Revert per-index collation version tracking feature.

Design problems were discovered in the handling of composite types and
record types that would cause some relevant versions not to be recorded.
Misgivings were also expressed about the use of the pg_depend catalog
for this purpose.  We're out of time for this release so we'll revert
and try again.

Commits reverted:

1bf946bd: Doc: Document known problem with Windows collation versions.
cf002008: Remove no-longer-relevant test case.
ef387bed: Fix bogus collation-version-recording logic.
0fb0a050: Hide internal error for pg_collation_actual_version(<bad OID>).
ff942057: Suppress "warning: variable 'collcollate' set but not used".
d50e3b1f: Fix assertion in collation version lookup.
f24b1569: Rethink extraction of collation dependencies.
257836a7: Track collation versions for indexes.
cd6f479e: Add pg_depend.refobjversion.
7d1297df: Remove pg_collation.collversion.

Discussion: https://postgr.es/m/CA%2BhUKGLhj5t1fcjqAu8iD9B3ixJtsTNqyCCD4V0aTO9kAKAjjA%40mail.gmail.com

3 files changed, 104 insertions, 33 deletions

diff --git a/src/backend/commands/collationcmds.c b/src/backend/commands/collationcmds.c
index b8ec6f57564..ebb0994db32 100644
--- a/src/backend/commands/collationcmds.c
+++ b/src/backend/commands/collationcmds.c
@@ -62,12 +62,14 @@ DefineCollation(ParseState *pstate, List *names, List *parameters, bool if_not_e
 	DefElem    *lcctypeEl = NULL;
 	DefElem    *providerEl = NULL;
 	DefElem    *deterministicEl = NULL;
+	DefElem    *versionEl = NULL;
 	char	   *collcollate = NULL;
 	char	   *collctype = NULL;
 	char	   *collproviderstr = NULL;
 	bool		collisdeterministic = true;
 	int			collencoding = 0;
 	char		collprovider = 0;
+	char	   *collversion = NULL;
 	Oid			newoid;
 	ObjectAddress address;
 
@@ -95,6 +97,8 @@ DefineCollation(ParseState *pstate, List *names, List *parameters, bool if_not_e
 			defelp = &providerEl;
 		else if (strcmp(defel->defname, "deterministic") == 0)
 			defelp = &deterministicEl;
+		else if (strcmp(defel->defname, "version") == 0)
+			defelp = &versionEl;
 		else
 		{
 			ereport(ERROR,
@@ -163,6 +167,9 @@ DefineCollation(ParseState *pstate, List *names, List *parameters, bool if_not_e
 	if (deterministicEl)
 		collisdeterministic = defGetBoolean(deterministicEl);
 
+	if (versionEl)
+		collversion = defGetString(versionEl);
+
 	if (collproviderstr)
 	{
 		if (pg_strcasecmp(collproviderstr, "icu") == 0)
@@ -209,6 +216,9 @@ DefineCollation(ParseState *pstate, List *names, List *parameters, bool if_not_e
 		}
 	}
 
+	if (!collversion)
+		collversion = get_collation_actual_version(collprovider, collcollate);
+
 	newoid = CollationCreate(collName,
 							 collNamespace,
 							 GetUserId(),
@@ -217,6 +227,7 @@ DefineCollation(ParseState *pstate, List *names, List *parameters, bool if_not_e
 							 collencoding,
 							 collcollate,
 							 collctype,
+							 collversion,
 							 if_not_exists,
 							 false);	/* not quiet */
 
@@ -267,13 +278,101 @@ IsThereCollationInNamespace(const char *collname, Oid nspOid)
 						collname, get_namespace_name(nspOid))));
 }
 
+/*
+ * ALTER COLLATION
+ */
+ObjectAddress
+AlterCollation(AlterCollationStmt *stmt)
+{
+	Relation	rel;
+	Oid			collOid;
+	HeapTuple	tup;
+	Form_pg_collation collForm;
+	Datum		collversion;
+	bool		isnull;
+	char	   *oldversion;
+	char	   *newversion;
+	ObjectAddress address;
+
+	rel = table_open(CollationRelationId, RowExclusiveLock);
+	collOid = get_collation_oid(stmt->collname, false);
+
+	if (!pg_collation_ownercheck(collOid, GetUserId()))
+		aclcheck_error(ACLCHECK_NOT_OWNER, OBJECT_COLLATION,
+					   NameListToString(stmt->collname));
+
+	tup = SearchSysCacheCopy1(COLLOID, ObjectIdGetDatum(collOid));
+	if (!HeapTupleIsValid(tup))
+		elog(ERROR, "cache lookup failed for collation %u", collOid);
+
+	collForm = (Form_pg_collation) GETSTRUCT(tup);
+	collversion = SysCacheGetAttr(COLLOID, tup, Anum_pg_collation_collversion,
+								  &isnull);
+	oldversion = isnull ? NULL : TextDatumGetCString(collversion);
+
+	newversion = get_collation_actual_version(collForm->collprovider, NameStr(collForm->collcollate));
+
+	/* 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_collation];
+		bool		replaces[Natts_pg_collation];
+		Datum		values[Natts_pg_collation];
+
+		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_collation_collversion - 1] = CStringGetTextDatum(newversion);
+		replaces[Anum_pg_collation_collversion - 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(CollationRelationId, collOid, 0);
+
+	ObjectAddressSet(address, CollationRelationId, collOid);
+
+	heap_freetuple(tup);
+	table_close(rel, NoLock);
+
+	return address;
+}
+
+
 Datum
 pg_collation_actual_version(PG_FUNCTION_ARGS)
 {
 	Oid			collid = PG_GETARG_OID(0);
+	HeapTuple	tp;
+	char	   *collcollate;
+	char		collprovider;
 	char	   *version;
 
-	version = get_collation_version_for_oid(collid, true);
+	tp = SearchSysCache1(COLLOID, ObjectIdGetDatum(collid));
+	if (!HeapTupleIsValid(tp))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("collation with OID %u does not exist", collid)));
+
+	collcollate = pstrdup(NameStr(((Form_pg_collation) GETSTRUCT(tp))->collcollate));
+	collprovider = ((Form_pg_collation) GETSTRUCT(tp))->collprovider;
+
+	ReleaseSysCache(tp);
+
+	version = get_collation_actual_version(collprovider, collcollate);
 
 	if (version)
 		PG_RETURN_TEXT_P(cstring_to_text(version));
@@ -495,6 +594,7 @@ pg_import_system_collations(PG_FUNCTION_ARGS)
 			collid = CollationCreate(localebuf, nspid, GetUserId(),
 									 COLLPROVIDER_LIBC, true, enc,
 									 localebuf, localebuf,
+									 get_collation_actual_version(COLLPROVIDER_LIBC, localebuf),
 									 true, true);
 			if (OidIsValid(collid))
 			{
@@ -555,6 +655,7 @@ pg_import_system_collations(PG_FUNCTION_ARGS)
 			collid = CollationCreate(alias, nspid, GetUserId(),
 									 COLLPROVIDER_LIBC, true, enc,
 									 locale, locale,
+									 get_collation_actual_version(COLLPROVIDER_LIBC, locale),
 									 true, true);
 			if (OidIsValid(collid))
 			{
@@ -616,6 +717,7 @@ pg_import_system_collations(PG_FUNCTION_ARGS)
 									 nspid, GetUserId(),
 									 COLLPROVIDER_ICU, true, -1,
 									 collcollate, collcollate,
+									 get_collation_actual_version(COLLPROVIDER_ICU, collcollate),
 									 true, true);
 			if (OidIsValid(collid))
 			{
diff --git a/src/backend/commands/statscmds.c b/src/backend/commands/statscmds.c
index df4768952d5..acae19176c0 100644
--- a/src/backend/commands/statscmds.c
+++ b/src/backend/commands/statscmds.c
@@ -555,7 +555,7 @@ CreateStatistics(CreateStatsStmt *stmt)
 										(Node *) stxexprs,
 										relid,
 										DEPENDENCY_NORMAL,
-										DEPENDENCY_AUTO, false, true);
+										DEPENDENCY_AUTO, false);
 
 	/*
 	 * Also add dependencies on namespace and owner.  These are required
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 0da61784d7a..3b5d4116839 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -94,7 +94,6 @@
 #include "utils/lsyscache.h"
 #include "utils/memutils.h"
 #include "utils/partcache.h"
-#include "utils/pg_locale.h"
 #include "utils/relcache.h"
 #include "utils/ruleutils.h"
 #include "utils/snapmgr.h"
@@ -602,7 +601,6 @@ static void refuseDupeIndexAttach(Relation parentIdx, Relation partIdx,
 								  Relation partitionTbl);
 static List *GetParentedForeignKeyRefs(Relation partition);
 static void ATDetachCheckNoForeignKeyRefs(Relation partition);
-static void ATExecAlterCollationRefreshVersion(Relation rel, List *coll);
 static char GetAttributeCompression(Form_pg_attribute att, char *compression);
 
 
@@ -4333,10 +4331,6 @@ AlterTableGetLockLevel(List *cmds)
 				cmd_lockmode = AccessShareLock;
 				break;
 
-			case AT_AlterCollationRefreshVersion:
-				cmd_lockmode = AccessExclusiveLock;
-				break;
-
 			default:			/* oops */
 				elog(ERROR, "unrecognized alter table type: %d",
 					 (int) cmd->subtype);
@@ -4524,12 +4518,6 @@ ATPrepCmd(List **wqueue, Relation rel, AlterTableCmd *cmd,
 			/* This command never recurses */
 			pass = AT_PASS_MISC;
 			break;
-		case AT_AlterCollationRefreshVersion:	/* ALTER COLLATION ... REFRESH
-												 * VERSION */
-			ATSimplePermissions(rel, ATT_INDEX);
-			/* This command never recurses */
-			pass = AT_PASS_MISC;
-			break;
 		case AT_SetStorage:		/* ALTER COLUMN SET STORAGE */
 			ATSimplePermissions(rel, ATT_TABLE | ATT_MATVIEW | ATT_FOREIGN_TABLE);
 			ATSimpleRecursion(wqueue, rel, cmd, recurse, lockmode, context);
@@ -5139,11 +5127,6 @@ ATExecCmd(List **wqueue, AlteredTableInfo *tab,
 		case AT_DetachPartitionFinalize:
 			ATExecDetachPartitionFinalize(rel, ((PartitionCmd *) cmd->def)->name);
 			break;
-		case AT_AlterCollationRefreshVersion:
-			/* ATPrepCmd ensured it must be an index */
-			Assert(rel->rd_rel->relkind == RELKIND_INDEX);
-			ATExecAlterCollationRefreshVersion(rel, cmd->object);
-			break;
 		default:				/* oops */
 			elog(ERROR, "unrecognized alter table type: %d",
 				 (int) cmd->subtype);
@@ -18627,20 +18610,6 @@ ATDetachCheckNoForeignKeyRefs(Relation partition)
 }
 
 /*
- * ALTER INDEX ... ALTER COLLATION ... REFRESH VERSION
- *
- * Update refobjversion to the current collation version by force.  This clears
- * warnings about version mismatches without the need to run REINDEX,
- * potentially hiding corruption due to ordering changes.
- */
-static void
-ATExecAlterCollationRefreshVersion(Relation rel, List *coll)
-{
-	index_update_collation_versions(rel->rd_id, get_collation_oid(coll, false));
-	CacheInvalidateRelcache(rel);
-}
-
-/*
  * resolve column compression specification to compression method.
  */
 static char