RowExclusiveLock);
 
 	if (!get_db_info(dbname, AccessExclusiveLock, &db_id, NULL, NULL,
-					 NULL, NULL, NULL, NULL, &src_tblspcoid, NULL, NULL))
+					 NULL, NULL, NULL, NULL, &src_tblspcoid, NULL, NULL, NULL))
 		ereport(ERROR,
 				(errcode(ERRCODE_UNDEFINED_DATABASE),
 				 errmsg("database \"%s\" does not exist", dbname)));
@@ -1643,6 +1670,76 @@ AlterDatabase(ParseState *pstate, AlterDatabaseStmt *stmt, bool isTopLevel)
 }
 
 
+/*
+ * ALTER DATABASE name REFRESH COLLATION VERSION
+ */
+Oid
+AlterDatabaseRefreshColl(AlterDatabaseRefreshCollStmt *stmt)
+{
+	Relation	rel;
+	Oid			dboid;
+	HeapTuple	tup;
+	Datum		datum;
+	bool		isnull;
+	char	   *oldversion;
+	char	   *newversion;
+
+	rel = table_open(DatabaseRelationId, RowExclusiveLock);
+	dboid = get_database_oid(stmt->dbname, false);
+
+	if (!pg_database_ownercheck(dboid, GetUserId()))
+		aclcheck_error(ACLCHECK_NOT_OWNER, OBJECT_DATABASE,
+					   stmt->dbname);
+
+	tup = SearchSysCacheCopy1(DATABASEOID, ObjectIdGetDatum(dboid));
+	if (!HeapTupleIsValid(tup))
+		elog(ERROR, "cache lookup failed for database %u", dboid);
+
+	datum = SysCacheGetAttr(DATABASEOID, tup, Anum_pg_database_datcollversion, &isnull);
+	oldversion = isnull ? NULL : TextDatumGetCString(datum);
+
+	datum = SysCacheGetAttr(DATABASEOID, tup, Anum_pg_database_datcollate, &isnull);
+	Assert(!isnull);
+	newversion = get_collation_actual_version(COLLPROVIDER_LIBC, TextDatumGetCString(datum));
+
+	/* cannot change from NULL to non-NULL or vice versa */
+	if ((!oldversion && newversion) || (oldversion && !newversion))
+		elog(ERROR, "invalid collation version change");
+	else if (oldversion && newversion && strcmp(newversion, oldversion) != 0)
+	{
+		bool		nulls[Natts_pg_database];
+		bool		replaces[Natts_pg_database];
+		Datum		values[Natts_pg_database];
+
+		ereport(NOTICE,
+				(errmsg("changing version from %s to %s",
+						oldversion, newversion)));
+
+		memset(values, 0, sizeof(values));
+		memset(nulls, false, sizeof(nulls));
+		memset(replaces, false, sizeof(replaces));
+
+		values[Anum_pg_database_datcollversion - 1] = CStringGetTextDatum(newversion);
+		replaces[Anum_pg_database_datcollversion - 1] = true;
+
+		tup = heap_modify_tuple(tup, RelationGetDescr(rel),
+								values, nulls, replaces);
+	}
+	else
+		ereport(NOTICE,
+				(errmsg("version has not changed")));
+
+	CatalogTupleUpdate(rel, &tup->t_self, tup);
+
+	InvokeObjectPostAlterHook(DatabaseRelationId, dboid, 0);
+
+	heap_freetuple(tup);
+	table_close(rel, NoLock);
+
+	return dboid;
+}
+
+
 /*
  * ALTER DATABASE name SET ...
  */
@@ -1785,6 +1882,34 @@ AlterDatabaseOwner(const char *dbname, Oid newOwnerId)
 }
 
 
+Datum
+pg_database_collation_actual_version(PG_FUNCTION_ARGS)
+{
+	Oid			dbid = PG_GETARG_OID(0);
+	HeapTuple	tp;
+	Datum		datum;
+	bool		isnull;
+	char	   *version;
+
+	tp = SearchSysCache1(DATABASEOID, ObjectIdGetDatum(dbid));
+	if (!HeapTupleIsValid(tp))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("database with OID %u does not exist", dbid)));
+
+	datum = SysCacheGetAttr(DATABASEOID, tp, Anum_pg_database_datcollate, &isnull);
+	Assert(!isnull);
+	version = get_collation_actual_version(COLLPROVIDER_LIBC, TextDatumGetCString(datum));
+
+	ReleaseSysCache(tp);
+
+	if (version)
+		PG_RETURN_TEXT_P(cstring_to_text(version));
+	else
+		PG_RETURN_NULL();
+}
+
+
 /*
  * Helper functions
  */
@@ -1800,7 +1925,8 @@ get_db_info(const char *name, LOCKMODE lockmode,
 			Oid *dbIdP, Oid *ownerIdP,
 			int *encodingP, bool *dbIsTemplateP, bool *dbAllowConnP,
 			TransactionId *dbFrozenXidP, MultiXactId *dbMinMultiP,
-			Oid *dbTablespace, char **dbCollate, char **dbCtype)
+			Oid *dbTablespace, char **dbCollate, char **dbCtype,
+			char **dbCollversion)
 {
 	bool		result = false;
 	Relation	relation;
@@ -1905,6 +2031,14 @@ get_db_info(const char *name, LOCKMODE lockmode,
 					Assert(!isnull);
 					*dbCtype = TextDatumGetCString(datum);
 				}
+				if (dbCollversion)
+				{
+					datum = SysCacheGetAttr(DATABASEOID, tuple, Anum_pg_database_datcollversion, &isnull);
+					if (isnull)
+						*dbCollversion = NULL;
+					else
+						*dbCollversion = TextDatumGetCString(datum);
+				}
 				ReleaseSysCache(tuple);
 				result = true;
 				break;
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index c4f3242506..92f93cfc72 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -10465,6 +10465,12 @@ AlterDatabaseStmt:
 														(Node *)makeString($6), @6));
 					$$ = (Node *)n;
 				 }
+			| ALTER DATABASE name REFRESH COLLATION VERSION_P
+				 {
+					AlterDatabaseRefreshCollStmt *n = makeNode(AlterDatabaseRefreshCollStmt);
+					n->dbname = $3;
+					$$ = (Node *)n;
+				 }
 		;
 
 AlterDatabaseSetStmt:
diff --git a/src/backend/tcop/utility.c b/src/backend/tcop/utility.c
index 83e4e37c78..3780c6e812 100644
--- a/src/backend/tcop/utility.c
+++ b/src/backend/tcop/utility.c
@@ -136,6 +136,7 @@ ClassifyUtilityCommandAsReadOnly(Node *parsetree)
 	switch (nodeTag(parsetree))
 	{
 		case T_AlterCollationStmt:
+		case T_AlterDatabaseRefreshCollStmt:
 		case T_AlterDatabaseSetStmt:
 		case T_AlterDatabaseStmt:
 		case T_AlterDefaultPrivilegesStmt:
@@ -779,6 +780,11 @@ standard_ProcessUtility(PlannedStmt *pstmt,
 			AlterDatabase(pstate, (AlterDatabaseStmt *) parsetree, isTopLevel);
 			break;
 
+		case T_AlterDatabaseRefreshCollStmt:
+			/* no event triggers for global objects */
+			AlterDatabaseRefreshColl((AlterDatabaseRefreshCollStmt *) parsetree);
+			break;
+
 		case T_AlterDatabaseSetStmt:
 			/* no event triggers for global objects */
 			AlterDatabaseSet((AlterDatabaseSetStmt *) parsetree);
@@ -2801,9 +2807,7 @@ CreateCommandTag(Node *parsetree)
 			break;
 
 		case T_AlterDatabaseStmt:
-			tag = CMDTAG_ALTER_DATABASE;
-			break;
-
+		case T_AlterDatabaseRefreshCollStmt:
 		case T_AlterDatabaseSetStmt:
 			tag = CMDTAG_ALTER_DATABASE;
 			break;
@@ -3444,9 +3448,7 @@ GetCommandLogLevel(Node *parsetree)
 			break;
 
 		case T_AlterDatabaseStmt:
-			lev = LOGSTMT_DDL;
-			break;
-
+		case T_AlterDatabaseRefreshCollStmt:
 		case T_AlterDatabaseSetStmt:
 			lev = LOGSTMT_DDL;
 			break;
diff --git a/src/backend/utils/init/postinit.c b/src/backend/utils/init/postinit.c
index 5b9ed2f6f5..f79e89a915 100644
--- a/src/backend/utils/init/postinit.c
+++ b/src/backend/utils/init/postinit.c
@@ -31,6 +31,7 @@
 #include "catalog/catalog.h"
 #include "catalog/namespace.h"
 #include "catalog/pg_authid.h"
+#include "catalog/pg_collation.h"
 #include "catalog/pg_database.h"
 #include "catalog/pg_db_role_setting.h"
 #include "catalog/pg_tablespace.h"
@@ -414,6 +415,38 @@ CheckMyDatabase(const char *name, bool am_superuser, bool override_allow_connect
 						   " which is not recognized by setlocale().", ctype),
 				 errhint("Recreate the database with another locale or install the missing locale.")));
 
+	/*
+	 * Check collation version.  See similar code in
+	 * pg_newlocale_from_collation().
+	 */
+	datum = SysCacheGetAttr(DATABASEOID, tup, Anum_pg_database_datcollversion,
+							&isnull);
+	if (!isnull)
+	{
+		char	   *actual_versionstr;
+		char	   *collversionstr;
+
+		collversionstr = TextDatumGetCString(datum);
+
+		actual_versionstr = get_collation_actual_version(COLLPROVIDER_LIBC, collate);
+		if (!actual_versionstr)
+			ereport(WARNING,
+					(errmsg("database \"%s\" has no actual collation version, but a version was specified",
+							name)));
+
+		if (strcmp(actual_versionstr, collversionstr) != 0)
+			ereport(WARNING,
+					(errmsg("database \"%s\" has a collation version mismatch",
+							name),
+					 errdetail("The database was created using collation version %s, "
+							   "but the operating system provides version %s.",
+							   collversionstr, actual_versionstr),
+					 errhint("Rebuild all objects affected by collation in this database and run "
+							 "ALTER DATABASE %s REFRESH COLLATION VERSION, "
+							 "or build PostgreSQL with the right library version.",
+							 quote_identifier(name))));
+	}
+
 	/* Make the locale settings visible as GUC variables, too */
 	SetConfigOption("lc_collate", collate, PGC_INTERNAL, PGC_S_OVERRIDE);
 	SetConfigOption("lc_ctype", ctype, PGC_INTERNAL, PGC_S_OVERRIDE);
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index d78e8e67b8..6e70d1b724 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -1857,6 +1857,18 @@ make_template0(FILE *cmdfd)
 		"CREATE DATABASE template0 IS_TEMPLATE = true ALLOW_CONNECTIONS = false OID = "
 		CppAsString2(Template0ObjectId) ";\n\n",
 
+		/*
+		 * template0 shouldn't have any collation-dependent objects, so unset
+		 * the collation version.  This avoids warnings when making a new
+		 * database from it.
+		 */
+		"UPDATE pg_database SET datcollversion = NULL WHERE datname = 'template0';\n\n",
+
+		/*
+		 * While we are here, do set the collation version on template1.
+		 */
+		"UPDATE pg_database SET datcollversion = pg_database_collation_actual_version(oid) WHERE datname = 'template1';\n\n",
+
 		/*
 		 * Explicitly revoke public create-schema and create-temp-table
 		 * privileges in template1 and template0; else the latter would be on
diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index 3499c0a4d5..7df576961e 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -2761,6 +2761,7 @@ dumpDatabase(Archive *fout)
 				i_acldefault,
 				i_datistemplate,
 				i_datconnlimit,
+				i_datcollversion,
 				i_tablespace;
 	CatalogId	dbCatId;
 	DumpId		dbDumpId;
@@ -2792,6 +2793,10 @@ dumpDatabase(Archive *fout)
 		appendPQExpBuffer(dbQry, "datminmxid, ");
 	else
 		appendPQExpBuffer(dbQry, "0 AS datminmxid, ");
+	if (fout->remoteVersion >= 150000)
+		appendPQExpBuffer(dbQry, "datcollversion, ");
+	else
+		appendPQExpBuffer(dbQry, "NULL AS datcollversion, ");
 	appendPQExpBuffer(dbQry,
 					  "(SELECT spcname FROM pg_tablespace t WHERE t.oid = dattablespace) AS tablespace, "
 					  "shobj_description(oid, 'pg_database') AS description "
@@ -2813,6 +2818,7 @@ dumpDatabase(Archive *fout)
 	i_acldefault = PQfnumber(res, "acldefault");
 	i_datistemplate = PQfnumber(res, "datistemplate");
 	i_datconnlimit = PQfnumber(res, "datconnlimit");
+	i_datcollversion = PQfnumber(res, "datcollversion");
 	i_tablespace = PQfnumber(res, "tablespace");
 
 	dbCatId.tableoid = atooid(PQgetvalue(res, 0, i_tableoid));
@@ -2871,6 +2877,20 @@ dumpDatabase(Archive *fout)
 			appendStringLiteralAH(creaQry, ctype, fout);
 		}
 	}
+	/*
+	 * For binary upgrade, carry over the collation version.  For normal
+	 * dump/restore, omit the version, so that it is computed upon restore.
+	 */
+	if (dopt->binary_upgrade)
+	{
+		if (!PQgetisnull(res, 0, i_datcollversion))
+		{
+			appendPQExpBufferStr(creaQry, " COLLATION_VERSION = ");
+			appendStringLiteralAH(creaQry,
+								  PQgetvalue(res, 0, i_datcollversion),
+								  fout);
+		}
+	}
 
 	/*
 	 * Note: looking at dopt->outputNoTablespaces here is completely the wrong
diff --git a/src/bin/psql/tab-complete.c b/src/bin/psql/tab-complete.c
index d1e421bc0f..d8ea142856 100644
--- a/src/bin/psql/tab-complete.c
+++ b/src/bin/psql/tab-complete.c
@@ -1839,7 +1839,7 @@ psql_completion(const char *text, int start, int end)
 
 	/* ALTER DATABASE <name> */
 	else if (Matches("ALTER", "DATABASE", MatchAny))
-		COMPLETE_WITH("RESET", "SET", "OWNER TO", "RENAME TO",
+		COMPLETE_WITH("RESET", "SET", "OWNER TO", "REFRESH COLLATION VERSION", "RENAME TO",
 					  "IS_TEMPLATE", "ALLOW_CONNECTIONS",
 					  "CONNECTION LIMIT");
 
diff --git a/src/include/catalog/pg_database.h b/src/include/catalog/pg_database.h
index 90b43a4ecc..76adbd4aad 100644
--- a/src/include/catalog/pg_database.h
+++ b/src/include/catalog/pg_database.h
@@ -65,6 +65,9 @@ CATALOG(pg_database,1262,DatabaseRelationId) BKI_SHARED_RELATION BKI_ROWTYPE_OID
 	/* LC_CTYPE setting */
 	text		datctype BKI_FORCE_NOT_NULL;
 
+	/* provider-dependent version of collation data */
+	text		datcollversion BKI_DEFAULT(_null_);
+
 	/* access permissions */
 	aclitem		datacl[1];
 #endif
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 7024dbe10a..2f45c764e2 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -11615,6 +11615,11 @@
   proname => 'pg_collation_actual_version', procost => '100',
   provolatile => 'v', prorettype => 'text', proargtypes => 'oid',
   prosrc => 'pg_collation_actual_version' },
+{ oid => '9167',
+  descr => 'get actual version of database collation from operating system',
+  proname => 'pg_database_collation_actual_version', procost => '100',
+  provolatile => 'v', prorettype => 'text', proargtypes => 'oid',
+  prosrc => 'pg_database_collation_actual_version' },
 
 # system management/monitoring related functions
 { oid => '3353', descr => 'list files in the log directory',
diff --git a/src/include/commands/dbcommands.h b/src/include/commands/dbcommands.h
index b1e8b5eb96..7faf6bf41c 100644
--- a/src/include/commands/dbcommands.h
+++ b/src/include/commands/dbcommands.h
@@ -24,6 +24,7 @@ extern void dropdb(const char *dbname, bool missing_ok, bool force);
 extern void DropDatabase(ParseState *pstate, DropdbStmt *stmt);
 extern ObjectAddress RenameDatabase(const char *oldname, const char *newname);
 extern Oid	AlterDatabase(ParseState *pstate, AlterDatabaseStmt *stmt, bool isTopLevel);
+extern Oid	AlterDatabaseRefreshColl(AlterDatabaseRefreshCollStmt *stmt);
 extern Oid	AlterDatabaseSet(AlterDatabaseSetStmt *stmt);
 extern ObjectAddress AlterDatabaseOwner(const char *dbname, Oid newOwnerId);
 
diff --git a/src/include/nodes/nodes.h b/src/include/nodes/nodes.h
index da35f2c272..5d075f0c34 100644
--- a/src/include/nodes/nodes.h
+++ b/src/include/nodes/nodes.h
@@ -370,6 +370,7 @@ typedef enum NodeTag
 	T_CheckPointStmt,
 	T_CreateSchemaStmt,
 	T_AlterDatabaseStmt,
+	T_AlterDatabaseRefreshCollStmt,
 	T_AlterDatabaseSetStmt,
 	T_AlterRoleSetStmt,
 	T_CreateConversionStmt,
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 37fcc4c9b5..34218b718c 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -3308,6 +3308,12 @@ typedef struct AlterDatabaseStmt
 	List	   *options;		/* List of DefElem nodes */
 } AlterDatabaseStmt;
 
+typedef struct AlterDatabaseRefreshCollStmt
+{
+	NodeTag		type;
+	char	   *dbname;
+} AlterDatabaseRefreshCollStmt;
+
 typedef struct AlterDatabaseSetStmt
 {
 	NodeTag		type;
-- 
2.35.1

From 290ebb9ca743a2272181f435d5ea76d8a7280a0a Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <peter@eisentraut.org>
Date: Thu, 10 Feb 2022 09:44:20 +0100
Subject: [PATCH v4] Database-level collation version tracking

This adds to database objects the same version tracking that collation
objects have.  There is a new pg_database column datcollversion that
stores the version, a new function
pg_database_collation_actual_version() to get the version from the
operating system, and a new subcommand ALTER DATABASE ... REFRESH
COLLATION VERSION.

This was not originally added together with pg_collation.collversion,
since originally version tracking was only supported for ICU, and ICU
on a database-level is not currently supported.  But we now have
version tracking for glibc (since PG13), FreeBSD (since PG14), and
Windows (since PG13), so this is useful to have now.

Discussion: https://www.postgresql.org/message-id/flat/f0ff3190-29a3-5b39-a179-fa32eee57db6%40enterprisedb.com

XXX catversion bump
---
 doc/src/sgml/catalogs.sgml                    |  11 +
 doc/src/sgml/func.sgml                        |  18 ++
 doc/src/sgml/ref/alter_collation.sgml         |   3 +-
 doc/src/sgml/ref/alter_database.sgml          |  12 ++
 doc/src/sgml/ref/create_database.sgml         |  21 ++
 src/backend/commands/dbcommands.c             | 194 +++++++++++++++++-
 src/backend/parser/gram.y                     |   6 +
 src/backend/tcop/utility.c                    |  14 +-
 src/backend/utils/init/postinit.c             |  34 +++
 src/bin/initdb/initdb.c                       |  12 ++
 src/bin/pg_dump/pg_dump.c                     |  21 ++
 src/bin/psql/tab-complete.c                   |   2 +-
 src/include/catalog/pg_database.h             |   3 +
 src/include/catalog/pg_proc.dat               |   5 +
 src/include/commands/dbcommands.h             |   1 +
 src/include/nodes/nodes.h                     |   1 +
 src/include/nodes/parsenodes.h                |   6 +
 .../regress/expected/collate.icu.utf8.out     |   4 +
 .../regress/expected/collate.linux.utf8.out   |   4 +
 src/test/regress/sql/collate.icu.utf8.sql     |   4 +
 src/test/regress/sql/collate.linux.utf8.sql   |   4 +
 21 files changed, 366 insertions(+), 14 deletions(-)

diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index 879d2dbce0..5a1627a394 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -3043,6 +3043,17 @@ <title><structname>pg_database</structname> Columns</title>
       </para></entry>
      </row>
 
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>datcollversion</structfield> <type>text</type>
+      </para>
+      <para>
+       Provider-specific version of the collation.  This is recorded when the
+       database is created and then checked when it is used, to detect
+       changes in the collation definition that could lead to data corruption.
+      </para></entry>
+     </row>
+
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>datacl</structfield> <type>aclitem[]</type>
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 1b064b4feb..df3cd5987b 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -27061,6 +27061,24 @@ <title>Collation Management Functions</title>
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_database_collation_actual_version</primary>
+        </indexterm>
+        <function>pg_database_collation_actual_version</function> ( <type>oid</type> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Returns the actual version of the database's collation as it is currently
+        installed in the operating system.  If this is different from the
+        value in
+        <structname>pg_database</structname>.<structfield>datcollversion</structfield>,
+        then objects depending on the collation might need to be rebuilt.  See
+        also <xref linkend="sql-alterdatabase"/>.
+       </para></entry>
+      </row>
+
       <row>
        <entry role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/doc/src/sgml/ref/alter_collation.sgml b/doc/src/sgml/ref/alter_collation.sgml
index 892c466565..a8c831d728 100644
--- a/doc/src/sgml/ref/alter_collation.sgml
+++ b/doc/src/sgml/ref/alter_collation.sgml
@@ -151,7 +151,8 @@ <title>Notes</title>
    </para>
   </note>
   <para>
-   Currently, there is no version tracking for the database default collation.
+   For the database default collation, there is an analogous command
+   <literal>ALTER DATABASE ... REFRESH COLLATION VERSION</literal>.
   </para>
 
   <para>
diff --git a/doc/src/sgml/ref/alter_database.sgml b/doc/src/sgml/ref/alter_database.sgml
index 81e37536a3..89ed261b4c 100644
--- a/doc/src/sgml/ref/alter_database.sgml
+++ b/doc/src/sgml/ref/alter_database.sgml
@@ -35,6 +35,8 @@
 
 ALTER DATABASE <replaceable class="parameter">name</replaceable> SET TABLESPACE <replaceable class="parameter">new_tablespace</replaceable>
 
+ALTER DATABASE <replaceable class="parameter">name</replaceable> REFRESH COLLATION VERSION
+
 ALTER DATABASE <replaceable class="parameter">name</replaceable> SET <replaceable>configuration_parameter</replaceable> { TO | = } { <replaceable>value</replaceable> | DEFAULT }
 ALTER DATABASE <replaceable class="parameter">name</replaceable> SET <replaceable>configuration_parameter</replaceable> FROM CURRENT
 ALTER DATABASE <replaceable class="parameter">name</replaceable> RESET <replaceable>configuration_parameter</replaceable>
@@ -171,6 +173,16 @@ <title>Parameters</title>
     </listitem>
    </varlistentry>
 
+   <varlistentry>
+    <term><literal>REFRESH COLLATION VERSION</literal></term>
+    <listitem>
+     <para>
+      Update the database collation version.  See <xref
+      linkend="sql-altercollation-notes"/> for background.
+     </para>
+    </listitem>
+   </varlistentry>
+
      <varlistentry>
       <term><replaceable>configuration_parameter</replaceable></term>
       <term><replaceable>value</replaceable></term>
diff --git a/doc/src/sgml/ref/create_database.sgml b/doc/src/sgml/ref/create_database.sgml
index f22e28dc81..f70d0c75b4 100644
--- a/doc/src/sgml/ref/create_database.sgml
+++ b/doc/src/sgml/ref/create_database.sgml
@@ -28,6 +28,7 @@
            [ LOCALE [=] <replaceable class="parameter">locale</replaceable> ]
            [ LC_COLLATE [=] <replaceable class="parameter">lc_collate</replaceable> ]
            [ LC_CTYPE [=] <replaceable class="parameter">lc_ctype</replaceable> ]
+           [ COLLATION_VERSION = <replaceable>collation_version</replaceable> ]
            [ TABLESPACE [=] <replaceable class="parameter">tablespace_name</replaceable> ]
            [ ALLOW_CONNECTIONS [=] <replaceable class="parameter">allowconn</replaceable> ]
            [ CONNECTION LIMIT [=] <replaceable class="parameter">connlimit</replaceable> ]
@@ -158,6 +159,26 @@ <title>Parameters</title>
        </para>
       </listitem>
      </varlistentry>
+
+     <varlistentry>
+      <term><replaceable>collation_version</replaceable></term>
+
+      <listitem>
+       <para>
+        Specifies the collation version string to store with the database.
+        Normally, this should be omitted, which will cause the version to be
+        computed from the actual version of the database collation as provided
+        by the operating system.  This option is intended to be used by
+        <command>pg_upgrade</command> for copying the version from an existing
+        installation.
+       </para>
+
+       <para>
+        See also <xref linkend="sql-alterdatabase"/> for how to handle
+        database collation version mismatches.
+       </para>
+     </listitem>
+    </varlistentry>
      <varlistentry>
       <term><replaceable class="parameter">tablespace_name</replaceable></term>
       <listitem>
diff --git a/src/backend/commands/dbcommands.c b/src/backend/commands/dbcommands.c
index e673138cbd..5397a27754 100644
--- a/src/backend/commands/dbcommands.c
+++ b/src/backend/commands/dbcommands.c
@@ -36,6 +36,7 @@
 #include "catalog/indexing.h"
 #include "catalog/objectaccess.h"
 #include "catalog/pg_authid.h"
+#include "catalog/pg_collation.h"
 #include "catalog/pg_database.h"
 #include "catalog/pg_db_role_setting.h"
 #include "catalog/pg_subscription.h"
@@ -85,7 +86,8 @@ static bool get_db_info(const char *name, LOCKMODE lockmode,
 						Oid *dbIdP, Oid *ownerIdP,
 						int *encodingP, bool *dbIsTemplateP, bool *dbAllowConnP,
 						TransactionId *dbFrozenXidP, MultiXactId *dbMinMultiP,
-						Oid *dbTablespace, char **dbCollate, char **dbCtype);
+						Oid *dbTablespace, char **dbCollate, char **dbCtype,
+						char **dbCollversion);
 static bool have_createdb_privilege(void);
 static void remove_dbtablespaces(Oid db_id);
 static bool check_db_file_conflict(Oid db_id);
@@ -105,6 +107,7 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 	int			src_encoding = -1;
 	char	   *src_collate = NULL;
 	char	   *src_ctype = NULL;
+	char	   *src_collversion = NULL;
 	bool		src_istemplate;
 	bool		src_allowconn;
 	TransactionId src_frozenxid = InvalidTransactionId;
@@ -128,6 +131,7 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 	DefElem    *distemplate = NULL;
 	DefElem    *dallowconnections = NULL;
 	DefElem    *dconnlimit = NULL;
+	DefElem    *dcollversion = NULL;
 	char	   *dbname = stmt->dbname;
 	char	   *dbowner = NULL;
 	const char *dbtemplate = NULL;
@@ -138,6 +142,7 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 	bool		dbistemplate = false;
 	bool		dballowconnections = true;
 	int			dbconnlimit = -1;
+	char	   *dbcollversion = NULL;
 	int			notherbackends;
 	int			npreparedxacts;
 	createdb_failure_params fparms;
@@ -207,6 +212,12 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 				errorConflictingDefElem(defel, pstate);
 			dconnlimit = defel;
 		}
+		else if (strcmp(defel->defname, "collation_version") == 0)
+		{
+			if (dcollversion)
+				errorConflictingDefElem(defel, pstate);
+			dcollversion = defel;
+		}
 		else if (strcmp(defel->defname, "location") == 0)
 		{
 			ereport(WARNING,
@@ -305,6 +316,8 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 					 errmsg("invalid connection limit: %d", dbconnlimit)));
 	}
+	if (dcollversion)
+		dbcollversion = defGetString(dcollversion);
 
 	/* obtain OID of proposed owner */
 	if (dbowner)
@@ -342,7 +355,7 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 					 &src_dboid, &src_owner, &src_encoding,
 					 &src_istemplate, &src_allowconn,
 					 &src_frozenxid, &src_minmxid, &src_deftablespace,
-					 &src_collate, &src_ctype))
+					 &src_collate, &src_ctype, &src_collversion))
 		ereport(ERROR,
 				(errcode(ERRCODE_UNDEFINED_DATABASE),
 				 errmsg("template database \"%s\" does not exist",
@@ -424,6 +437,52 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 					 errhint("Use the same LC_CTYPE as in the template database, or use template0 as template.")));
 	}
 
+	/*
+	 * If we got a collation version for the template database, check that it
+	 * matches the actual OS collation version.  Otherwise error; the user
+	 * needs to fix the template database first.  Don't complain if a
+	 * collation version was specified explicitly as an statement option; that
+	 * is used by pg_upgrade to reproduce the old state exactly.
+	 *
+	 * (If the template database has no collation version, then either the
+	 * platform/provider does not support collation versioning, or it's
+	 * template0, for which we stipulate that it does not contain
+	 * collation-using objects.)
+	 */
+	if (src_collversion && !dcollversion)
+	{
+		char	   *actual_versionstr;
+
+		actual_versionstr = get_collation_actual_version(COLLPROVIDER_LIBC, dbcollate);
+		if (!actual_versionstr)
+			ereport(ERROR,
+					(errmsg("template database \"%s\" has a collation version, but no actual collation version could be determined",
+							dbtemplate)));
+
+		if (strcmp(actual_versionstr, src_collversion) != 0)
+			ereport(ERROR,
+					(errmsg("template database \"%s\" has a collation version mismatch",
+							dbtemplate),
+					 errdetail("The template database was created using collation version %s, "
+							   "but the operating system provides version %s.",
+							   src_collversion, actual_versionstr),
+					 errhint("Rebuild all objects affected by collation in the template database and run "
+							 "ALTER DATABASE %s REFRESH COLLATION VERSION, "
+							 "or build PostgreSQL with the right library version.",
+							 quote_identifier(dbtemplate))));
+	}
+
+	if (dbcollversion == NULL)
+		dbcollversion = src_collversion;
+
+	/*
+	 * Normally, we copy the collation version from the template database.
+	 * This last resort only applies if the template database does not have a
+	 * collation version, which is normally only the case for template0.
+	 */
+	if (dbcollversion == NULL)
+		dbcollversion = get_collation_actual_version(COLLPROVIDER_LIBC, dbcollate);
+
 	/* Resolve default tablespace for new database */
 	if (dtablespacename && dtablespacename->arg)
 	{
@@ -578,6 +637,10 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 	new_record[Anum_pg_database_dattablespace - 1] = ObjectIdGetDatum(dst_deftablespace);
 	new_record[Anum_pg_database_datcollate - 1] = CStringGetTextDatum(dbcollate);
 	new_record[Anum_pg_database_datctype - 1] = CStringGetTextDatum(dbctype);
+	if (dbcollversion)
+		new_record[Anum_pg_database_datcollversion - 1] = CStringGetTextDatum(dbcollversion);
+	else
+		new_record_nulls[Anum_pg_database_datcollversion - 1] = true;
 
 	/*
 	 * We deliberately set datacl to default (NULL), rather than copying it
@@ -844,7 +907,7 @@ dropdb(const char *dbname, bool missing_ok, bool force)
 	pgdbrel = table_open(DatabaseRelationId, RowExclusiveLock);
 
 	if (!get_db_info(dbname, AccessExclusiveLock, &db_id, NULL, NULL,
-					 &db_istemplate, NULL, NULL, NULL, NULL, NULL, NULL))
+					 &db_istemplate, NULL, NULL, NULL, NULL, NULL, NULL, NULL))
 	{
 		if (!missing_ok)
 		{
@@ -1043,7 +1106,7 @@ RenameDatabase(const char *oldname, const char *newname)
 	rel = table_open(DatabaseRelationId, RowExclusiveLock);
 
 	if (!get_db_info(oldname, AccessExclusiveLock, &db_id, NULL, NULL,
-					 NULL, NULL, NULL, NULL, NULL, NULL, NULL))
+					 NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL))
 		ereport(ERROR,
 				(errcode(ERRCODE_UNDEFINED_DATABASE),
 				 errmsg("database \"%s\" does not exist", oldname)));
@@ -1156,7 +1219,7 @@ movedb(const char *dbname, const char *tblspcname)
 	pgdbrel = table_open(DatabaseRelationId, RowExclusiveLock);
 
 	if (!get_db_info(dbname, AccessExclusiveLock, &db_id, NULL, NULL,
-					 NULL, NULL, NULL, NULL, &src_tblspcoid, NULL, NULL))
+					 NULL, NULL, NULL, NULL, &src_tblspcoid, NULL, NULL, NULL))
 		ereport(ERROR,
 				(errcode(ERRCODE_UNDEFINED_DATABASE),
 				 errmsg("database \"%s\" does not exist", dbname)));
@@ -1643,6 +1706,88 @@ AlterDatabase(ParseState *pstate, AlterDatabaseStmt *stmt, bool isTopLevel)
 }
 
 
+/*
+ * ALTER DATABASE name REFRESH COLLATION VERSION
+ */
+ObjectAddress
+AlterDatabaseRefreshColl(AlterDatabaseRefreshCollStmt *stmt)
+{
+	Relation	rel;
+	ScanKeyData scankey;
+	SysScanDesc scan;
+	Oid			db_id;
+	HeapTuple	tuple;
+	Form_pg_database datForm;
+	ObjectAddress address;
+	Datum		datum;
+	bool		isnull;
+	char	   *oldversion;
+	char	   *newversion;
+
+	rel = table_open(DatabaseRelationId, RowExclusiveLock);
+	ScanKeyInit(&scankey,
+				Anum_pg_database_datname,
+				BTEqualStrategyNumber, F_NAMEEQ,
+				CStringGetDatum(stmt->dbname));
+	scan = systable_beginscan(rel, DatabaseNameIndexId, true,
+							  NULL, 1, &scankey);
+	tuple = systable_getnext(scan);
+	if (!HeapTupleIsValid(tuple))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_DATABASE),
+				 errmsg("database \"%s\" does not exist", stmt->dbname)));
+
+	datForm = (Form_pg_database) GETSTRUCT(tuple);
+	db_id = datForm->oid;
+
+	if (!pg_database_ownercheck(db_id, GetUserId()))
+		aclcheck_error(ACLCHECK_NOT_OWNER, OBJECT_DATABASE,
+					   stmt->dbname);
+
+	datum = heap_getattr(tuple, Anum_pg_database_datcollversion, RelationGetDescr(rel), &isnull);
+	oldversion = isnull ? NULL : TextDatumGetCString(datum);
+
+	datum = heap_getattr(tuple, Anum_pg_database_datcollate, RelationGetDescr(rel), &isnull);
+	Assert(!isnull);
+	newversion = get_collation_actual_version(COLLPROVIDER_LIBC, TextDatumGetCString(datum));
+
+	/* cannot change from NULL to non-NULL or vice versa */
+	if ((!oldversion && newversion) || (oldversion && !newversion))
+		elog(ERROR, "invalid collation version change");
+	else if (oldversion && newversion && strcmp(newversion, oldversion) != 0)
+	{
+		bool		nulls[Natts_pg_database] = {0};
+		bool		replaces[Natts_pg_database] = {0};
+		Datum		values[Natts_pg_database] = {0};
+
+		ereport(NOTICE,
+				(errmsg("changing version from %s to %s",
+						oldversion, newversion)));
+
+		values[Anum_pg_database_datcollversion - 1] = CStringGetTextDatum(newversion);
+		replaces[Anum_pg_database_datcollversion - 1] = true;
+
+		tuple = heap_modify_tuple(tuple, RelationGetDescr(rel),
+								  values, nulls, replaces);
+		CatalogTupleUpdate(rel, &tuple->t_self, tuple);
+		heap_freetuple(tuple);
+	}
+	else
+		ereport(NOTICE,
+				(errmsg("version has not changed")));
+
+	InvokeObjectPostAlterHook(DatabaseRelationId, db_id, 0);
+
+	ObjectAddressSet(address, DatabaseRelationId, db_id);
+
+	systable_endscan(scan);
+
+	table_close(rel, NoLock);
+
+	return address;
+}
+
+
 /*
  * ALTER DATABASE name SET ...
  */
@@ -1785,6 +1930,34 @@ AlterDatabaseOwner(const char *dbname, Oid newOwnerId)
 }
 
 
+Datum
+pg_database_collation_actual_version(PG_FUNCTION_ARGS)
+{
+	Oid			dbid = PG_GETARG_OID(0);
+	HeapTuple	tp;
+	Datum		datum;
+	bool		isnull;
+	char	   *version;
+
+	tp = SearchSysCache1(DATABASEOID, ObjectIdGetDatum(dbid));
+	if (!HeapTupleIsValid(tp))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("database with OID %u does not exist", dbid)));
+
+	datum = SysCacheGetAttr(DATABASEOID, tp, Anum_pg_database_datcollate, &isnull);
+	Assert(!isnull);
+	version = get_collation_actual_version(COLLPROVIDER_LIBC, TextDatumGetCString(datum));
+
+	ReleaseSysCache(tp);
+
+	if (version)
+		PG_RETURN_TEXT_P(cstring_to_text(version));
+	else
+		PG_RETURN_NULL();
+}
+
+
 /*
  * Helper functions
  */
@@ -1800,7 +1973,8 @@ get_db_info(const char *name, LOCKMODE lockmode,
 			Oid *dbIdP, Oid *ownerIdP,
 			int *encodingP, bool *dbIsTemplateP, bool *dbAllowConnP,
 			TransactionId *dbFrozenXidP, MultiXactId *dbMinMultiP,
-			Oid *dbTablespace, char **dbCollate, char **dbCtype)
+			Oid *dbTablespace, char **dbCollate, char **dbCtype,
+			char **dbCollversion)
 {
 	bool		result = false;
 	Relation	relation;
@@ -1905,6 +2079,14 @@ get_db_info(const char *name, LOCKMODE lockmode,
 					Assert(!isnull);
 					*dbCtype = TextDatumGetCString(datum);
 				}
+				if (dbCollversion)
+				{
+					datum = SysCacheGetAttr(DATABASEOID, tuple, Anum_pg_database_datcollversion, &isnull);
+					if (isnull)
+						*dbCollversion = NULL;
+					else
+						*dbCollversion = TextDatumGetCString(datum);
+				}
 				ReleaseSysCache(tuple);
 				result = true;
 				break;
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index c4f3242506..92f93cfc72 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -10465,6 +10465,12 @@ AlterDatabaseStmt:
 														(Node *)makeString($6), @6));
 					$$ = (Node *)n;
 				 }
+			| ALTER DATABASE name REFRESH COLLATION VERSION_P
+				 {
+					AlterDatabaseRefreshCollStmt *n = makeNode(AlterDatabaseRefreshCollStmt);
+					n->dbname = $3;
+					$$ = (Node *)n;
+				 }
 		;
 
 AlterDatabaseSetStmt:
diff --git a/src/backend/tcop/utility.c b/src/backend/tcop/utility.c
index 83e4e37c78..3780c6e812 100644
--- a/src/backend/tcop/utility.c
+++ b/src/backend/tcop/utility.c
@@ -136,6 +136,7 @@ ClassifyUtilityCommandAsReadOnly(Node *parsetree)
 	switch (nodeTag(parsetree))
 	{
 		case T_AlterCollationStmt:
+		case T_AlterDatabaseRefreshCollStmt:
 		case T_AlterDatabaseSetStmt:
 		case T_AlterDatabaseStmt:
 		case T_AlterDefaultPrivilegesStmt:
@@ -779,6 +780,11 @@ standard_ProcessUtility(PlannedStmt *pstmt,
 			AlterDatabase(pstate, (AlterDatabaseStmt *) parsetree, isTopLevel);
 			break;
 
+		case T_AlterDatabaseRefreshCollStmt:
+			/* no event triggers for global objects */
+			AlterDatabaseRefreshColl((AlterDatabaseRefreshCollStmt *) parsetree);
+			break;
+
 		case T_AlterDatabaseSetStmt:
 			/* no event triggers for global objects */
 			AlterDatabaseSet((AlterDatabaseSetStmt *) parsetree);
@@ -2801,9 +2807,7 @@ CreateCommandTag(Node *parsetree)
 			break;
 
 		case T_AlterDatabaseStmt:
-			tag = CMDTAG_ALTER_DATABASE;
-			break;
-
+		case T_AlterDatabaseRefreshCollStmt:
 		case T_AlterDatabaseSetStmt:
 			tag = CMDTAG_ALTER_DATABASE;
 			break;
@@ -3444,9 +3448,7 @@ GetCommandLogLevel(Node *parsetree)
 			break;
 
 		case T_AlterDatabaseStmt:
-			lev = LOGSTMT_DDL;
-			break;
-
+		case T_AlterDatabaseRefreshCollStmt:
 		case T_AlterDatabaseSetStmt:
 			lev = LOGSTMT_DDL;
 			break;
diff --git a/src/backend/utils/init/postinit.c b/src/backend/utils/init/postinit.c
index ca53912f15..6c9f948dc5 100644
--- a/src/backend/utils/init/postinit.c
+++ b/src/backend/utils/init/postinit.c
@@ -32,6 +32,7 @@
 #include "catalog/catalog.h"
 #include "catalog/namespace.h"
 #include "catalog/pg_authid.h"
+#include "catalog/pg_collation.h"
 #include "catalog/pg_database.h"
 #include "catalog/pg_db_role_setting.h"
 #include "catalog/pg_tablespace.h"
@@ -418,6 +419,39 @@ CheckMyDatabase(const char *name, bool am_superuser, bool override_allow_connect
 						   " which is not recognized by setlocale().", ctype),
 				 errhint("Recreate the database with another locale or install the missing locale.")));
 
+	/*
+	 * Check collation version.  See similar code in
+	 * pg_newlocale_from_collation().  Note that here we warn instead of error
+	 * in any case, so that we don't prevent connecting.
+	 */
+	datum = SysCacheGetAttr(DATABASEOID, tup, Anum_pg_database_datcollversion,
+							&isnull);
+	if (!isnull)
+	{
+		char	   *actual_versionstr;
+		char	   *collversionstr;
+
+		collversionstr = TextDatumGetCString(datum);
+
+		actual_versionstr = get_collation_actual_version(COLLPROVIDER_LIBC, collate);
+		if (!actual_versionstr)
+			ereport(WARNING,
+					(errmsg("database \"%s\" has no actual collation version, but a version was recorded",
+							name)));
+
+		if (strcmp(actual_versionstr, collversionstr) != 0)
+			ereport(WARNING,
+					(errmsg("database \"%s\" has a collation version mismatch",
+							name),
+					 errdetail("The database was created using collation version %s, "
+							   "but the operating system provides version %s.",
+							   collversionstr, actual_versionstr),
+					 errhint("Rebuild all objects affected by collation in this database and run "
+							 "ALTER DATABASE %s REFRESH COLLATION VERSION, "
+							 "or build PostgreSQL with the right library version.",
+							 quote_identifier(name))));
+	}
+
 	/* Make the locale settings visible as GUC variables, too */
 	SetConfigOption("lc_collate", collate, PGC_INTERNAL, PGC_S_OVERRIDE);
 	SetConfigOption("lc_ctype", ctype, PGC_INTERNAL, PGC_S_OVERRIDE);
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index d78e8e67b8..97f15971e2 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -1857,6 +1857,18 @@ make_template0(FILE *cmdfd)
 		"CREATE DATABASE template0 IS_TEMPLATE = true ALLOW_CONNECTIONS = false OID = "
 		CppAsString2(Template0ObjectId) ";\n\n",
 
+		/*
+		 * template0 shouldn't have any collation-dependent objects, so unset
+		 * the collation version.  This disables collation version checks when
+		 * making a new database from it.
+		 */
+		"UPDATE pg_database SET datcollversion = NULL WHERE datname = 'template0';\n\n",
+
+		/*
+		 * While we are here, do set the collation version on template1.
+		 */
+		"UPDATE pg_database SET datcollversion = pg_database_collation_actual_version(oid) WHERE datname = 'template1';\n\n",
+
 		/*
 		 * Explicitly revoke public create-schema and create-temp-table
 		 * privileges in template1 and template0; else the latter would be on
diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index 3499c0a4d5..a3b36ecf21 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -2761,6 +2761,7 @@ dumpDatabase(Archive *fout)
 				i_acldefault,
 				i_datistemplate,
 				i_datconnlimit,
+				i_datcollversion,
 				i_tablespace;
 	CatalogId	dbCatId;
 	DumpId		dbDumpId;
@@ -2792,6 +2793,10 @@ dumpDatabase(Archive *fout)
 		appendPQExpBuffer(dbQry, "datminmxid, ");
 	else
 		appendPQExpBuffer(dbQry, "0 AS datminmxid, ");
+	if (fout->remoteVersion >= 150000)
+		appendPQExpBuffer(dbQry, "datcollversion, ");
+	else
+		appendPQExpBuffer(dbQry, "NULL AS datcollversion, ");
 	appendPQExpBuffer(dbQry,
 					  "(SELECT spcname FROM pg_tablespace t WHERE t.oid = dattablespace) AS tablespace, "
 					  "shobj_description(oid, 'pg_database') AS description "
@@ -2813,6 +2818,7 @@ dumpDatabase(Archive *fout)
 	i_acldefault = PQfnumber(res, "acldefault");
 	i_datistemplate = PQfnumber(res, "datistemplate");
 	i_datconnlimit = PQfnumber(res, "datconnlimit");
+	i_datcollversion = PQfnumber(res, "datcollversion");
 	i_tablespace = PQfnumber(res, "tablespace");
 
 	dbCatId.tableoid = atooid(PQgetvalue(res, 0, i_tableoid));
@@ -2872,6 +2878,21 @@ dumpDatabase(Archive *fout)
 		}
 	}
 
+	/*
+	 * For binary upgrade, carry over the collation version.  For normal
+	 * dump/restore, omit the version, so that it is computed upon restore.
+	 */
+	if (dopt->binary_upgrade)
+	{
+		if (!PQgetisnull(res, 0, i_datcollversion))
+		{
+			appendPQExpBufferStr(creaQry, " COLLATION_VERSION = ");
+			appendStringLiteralAH(creaQry,
+								  PQgetvalue(res, 0, i_datcollversion),
+								  fout);
+		}
+	}
+
 	/*
 	 * Note: looking at dopt->outputNoTablespaces here is completely the wrong
 	 * thing; the decision whether to specify a tablespace should be left till
diff --git a/src/bin/psql/tab-complete.c b/src/bin/psql/tab-complete.c
index 25d3abbcf1..0b534874d3 100644
--- a/src/bin/psql/tab-complete.c
+++ b/src/bin/psql/tab-complete.c
@@ -1849,7 +1849,7 @@ psql_completion(const char *text, int start, int end)
 
 	/* ALTER DATABASE <name> */
 	else if (Matches("ALTER", "DATABASE", MatchAny))
-		COMPLETE_WITH("RESET", "SET", "OWNER TO", "RENAME TO",
+		COMPLETE_WITH("RESET", "SET", "OWNER TO", "REFRESH COLLATION VERSION", "RENAME TO",
 					  "IS_TEMPLATE", "ALLOW_CONNECTIONS",
 					  "CONNECTION LIMIT");
 
diff --git a/src/include/catalog/pg_database.h b/src/include/catalog/pg_database.h
index 90b43a4ecc..76adbd4aad 100644
--- a/src/include/catalog/pg_database.h
+++ b/src/include/catalog/pg_database.h
@@ -65,6 +65,9 @@ CATALOG(pg_database,1262,DatabaseRelationId) BKI_SHARED_RELATION BKI_ROWTYPE_OID
 	/* LC_CTYPE setting */
 	text		datctype BKI_FORCE_NOT_NULL;
 
+	/* provider-dependent version of collation data */
+	text		datcollversion BKI_DEFAULT(_null_);
+
 	/* access permissions */
 	aclitem		datacl[1];
 #endif
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 62f36daa98..7f1ee97f55 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -11627,6 +11627,11 @@
   proname => 'pg_collation_actual_version', procost => '100',
   provolatile => 'v', prorettype => 'text', proargtypes => 'oid',
   prosrc => 'pg_collation_actual_version' },
+{ oid => '9167',
+  descr => 'get actual version of database collation from operating system',
+  proname => 'pg_database_collation_actual_version', procost => '100',
+  provolatile => 'v', prorettype => 'text', proargtypes => 'oid',
+  prosrc => 'pg_database_collation_actual_version' },
 
 # system management/monitoring related functions
 { oid => '3353', descr => 'list files in the log directory',
diff --git a/src/include/commands/dbcommands.h b/src/include/commands/dbcommands.h
index b1e8b5eb96..c4947fa71f 100644
--- a/src/include/commands/dbcommands.h
+++ b/src/include/commands/dbcommands.h
@@ -24,6 +24,7 @@ extern void dropdb(const char *dbname, bool missing_ok, bool force);
 extern void DropDatabase(ParseState *pstate, DropdbStmt *stmt);
 extern ObjectAddress RenameDatabase(const char *oldname, const char *newname);
 extern Oid	AlterDatabase(ParseState *pstate, AlterDatabaseStmt *stmt, bool isTopLevel);
+extern ObjectAddress AlterDatabaseRefreshColl(AlterDatabaseRefreshCollStmt *stmt);
 extern Oid	AlterDatabaseSet(AlterDatabaseSetStmt *stmt);
 extern ObjectAddress AlterDatabaseOwner(const char *dbname, Oid newOwnerId);
 
diff --git a/src/include/nodes/nodes.h b/src/include/nodes/nodes.h
index da35f2c272..5d075f0c34 100644
--- a/src/include/nodes/nodes.h
+++ b/src/include/nodes/nodes.h
@@ -370,6 +370,7 @@ typedef enum NodeTag
 	T_CheckPointStmt,
 	T_CreateSchemaStmt,
 	T_AlterDatabaseStmt,
+	T_AlterDatabaseRefreshCollStmt,
 	T_AlterDatabaseSetStmt,
 	T_AlterRoleSetStmt,
 	T_CreateConversionStmt,
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 37fcc4c9b5..34218b718c 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -3308,6 +3308,12 @@ typedef struct AlterDatabaseStmt
 	List	   *options;		/* List of DefElem nodes */
 } AlterDatabaseStmt;
 
+typedef struct AlterDatabaseRefreshCollStmt
+{
+	NodeTag		type;
+	char	   *dbname;
+} AlterDatabaseRefreshCollStmt;
+
 typedef struct AlterDatabaseSetStmt
 {
 	NodeTag		type;
diff --git a/src/test/regress/expected/collate.icu.utf8.out b/src/test/regress/expected/collate.icu.utf8.out
index 70133df804..9699ca16cf 100644
--- a/src/test/regress/expected/collate.icu.utf8.out
+++ b/src/test/regress/expected/collate.icu.utf8.out
@@ -1085,6 +1085,10 @@ DROP ROLE regress_test_role;
 -- ALTER
 ALTER COLLATION "en-x-icu" REFRESH VERSION;
 NOTICE:  version has not changed
+-- also test for database while we are here
+SELECT current_database() AS datname \gset
+ALTER DATABASE :"datname" REFRESH COLLATION VERSION;
+NOTICE:  version has not changed
 -- dependencies
 CREATE COLLATION test0 FROM "C";
 CREATE TABLE collate_dep_test1 (a int, b text COLLATE test0);
diff --git a/src/test/regress/expected/collate.linux.utf8.out b/src/test/regress/expected/collate.linux.utf8.out
index f06ae543e4..f2d0eb94f2 100644
--- a/src/test/regress/expected/collate.linux.utf8.out
+++ b/src/test/regress/expected/collate.linux.utf8.out
@@ -1096,6 +1096,10 @@ DROP ROLE regress_test_role;
 -- ALTER
 ALTER COLLATION "en_US" REFRESH VERSION;
 NOTICE:  version has not changed
+-- also test for database while we are here
+SELECT current_database() AS datname \gset
+ALTER DATABASE :"datname" REFRESH COLLATION VERSION;
+NOTICE:  version has not changed
 -- dependencies
 CREATE COLLATION test0 FROM "C";
 CREATE TABLE collate_dep_test1 (a int, b text COLLATE test0);
diff --git a/src/test/regress/sql/collate.icu.utf8.sql b/src/test/regress/sql/collate.icu.utf8.sql
index 9cee3d0042..242a7ce6b7 100644
--- a/src/test/regress/sql/collate.icu.utf8.sql
+++ b/src/test/regress/sql/collate.icu.utf8.sql
@@ -409,6 +409,10 @@ CREATE COLLATION test5 FROM test0;
 
 ALTER COLLATION "en-x-icu" REFRESH VERSION;
 
+-- also test for database while we are here
+SELECT current_database() AS datname \gset
+ALTER DATABASE :"datname" REFRESH COLLATION VERSION;
+
 
 -- dependencies
 
diff --git a/src/test/regress/sql/collate.linux.utf8.sql b/src/test/regress/sql/collate.linux.utf8.sql
index cbbd2203e4..0f6dd1b02e 100644
--- a/src/test/regress/sql/collate.linux.utf8.sql
+++ b/src/test/regress/sql/collate.linux.utf8.sql
@@ -410,6 +410,10 @@ CREATE COLLATION test5 FROM test0;
 
 ALTER COLLATION "en_US" REFRESH VERSION;
 
+-- also test for database while we are here
+SELECT current_database() AS datname \gset
+ALTER DATABASE :"datname" REFRESH COLLATION VERSION;
+
 
 -- dependencies
 
-- 
2.35.1