DDL support for collations

- collowner field
- CREATE COLLATION
- ALTER COLLATION
- DROP COLLATION
- COMMENT ON COLLATION
- integration with extensions
- pg_dump support for the above
- dependency management
- psql tab completion
- psql \dO command

src/backend/commands/Makefile

@@ -13,7 +13,7 @@ top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
 OBJS = aggregatecmds.o alter.o analyze.o async.o cluster.o comment.o  \
-	constraint.o conversioncmds.o copy.o \
+	collationcmds.o constraint.o conversioncmds.o copy.o \
 	dbcommands.o define.o discard.o explain.o extension.o \
 	foreigncmds.o functioncmds.o \
 	indexcmds.o lockcmds.o operatorcmds.o opclasscmds.o \

src/backend/commands/alter.c

@@ -20,6 +20,7 @@
 #include "catalog/pg_largeobject.h"
 #include "catalog/pg_namespace.h"
 #include "commands/alter.h"
+#include "commands/collationcmds.h"
 #include "commands/conversioncmds.h"
 #include "commands/dbcommands.h"
 #include "commands/defrem.h"
@@ -53,6 +54,10 @@ ExecRenameStmt(RenameStmt *stmt)
 			RenameAggregate(stmt->object, stmt->objarg, stmt->newname);
 			break;
 
+		case OBJECT_COLLATION:
+			RenameCollation(stmt->object, stmt->newname);
+			break;
+
 		case OBJECT_CONVERSION:
 			RenameConversion(stmt->object, stmt->newname);
 			break;
@@ -185,6 +190,10 @@ ExecAlterObjectSchemaStmt(AlterObjectSchemaStmt *stmt)
 								   stmt->newschema);
 			break;
 
+		case OBJECT_COLLATION:
+			AlterCollationNamespace(stmt->object, stmt->newschema);
+			break;
+
 		case OBJECT_CONVERSION:
 			AlterConversionNamespace(stmt->object, stmt->newschema);
 			break;
@@ -302,6 +311,10 @@ AlterObjectNamespace_oid(Oid classId, Oid objid, Oid nspOid)
 			oldNspOid = AlterTypeNamespace_oid(objid, nspOid);
 			break;
 
+		case OCLASS_COLLATION:
+			oldNspOid = AlterCollationNamespace_oid(objid, nspOid);
+			break;
+
 		case OCLASS_CONVERSION:
 			oldNspOid = AlterConversionNamespace_oid(objid, nspOid);
 			break;
@@ -478,6 +491,10 @@ ExecAlterOwnerStmt(AlterOwnerStmt *stmt)
 			AlterAggregateOwner(stmt->object, stmt->objarg, newowner);
 			break;
 
+		case OBJECT_COLLATION:
+			AlterCollationOwner(stmt->object, newowner);
+			break;
+
 		case OBJECT_CONVERSION:
 			AlterConversionOwner(stmt->object, newowner);
 			break;

src/backend/commands/collationcmds.c

@@ -0,0 +1,401 @@
+/*-------------------------------------------------------------------------
+ *
+ * collationcmds.c
+ *	  collation creation command support code
+ *
+ * Portions Copyright (c) 1996-2011, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/commands/collationcmds.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/heapam.h"
+#include "catalog/dependency.h"
+#include "catalog/indexing.h"
+#include "catalog/namespace.h"
+#include "catalog/pg_collation.h"
+#include "catalog/pg_collation_fn.h"
+#include "commands/alter.h"
+#include "commands/collationcmds.h"
+#include "commands/dbcommands.h"
+#include "commands/defrem.h"
+#include "mb/pg_wchar.h"
+#include "miscadmin.h"
+#include "parser/parse_type.h"
+#include "utils/acl.h"
+#include "utils/builtins.h"
+#include "utils/lsyscache.h"
+#include "utils/syscache.h"
+
+static void AlterCollationOwner_internal(Relation rel, Oid collationOid,
+							  Oid newOwnerId);
+
+/*
+ * CREATE COLLATION
+ */
+void
+DefineCollation(List *names, List *parameters)
+{
+	char	   *collName;
+	Oid			collNamespace;
+	AclResult	aclresult;
+	ListCell   *pl;
+	DefElem	   *fromEl = NULL;
+	DefElem	   *localeEl = NULL;
+	DefElem	   *lccollateEl = NULL;
+	DefElem	   *lcctypeEl = NULL;
+	char	   *collcollate = NULL;
+	char	   *collctype = NULL;
+
+	collNamespace = QualifiedNameGetCreationNamespace(names, &collName);
+
+	aclresult = pg_namespace_aclcheck(collNamespace, GetUserId(), ACL_CREATE);
+	if (aclresult != ACLCHECK_OK)
+		aclcheck_error(aclresult, ACL_KIND_NAMESPACE,
+					   get_namespace_name(collNamespace));
+
+	foreach(pl, parameters)
+	{
+		DefElem	   *defel = (DefElem *) lfirst(pl);
+		DefElem   **defelp;
+
+		if (pg_strcasecmp(defel->defname, "from") == 0)
+			defelp = &fromEl;
+		else if (pg_strcasecmp(defel->defname, "locale") == 0)
+			defelp = &localeEl;
+		else if (pg_strcasecmp(defel->defname, "lc_collate") == 0)
+			defelp = &lccollateEl;
+		else if (pg_strcasecmp(defel->defname, "lc_ctype") == 0)
+			defelp = &lcctypeEl;
+		else
+		{
+			ereport(ERROR,
+					(errcode(ERRCODE_SYNTAX_ERROR),
+					 errmsg("collation attribute \"%s\" not recognized",
+							defel->defname)));
+			break;
+		}
+
+		*defelp = defel;
+	}
+
+	if ((localeEl && (lccollateEl || lcctypeEl))
+		|| (fromEl && list_length(parameters) != 1))
+		ereport(ERROR,
+				(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg("conflicting or redundant options")));
+
+	if (fromEl)
+	{
+		Oid			collid;
+		HeapTuple	tp;
+
+		collid = LookupCollation(NULL, defGetQualifiedName(fromEl), -1);
+		tp = SearchSysCache1(COLLOID, ObjectIdGetDatum(collid));
+		if (!HeapTupleIsValid(tp))
+			elog(ERROR, "cache lookup failed for collation %u", collid);
+
+		collcollate = pstrdup(NameStr(((Form_pg_collation) GETSTRUCT(tp))->collcollate));
+		collctype = pstrdup(NameStr(((Form_pg_collation) GETSTRUCT(tp))->collctype));
+
+		ReleaseSysCache(tp);
+	}
+
+	if (localeEl)
+	{
+		collcollate = defGetString(localeEl);
+		collctype = defGetString(localeEl);
+	}
+
+	if (lccollateEl)
+		collcollate = defGetString(lccollateEl);
+
+	if (lcctypeEl)
+		collctype = defGetString(lcctypeEl);
+
+	if (!collcollate)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("parameter \"lc_collate\" parameter must be specified")));
+
+	if (!collctype)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("parameter \"lc_ctype\" must be specified")));
+
+	check_encoding_locale_matches(GetDatabaseEncoding(), collcollate, collctype);
+
+	CollationCreate(collName,
+					collNamespace,
+					GetUserId(),
+					GetDatabaseEncoding(),
+					collcollate,
+					collctype);
+}
+
+/*
+ * DROP COLLATION
+ */
+void
+DropCollationsCommand(DropStmt *drop)
+{
+	ObjectAddresses *objects;
+	ListCell   *cell;
+
+	/*
+	 * First we identify all the collations, then we delete them in a single
+	 * performMultipleDeletions() call.  This is to avoid unwanted DROP
+	 * RESTRICT errors if one of the collations depends on another. (Not that
+	 * that is very likely, but we may as well do this consistently.)
+	 */
+	objects = new_object_addresses();
+
+	foreach(cell, drop->objects)
+	{
+		List	   *name = (List *) lfirst(cell);
+		Oid			collationOid;
+		HeapTuple	tuple;
+		Form_pg_collation coll;
+		ObjectAddress object;
+
+		collationOid = get_collation_oid(name, drop->missing_ok);
+
+		if (!OidIsValid(collationOid))
+		{
+			ereport(NOTICE,
+					(errmsg("collation \"%s\" does not exist, skipping",
+							NameListToString(name))));
+			continue;
+		}
+
+		tuple = SearchSysCache1(COLLOID, ObjectIdGetDatum(collationOid));
+		if (!HeapTupleIsValid(tuple))
+			elog(ERROR, "cache lookup failed for collation %u",
+				 collationOid);
+		coll = (Form_pg_collation) GETSTRUCT(tuple);
+
+		/* Permission check: must own collation or its namespace */
+		if (!pg_collation_ownercheck(collationOid, GetUserId()) &&
+			!pg_namespace_ownercheck(coll->collnamespace, GetUserId()))
+			aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_COLLATION,
+						   NameStr(coll->collname));
+
+		object.classId = CollationRelationId;
+		object.objectId = collationOid;
+		object.objectSubId = 0;
+
+		add_exact_object_address(&object, objects);
+
+		ReleaseSysCache(tuple);
+	}
+
+	performMultipleDeletions(objects, drop->behavior);
+
+	free_object_addresses(objects);
+}
+
+/*
+ * Rename collation
+ */
+void
+RenameCollation(List *name, const char *newname)
+{
+	Oid			collationOid;
+	Oid			namespaceOid;
+	HeapTuple	tup;
+	Relation	rel;
+	AclResult	aclresult;
+
+	rel = heap_open(CollationRelationId, RowExclusiveLock);
+
+	collationOid = get_collation_oid(name, false);
+
+	tup = SearchSysCacheCopy1(COLLOID, ObjectIdGetDatum(collationOid));
+	if (!HeapTupleIsValid(tup)) /* should not happen */
+		elog(ERROR, "cache lookup failed for collation %u", collationOid);
+
+	namespaceOid = ((Form_pg_collation) GETSTRUCT(tup))->collnamespace;
+
+	/* make sure the new name doesn't exist */
+	if (SearchSysCacheExists3(COLLNAMEENCNSP,
+							  CStringGetDatum(newname),
+							  Int32GetDatum(GetDatabaseEncoding()),
+							  ObjectIdGetDatum(namespaceOid)))
+		ereport(ERROR,
+				(errcode(ERRCODE_DUPLICATE_OBJECT),
+				 errmsg("collation \"%s\" for current database encoding \"%s\" already exists in schema \"%s\"",
+						newname,
+						GetDatabaseEncodingName(),
+						get_namespace_name(namespaceOid))));
+
+	/* must be owner */
+	if (!pg_collation_ownercheck(collationOid, GetUserId()))
+		aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_COLLATION,
+					   NameListToString(name));
+
+	/* must have CREATE privilege on namespace */
+	aclresult = pg_namespace_aclcheck(namespaceOid, GetUserId(), ACL_CREATE);
+	if (aclresult != ACLCHECK_OK)
+		aclcheck_error(aclresult, ACL_KIND_NAMESPACE,
+					   get_namespace_name(namespaceOid));
+
+	/* rename */
+	namestrcpy(&(((Form_pg_collation) GETSTRUCT(tup))->collname), newname);
+	simple_heap_update(rel, &tup->t_self, tup);
+	CatalogUpdateIndexes(rel, tup);
+
+	heap_close(rel, NoLock);
+	heap_freetuple(tup);
+}
+
+/*
+ * Change collation owner, by name
+ */
+void
+AlterCollationOwner(List *name, Oid newOwnerId)
+{
+	Oid			collationOid;
+	Relation	rel;
+
+	rel = heap_open(CollationRelationId, RowExclusiveLock);
+
+	collationOid = get_collation_oid(name, false);
+
+	AlterCollationOwner_internal(rel, collationOid, newOwnerId);
+
+	heap_close(rel, NoLock);
+}
+
+/*
+ * Change collation owner, by oid
+ */
+void
+AlterCollationOwner_oid(Oid collationOid, Oid newOwnerId)
+{
+	Relation	rel;
+
+	rel = heap_open(CollationRelationId, RowExclusiveLock);
+
+	AlterCollationOwner_internal(rel, collationOid, newOwnerId);
+
+	heap_close(rel, NoLock);
+}
+
+/*
+ * AlterCollationOwner_internal
+ *
+ * Internal routine for changing the owner.  rel must be pg_collation, already
+ * open and suitably locked; it will not be closed.
+ */
+static void
+AlterCollationOwner_internal(Relation rel, Oid collationOid, Oid newOwnerId)
+{
+	Form_pg_collation collForm;
+	HeapTuple	tup;
+
+	Assert(RelationGetRelid(rel) == CollationRelationId);
+
+	tup = SearchSysCacheCopy1(COLLOID, ObjectIdGetDatum(collationOid));
+	if (!HeapTupleIsValid(tup)) /* should not happen */
+		elog(ERROR, "cache lookup failed for collation %u", collationOid);
+
+	collForm = (Form_pg_collation) GETSTRUCT(tup);
+
+	/*
+	 * If the new owner is the same as the existing owner, consider the
+	 * command to have succeeded.  This is for dump restoration purposes.
+	 */
+	if (collForm->collowner != newOwnerId)
+	{
+		AclResult	aclresult;
+
+		/* Superusers can always do it */
+		if (!superuser())
+		{
+			/* Otherwise, must be owner of the existing object */
+			if (!pg_collation_ownercheck(HeapTupleGetOid(tup), GetUserId()))
+				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_COLLATION,
+							   NameStr(collForm->collname));
+
+			/* Must be able to become new owner */
+			check_is_member_of_role(GetUserId(), newOwnerId);
+
+			/* New owner must have CREATE privilege on namespace */
+			aclresult = pg_namespace_aclcheck(collForm->collnamespace,
+											  newOwnerId,
+											  ACL_CREATE);
+			if (aclresult != ACLCHECK_OK)
+				aclcheck_error(aclresult, ACL_KIND_NAMESPACE,
+							   get_namespace_name(collForm->collnamespace));
+		}
+
+		/*
+		 * Modify the owner --- okay to scribble on tup because it's a copy
+		 */
+		collForm->collowner = newOwnerId;
+
+		simple_heap_update(rel, &tup->t_self, tup);
+
+		CatalogUpdateIndexes(rel, tup);
+
+		/* Update owner dependency reference */
+		changeDependencyOnOwner(CollationRelationId, collationOid,
+								newOwnerId);
+	}
+
+	heap_freetuple(tup);
+}
+
+/*
+ * Execute ALTER COLLATION SET SCHEMA
+ */
+void
+AlterCollationNamespace(List *name, const char *newschema)
+{
+	Oid			collOid, nspOid;
+	Relation	rel;
+
+	rel = heap_open(CollationRelationId, RowExclusiveLock);
+
+	collOid = get_collation_oid(name, false);
+
+	/* get schema OID */
+	nspOid = LookupCreationNamespace(newschema);
+
+	AlterObjectNamespace(rel, COLLOID, -1,
+						 collOid, nspOid,
+						 Anum_pg_collation_collname,
+						 Anum_pg_collation_collnamespace,
+						 Anum_pg_collation_collowner,
+						 ACL_KIND_COLLATION);
+
+	heap_close(rel, NoLock);
+}
+
+/*
+ * Change collation schema, by oid
+ */
+Oid
+AlterCollationNamespace_oid(Oid collOid, Oid newNspOid)
+{
+	Oid         oldNspOid;
+	Relation	rel;
+
+	rel = heap_open(CollationRelationId, RowExclusiveLock);
+
+	oldNspOid = AlterObjectNamespace(rel, COLLOID, -1,
+									 collOid, newNspOid,
+									 Anum_pg_collation_collname,
+									 Anum_pg_collation_collnamespace,
+									 Anum_pg_collation_collowner,
+									 ACL_KIND_COLLATION);
+
+	heap_close(rel, RowExclusiveLock);
+
+	return oldNspOid;
+}

src/backend/commands/comment.c

@@ -133,6 +133,11 @@ CommentObject(CommentStmt *stmt)
 				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_NAMESPACE,
 							   strVal(linitial(stmt->objname)));
 			break;
+		case OBJECT_COLLATION:
+			if (!pg_collation_ownercheck(address.objectId, GetUserId()))
+				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_COLLATION,
+							   NameListToString(stmt->objname));
+			break;
 		case OBJECT_CONVERSION:
 			if (!pg_conversion_ownercheck(address.objectId, GetUserId()))
 				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_CONVERSION,

src/backend/commands/dbcommands.c

@@ -129,8 +129,6 @@ createdb(const CreatedbStmt *stmt)
 	char	   *dbctype = NULL;
 	int			encoding = -1;
 	int			dbconnlimit = -1;
-	int			ctype_encoding;
-	int			collate_encoding;
 	int			notherbackends;
 	int			npreparedxacts;
 	createdb_failure_params fparms;
@@ -334,60 +332,7 @@ createdb(const CreatedbStmt *stmt)
 				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
 				 errmsg("invalid locale name %s", dbctype)));
 
-	/*
-	 * Check whether chosen encoding matches chosen locale settings.  This
-	 * restriction is necessary because libc's locale-specific code usually
-	 * fails when presented with data in an encoding it's not expecting. We
-	 * allow mismatch in four cases:
-	 *
-	 * 1. locale encoding = SQL_ASCII, which means that the locale is C/POSIX
-	 * which works with any encoding.
-	 *
-	 * 2. locale encoding = -1, which means that we couldn't determine the
-	 * locale's encoding and have to trust the user to get it right.
-	 *
-	 * 3. selected encoding is UTF8 and platform is win32. This is because
-	 * UTF8 is a pseudo codepage that is supported in all locales since it's
-	 * converted to UTF16 before being used.
-	 *
-	 * 4. selected encoding is SQL_ASCII, but only if you're a superuser. This
-	 * is risky but we have historically allowed it --- notably, the
-	 * regression tests require it.
-	 *
-	 * Note: if you change this policy, fix initdb to match.
-	 */
-	ctype_encoding = pg_get_encoding_from_locale(dbctype, true);
-	collate_encoding = pg_get_encoding_from_locale(dbcollate, true);
-
-	if (!(ctype_encoding == encoding ||
-		  ctype_encoding == PG_SQL_ASCII ||
-		  ctype_encoding == -1 ||
-#ifdef WIN32
-		  encoding == PG_UTF8 ||
-#endif
-		  (encoding == PG_SQL_ASCII && superuser())))
-		ereport(ERROR,
-				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-				 errmsg("encoding %s does not match locale %s",
-						pg_encoding_to_char(encoding),
-						dbctype),
-			   errdetail("The chosen LC_CTYPE setting requires encoding %s.",
-						 pg_encoding_to_char(ctype_encoding))));
-
-	if (!(collate_encoding == encoding ||
-		  collate_encoding == PG_SQL_ASCII ||
-		  collate_encoding == -1 ||
-#ifdef WIN32
-		  encoding == PG_UTF8 ||
-#endif
-		  (encoding == PG_SQL_ASCII && superuser())))
-		ereport(ERROR,
-				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-				 errmsg("encoding %s does not match locale %s",
-						pg_encoding_to_char(encoding),
-						dbcollate),
-			 errdetail("The chosen LC_COLLATE setting requires encoding %s.",
-					   pg_encoding_to_char(collate_encoding))));
+	check_encoding_locale_matches(encoding, dbcollate, dbctype);
 
 	/*
 	 * Check that the new encoding and locale settings match the source
@@ -710,6 +655,65 @@ createdb(const CreatedbStmt *stmt)
 								PointerGetDatum(&fparms));
 }
 
+/*
+ * Check whether chosen encoding matches chosen locale settings.  This
+ * restriction is necessary because libc's locale-specific code usually
+ * fails when presented with data in an encoding it's not expecting. We
+ * allow mismatch in four cases:
+ *
+ * 1. locale encoding = SQL_ASCII, which means that the locale is C/POSIX
+ * which works with any encoding.
+ *
+ * 2. locale encoding = -1, which means that we couldn't determine the
+ * locale's encoding and have to trust the user to get it right.
+ *
+ * 3. selected encoding is UTF8 and platform is win32. This is because
+ * UTF8 is a pseudo codepage that is supported in all locales since it's
+ * converted to UTF16 before being used.
+ *
+ * 4. selected encoding is SQL_ASCII, but only if you're a superuser. This
+ * is risky but we have historically allowed it --- notably, the
+ * regression tests require it.
+ *
+ * Note: if you change this policy, fix initdb to match.
+ */
+void
+check_encoding_locale_matches(int encoding, const char *collate, const char *ctype)
+{
+	int ctype_encoding = pg_get_encoding_from_locale(ctype, true);
+	int collate_encoding = pg_get_encoding_from_locale(collate, true);
+
+	if (!(ctype_encoding == encoding ||
+		  ctype_encoding == PG_SQL_ASCII ||
+		  ctype_encoding == -1 ||
+#ifdef WIN32
+		  encoding == PG_UTF8 ||
+#endif
+		  (encoding == PG_SQL_ASCII && superuser())))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("encoding %s does not match locale %s",
+						pg_encoding_to_char(encoding),
+						ctype),
+			   errdetail("The chosen LC_CTYPE setting requires encoding %s.",
+						 pg_encoding_to_char(ctype_encoding))));
+
+	if (!(collate_encoding == encoding ||
+		  collate_encoding == PG_SQL_ASCII ||
+		  collate_encoding == -1 ||
+#ifdef WIN32
+		  encoding == PG_UTF8 ||
+#endif
+		  (encoding == PG_SQL_ASCII && superuser())))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("encoding %s does not match locale %s",
+						pg_encoding_to_char(encoding),
+						collate),
+			 errdetail("The chosen LC_COLLATE setting requires encoding %s.",
+					   pg_encoding_to_char(collate_encoding))));
+}
+
 /* Error cleanup callback for createdb */
 static void
 createdb_failure_callback(int code, Datum arg)

src/backend/commands/tablecmds.c

@@ -27,6 +27,7 @@
 #include "catalog/indexing.h"
 #include "catalog/namespace.h"
 #include "catalog/objectaccess.h"
+#include "catalog/pg_collation.h"
 #include "catalog/pg_constraint.h"
 #include "catalog/pg_depend.h"
 #include "catalog/pg_foreign_table.h"
@@ -293,7 +294,7 @@ static void ATPrepAddColumn(List **wqueue, Relation rel, bool recurse, bool recu
 				AlterTableCmd *cmd, LOCKMODE lockmode);
 static void ATExecAddColumn(AlteredTableInfo *tab, Relation rel,
 				ColumnDef *colDef, bool isOid, LOCKMODE lockmode);
-static void add_column_datatype_dependency(Oid relid, int32 attnum, Oid typid);
+static void add_column_datatype_dependency(Oid relid, int32 attnum, Oid typid, Oid collid);
 static void ATPrepAddOids(List **wqueue, Relation rel, bool recurse,
 			  AlterTableCmd *cmd, LOCKMODE lockmode);
 static void ATExecDropNotNull(Relation rel, const char *colName, LOCKMODE lockmode);
@@ -4369,14 +4370,14 @@ ATExecAddColumn(AlteredTableInfo *tab, Relation rel,
 	/*
 	 * Add needed dependency entries for the new column.
 	 */
-	add_column_datatype_dependency(myrelid, newattnum, attribute.atttypid);
+	add_column_datatype_dependency(myrelid, newattnum, attribute.atttypid, attribute.attcollation);
 }
 
 /*
  * Install a column's dependency on its datatype.
  */
 static void
-add_column_datatype_dependency(Oid relid, int32 attnum, Oid typid)
+add_column_datatype_dependency(Oid relid, int32 attnum, Oid typid, Oid collid)
 {
 	ObjectAddress myself,
 				referenced;
@@ -4388,6 +4389,14 @@ add_column_datatype_dependency(Oid relid, int32 attnum, Oid typid)
 	referenced.objectId = typid;
 	referenced.objectSubId = 0;
 	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	if (collid)
+	{
+		referenced.classId = CollationRelationId;
+		referenced.objectId = collid;
+		referenced.objectSubId = 0;
+		recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+	}
 }
 
 /*
@@ -6877,6 +6886,7 @@ ATExecAlterColumnType(AlteredTableInfo *tab, Relation rel,
 			case OCLASS_PROC:
 			case OCLASS_TYPE:
 			case OCLASS_CAST:
+			case OCLASS_COLLATION:
 			case OCLASS_CONVERSION:
 			case OCLASS_LANGUAGE:
 			case OCLASS_LARGEOBJECT:
@@ -6918,7 +6928,7 @@ ATExecAlterColumnType(AlteredTableInfo *tab, Relation rel,
 	/*
 	 * Now scan for dependencies of this column on other things.  The only
 	 * thing we should find is the dependency on the column datatype, which we
-	 * want to remove.
+	 * want to remove, and possibly an associated collation.
 	 */
 	ScanKeyInit(&key[0],
 				Anum_pg_depend_classid,
@@ -6943,8 +6953,10 @@ ATExecAlterColumnType(AlteredTableInfo *tab, Relation rel,
 		if (foundDep->deptype != DEPENDENCY_NORMAL)
 			elog(ERROR, "found unexpected dependency type '%c'",
 				 foundDep->deptype);
-		if (foundDep->refclassid != TypeRelationId ||
-			foundDep->refobjid != attTup->atttypid)
+		if (!(foundDep->refclassid == TypeRelationId &&
+			  foundDep->refobjid == attTup->atttypid) &&
+			!(foundDep->refclassid == CollationRelationId &&
+			  foundDep->refobjid == attTup->attcollation))
 			elog(ERROR, "found unexpected dependency for column");
 
 		simple_heap_delete(depRel, &depTup->t_self);
@@ -6977,7 +6989,7 @@ ATExecAlterColumnType(AlteredTableInfo *tab, Relation rel,
 	heap_close(attrelation, RowExclusiveLock);
 
 	/* Install dependency on new datatype */
-	add_column_datatype_dependency(RelationGetRelid(rel), attnum, targettype);
+	add_column_datatype_dependency(RelationGetRelid(rel), attnum, targettype, targetcollid);
 
 	/*
 	 * Drop any pg_statistic entry for the column, since it's now wrong type

src/backend/commands/typecmds.c

@@ -1736,6 +1736,7 @@ AlterDomainDefault(List *names, Node *defaultRaw)
 							 InvalidOid,
 							 false,		/* a domain isn't an implicit array */
 							 typTup->typbasetype,
+							 typTup->typcollation,
 							 defaultExpr,
 							 true);		/* Rebuild is true */