get_whatever_oid, part 1: object types with unqualifed names

diff --git a/src/backend/catalog/aclchk.c b/src/backend/catalog/aclchk.c
index 23d604e..2b2c326 100644
--- a/src/backend/catalog/aclchk.c
+++ b/src/backend/catalog/aclchk.c
@@ -43,6 +43,8 @@
 #include "catalog/pg_ts_config.h"
 #include "catalog/pg_ts_dict.h"
 #include "commands/dbcommands.h"
+#include "commands/proclang.h"
+#include "commands/tablespace.h"
 #include "foreign/foreign.h"
 #include "miscadmin.h"
 #include "parser/parse_func.h"
@@ -419,7 +421,7 @@ ExecuteGrantStmt(GrantStmt *stmt)
 		else
 			istmt.grantees =
 				lappend_oid(istmt.grantees,
-							get_roleid_checked(grantee->rolname));
+							get_role_oid(grantee->rolname, false));
 	}
 
 	/*
@@ -607,12 +609,7 @@ objectNamesToOids(GrantObjectType objtype, List *objnames)
 				char	   *dbname = strVal(lfirst(cell));
 				Oid			dbid;
 
-				dbid = get_database_oid(dbname);
-				if (!OidIsValid(dbid))
-					ereport(ERROR,
-							(errcode(ERRCODE_UNDEFINED_DATABASE),
-							 errmsg("database \"%s\" does not exist",
-									dbname)));
+				dbid = get_database_oid(dbname, false);
 				objects = lappend_oid(objects, dbid);
 			}
 			break;
@@ -631,18 +628,10 @@ objectNamesToOids(GrantObjectType objtype, List *objnames)
 			foreach(cell, objnames)
 			{
 				char	   *langname = strVal(lfirst(cell));
-				HeapTuple	tuple;
-
-				tuple = SearchSysCache1(LANGNAME, PointerGetDatum(langname));
-				if (!HeapTupleIsValid(tuple))
-					ereport(ERROR,
-							(errcode(ERRCODE_UNDEFINED_OBJECT),
-							 errmsg("language \"%s\" does not exist",
-									langname)));
+				Oid			oid;
 
-				objects = lappend_oid(objects, HeapTupleGetOid(tuple));
-
-				ReleaseSysCache(tuple);
+				oid = get_language_oid(langname, false);
+				objects = lappend_oid(objects, oid);
 			}
 			break;
 		case ACL_OBJECT_LARGEOBJECT:
@@ -663,49 +652,20 @@ objectNamesToOids(GrantObjectType objtype, List *objnames)
 			foreach(cell, objnames)
 			{
 				char	   *nspname = strVal(lfirst(cell));
-				HeapTuple	tuple;
-
-				tuple = SearchSysCache1(NAMESPACENAME,
-										CStringGetDatum(nspname));
-				if (!HeapTupleIsValid(tuple))
-					ereport(ERROR,
-							(errcode(ERRCODE_UNDEFINED_SCHEMA),
-							 errmsg("schema \"%s\" does not exist",
-									nspname)));
-
-				objects = lappend_oid(objects, HeapTupleGetOid(tuple));
+				Oid			oid;
 
-				ReleaseSysCache(tuple);
+				oid = get_namespace_oid(nspname, false);
+				objects = lappend_oid(objects, oid);
 			}
 			break;
 		case ACL_OBJECT_TABLESPACE:
 			foreach(cell, objnames)
 			{
 				char	   *spcname = strVal(lfirst(cell));
-				ScanKeyData entry[1];
-				HeapScanDesc scan;
-				HeapTuple	tuple;
-				Relation	relation;
+				Oid			spcoid;
 
-				relation = heap_open(TableSpaceRelationId, AccessShareLock);
-
-				ScanKeyInit(&entry[0],
-							Anum_pg_tablespace_spcname,
-							BTEqualStrategyNumber, F_NAMEEQ,
-							CStringGetDatum(spcname));
-
-				scan = heap_beginscan(relation, SnapshotNow, 1, entry);
-				tuple = heap_getnext(scan, ForwardScanDirection);
-				if (!HeapTupleIsValid(tuple))
-					ereport(ERROR,
-							(errcode(ERRCODE_UNDEFINED_OBJECT),
-					   errmsg("tablespace \"%s\" does not exist", spcname)));
-
-				objects = lappend_oid(objects, HeapTupleGetOid(tuple));
-
-				heap_endscan(scan);
-
-				heap_close(relation, AccessShareLock);
+				spcoid = get_tablespace_oid(spcname, false);
+				objects = lappend_oid(objects, spcoid);
 			}
 			break;
 		case ACL_OBJECT_FDW:
@@ -913,7 +873,7 @@ ExecAlterDefaultPrivilegesStmt(AlterDefaultPrivilegesStmt *stmt)
 		else
 			iacls.grantees =
 				lappend_oid(iacls.grantees,
-							get_roleid_checked(grantee->rolname));
+							get_role_oid(grantee->rolname, false));
 	}
 
 	/*
@@ -996,7 +956,7 @@ ExecAlterDefaultPrivilegesStmt(AlterDefaultPrivilegesStmt *stmt)
 		{
 			char	   *rolename = strVal(lfirst(rolecell));
 
-			iacls.roleid = get_roleid_checked(rolename);
+			iacls.roleid = get_role_oid(rolename, false);
 
 			/*
 			 * We insist that calling user be a member of each target role. If
@@ -1037,18 +997,12 @@ SetDefaultACLsInSchemas(InternalDefaultACL *iacls, List *nspnames)
 			AclResult	aclresult;
 
 			/*
-			 * Normally we'd use LookupCreationNamespace here, but it's
-			 * important to do the permissions check against the target role
-			 * not the calling user, so write it out in full.  We require
-			 * CREATE privileges, since without CREATE you won't be able to do
-			 * anything using the default privs anyway.
+			 * Note that we must do the permissions check against the target
+			 * role not the calling user.  We require CREATE privileges,
+			 * since without CREATE you won't be able to do anything using the
+			 * default privs anyway.
 			 */
-			iacls->nspid = GetSysCacheOid1(NAMESPACENAME,
-										   CStringGetDatum(nspname));
-			if (!OidIsValid(iacls->nspid))
-				ereport(ERROR,
-						(errcode(ERRCODE_UNDEFINED_SCHEMA),
-						 errmsg("schema \"%s\" does not exist", nspname)));
+			iacls->nspid = get_namespace_oid(nspname, false);
 
 			aclresult = pg_namespace_aclcheck(iacls->nspid, iacls->roleid,
 											  ACL_CREATE);
diff --git a/src/backend/catalog/namespace.c b/src/backend/catalog/namespace.c
index 5581346..52acc23 100644
--- a/src/backend/catalog/namespace.c
+++ b/src/backend/catalog/namespace.c
@@ -332,13 +332,7 @@ RangeVarGetCreationNamespace(const RangeVar *newRelation)
 			return myTempNamespace;
 		}
 		/* use exact schema given */
-		namespaceId = GetSysCacheOid1(NAMESPACENAME,
-								   CStringGetDatum(newRelation->schemaname));
-		if (!OidIsValid(namespaceId))
-			ereport(ERROR,
-					(errcode(ERRCODE_UNDEFINED_SCHEMA),
-					 errmsg("schema \"%s\" does not exist",
-							newRelation->schemaname)));
+		namespaceId = get_namespace_oid(newRelation->schemaname, false);
 		/* we do not check for USAGE rights here! */
 	}
 	else
@@ -2270,7 +2264,7 @@ LookupNamespaceNoError(const char *nspname)
 		return InvalidOid;
 	}
 
-	return GetSysCacheOid1(NAMESPACENAME, CStringGetDatum(nspname));
+	return get_namespace_oid(nspname, true);
 }
 
 /*
@@ -2300,11 +2294,7 @@ LookupExplicitNamespace(const char *nspname)
 		 */
 	}
 
-	namespaceId = GetSysCacheOid1(NAMESPACENAME, CStringGetDatum(nspname));
-	if (!OidIsValid(namespaceId))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_SCHEMA),
-				 errmsg("schema \"%s\" does not exist", nspname)));
+	namespaceId = get_namespace_oid(nspname, false);
 
 	aclresult = pg_namespace_aclcheck(namespaceId, GetUserId(), ACL_USAGE);
 	if (aclresult != ACLCHECK_OK)
@@ -2339,11 +2329,7 @@ LookupCreationNamespace(const char *nspname)
 		return myTempNamespace;
 	}
 
-	namespaceId = GetSysCacheOid1(NAMESPACENAME, CStringGetDatum(nspname));
-	if (!OidIsValid(namespaceId))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_SCHEMA),
-				 errmsg("schema \"%s\" does not exist", nspname)));
+	namespaceId = get_namespace_oid(nspname, false);
 
 	aclresult = pg_namespace_aclcheck(namespaceId, GetUserId(), ACL_CREATE);
 	if (aclresult != ACLCHECK_OK)
@@ -2385,12 +2371,7 @@ QualifiedNameGetCreationNamespace(List *names, char **objname_p)
 			return myTempNamespace;
 		}
 		/* use exact schema given */
-		namespaceId = GetSysCacheOid1(NAMESPACENAME,
-									  CStringGetDatum(schemaname));
-		if (!OidIsValid(namespaceId))
-			ereport(ERROR,
-					(errcode(ERRCODE_UNDEFINED_SCHEMA),
-					 errmsg("schema \"%s\" does not exist", schemaname)));
+		namespaceId = get_namespace_oid(schemaname, false);
 		/* we do not check for USAGE rights here! */
 	}
 	else
@@ -2414,6 +2395,26 @@ QualifiedNameGetCreationNamespace(List *names, char **objname_p)
 }
 
 /*
+ * get_namespace_oid - given a namespace name, look up the OID
+ *
+ * If missing_ok is false, throw an error if namespace name not found.  If
+ * true, just return InvalidOid.
+ */
+Oid
+get_namespace_oid(const char *nspname, bool missing_ok)
+{
+	Oid			oid;
+
+	oid = GetSysCacheOid1(NAMESPACENAME, CStringGetDatum(nspname));
+	if (!OidIsValid(oid) && !missing_ok)
+        ereport(ERROR,
+                (errcode(ERRCODE_UNDEFINED_SCHEMA),
+                 errmsg("schema \"%s\" does not exist", nspname)));
+
+	return oid;
+}
+
+/*
  * makeRangeVarFromNameList
  *		Utility routine to convert a qualified-name list into RangeVar form.
  */
@@ -2897,8 +2898,7 @@ recomputeNamespacePath(void)
 				char	   *rname;
 
 				rname = NameStr(((Form_pg_authid) GETSTRUCT(tuple))->rolname);
-				namespaceId = GetSysCacheOid1(NAMESPACENAME,
-											  CStringGetDatum(rname));
+				namespaceId = get_namespace_oid(rname, true);
 				ReleaseSysCache(tuple);
 				if (OidIsValid(namespaceId) &&
 					!list_member_oid(oidlist, namespaceId) &&
@@ -2925,8 +2925,7 @@ recomputeNamespacePath(void)
 		else
 		{
 			/* normal namespace reference */
-			namespaceId = GetSysCacheOid1(NAMESPACENAME,
-										  CStringGetDatum(curname));
+			namespaceId = get_namespace_oid(curname, true);
 			if (OidIsValid(namespaceId) &&
 				!list_member_oid(oidlist, namespaceId) &&
 				pg_namespace_aclcheck(namespaceId, roleid,
@@ -3033,8 +3032,7 @@ InitTempTableNamespace(void)
 
 	snprintf(namespaceName, sizeof(namespaceName), "pg_temp_%d", MyBackendId);
 
-	namespaceId = GetSysCacheOid1(NAMESPACENAME,
-								  CStringGetDatum(namespaceName));
+	namespaceId = get_namespace_oid(namespaceName, true);
 	if (!OidIsValid(namespaceId))
 	{
 		/*
@@ -3066,8 +3064,7 @@ InitTempTableNamespace(void)
 	snprintf(namespaceName, sizeof(namespaceName), "pg_toast_temp_%d",
 			 MyBackendId);
 
-	toastspaceId = GetSysCacheOid1(NAMESPACENAME,
-								   CStringGetDatum(namespaceName));
+	toastspaceId = get_namespace_oid(namespaceName, true);
 	if (!OidIsValid(toastspaceId))
 	{
 		toastspaceId = NamespaceCreate(namespaceName, BOOTSTRAP_SUPERUSERID);
diff --git a/src/backend/commands/alter.c b/src/backend/commands/alter.c
index a6c4755..f09d595 100644
--- a/src/backend/commands/alter.c
+++ b/src/backend/commands/alter.c
@@ -211,7 +211,7 @@ ExecAlterObjectSchemaStmt(AlterObjectSchemaStmt *stmt)
 void
 ExecAlterOwnerStmt(AlterOwnerStmt *stmt)
 {
-	Oid			newowner = get_roleid_checked(stmt->newowner);
+	Oid			newowner = get_role_oid(stmt->newowner, false);
 
 	switch (stmt->objectType)
 	{
diff --git a/src/backend/commands/comment.c b/src/backend/commands/comment.c
index b613cbf..2ba2368 100644
--- a/src/backend/commands/comment.c
+++ b/src/backend/commands/comment.c
@@ -42,6 +42,8 @@
 #include "catalog/pg_type.h"
 #include "commands/comment.h"
 #include "commands/dbcommands.h"
+#include "commands/defrem.h"
+#include "commands/proclang.h"
 #include "commands/tablespace.h"
 #include "libpq/be-fsstubs.h"
 #include "miscadmin.h"
@@ -686,11 +688,10 @@ CommentDatabase(List *qualname, char *comment)
 	 * of the database.  Erroring out would prevent pg_restore from completing
 	 * (which is really pg_restore's fault, but for now we will work around
 	 * the problem here).  Consensus is that the best fix is to treat wrong
-	 * database name as a WARNING not an ERROR.
+	 * database name as a WARNING not an ERROR (thus, we tell get_database_oid
+	 * to ignore the error so that we can handle it differently here).
 	 */
-
-	/* First get the database OID */
-	oid = get_database_oid(database);
+	oid = get_database_oid(database, true);
 	if (!OidIsValid(oid))
 	{
 		ereport(WARNING,
@@ -729,14 +730,7 @@ CommentTablespace(List *qualname, char *comment)
 				 errmsg("tablespace name cannot be qualified")));
 	tablespace = strVal(linitial(qualname));
 
-	oid = get_tablespace_oid(tablespace);
-	if (!OidIsValid(oid))
-	{
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_OBJECT),
-				 errmsg("tablespace \"%s\" does not exist", tablespace)));
-		return;
-	}
+	oid = get_tablespace_oid(tablespace, false);
 
 	/* Check object security */
 	if (!pg_tablespace_ownercheck(oid, GetUserId()))
@@ -766,7 +760,7 @@ CommentRole(List *qualname, char *comment)
 				 errmsg("role name cannot be qualified")));
 	role = strVal(linitial(qualname));
 
-	oid = get_roleid_checked(role);
+	oid = get_role_oid(role, false);
 
 	/* Check object security */
 	if (!has_privs_of_role(GetUserId(), oid))
@@ -799,11 +793,7 @@ CommentNamespace(List *qualname, char *comment)
 				 errmsg("schema name cannot be qualified")));
 	namespace = strVal(linitial(qualname));
 
-	oid = GetSysCacheOid1(NAMESPACENAME, CStringGetDatum(namespace));
-	if (!OidIsValid(oid))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_SCHEMA),
-				 errmsg("schema \"%s\" does not exist", namespace)));
+	oid = get_namespace_oid(namespace, false);
 
 	/* Check object security */
 	if (!pg_namespace_ownercheck(oid, GetUserId()))
@@ -1213,11 +1203,7 @@ CommentLanguage(List *qualname, char *comment)
 				 errmsg("language name cannot be qualified")));
 	language = strVal(linitial(qualname));
 
-	oid = GetSysCacheOid1(LANGNAME, CStringGetDatum(language));
-	if (!OidIsValid(oid))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_SCHEMA),
-				 errmsg("language \"%s\" does not exist", language)));
+	oid = get_language_oid(language, false);
 
 	/* Check object security */
 	if (!superuser())
@@ -1254,12 +1240,7 @@ CommentOpClass(List *qualname, List *arguments, char *comment)
 	/*
 	 * Get the access method's OID.
 	 */
-	amID = GetSysCacheOid1(AMNAME, CStringGetDatum(amname));
-	if (!OidIsValid(amID))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_OBJECT),
-				 errmsg("access method \"%s\" does not exist",
-						amname)));
+	amID = get_am_oid(amname, false);
 
 	/*
 	 * Look up the opclass.
@@ -1335,12 +1316,7 @@ CommentOpFamily(List *qualname, List *arguments, char *comment)
 	/*
 	 * Get the access method's OID.
 	 */
-	amID = GetSysCacheOid1(AMNAME, CStringGetDatum(amname));
-	if (!OidIsValid(amID))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_OBJECT),
-				 errmsg("access method \"%s\" does not exist",
-						amname)));
+	amID = get_am_oid(amname, false);
 
 	/*
 	 * Look up the opfamily.
diff --git a/src/backend/commands/dbcommands.c b/src/backend/commands/dbcommands.c
index e7dac22..9937083 100644
--- a/src/backend/commands/dbcommands.c
+++ b/src/backend/commands/dbcommands.c
@@ -255,7 +255,7 @@ createdb(const CreatedbStmt *stmt)
 
 	/* obtain OID of proposed owner */
 	if (dbowner)
-		datdba = get_roleid_checked(dbowner);
+		datdba = get_role_oid(dbowner, false);
 	else
 		datdba = GetUserId();
 
@@ -429,12 +429,7 @@ createdb(const CreatedbStmt *stmt)
 		AclResult	aclresult;
 
 		tablespacename = strVal(dtablespacename->arg);
-		dst_deftablespace = get_tablespace_oid(tablespacename);
-		if (!OidIsValid(dst_deftablespace))
-			ereport(ERROR,
-					(errcode(ERRCODE_UNDEFINED_OBJECT),
-					 errmsg("tablespace \"%s\" does not exist",
-							tablespacename)));
+		dst_deftablespace = get_tablespace_oid(tablespacename, false);
 		/* check permissions */
 		aclresult = pg_tablespace_aclcheck(dst_deftablespace, GetUserId(),
 										   ACL_CREATE);
@@ -491,7 +486,7 @@ createdb(const CreatedbStmt *stmt)
 	 * message than "unique index violation".  There's a race condition but
 	 * we're willing to accept the less friendly message in that case.
 	 */
-	if (OidIsValid(get_database_oid(dbname)))
+	if (OidIsValid(get_database_oid(dbname, true)))
 		ereport(ERROR,
 				(errcode(ERRCODE_DUPLICATE_DATABASE),
 				 errmsg("database \"%s\" already exists", dbname)));
@@ -919,7 +914,7 @@ RenameDatabase(const char *oldname, const char *newname)
 	 * Make sure the new name doesn't exist.  See notes for same error in
 	 * CREATE DATABASE.
 	 */
-	if (OidIsValid(get_database_oid(newname)))
+	if (OidIsValid(get_database_oid(newname, true)))
 		ereport(ERROR,
 				(errcode(ERRCODE_DUPLICATE_DATABASE),
 				 errmsg("database \"%s\" already exists", newname)));
@@ -1030,11 +1025,7 @@ movedb(const char *dbname, const char *tblspcname)
 	/*
 	 * Get tablespace's oid
 	 */
-	dst_tblspcoid = get_tablespace_oid(tblspcname);
-	if (dst_tblspcoid == InvalidOid)
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_DATABASE),
-				 errmsg("tablespace \"%s\" does not exist", tblspcname)));
+	dst_tblspcoid = get_tablespace_oid(tblspcname, false);
 
 	/*
 	 * Permission checks
@@ -1402,12 +1393,7 @@ AlterDatabase(AlterDatabaseStmt *stmt, bool isTopLevel)
 void
 AlterDatabaseSet(AlterDatabaseSetStmt *stmt)
 {
-	Oid			datid = get_database_oid(stmt->dbname);
-
-	if (!OidIsValid(datid))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_DATABASE),
-				 errmsg("database \"%s\" does not exist", stmt->dbname)));
+	Oid			datid = get_database_oid(stmt->dbname, false);
 
 	/*
 	 * Obtain a lock on the database and make sure it didn't go away in the
@@ -1818,10 +1804,11 @@ errdetail_busy_db(int notherbackends, int npreparedxacts)
 /*
  * get_database_oid - given a database name, look up the OID
  *
- * Returns InvalidOid if database name not found.
+ * If missing_ok is false, throw an error if database name not found.  If
+ * true, just return InvalidOid.
  */
 Oid
-get_database_oid(const char *dbname)
+get_database_oid(const char *dbname, bool missing_ok)
 {
 	Relation	pg_database;
 	ScanKeyData entry[1];
@@ -1852,6 +1839,12 @@ get_database_oid(const char *dbname)
 	systable_endscan(scan);
 	heap_close(pg_database, AccessShareLock);
 
+	if (!OidIsValid(oid) && !missing_ok)
+        ereport(ERROR,
+                (errcode(ERRCODE_UNDEFINED_DATABASE),
+                 errmsg("database \"%s\" does not exist",
+                        dbname)));
+
 	return oid;
 }
 
diff --git a/src/backend/commands/foreigncmds.c b/src/backend/commands/foreigncmds.c
index 14356a2..6b22570 100644
--- a/src/backend/commands/foreigncmds.c
+++ b/src/backend/commands/foreigncmds.c
@@ -184,7 +184,7 @@ GetUserOidFromMapping(const char *username, bool missing_ok)
 		return GetUserId();
 
 	/* map to provided user */
-	return missing_ok ? get_roleid(username) : get_roleid_checked(username);
+	return get_role_oid(username, missing_ok);
 }
 
 
diff --git a/src/backend/commands/indexcmds.c b/src/backend/commands/indexcmds.c
index 503148f..60f4c44 100644
--- a/src/backend/commands/indexcmds.c
+++ b/src/backend/commands/indexcmds.c
@@ -218,12 +218,7 @@ DefineIndex(RangeVar *heapRelation,
 	 */
 	if (tableSpaceName)
 	{
-		tablespaceId = get_tablespace_oid(tableSpaceName);
-		if (!OidIsValid(tablespaceId))
-			ereport(ERROR,
-					(errcode(ERRCODE_UNDEFINED_OBJECT),
-					 errmsg("tablespace \"%s\" does not exist",
-							tableSpaceName)));
+		tablespaceId = get_tablespace_oid(tableSpaceName, false);
 	}
 	else
 	{
diff --git a/src/backend/commands/opclasscmds.c b/src/backend/commands/opclasscmds.c
index ac0270f..fef2113 100644
--- a/src/backend/commands/opclasscmds.c
+++ b/src/backend/commands/opclasscmds.c
@@ -661,20 +661,11 @@ DefineOpFamily(CreateOpFamilyStmt *stmt)
 		aclcheck_error(aclresult, ACL_KIND_NAMESPACE,
 					   get_namespace_name(namespaceoid));
 
-	/* Get necessary info about access method */
-	tup = SearchSysCache1(AMNAME, CStringGetDatum(stmt->amname));
-	if (!HeapTupleIsValid(tup))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_OBJECT),
-				 errmsg("access method \"%s\" does not exist",
-						stmt->amname)));
-
-	amoid = HeapTupleGetOid(tup);
+	/* Get access method OID, throwing an error if it doesn't exist. */
+	amoid = get_am_oid(stmt->amname, false);
 
 	/* XXX Should we make any privilege check against the AM? */
 
-	ReleaseSysCache(tup);
-
 	/*
 	 * Currently, we require superuser privileges to create an opfamily. See
 	 * comments in DefineOpClass.
@@ -1488,12 +1479,7 @@ RemoveOpClass(RemoveOpClassStmt *stmt)
 	/*
 	 * Get the access method's OID.
 	 */
-	amID = GetSysCacheOid1(AMNAME, CStringGetDatum(stmt->amname));
-	if (!OidIsValid(amID))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_OBJECT),
-				 errmsg("access method \"%s\" does not exist",
-						stmt->amname)));
+	amID = get_am_oid(stmt->amname, false);
 
 	/*
 	 * Look up the opclass.
@@ -1549,12 +1535,7 @@ RemoveOpFamily(RemoveOpFamilyStmt *stmt)
 	/*
 	 * Get the access method's OID.
 	 */
-	amID = GetSysCacheOid1(AMNAME, CStringGetDatum(stmt->amname));
-	if (!OidIsValid(amID))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_OBJECT),
-				 errmsg("access method \"%s\" does not exist",
-						stmt->amname)));
+	amID = get_am_oid(stmt->amname, false);
 
 	/*
 	 * Look up the opfamily.
@@ -1711,12 +1692,7 @@ RenameOpClass(List *name, const char *access_method, const char *newname)
 	Relation	rel;
 	AclResult	aclresult;
 
-	amOid = GetSysCacheOid1(AMNAME, CStringGetDatum(access_method));
-	if (!OidIsValid(amOid))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_OBJECT),
-				 errmsg("access method \"%s\" does not exist",
-						access_method)));
+	amOid = get_am_oid(access_method, false);
 
 	rel = heap_open(OperatorClassRelationId, RowExclusiveLock);
 
@@ -1805,12 +1781,7 @@ RenameOpFamily(List *name, const char *access_method, const char *newname)
 	Relation	rel;
 	AclResult	aclresult;
 
-	amOid = GetSysCacheOid1(AMNAME, CStringGetDatum(access_method));
-	if (!OidIsValid(amOid))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_OBJECT),
-				 errmsg("access method \"%s\" does not exist",
-						access_method)));
+	amOid = get_am_oid(access_method, false);
 
 	rel = heap_open(OperatorFamilyRelationId, RowExclusiveLock);
 
@@ -1896,12 +1867,7 @@ AlterOpClassOwner(List *name, const char *access_method, Oid newOwnerId)
 	char	   *opcname;
 	char	   *schemaname;
 
-	amOid = GetSysCacheOid1(AMNAME, CStringGetDatum(access_method));
-	if (!OidIsValid(amOid))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_OBJECT),
-				 errmsg("access method \"%s\" does not exist",
-						access_method)));
+	amOid = get_am_oid(access_method, false);
 
 	rel = heap_open(OperatorClassRelationId, RowExclusiveLock);
 
@@ -2018,12 +1984,7 @@ AlterOpFamilyOwner(List *name, const char *access_method, Oid newOwnerId)
 	char	   *opfname;
 	char	   *schemaname;
 
-	amOid = GetSysCacheOid1(AMNAME, CStringGetDatum(access_method));
-	if (!OidIsValid(amOid))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_OBJECT),
-				 errmsg("access method \"%s\" does not exist",
-						access_method)));
+	amOid = get_am_oid(access_method, false);
 
 	rel = heap_open(OperatorFamilyRelationId, RowExclusiveLock);
 
@@ -2127,3 +2088,22 @@ AlterOpFamilyOwner_internal(Relation rel, HeapTuple tup, Oid newOwnerId)
 								newOwnerId);
 	}
 }
+
+/*
+ * get_am_oid - given an access method name, look up the OID
+ *
+ * If missing_ok is false, throw an error if access method not found.  If
+ * true, just return InvalidOid.
+ */
+Oid
+get_am_oid(const char *amname, bool missing_ok)
+{
+	Oid			oid;
+
+	oid = GetSysCacheOid1(AMNAME, CStringGetDatum(amname));
+	if (!OidIsValid(oid) && !missing_ok)
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("access method \"%s\" does not exist", amname)));
+	return oid;
+}
diff --git a/src/backend/commands/proclang.c b/src/backend/commands/proclang.c
index 633a093..a4e3afe 100644
--- a/src/backend/commands/proclang.c
+++ b/src/backend/commands/proclang.c
@@ -514,7 +514,7 @@ void
 DropProceduralLanguage(DropPLangStmt *stmt)
 {
 	char	   *languageName;
-	HeapTuple	langTup;
+	Oid			oid;
 	ObjectAddress object;
 
 	/*
@@ -522,34 +522,26 @@ DropProceduralLanguage(DropPLangStmt *stmt)
 	 */
 	languageName = case_translate_language_name(stmt->plname);
 
-	langTup = SearchSysCache1(LANGNAME, CStringGetDatum(languageName));
-	if (!HeapTupleIsValid(langTup))
+	oid = get_language_oid(languageName, stmt->missing_ok);
+	if (!OidIsValid(oid))
 	{
-		if (!stmt->missing_ok)
-			ereport(ERROR,
-					(errcode(ERRCODE_UNDEFINED_OBJECT),
-					 errmsg("language \"%s\" does not exist", languageName)));
-		else
-			ereport(NOTICE,
-					(errmsg("language \"%s\" does not exist, skipping",
-							languageName)));
-
+		ereport(NOTICE,
+				(errmsg("language \"%s\" does not exist, skipping",
+						languageName)));
 		return;
 	}
 
 	/*
 	 * Check permission
 	 */
-	if (!pg_language_ownercheck(HeapTupleGetOid(langTup), GetUserId()))
+	if (!pg_language_ownercheck(oid, GetUserId()))
 		aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_LANGUAGE,
 					   languageName);
 
 	object.classId = LanguageRelationId;
-	object.objectId = HeapTupleGetOid(langTup);
+	object.objectId = oid;
 	object.objectSubId = 0;
 
-	ReleaseSysCache(langTup);
-
 	/*
 	 * Do the deletion
 	 */
@@ -735,3 +727,22 @@ AlterLanguageOwner_internal(HeapTuple tup, Relation rel, Oid newOwnerId)
 								newOwnerId);
 	}
 }
+
+/*
+ * get_language_oid - given a language name, look up the OID
+ *
+ * If missing_ok is false, throw an error if language name not found.  If
+ * true, just return InvalidOid.
+ */
+Oid
+get_language_oid(const char *langname, bool missing_ok)
+{
+	Oid			oid;
+
+	oid = GetSysCacheOid1(LANGNAME, CStringGetDatum(langname));
+	if (!OidIsValid(oid) && !missing_ok)
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("language \"%s\" does not exist", langname)));
+	return oid;
+}
diff --git a/src/backend/commands/schemacmds.c b/src/backend/commands/schemacmds.c
index b0a9a22..9edd59d 100644
--- a/src/backend/commands/schemacmds.c
+++ b/src/backend/commands/schemacmds.c
@@ -57,7 +57,7 @@ CreateSchemaCommand(CreateSchemaStmt *stmt, const char *queryString)
 	 * Who is supposed to own the new schema?
 	 */
 	if (authId)
-		owner_uid = get_roleid_checked(authId);
+		owner_uid = get_role_oid(authId, false);
 	else
 		owner_uid = saved_uid;
 
@@ -178,24 +178,13 @@ RemoveSchemas(DropStmt *drop)
 					 errmsg("schema name cannot be qualified")));
 		namespaceName = strVal(linitial(names));
 
-		namespaceId = GetSysCacheOid1(NAMESPACENAME,
-									  CStringGetDatum(namespaceName));
+		namespaceId = get_namespace_oid(namespaceName, drop->missing_ok);
 
 		if (!OidIsValid(namespaceId))
 		{
-			if (!drop->missing_ok)
-			{
-				ereport(ERROR,
-						(errcode(ERRCODE_UNDEFINED_SCHEMA),
-						 errmsg("schema \"%s\" does not exist",
-								namespaceName)));
-			}
-			else
-			{
-				ereport(NOTICE,
-						(errmsg("schema \"%s\" does not exist, skipping",
-								namespaceName)));
-			}
+			ereport(NOTICE,
+					(errmsg("schema \"%s\" does not exist, skipping",
+							namespaceName)));
 			continue;
 		}
 
@@ -264,9 +253,7 @@ RenameSchema(const char *oldname, const char *newname)
 				 errmsg("schema \"%s\" does not exist", oldname)));
 
 	/* make sure the new name doesn't exist */
-	if (HeapTupleIsValid(
-						 SearchSysCache1(NAMESPACENAME,
-										 CStringGetDatum(newname))))
+	if (OidIsValid(get_namespace_oid(newname, true)))
 		ereport(ERROR,
 				(errcode(ERRCODE_DUPLICATE_SCHEMA),
 				 errmsg("schema \"%s\" already exists", newname)));
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 9b5ce65..9a9d9ae 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -411,12 +411,7 @@ DefineRelation(CreateStmt *stmt, char relkind)
 	 */
 	if (stmt->tablespacename)
 	{
-		tablespaceId = get_tablespace_oid(stmt->tablespacename);
-		if (!OidIsValid(tablespaceId))
-			ereport(ERROR,
-					(errcode(ERRCODE_UNDEFINED_OBJECT),
-					 errmsg("tablespace \"%s\" does not exist",
-							stmt->tablespacename)));
+		tablespaceId = get_tablespace_oid(stmt->tablespacename, false);
 	}
 	else
 	{
@@ -2750,7 +2745,7 @@ ATExecCmd(List **wqueue, AlteredTableInfo *tab, Relation rel,
 			break;
 		case AT_ChangeOwner:	/* ALTER OWNER */
 			ATExecChangeOwner(RelationGetRelid(rel),
-							  get_roleid_checked(cmd->name),
+							  get_role_oid(cmd->name, false),
 							  false);
 			break;
 		case AT_ClusterOn:		/* CLUSTER ON */
@@ -6739,11 +6734,7 @@ ATPrepSetTableSpace(AlteredTableInfo *tab, Relation rel, char *tablespacename)
 	AclResult	aclresult;
 
 	/* Check that the tablespace exists */
-	tablespaceId = get_tablespace_oid(tablespacename);
-	if (!OidIsValid(tablespaceId))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_OBJECT),
-				 errmsg("tablespace \"%s\" does not exist", tablespacename)));
+	tablespaceId = get_tablespace_oid(tablespacename, false);
 
 	/* Check its permissions */
 	aclresult = pg_tablespace_aclcheck(tablespaceId, GetUserId(), ACL_CREATE);
diff --git a/src/backend/commands/tablespace.c b/src/backend/commands/tablespace.c
index 862cd2d..db17841 100644
--- a/src/backend/commands/tablespace.c
+++ b/src/backend/commands/tablespace.c
@@ -246,7 +246,7 @@ CreateTableSpace(CreateTableSpaceStmt *stmt)
 
 	/* However, the eventual owner of the tablespace need not be */
 	if (stmt->owner)
-		ownerId = get_roleid_checked(stmt->owner);
+		ownerId = get_role_oid(stmt->owner, false);
 	else
 		ownerId = GetUserId();
 
@@ -298,7 +298,7 @@ CreateTableSpace(CreateTableSpaceStmt *stmt)
 	 * index would catch this anyway, but might as well give a friendlier
 	 * message.)
 	 */
-	if (OidIsValid(get_tablespace_oid(stmt->tablespacename)))
+	if (OidIsValid(get_tablespace_oid(stmt->tablespacename, true)))
 		ereport(ERROR,
 				(errcode(ERRCODE_DUPLICATE_OBJECT),
 				 errmsg("tablespace \"%s\" already exists",
@@ -999,7 +999,7 @@ assign_default_tablespace(const char *newval, bool doit, GucSource source)
 	if (IsTransactionState())
 	{
 		if (newval[0] != '\0' &&
-			!OidIsValid(get_tablespace_oid(newval)))
+			!OidIsValid(get_tablespace_oid(newval, true)))
 		{
 			ereport(GUC_complaint_elevel(source),
 					(errcode(ERRCODE_UNDEFINED_OBJECT),
@@ -1049,7 +1049,7 @@ GetDefaultTablespace(bool forTemp)
 	 * to refer to an existing tablespace; we just silently return InvalidOid,
 	 * causing the new object to be created in the database's tablespace.
 	 */
-	result = get_tablespace_oid(default_tablespace);
+	result = get_tablespace_oid(default_tablespace, true);
 
 	/*
 	 * Allow explicit specification of database's default tablespace in
@@ -1116,21 +1116,13 @@ assign_temp_tablespaces(const char *newval, bool doit, GucSource source)
 				continue;
 			}
 
-			/* Else verify that name is a valid tablespace name */
-			curoid = get_tablespace_oid(curname);
+			/*
+			 * In an interactive SET command, we ereport for bad info.
+			 * Otherwise, silently ignore any bad list elements.
+			 */
+			curoid = get_tablespace_oid(curname, source < PGC_S_INTERACTIVE);
 			if (curoid == InvalidOid)
-			{
-				/*
-				 * In an interactive SET command, we ereport for bad info.
-				 * Otherwise, silently ignore any bad list elements.
-				 */
-				if (source >= PGC_S_INTERACTIVE)
-					ereport(ERROR,
-							(errcode(ERRCODE_UNDEFINED_OBJECT),
-							 errmsg("tablespace \"%s\" does not exist",
-									curname)));
 				continue;
-			}
 
 			/*
 			 * Allow explicit specification of database's default tablespace
@@ -1229,10 +1221,10 @@ PrepareTempTablespaces(void)
 		}
 
 		/* Else verify that name is a valid tablespace name */
-		curoid = get_tablespace_oid(curname);
+		curoid = get_tablespace_oid(curname, true);
 		if (curoid == InvalidOid)
 		{
-			/* Silently ignore any bad list elements */
+			/* Skip any bad list elements */
 			continue;
 		}
 
@@ -1265,10 +1257,11 @@ PrepareTempTablespaces(void)
 /*
  * get_tablespace_oid - given a tablespace name, look up the OID
  *
- * Returns InvalidOid if tablespace name not found.
+ * If missing_ok is false, throw an error if tablespace name not found.  If
+ * true, just return InvalidOid.
  */
 Oid
-get_tablespace_oid(const char *tablespacename)
+get_tablespace_oid(const char *tablespacename, bool missing_ok)
 {
 	Oid			result;
 	Relation	rel;
@@ -1299,6 +1292,12 @@ get_tablespace_oid(const char *tablespacename)
 	heap_endscan(scandesc);
 	heap_close(rel, AccessShareLock);
 
+	if (!OidIsValid(result) && !missing_ok)
+        ereport(ERROR,
+                (errcode(ERRCODE_UNDEFINED_OBJECT),
+                 errmsg("tablespace \"%s\" does not exist",
+                        tablespacename)));
+
 	return result;
 }
 
diff --git a/src/backend/commands/user.c b/src/backend/commands/user.c
index 2f0788e..1c73d9b 100644
--- a/src/backend/commands/user.c
+++ b/src/backend/commands/user.c
@@ -293,8 +293,7 @@ CreateRole(CreateRoleStmt *stmt)
 	pg_authid_rel = heap_open(AuthIdRelationId, RowExclusiveLock);
 	pg_authid_dsc = RelationGetDescr(pg_authid_rel);
 
-	tuple = SearchSysCache1(AUTHNAME, PointerGetDatum(stmt->role));
-	if (HeapTupleIsValid(tuple))
+	if (OidIsValid(get_role_oid(stmt->role, true)))
 		ereport(ERROR,
 				(errcode(ERRCODE_DUPLICATE_OBJECT),
 				 errmsg("role \"%s\" already exists",
@@ -384,7 +383,7 @@ CreateRole(CreateRoleStmt *stmt)
 	foreach(item, addroleto)
 	{
 		char	   *oldrolename = strVal(lfirst(item));
-		Oid			oldroleid = get_roleid_checked(oldrolename);
+		Oid			oldroleid = get_role_oid(oldrolename, false);
 
 		AddRoleMems(oldrolename, oldroleid,
 					list_make1(makeString(stmt->role)),
@@ -795,11 +794,7 @@ AlterRoleSet(AlterRoleSetStmt *stmt)
 	/* look up and lock the database, if specified */
 	if (stmt->database != NULL)
 	{
-		databaseid = get_database_oid(stmt->database);
-		if (!OidIsValid(databaseid))
-			ereport(ERROR,
-					(errcode(ERRCODE_UNDEFINED_OBJECT),
-					 errmsg("database \"%s\" not found", stmt->database)));
+		databaseid = get_database_oid(stmt->database, false);
 		shdepLockAndCheckObject(DatabaseRelationId, databaseid);
 	}
 
@@ -1099,7 +1094,7 @@ GrantRole(GrantRoleStmt *stmt)
 	ListCell   *item;
 
 	if (stmt->grantor)
-		grantor = get_roleid_checked(stmt->grantor);
+		grantor = get_role_oid(stmt->grantor, false);
 	else
 		grantor = GetUserId();
 
@@ -1127,7 +1122,7 @@ GrantRole(GrantRoleStmt *stmt)
 					(errcode(ERRCODE_INVALID_GRANT_OPERATION),
 			errmsg("column names cannot be included in GRANT/REVOKE ROLE")));
 
-		roleid = get_roleid_checked(rolename);
+		roleid = get_role_oid(rolename, false);
 		if (stmt->is_grant)
 			AddRoleMems(rolename, roleid,
 						stmt->grantee_roles, grantee_ids,
@@ -1194,7 +1189,7 @@ ReassignOwnedObjects(ReassignOwnedStmt *stmt)
 	}
 
 	/* Must have privileges on the receiving side too */
-	newrole = get_roleid_checked(stmt->newrole);
+	newrole = get_role_oid(stmt->newrole, false);
 
 	if (!has_privs_of_role(GetUserId(), newrole))
 		ereport(ERROR,
@@ -1220,7 +1215,7 @@ roleNamesToIds(List *memberNames)
 	foreach(l, memberNames)
 	{
 		char	   *rolename = strVal(lfirst(l));
-		Oid			roleid = get_roleid_checked(rolename);
+		Oid			roleid = get_role_oid(rolename, false);
 
 		result = lappend_oid(result, roleid);
 	}
diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
index d299310..857483a 100644
--- a/src/backend/executor/execMain.c
+++ b/src/backend/executor/execMain.c
@@ -2118,12 +2118,7 @@ OpenIntoRel(QueryDesc *queryDesc)
 	 */
 	if (into->tableSpaceName)
 	{
-		tablespaceId = get_tablespace_oid(into->tableSpaceName);
-		if (!OidIsValid(tablespaceId))
-			ereport(ERROR,
-					(errcode(ERRCODE_UNDEFINED_OBJECT),
-					 errmsg("tablespace \"%s\" does not exist",
-							into->tableSpaceName)));
+		tablespaceId = get_tablespace_oid(into->tableSpaceName, false);
 	}
 	else
 	{
diff --git a/src/backend/libpq/hba.c b/src/backend/libpq/hba.c
index c967364..7ee7842 100644
--- a/src/backend/libpq/hba.c
+++ b/src/backend/libpq/hba.c
@@ -459,7 +459,7 @@ is_member(Oid userid, const char *role)
 	if (!OidIsValid(userid))
 		return false;			/* if user not exist, say "no" */
 
-	roleid = get_roleid(role);
+	roleid = get_role_oid(role, true);
 
 	if (!OidIsValid(roleid))
 		return false;			/* if target role not exist, say "no" */
@@ -1327,7 +1327,7 @@ check_hba(hbaPort *port)
 	HbaLine    *hba;
 
 	/* Get the target role's OID.  Note we do not error out for bad role. */
-	roleid = get_roleid(port->user_name);
+	roleid = get_role_oid(port->user_name, true);
 
 	foreach(line, parsed_hba_lines)
 	{
diff --git a/src/backend/utils/adt/acl.c b/src/backend/utils/adt/acl.c
index faad11e..b320569 100644
--- a/src/backend/utils/adt/acl.c
+++ b/src/backend/utils/adt/acl.c
@@ -22,6 +22,7 @@
 #include "catalog/pg_type.h"
 #include "catalog/pg_class.h"
 #include "commands/dbcommands.h"
+#include "commands/proclang.h"
 #include "commands/tablespace.h"
 #include "foreign/foreign.h"
 #include "funcapi.h"
@@ -324,7 +325,7 @@ aclparse(const char *s, AclItem *aip)
 	if (name[0] == '\0')
 		aip->ai_grantee = ACL_ID_PUBLIC;
 	else
-		aip->ai_grantee = get_roleid_checked(name);
+		aip->ai_grantee = get_role_oid(name, false);
 
 	/*
 	 * XXX Allow a degree of backward compatibility by defaulting the grantor
@@ -337,7 +338,7 @@ aclparse(const char *s, AclItem *aip)
 			ereport(ERROR,
 					(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
 					 errmsg("a name must follow the \"/\" sign")));
-		aip->ai_grantor = get_roleid_checked(name2);
+		aip->ai_grantor = get_role_oid(name2, false);
 	}
 	else
 	{
@@ -1790,7 +1791,7 @@ has_table_privilege_name_name(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*rolename));
+	roleid = get_role_oid(NameStr(*rolename), false);
 	tableoid = convert_table_name(tablename);
 	mode = convert_table_priv_string(priv_type_text);
 
@@ -1839,7 +1840,7 @@ has_table_privilege_name_id(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	mode = convert_table_priv_string(priv_type_text);
 
 	if (!SearchSysCacheExists1(RELOID, ObjectIdGetDatum(tableoid)))
@@ -1997,7 +1998,7 @@ has_sequence_privilege_name_name(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*rolename));
+	roleid = get_role_oid(NameStr(*rolename), false);
 	mode = convert_sequence_priv_string(priv_type_text);
 	sequenceoid = convert_table_name(sequencename);
 	if (get_rel_relkind(sequenceoid) != RELKIND_SEQUENCE)
@@ -2057,7 +2058,7 @@ has_sequence_privilege_name_id(PG_FUNCTION_ARGS)
 	AclResult	aclresult;
 	char		relkind;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	mode = convert_sequence_priv_string(priv_type_text);
 	relkind = get_rel_relkind(sequenceoid);
 	if (relkind == '\0')
@@ -2208,7 +2209,7 @@ has_any_column_privilege_name_name(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*rolename));
+	roleid = get_role_oid(NameStr(*rolename), false);
 	tableoid = convert_table_name(tablename);
 	mode = convert_column_priv_string(priv_type_text);
 
@@ -2265,7 +2266,7 @@ has_any_column_privilege_name_id(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	mode = convert_column_priv_string(priv_type_text);
 
 	if (!SearchSysCacheExists1(RELOID, ObjectIdGetDatum(tableoid)))
@@ -2450,7 +2451,7 @@ has_column_privilege_name_name_name(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	int			privresult;
 
-	roleid = get_roleid_checked(NameStr(*rolename));
+	roleid = get_role_oid(NameStr(*rolename), false);
 	tableoid = convert_table_name(tablename);
 	colattnum = convert_column_name(tableoid, column);
 	mode = convert_column_priv_string(priv_type_text);
@@ -2478,7 +2479,7 @@ has_column_privilege_name_name_attnum(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	int			privresult;
 
-	roleid = get_roleid_checked(NameStr(*rolename));
+	roleid = get_role_oid(NameStr(*rolename), false);
 	tableoid = convert_table_name(tablename);
 	mode = convert_column_priv_string(priv_type_text);
 
@@ -2505,7 +2506,7 @@ has_column_privilege_name_id_name(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	int			privresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	colattnum = convert_column_name(tableoid, column);
 	mode = convert_column_priv_string(priv_type_text);
 
@@ -2531,7 +2532,7 @@ has_column_privilege_name_id_attnum(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	int			privresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	mode = convert_column_priv_string(priv_type_text);
 
 	privresult = column_privilege_check(tableoid, colattnum, roleid, mode);
@@ -2822,7 +2823,7 @@ has_database_privilege_name_name(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	databaseoid = convert_database_name(databasename);
 	mode = convert_database_priv_string(priv_type_text);
 
@@ -2871,7 +2872,7 @@ has_database_privilege_name_id(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	mode = convert_database_priv_string(priv_type_text);
 
 	if (!SearchSysCacheExists1(DATABASEOID, ObjectIdGetDatum(databaseoid)))
@@ -2966,15 +2967,8 @@ static Oid
 convert_database_name(text *databasename)
 {
 	char	   *dbname = text_to_cstring(databasename);
-	Oid			oid;
 
-	oid = get_database_oid(dbname);
-	if (!OidIsValid(oid))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_DATABASE),
-				 errmsg("database \"%s\" does not exist", dbname)));
-
-	return oid;
+	return get_database_oid(dbname, false);
 }
 
 /*
@@ -3027,7 +3021,7 @@ has_foreign_data_wrapper_privilege_name_name(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	fdwid = convert_foreign_data_wrapper_name(fdwname);
 	mode = convert_foreign_data_wrapper_priv_string(priv_type_text);
 
@@ -3076,7 +3070,7 @@ has_foreign_data_wrapper_privilege_name_id(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	mode = convert_foreign_data_wrapper_priv_string(priv_type_text);
 
 	aclresult = pg_foreign_data_wrapper_aclcheck(fdwid, roleid, mode);
@@ -3209,7 +3203,7 @@ has_function_privilege_name_name(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	functionoid = convert_function_name(functionname);
 	mode = convert_function_priv_string(priv_type_text);
 
@@ -3258,7 +3252,7 @@ has_function_privilege_name_id(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	mode = convert_function_priv_string(priv_type_text);
 
 	if (!SearchSysCacheExists1(PROCOID, ObjectIdGetDatum(functionoid)))
@@ -3409,7 +3403,7 @@ has_language_privilege_name_name(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	languageoid = convert_language_name(languagename);
 	mode = convert_language_priv_string(priv_type_text);
 
@@ -3458,7 +3452,7 @@ has_language_privilege_name_id(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	mode = convert_language_priv_string(priv_type_text);
 
 	if (!SearchSysCacheExists1(LANGOID, ObjectIdGetDatum(languageoid)))
@@ -3553,15 +3547,8 @@ static Oid
 convert_language_name(text *languagename)
 {
 	char	   *langname = text_to_cstring(languagename);
-	Oid			oid;
 
-	oid = GetSysCacheOid1(LANGNAME, CStringGetDatum(langname));
-	if (!OidIsValid(oid))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_OBJECT),
-				 errmsg("language \"%s\" does not exist", langname)));
-
-	return oid;
+	return get_language_oid(langname, false);
 }
 
 /*
@@ -3607,7 +3594,7 @@ has_schema_privilege_name_name(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	schemaoid = convert_schema_name(schemaname);
 	mode = convert_schema_priv_string(priv_type_text);
 
@@ -3656,7 +3643,7 @@ has_schema_privilege_name_id(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	mode = convert_schema_priv_string(priv_type_text);
 
 	if (!SearchSysCacheExists1(NAMESPACEOID, ObjectIdGetDatum(schemaoid)))
@@ -3751,15 +3738,8 @@ static Oid
 convert_schema_name(text *schemaname)
 {
 	char	   *nspname = text_to_cstring(schemaname);
-	Oid			oid;
-
-	oid = GetSysCacheOid1(NAMESPACENAME, CStringGetDatum(nspname));
-	if (!OidIsValid(oid))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_SCHEMA),
-				 errmsg("schema \"%s\" does not exist", nspname)));
 
-	return oid;
+	return get_namespace_oid(nspname, false);
 }
 
 /*
@@ -3807,7 +3787,7 @@ has_server_privilege_name_name(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	serverid = convert_server_name(servername);
 	mode = convert_server_priv_string(priv_type_text);
 
@@ -3856,7 +3836,7 @@ has_server_privilege_name_id(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	mode = convert_server_priv_string(priv_type_text);
 
 	aclresult = pg_foreign_server_aclcheck(serverid, roleid, mode);
@@ -3989,7 +3969,7 @@ has_tablespace_privilege_name_name(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	tablespaceoid = convert_tablespace_name(tablespacename);
 	mode = convert_tablespace_priv_string(priv_type_text);
 
@@ -4038,7 +4018,7 @@ has_tablespace_privilege_name_id(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	mode = convert_tablespace_priv_string(priv_type_text);
 
 	aclresult = pg_tablespace_aclcheck(tablespaceoid, roleid, mode);
@@ -4124,16 +4104,8 @@ static Oid
 convert_tablespace_name(text *tablespacename)
 {
 	char	   *spcname = text_to_cstring(tablespacename);
-	Oid			oid;
 
-	oid = get_tablespace_oid(spcname);
-
-	if (!OidIsValid(oid))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_OBJECT),
-				 errmsg("tablespace \"%s\" does not exist", spcname)));
-
-	return oid;
+	return get_tablespace_oid(spcname, false);
 }
 
 /*
@@ -4178,8 +4150,8 @@ pg_has_role_name_name(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
-	roleoid = get_roleid_checked(NameStr(*rolename));
+	roleid = get_role_oid(NameStr(*username), false);
+	roleoid = get_role_oid(NameStr(*rolename), false);
 	mode = convert_role_priv_string(priv_type_text);
 
 	aclresult = pg_role_aclcheck(roleoid, roleid, mode);
@@ -4204,7 +4176,7 @@ pg_has_role_name(PG_FUNCTION_ARGS)
 	AclResult	aclresult;
 
 	roleid = GetUserId();
-	roleoid = get_roleid_checked(NameStr(*rolename));
+	roleoid = get_role_oid(NameStr(*rolename), false);
 	mode = convert_role_priv_string(priv_type_text);
 
 	aclresult = pg_role_aclcheck(roleoid, roleid, mode);
@@ -4227,7 +4199,7 @@ pg_has_role_name_id(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	mode = convert_role_priv_string(priv_type_text);
 
 	aclresult = pg_role_aclcheck(roleoid, roleid, mode);
@@ -4273,7 +4245,7 @@ pg_has_role_id_name(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleoid = get_roleid_checked(NameStr(*rolename));
+	roleoid = get_role_oid(NameStr(*rolename), false);
 	mode = convert_role_priv_string(priv_type_text);
 
 	aclresult = pg_role_aclcheck(roleoid, roleid, mode);
@@ -4830,3 +4802,22 @@ select_best_grantor(Oid roleId, AclMode privileges,
 		}
 	}
 }
+
+/*
+ * get_role_oid - Given a role name, look up the role's OID.
+ *
+ * If missing_ok is false, throw an error if tablespace name not found.  If
+ * true, just return InvalidOid.
+ */
+Oid
+get_role_oid(const char *rolname, bool missing_ok)
+{
+	Oid			oid;
+
+	oid = GetSysCacheOid1(AUTHNAME, CStringGetDatum(rolname));
+	if (!OidIsValid(oid) && !missing_ok)
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("role \"%s\" does not exist", rolname)));
+	return oid;
+}
diff --git a/src/backend/utils/adt/dbsize.c b/src/backend/utils/adt/dbsize.c
index a4e0252..8ec6b71 100644
--- a/src/backend/utils/adt/dbsize.c
+++ b/src/backend/utils/adt/dbsize.c
@@ -141,13 +141,7 @@ Datum
 pg_database_size_name(PG_FUNCTION_ARGS)
 {
 	Name		dbName = PG_GETARG_NAME(0);
-	Oid			dbOid = get_database_oid(NameStr(*dbName));
-
-	if (!OidIsValid(dbOid))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_DATABASE),
-				 errmsg("database \"%s\" does not exist",
-						NameStr(*dbName))));
+	Oid			dbOid = get_database_oid(NameStr(*dbName), false);
 
 	PG_RETURN_INT64(calculate_database_size(dbOid));
 }
@@ -240,13 +234,7 @@ Datum
 pg_tablespace_size_name(PG_FUNCTION_ARGS)
 {
 	Name		tblspcName = PG_GETARG_NAME(0);
-	Oid			tblspcOid = get_tablespace_oid(NameStr(*tblspcName));
-
-	if (!OidIsValid(tblspcOid))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_OBJECT),
-				 errmsg("tablespace \"%s\" does not exist",
-						NameStr(*tblspcName))));
+	Oid			tblspcOid = get_tablespace_oid(NameStr(*tblspcName), false);
 
 	PG_RETURN_INT64(calculate_tablespace_size(tblspcOid));
 }
diff --git a/src/backend/utils/cache/lsyscache.c b/src/backend/utils/cache/lsyscache.c
index aad6c35..9932415 100644
--- a/src/backend/utils/cache/lsyscache.c
+++ b/src/backend/utils/cache/lsyscache.c
@@ -2626,34 +2626,3 @@ get_namespace_name(Oid nspid)
 	else
 		return NULL;
 }
-
-/*				---------- PG_AUTHID CACHE ----------					 */
-
-/*
- * get_roleid
- *	  Given a role name, look up the role's OID.
- *	  Returns InvalidOid if no such role.
- */
-Oid
-get_roleid(const char *rolname)
-{
-	return GetSysCacheOid1(AUTHNAME, PointerGetDatum(rolname));
-}
-
-/*
- * get_roleid_checked
- *	  Given a role name, look up the role's OID.
- *	  ereports if no such role.
- */
-Oid
-get_roleid_checked(const char *rolname)
-{
-	Oid			roleid;
-
-	roleid = get_roleid(rolname);
-	if (!OidIsValid(roleid))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_OBJECT),
-				 errmsg("role \"%s\" does not exist", rolname)));
-	return roleid;
-}
diff --git a/src/include/catalog/namespace.h b/src/include/catalog/namespace.h
index fe3b783..0fd61a9 100644
--- a/src/include/catalog/namespace.h
+++ b/src/include/catalog/namespace.h
@@ -91,6 +91,7 @@ extern void DeconstructQualifiedName(List *names,
 						 char **objname_p);
 extern Oid	LookupNamespaceNoError(const char *nspname);
 extern Oid	LookupExplicitNamespace(const char *nspname);
+extern Oid	get_namespace_oid(const char *nspname, bool missing_ok);
 
 extern Oid	LookupCreationNamespace(const char *nspname);
 extern Oid	QualifiedNameGetCreationNamespace(List *names, char **objname_p);
diff --git a/src/include/commands/dbcommands.h b/src/include/commands/dbcommands.h
index 542fc27..8c5ba1b 100644
--- a/src/include/commands/dbcommands.h
+++ b/src/include/commands/dbcommands.h
@@ -59,7 +59,7 @@ extern void AlterDatabase(AlterDatabaseStmt *stmt, bool isTopLevel);
 extern void AlterDatabaseSet(AlterDatabaseSetStmt *stmt);
 extern void AlterDatabaseOwner(const char *dbname, Oid newOwnerId);
 
-extern Oid	get_database_oid(const char *dbname);
+extern Oid	get_database_oid(const char *dbname, bool missingok);
 extern char *get_database_name(Oid dbid);
 
 extern void dbase_redo(XLogRecPtr lsn, XLogRecord *rptr);
diff --git a/src/include/commands/defrem.h b/src/include/commands/defrem.h
index e8dbe81..54011a0 100644
--- a/src/include/commands/defrem.h
+++ b/src/include/commands/defrem.h
@@ -97,6 +97,7 @@ extern void RenameOpClass(List *name, const char *access_method, const char *new
 extern void RenameOpFamily(List *name, const char *access_method, const char *newname);
 extern void AlterOpClassOwner(List *name, const char *access_method, Oid newOwnerId);
 extern void AlterOpFamilyOwner(List *name, const char *access_method, Oid newOwnerId);
+extern Oid get_am_oid(const char *amname, bool missing_ok);
 
 /* commands/tsearchcmds.c */
 extern void DefineTSParser(List *names, List *parameters);
diff --git a/src/include/commands/proclang.h b/src/include/commands/proclang.h
index 5feff87..16c1d14 100644
--- a/src/include/commands/proclang.h
+++ b/src/include/commands/proclang.h
@@ -21,5 +21,6 @@ extern void RenameLanguage(const char *oldname, const char *newname);
 extern void AlterLanguageOwner(const char *name, Oid newOwnerId);
 extern void AlterLanguageOwner_oid(Oid oid, Oid newOwnerId);
 extern bool PLTemplateExists(const char *languageName);
+extern Oid get_language_oid(const char *langname, bool missing_ok);
 
 #endif   /* PROCLANG_H */
diff --git a/src/include/commands/tablespace.h b/src/include/commands/tablespace.h
index cf005ee..98a9b86 100644
--- a/src/include/commands/tablespace.h
+++ b/src/include/commands/tablespace.h
@@ -51,7 +51,7 @@ extern Oid	GetDefaultTablespace(bool forTemp);
 
 extern void PrepareTempTablespaces(void);
 
-extern Oid	get_tablespace_oid(const char *tablespacename);
+extern Oid	get_tablespace_oid(const char *tablespacename, bool missing_ok);
 extern char *get_tablespace_name(Oid spc_oid);
 
 extern bool directory_is_empty(const char *path);
diff --git a/src/include/utils/acl.h b/src/include/utils/acl.h
index 9c38bd1..d9921e8 100644
--- a/src/include/utils/acl.h
+++ b/src/include/utils/acl.h
@@ -223,6 +223,7 @@ extern bool is_member_of_role(Oid member, Oid role);
 extern bool is_member_of_role_nosuper(Oid member, Oid role);
 extern bool is_admin_of_role(Oid member, Oid role);
 extern void check_is_member_of_role(Oid member, Oid role);
+extern Oid get_role_oid(const char *rolname, bool missing_ok);
 
 extern void select_best_grantor(Oid roleId, AclMode privileges,
 					const Acl *acl, Oid ownerId,
diff --git a/src/include/utils/lsyscache.h b/src/include/utils/lsyscache.h
index 131acb7..066ad76 100644
--- a/src/include/utils/lsyscache.h
+++ b/src/include/utils/lsyscache.h
@@ -136,8 +136,6 @@ extern void free_attstatsslot(Oid atttype,
 				  Datum *values, int nvalues,
 				  float4 *numbers, int nnumbers);
 extern char *get_namespace_name(Oid nspid);
-extern Oid	get_roleid(const char *rolname);
-extern Oid	get_roleid_checked(const char *rolname);
 
 #define type_is_array(typid)  (get_element_type(typid) != InvalidOid)
 

commit 56bbe72673a6f853e0d868a3c743ab1a926bf2b0
Author: Robert Haas <robertmhaas@gmail.com>
Date:   Sun May 23 00:02:54 2010 -0400

    Standardize get_whatever_oid functions for object types with
    unqualified names.
    
    - Add a missing_ok parameter to get_tablespace_oid.
    - Avoid duplicating get_tablespace_od guts in objectNamesToOids.
    - Add a missing_ok parameter to get_database_oid.
    - Replace get_roleid and get_role_checked with get_role_oid.
    - Add get_namespace_oid, get_language_oid, get_am_oid.
    - Refactor existing code to use new interfaces.

diff --git a/src/backend/catalog/aclchk.c b/src/backend/catalog/aclchk.c
index 23d604e..2b2c326 100644
--- a/src/backend/catalog/aclchk.c
+++ b/src/backend/catalog/aclchk.c
@@ -43,6 +43,8 @@
 #include "catalog/pg_ts_config.h"
 #include "catalog/pg_ts_dict.h"
 #include "commands/dbcommands.h"
+#include "commands/proclang.h"
+#include "commands/tablespace.h"
 #include "foreign/foreign.h"
 #include "miscadmin.h"
 #include "parser/parse_func.h"
@@ -419,7 +421,7 @@ ExecuteGrantStmt(GrantStmt *stmt)
 		else
 			istmt.grantees =
 				lappend_oid(istmt.grantees,
-							get_roleid_checked(grantee->rolname));
+							get_role_oid(grantee->rolname, false));
 	}
 
 	/*
@@ -607,12 +609,7 @@ objectNamesToOids(GrantObjectType objtype, List *objnames)
 				char	   *dbname = strVal(lfirst(cell));
 				Oid			dbid;
 
-				dbid = get_database_oid(dbname);
-				if (!OidIsValid(dbid))
-					ereport(ERROR,
-							(errcode(ERRCODE_UNDEFINED_DATABASE),
-							 errmsg("database \"%s\" does not exist",
-									dbname)));
+				dbid = get_database_oid(dbname, false);
 				objects = lappend_oid(objects, dbid);
 			}
 			break;
@@ -631,18 +628,10 @@ objectNamesToOids(GrantObjectType objtype, List *objnames)
 			foreach(cell, objnames)
 			{
 				char	   *langname = strVal(lfirst(cell));
-				HeapTuple	tuple;
-
-				tuple = SearchSysCache1(LANGNAME, PointerGetDatum(langname));
-				if (!HeapTupleIsValid(tuple))
-					ereport(ERROR,
-							(errcode(ERRCODE_UNDEFINED_OBJECT),
-							 errmsg("language \"%s\" does not exist",
-									langname)));
+				Oid			oid;
 
-				objects = lappend_oid(objects, HeapTupleGetOid(tuple));
-
-				ReleaseSysCache(tuple);
+				oid = get_language_oid(langname, false);
+				objects = lappend_oid(objects, oid);
 			}
 			break;
 		case ACL_OBJECT_LARGEOBJECT:
@@ -663,49 +652,20 @@ objectNamesToOids(GrantObjectType objtype, List *objnames)
 			foreach(cell, objnames)
 			{
 				char	   *nspname = strVal(lfirst(cell));
-				HeapTuple	tuple;
-
-				tuple = SearchSysCache1(NAMESPACENAME,
-										CStringGetDatum(nspname));
-				if (!HeapTupleIsValid(tuple))
-					ereport(ERROR,
-							(errcode(ERRCODE_UNDEFINED_SCHEMA),
-							 errmsg("schema \"%s\" does not exist",
-									nspname)));
-
-				objects = lappend_oid(objects, HeapTupleGetOid(tuple));
+				Oid			oid;
 
-				ReleaseSysCache(tuple);
+				oid = get_namespace_oid(nspname, false);
+				objects = lappend_oid(objects, oid);
 			}
 			break;
 		case ACL_OBJECT_TABLESPACE:
 			foreach(cell, objnames)
 			{
 				char	   *spcname = strVal(lfirst(cell));
-				ScanKeyData entry[1];
-				HeapScanDesc scan;
-				HeapTuple	tuple;
-				Relation	relation;
+				Oid			spcoid;
 
-				relation = heap_open(TableSpaceRelationId, AccessShareLock);
-
-				ScanKeyInit(&entry[0],
-							Anum_pg_tablespace_spcname,
-							BTEqualStrategyNumber, F_NAMEEQ,
-							CStringGetDatum(spcname));
-
-				scan = heap_beginscan(relation, SnapshotNow, 1, entry);
-				tuple = heap_getnext(scan, ForwardScanDirection);
-				if (!HeapTupleIsValid(tuple))
-					ereport(ERROR,
-							(errcode(ERRCODE_UNDEFINED_OBJECT),
-					   errmsg("tablespace \"%s\" does not exist", spcname)));
-
-				objects = lappend_oid(objects, HeapTupleGetOid(tuple));
-
-				heap_endscan(scan);
-
-				heap_close(relation, AccessShareLock);
+				spcoid = get_tablespace_oid(spcname, false);
+				objects = lappend_oid(objects, spcoid);
 			}
 			break;
 		case ACL_OBJECT_FDW:
@@ -913,7 +873,7 @@ ExecAlterDefaultPrivilegesStmt(AlterDefaultPrivilegesStmt *stmt)
 		else
 			iacls.grantees =
 				lappend_oid(iacls.grantees,
-							get_roleid_checked(grantee->rolname));
+							get_role_oid(grantee->rolname, false));
 	}
 
 	/*
@@ -996,7 +956,7 @@ ExecAlterDefaultPrivilegesStmt(AlterDefaultPrivilegesStmt *stmt)
 		{
 			char	   *rolename = strVal(lfirst(rolecell));
 
-			iacls.roleid = get_roleid_checked(rolename);
+			iacls.roleid = get_role_oid(rolename, false);
 
 			/*
 			 * We insist that calling user be a member of each target role. If
@@ -1037,18 +997,12 @@ SetDefaultACLsInSchemas(InternalDefaultACL *iacls, List *nspnames)
 			AclResult	aclresult;
 
 			/*
-			 * Normally we'd use LookupCreationNamespace here, but it's
-			 * important to do the permissions check against the target role
-			 * not the calling user, so write it out in full.  We require
-			 * CREATE privileges, since without CREATE you won't be able to do
-			 * anything using the default privs anyway.
+			 * Note that we must do the permissions check against the target
+			 * role not the calling user.  We require CREATE privileges,
+			 * since without CREATE you won't be able to do anything using the
+			 * default privs anyway.
 			 */
-			iacls->nspid = GetSysCacheOid1(NAMESPACENAME,
-										   CStringGetDatum(nspname));
-			if (!OidIsValid(iacls->nspid))
-				ereport(ERROR,
-						(errcode(ERRCODE_UNDEFINED_SCHEMA),
-						 errmsg("schema \"%s\" does not exist", nspname)));
+			iacls->nspid = get_namespace_oid(nspname, false);
 
 			aclresult = pg_namespace_aclcheck(iacls->nspid, iacls->roleid,
 											  ACL_CREATE);
diff --git a/src/backend/catalog/namespace.c b/src/backend/catalog/namespace.c
index 5581346..52acc23 100644
--- a/src/backend/catalog/namespace.c
+++ b/src/backend/catalog/namespace.c
@@ -332,13 +332,7 @@ RangeVarGetCreationNamespace(const RangeVar *newRelation)
 			return myTempNamespace;
 		}
 		/* use exact schema given */
-		namespaceId = GetSysCacheOid1(NAMESPACENAME,
-								   CStringGetDatum(newRelation->schemaname));
-		if (!OidIsValid(namespaceId))
-			ereport(ERROR,
-					(errcode(ERRCODE_UNDEFINED_SCHEMA),
-					 errmsg("schema \"%s\" does not exist",
-							newRelation->schemaname)));
+		namespaceId = get_namespace_oid(newRelation->schemaname, false);
 		/* we do not check for USAGE rights here! */
 	}
 	else
@@ -2270,7 +2264,7 @@ LookupNamespaceNoError(const char *nspname)
 		return InvalidOid;
 	}
 
-	return GetSysCacheOid1(NAMESPACENAME, CStringGetDatum(nspname));
+	return get_namespace_oid(nspname, true);
 }
 
 /*
@@ -2300,11 +2294,7 @@ LookupExplicitNamespace(const char *nspname)
 		 */
 	}
 
-	namespaceId = GetSysCacheOid1(NAMESPACENAME, CStringGetDatum(nspname));
-	if (!OidIsValid(namespaceId))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_SCHEMA),
-				 errmsg("schema \"%s\" does not exist", nspname)));
+	namespaceId = get_namespace_oid(nspname, false);
 
 	aclresult = pg_namespace_aclcheck(namespaceId, GetUserId(), ACL_USAGE);
 	if (aclresult != ACLCHECK_OK)
@@ -2339,11 +2329,7 @@ LookupCreationNamespace(const char *nspname)
 		return myTempNamespace;
 	}
 
-	namespaceId = GetSysCacheOid1(NAMESPACENAME, CStringGetDatum(nspname));
-	if (!OidIsValid(namespaceId))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_SCHEMA),
-				 errmsg("schema \"%s\" does not exist", nspname)));
+	namespaceId = get_namespace_oid(nspname, false);
 
 	aclresult = pg_namespace_aclcheck(namespaceId, GetUserId(), ACL_CREATE);
 	if (aclresult != ACLCHECK_OK)
@@ -2385,12 +2371,7 @@ QualifiedNameGetCreationNamespace(List *names, char **objname_p)
 			return myTempNamespace;
 		}
 		/* use exact schema given */
-		namespaceId = GetSysCacheOid1(NAMESPACENAME,
-									  CStringGetDatum(schemaname));
-		if (!OidIsValid(namespaceId))
-			ereport(ERROR,
-					(errcode(ERRCODE_UNDEFINED_SCHEMA),
-					 errmsg("schema \"%s\" does not exist", schemaname)));
+		namespaceId = get_namespace_oid(schemaname, false);
 		/* we do not check for USAGE rights here! */
 	}
 	else
@@ -2414,6 +2395,26 @@ QualifiedNameGetCreationNamespace(List *names, char **objname_p)
 }
 
 /*
+ * get_namespace_oid - given a namespace name, look up the OID
+ *
+ * If missing_ok is false, throw an error if namespace name not found.  If
+ * true, just return InvalidOid.
+ */
+Oid
+get_namespace_oid(const char *nspname, bool missing_ok)
+{
+	Oid			oid;
+
+	oid = GetSysCacheOid1(NAMESPACENAME, CStringGetDatum(nspname));
+	if (!OidIsValid(oid) && !missing_ok)
+        ereport(ERROR,
+                (errcode(ERRCODE_UNDEFINED_SCHEMA),
+                 errmsg("schema \"%s\" does not exist", nspname)));
+
+	return oid;
+}
+
+/*
  * makeRangeVarFromNameList
  *		Utility routine to convert a qualified-name list into RangeVar form.
  */
@@ -2897,8 +2898,7 @@ recomputeNamespacePath(void)
 				char	   *rname;
 
 				rname = NameStr(((Form_pg_authid) GETSTRUCT(tuple))->rolname);
-				namespaceId = GetSysCacheOid1(NAMESPACENAME,
-											  CStringGetDatum(rname));
+				namespaceId = get_namespace_oid(rname, true);
 				ReleaseSysCache(tuple);
 				if (OidIsValid(namespaceId) &&
 					!list_member_oid(oidlist, namespaceId) &&
@@ -2925,8 +2925,7 @@ recomputeNamespacePath(void)
 		else
 		{
 			/* normal namespace reference */
-			namespaceId = GetSysCacheOid1(NAMESPACENAME,
-										  CStringGetDatum(curname));
+			namespaceId = get_namespace_oid(curname, true);
 			if (OidIsValid(namespaceId) &&
 				!list_member_oid(oidlist, namespaceId) &&
 				pg_namespace_aclcheck(namespaceId, roleid,
@@ -3033,8 +3032,7 @@ InitTempTableNamespace(void)
 
 	snprintf(namespaceName, sizeof(namespaceName), "pg_temp_%d", MyBackendId);
 
-	namespaceId = GetSysCacheOid1(NAMESPACENAME,
-								  CStringGetDatum(namespaceName));
+	namespaceId = get_namespace_oid(namespaceName, true);
 	if (!OidIsValid(namespaceId))
 	{
 		/*
@@ -3066,8 +3064,7 @@ InitTempTableNamespace(void)
 	snprintf(namespaceName, sizeof(namespaceName), "pg_toast_temp_%d",
 			 MyBackendId);
 
-	toastspaceId = GetSysCacheOid1(NAMESPACENAME,
-								   CStringGetDatum(namespaceName));
+	toastspaceId = get_namespace_oid(namespaceName, true);
 	if (!OidIsValid(toastspaceId))
 	{
 		toastspaceId = NamespaceCreate(namespaceName, BOOTSTRAP_SUPERUSERID);
diff --git a/src/backend/commands/alter.c b/src/backend/commands/alter.c
index a6c4755..f09d595 100644
--- a/src/backend/commands/alter.c
+++ b/src/backend/commands/alter.c
@@ -211,7 +211,7 @@ ExecAlterObjectSchemaStmt(AlterObjectSchemaStmt *stmt)
 void
 ExecAlterOwnerStmt(AlterOwnerStmt *stmt)
 {
-	Oid			newowner = get_roleid_checked(stmt->newowner);
+	Oid			newowner = get_role_oid(stmt->newowner, false);
 
 	switch (stmt->objectType)
 	{
diff --git a/src/backend/commands/comment.c b/src/backend/commands/comment.c
index b613cbf..2ba2368 100644
--- a/src/backend/commands/comment.c
+++ b/src/backend/commands/comment.c
@@ -42,6 +42,8 @@
 #include "catalog/pg_type.h"
 #include "commands/comment.h"
 #include "commands/dbcommands.h"
+#include "commands/defrem.h"
+#include "commands/proclang.h"
 #include "commands/tablespace.h"
 #include "libpq/be-fsstubs.h"
 #include "miscadmin.h"
@@ -686,11 +688,10 @@ CommentDatabase(List *qualname, char *comment)
 	 * of the database.  Erroring out would prevent pg_restore from completing
 	 * (which is really pg_restore's fault, but for now we will work around
 	 * the problem here).  Consensus is that the best fix is to treat wrong
-	 * database name as a WARNING not an ERROR.
+	 * database name as a WARNING not an ERROR (thus, we tell get_database_oid
+	 * to ignore the error so that we can handle it differently here).
 	 */
-
-	/* First get the database OID */
-	oid = get_database_oid(database);
+	oid = get_database_oid(database, true);
 	if (!OidIsValid(oid))
 	{
 		ereport(WARNING,
@@ -729,14 +730,7 @@ CommentTablespace(List *qualname, char *comment)
 				 errmsg("tablespace name cannot be qualified")));
 	tablespace = strVal(linitial(qualname));
 
-	oid = get_tablespace_oid(tablespace);
-	if (!OidIsValid(oid))
-	{
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_OBJECT),
-				 errmsg("tablespace \"%s\" does not exist", tablespace)));
-		return;
-	}
+	oid = get_tablespace_oid(tablespace, false);
 
 	/* Check object security */
 	if (!pg_tablespace_ownercheck(oid, GetUserId()))
@@ -766,7 +760,7 @@ CommentRole(List *qualname, char *comment)
 				 errmsg("role name cannot be qualified")));
 	role = strVal(linitial(qualname));
 
-	oid = get_roleid_checked(role);
+	oid = get_role_oid(role, false);
 
 	/* Check object security */
 	if (!has_privs_of_role(GetUserId(), oid))
@@ -799,11 +793,7 @@ CommentNamespace(List *qualname, char *comment)
 				 errmsg("schema name cannot be qualified")));
 	namespace = strVal(linitial(qualname));
 
-	oid = GetSysCacheOid1(NAMESPACENAME, CStringGetDatum(namespace));
-	if (!OidIsValid(oid))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_SCHEMA),
-				 errmsg("schema \"%s\" does not exist", namespace)));
+	oid = get_namespace_oid(namespace, false);
 
 	/* Check object security */
 	if (!pg_namespace_ownercheck(oid, GetUserId()))
@@ -1213,11 +1203,7 @@ CommentLanguage(List *qualname, char *comment)
 				 errmsg("language name cannot be qualified")));
 	language = strVal(linitial(qualname));
 
-	oid = GetSysCacheOid1(LANGNAME, CStringGetDatum(language));
-	if (!OidIsValid(oid))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_SCHEMA),
-				 errmsg("language \"%s\" does not exist", language)));
+	oid = get_language_oid(language, false);
 
 	/* Check object security */
 	if (!superuser())
@@ -1254,12 +1240,7 @@ CommentOpClass(List *qualname, List *arguments, char *comment)
 	/*
 	 * Get the access method's OID.
 	 */
-	amID = GetSysCacheOid1(AMNAME, CStringGetDatum(amname));
-	if (!OidIsValid(amID))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_OBJECT),
-				 errmsg("access method \"%s\" does not exist",
-						amname)));
+	amID = get_am_oid(amname, false);
 
 	/*
 	 * Look up the opclass.
@@ -1335,12 +1316,7 @@ CommentOpFamily(List *qualname, List *arguments, char *comment)
 	/*
 	 * Get the access method's OID.
 	 */
-	amID = GetSysCacheOid1(AMNAME, CStringGetDatum(amname));
-	if (!OidIsValid(amID))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_OBJECT),
-				 errmsg("access method \"%s\" does not exist",
-						amname)));
+	amID = get_am_oid(amname, false);
 
 	/*
 	 * Look up the opfamily.
diff --git a/src/backend/commands/dbcommands.c b/src/backend/commands/dbcommands.c
index e7dac22..9937083 100644
--- a/src/backend/commands/dbcommands.c
+++ b/src/backend/commands/dbcommands.c
@@ -255,7 +255,7 @@ createdb(const CreatedbStmt *stmt)
 
 	/* obtain OID of proposed owner */
 	if (dbowner)
-		datdba = get_roleid_checked(dbowner);
+		datdba = get_role_oid(dbowner, false);
 	else
 		datdba = GetUserId();
 
@@ -429,12 +429,7 @@ createdb(const CreatedbStmt *stmt)
 		AclResult	aclresult;
 
 		tablespacename = strVal(dtablespacename->arg);
-		dst_deftablespace = get_tablespace_oid(tablespacename);
-		if (!OidIsValid(dst_deftablespace))
-			ereport(ERROR,
-					(errcode(ERRCODE_UNDEFINED_OBJECT),
-					 errmsg("tablespace \"%s\" does not exist",
-							tablespacename)));
+		dst_deftablespace = get_tablespace_oid(tablespacename, false);
 		/* check permissions */
 		aclresult = pg_tablespace_aclcheck(dst_deftablespace, GetUserId(),
 										   ACL_CREATE);
@@ -491,7 +486,7 @@ createdb(const CreatedbStmt *stmt)
 	 * message than "unique index violation".  There's a race condition but
 	 * we're willing to accept the less friendly message in that case.
 	 */
-	if (OidIsValid(get_database_oid(dbname)))
+	if (OidIsValid(get_database_oid(dbname, true)))
 		ereport(ERROR,
 				(errcode(ERRCODE_DUPLICATE_DATABASE),
 				 errmsg("database \"%s\" already exists", dbname)));
@@ -919,7 +914,7 @@ RenameDatabase(const char *oldname, const char *newname)
 	 * Make sure the new name doesn't exist.  See notes for same error in
 	 * CREATE DATABASE.
 	 */
-	if (OidIsValid(get_database_oid(newname)))
+	if (OidIsValid(get_database_oid(newname, true)))
 		ereport(ERROR,
 				(errcode(ERRCODE_DUPLICATE_DATABASE),
 				 errmsg("database \"%s\" already exists", newname)));
@@ -1030,11 +1025,7 @@ movedb(const char *dbname, const char *tblspcname)
 	/*
 	 * Get tablespace's oid
 	 */
-	dst_tblspcoid = get_tablespace_oid(tblspcname);
-	if (dst_tblspcoid == InvalidOid)
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_DATABASE),
-				 errmsg("tablespace \"%s\" does not exist", tblspcname)));
+	dst_tblspcoid = get_tablespace_oid(tblspcname, false);
 
 	/*
 	 * Permission checks
@@ -1402,12 +1393,7 @@ AlterDatabase(AlterDatabaseStmt *stmt, bool isTopLevel)
 void
 AlterDatabaseSet(AlterDatabaseSetStmt *stmt)
 {
-	Oid			datid = get_database_oid(stmt->dbname);
-
-	if (!OidIsValid(datid))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_DATABASE),
-				 errmsg("database \"%s\" does not exist", stmt->dbname)));
+	Oid			datid = get_database_oid(stmt->dbname, false);
 
 	/*
 	 * Obtain a lock on the database and make sure it didn't go away in the
@@ -1818,10 +1804,11 @@ errdetail_busy_db(int notherbackends, int npreparedxacts)
 /*
  * get_database_oid - given a database name, look up the OID
  *
- * Returns InvalidOid if database name not found.
+ * If missing_ok is false, throw an error if database name not found.  If
+ * true, just return InvalidOid.
  */
 Oid
-get_database_oid(const char *dbname)
+get_database_oid(const char *dbname, bool missing_ok)
 {
 	Relation	pg_database;
 	ScanKeyData entry[1];
@@ -1852,6 +1839,12 @@ get_database_oid(const char *dbname)
 	systable_endscan(scan);
 	heap_close(pg_database, AccessShareLock);
 
+	if (!OidIsValid(oid) && !missing_ok)
+        ereport(ERROR,
+                (errcode(ERRCODE_UNDEFINED_DATABASE),
+                 errmsg("database \"%s\" does not exist",
+                        dbname)));
+
 	return oid;
 }
 
diff --git a/src/backend/commands/foreigncmds.c b/src/backend/commands/foreigncmds.c
index 14356a2..6b22570 100644
--- a/src/backend/commands/foreigncmds.c
+++ b/src/backend/commands/foreigncmds.c
@@ -184,7 +184,7 @@ GetUserOidFromMapping(const char *username, bool missing_ok)
 		return GetUserId();
 
 	/* map to provided user */
-	return missing_ok ? get_roleid(username) : get_roleid_checked(username);
+	return get_role_oid(username, missing_ok);
 }
 
 
diff --git a/src/backend/commands/indexcmds.c b/src/backend/commands/indexcmds.c
index 503148f..60f4c44 100644
--- a/src/backend/commands/indexcmds.c
+++ b/src/backend/commands/indexcmds.c
@@ -218,12 +218,7 @@ DefineIndex(RangeVar *heapRelation,
 	 */
 	if (tableSpaceName)
 	{
-		tablespaceId = get_tablespace_oid(tableSpaceName);
-		if (!OidIsValid(tablespaceId))
-			ereport(ERROR,
-					(errcode(ERRCODE_UNDEFINED_OBJECT),
-					 errmsg("tablespace \"%s\" does not exist",
-							tableSpaceName)));
+		tablespaceId = get_tablespace_oid(tableSpaceName, false);
 	}
 	else
 	{
diff --git a/src/backend/commands/opclasscmds.c b/src/backend/commands/opclasscmds.c
index 0d6aad1..d2d9f3a 100644
--- a/src/backend/commands/opclasscmds.c
+++ b/src/backend/commands/opclasscmds.c
@@ -661,20 +661,11 @@ DefineOpFamily(CreateOpFamilyStmt *stmt)
 		aclcheck_error(aclresult, ACL_KIND_NAMESPACE,
 					   get_namespace_name(namespaceoid));
 
-	/* Get necessary info about access method */
-	tup = SearchSysCache1(AMNAME, CStringGetDatum(stmt->amname));
-	if (!HeapTupleIsValid(tup))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_OBJECT),
-				 errmsg("access method \"%s\" does not exist",
-						stmt->amname)));
-
-	amoid = HeapTupleGetOid(tup);
+	/* Get access method OID, throwing an error if it doesn't exist. */
+	amoid = get_am_oid(stmt->amname, false);
 
 	/* XXX Should we make any privilege check against the AM? */
 
-	ReleaseSysCache(tup);
-
 	/*
 	 * Currently, we require superuser privileges to create an opfamily. See
 	 * comments in DefineOpClass.
@@ -1488,12 +1479,7 @@ RemoveOpClass(RemoveOpClassStmt *stmt)
 	/*
 	 * Get the access method's OID.
 	 */
-	amID = GetSysCacheOid1(AMNAME, CStringGetDatum(stmt->amname));
-	if (!OidIsValid(amID))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_OBJECT),
-				 errmsg("access method \"%s\" does not exist",
-						stmt->amname)));
+	amID = get_am_oid(stmt->amname, false);
 
 	/*
 	 * Look up the opclass.
@@ -1549,12 +1535,7 @@ RemoveOpFamily(RemoveOpFamilyStmt *stmt)
 	/*
 	 * Get the access method's OID.
 	 */
-	amID = GetSysCacheOid1(AMNAME, CStringGetDatum(stmt->amname));
-	if (!OidIsValid(amID))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_OBJECT),
-				 errmsg("access method \"%s\" does not exist",
-						stmt->amname)));
+	amID = get_am_oid(stmt->amname, false);
 
 	/*
 	 * Look up the opfamily.
@@ -1711,12 +1692,7 @@ RenameOpClass(List *name, const char *access_method, const char *newname)
 	Relation	rel;
 	AclResult	aclresult;
 
-	amOid = GetSysCacheOid1(AMNAME, CStringGetDatum(access_method));
-	if (!OidIsValid(amOid))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_OBJECT),
-				 errmsg("access method \"%s\" does not exist",
-						access_method)));
+	amOid = get_am_oid(access_method, false);
 
 	rel = heap_open(OperatorClassRelationId, RowExclusiveLock);
 
@@ -1805,12 +1781,7 @@ RenameOpFamily(List *name, const char *access_method, const char *newname)
 	Relation	rel;
 	AclResult	aclresult;
 
-	amOid = GetSysCacheOid1(AMNAME, CStringGetDatum(access_method));
-	if (!OidIsValid(amOid))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_OBJECT),
-				 errmsg("access method \"%s\" does not exist",
-						access_method)));
+	amOid = get_am_oid(access_method, false);
 
 	rel = heap_open(OperatorFamilyRelationId, RowExclusiveLock);
 
@@ -1896,12 +1867,7 @@ AlterOpClassOwner(List *name, const char *access_method, Oid newOwnerId)
 	char	   *opcname;
 	char	   *schemaname;
 
-	amOid = GetSysCacheOid1(AMNAME, CStringGetDatum(access_method));
-	if (!OidIsValid(amOid))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_OBJECT),
-				 errmsg("access method \"%s\" does not exist",
-						access_method)));
+	amOid = get_am_oid(access_method, false);
 
 	rel = heap_open(OperatorClassRelationId, RowExclusiveLock);
 
@@ -2039,12 +2005,7 @@ AlterOpFamilyOwner(List *name, const char *access_method, Oid newOwnerId)
 	char	   *opfname;
 	char	   *schemaname;
 
-	amOid = GetSysCacheOid1(AMNAME, CStringGetDatum(access_method));
-	if (!OidIsValid(amOid))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_OBJECT),
-				 errmsg("access method \"%s\" does not exist",
-						access_method)));
+	amOid = get_am_oid(access_method, false);
 
 	rel = heap_open(OperatorFamilyRelationId, RowExclusiveLock);
 
@@ -2169,3 +2130,22 @@ AlterOpFamilyOwner_internal(Relation rel, HeapTuple tup, Oid newOwnerId)
 								newOwnerId);
 	}
 }
+
+/*
+ * get_am_oid - given an access method name, look up the OID
+ *
+ * If missing_ok is false, throw an error if access method not found.  If
+ * true, just return InvalidOid.
+ */
+Oid
+get_am_oid(const char *amname, bool missing_ok)
+{
+	Oid			oid;
+
+	oid = GetSysCacheOid1(AMNAME, CStringGetDatum(amname));
+	if (!OidIsValid(oid) && !missing_ok)
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("access method \"%s\" does not exist", amname)));
+	return oid;
+}
diff --git a/src/backend/commands/proclang.c b/src/backend/commands/proclang.c
index 633a093..a4e3afe 100644
--- a/src/backend/commands/proclang.c
+++ b/src/backend/commands/proclang.c
@@ -514,7 +514,7 @@ void
 DropProceduralLanguage(DropPLangStmt *stmt)
 {
 	char	   *languageName;
-	HeapTuple	langTup;
+	Oid			oid;
 	ObjectAddress object;
 
 	/*
@@ -522,34 +522,26 @@ DropProceduralLanguage(DropPLangStmt *stmt)
 	 */
 	languageName = case_translate_language_name(stmt->plname);
 
-	langTup = SearchSysCache1(LANGNAME, CStringGetDatum(languageName));
-	if (!HeapTupleIsValid(langTup))
+	oid = get_language_oid(languageName, stmt->missing_ok);
+	if (!OidIsValid(oid))
 	{
-		if (!stmt->missing_ok)
-			ereport(ERROR,
-					(errcode(ERRCODE_UNDEFINED_OBJECT),
-					 errmsg("language \"%s\" does not exist", languageName)));
-		else
-			ereport(NOTICE,
-					(errmsg("language \"%s\" does not exist, skipping",
-							languageName)));
-
+		ereport(NOTICE,
+				(errmsg("language \"%s\" does not exist, skipping",
+						languageName)));
 		return;
 	}
 
 	/*
 	 * Check permission
 	 */
-	if (!pg_language_ownercheck(HeapTupleGetOid(langTup), GetUserId()))
+	if (!pg_language_ownercheck(oid, GetUserId()))
 		aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_LANGUAGE,
 					   languageName);
 
 	object.classId = LanguageRelationId;
-	object.objectId = HeapTupleGetOid(langTup);
+	object.objectId = oid;
 	object.objectSubId = 0;
 
-	ReleaseSysCache(langTup);
-
 	/*
 	 * Do the deletion
 	 */
@@ -735,3 +727,22 @@ AlterLanguageOwner_internal(HeapTuple tup, Relation rel, Oid newOwnerId)
 								newOwnerId);
 	}
 }
+
+/*
+ * get_language_oid - given a language name, look up the OID
+ *
+ * If missing_ok is false, throw an error if language name not found.  If
+ * true, just return InvalidOid.
+ */
+Oid
+get_language_oid(const char *langname, bool missing_ok)
+{
+	Oid			oid;
+
+	oid = GetSysCacheOid1(LANGNAME, CStringGetDatum(langname));
+	if (!OidIsValid(oid) && !missing_ok)
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("language \"%s\" does not exist", langname)));
+	return oid;
+}
diff --git a/src/backend/commands/schemacmds.c b/src/backend/commands/schemacmds.c
index b0a9a22..9edd59d 100644
--- a/src/backend/commands/schemacmds.c
+++ b/src/backend/commands/schemacmds.c
@@ -57,7 +57,7 @@ CreateSchemaCommand(CreateSchemaStmt *stmt, const char *queryString)
 	 * Who is supposed to own the new schema?
 	 */
 	if (authId)
-		owner_uid = get_roleid_checked(authId);
+		owner_uid = get_role_oid(authId, false);
 	else
 		owner_uid = saved_uid;
 
@@ -178,24 +178,13 @@ RemoveSchemas(DropStmt *drop)
 					 errmsg("schema name cannot be qualified")));
 		namespaceName = strVal(linitial(names));
 
-		namespaceId = GetSysCacheOid1(NAMESPACENAME,
-									  CStringGetDatum(namespaceName));
+		namespaceId = get_namespace_oid(namespaceName, drop->missing_ok);
 
 		if (!OidIsValid(namespaceId))
 		{
-			if (!drop->missing_ok)
-			{
-				ereport(ERROR,
-						(errcode(ERRCODE_UNDEFINED_SCHEMA),
-						 errmsg("schema \"%s\" does not exist",
-								namespaceName)));
-			}
-			else
-			{
-				ereport(NOTICE,
-						(errmsg("schema \"%s\" does not exist, skipping",
-								namespaceName)));
-			}
+			ereport(NOTICE,
+					(errmsg("schema \"%s\" does not exist, skipping",
+							namespaceName)));
 			continue;
 		}
 
@@ -264,9 +253,7 @@ RenameSchema(const char *oldname, const char *newname)
 				 errmsg("schema \"%s\" does not exist", oldname)));
 
 	/* make sure the new name doesn't exist */
-	if (HeapTupleIsValid(
-						 SearchSysCache1(NAMESPACENAME,
-										 CStringGetDatum(newname))))
+	if (OidIsValid(get_namespace_oid(newname, true)))
 		ereport(ERROR,
 				(errcode(ERRCODE_DUPLICATE_SCHEMA),
 				 errmsg("schema \"%s\" already exists", newname)));
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index b32cd4f..fb50827 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -411,12 +411,7 @@ DefineRelation(CreateStmt *stmt, char relkind)
 	 */
 	if (stmt->tablespacename)
 	{
-		tablespaceId = get_tablespace_oid(stmt->tablespacename);
-		if (!OidIsValid(tablespaceId))
-			ereport(ERROR,
-					(errcode(ERRCODE_UNDEFINED_OBJECT),
-					 errmsg("tablespace \"%s\" does not exist",
-							stmt->tablespacename)));
+		tablespaceId = get_tablespace_oid(stmt->tablespacename, false);
 	}
 	else
 	{
@@ -2750,7 +2745,7 @@ ATExecCmd(List **wqueue, AlteredTableInfo *tab, Relation rel,
 			break;
 		case AT_ChangeOwner:	/* ALTER OWNER */
 			ATExecChangeOwner(RelationGetRelid(rel),
-							  get_roleid_checked(cmd->name),
+							  get_role_oid(cmd->name, false),
 							  false);
 			break;
 		case AT_ClusterOn:		/* CLUSTER ON */
@@ -6739,11 +6734,7 @@ ATPrepSetTableSpace(AlteredTableInfo *tab, Relation rel, char *tablespacename)
 	AclResult	aclresult;
 
 	/* Check that the tablespace exists */
-	tablespaceId = get_tablespace_oid(tablespacename);
-	if (!OidIsValid(tablespaceId))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_OBJECT),
-				 errmsg("tablespace \"%s\" does not exist", tablespacename)));
+	tablespaceId = get_tablespace_oid(tablespacename, false);
 
 	/* Check its permissions */
 	aclresult = pg_tablespace_aclcheck(tablespaceId, GetUserId(), ACL_CREATE);
diff --git a/src/backend/commands/tablespace.c b/src/backend/commands/tablespace.c
index 58a7b75..08a8c48 100644
--- a/src/backend/commands/tablespace.c
+++ b/src/backend/commands/tablespace.c
@@ -246,7 +246,7 @@ CreateTableSpace(CreateTableSpaceStmt *stmt)
 
 	/* However, the eventual owner of the tablespace need not be */
 	if (stmt->owner)
-		ownerId = get_roleid_checked(stmt->owner);
+		ownerId = get_role_oid(stmt->owner, false);
 	else
 		ownerId = GetUserId();
 
@@ -298,7 +298,7 @@ CreateTableSpace(CreateTableSpaceStmt *stmt)
 	 * index would catch this anyway, but might as well give a friendlier
 	 * message.)
 	 */
-	if (OidIsValid(get_tablespace_oid(stmt->tablespacename)))
+	if (OidIsValid(get_tablespace_oid(stmt->tablespacename, true)))
 		ereport(ERROR,
 				(errcode(ERRCODE_DUPLICATE_OBJECT),
 				 errmsg("tablespace \"%s\" already exists",
@@ -1000,7 +1000,7 @@ assign_default_tablespace(const char *newval, bool doit, GucSource source)
 	if (IsTransactionState())
 	{
 		if (newval[0] != '\0' &&
-			!OidIsValid(get_tablespace_oid(newval)))
+			!OidIsValid(get_tablespace_oid(newval, true)))
 		{
 			ereport(GUC_complaint_elevel(source),
 					(errcode(ERRCODE_UNDEFINED_OBJECT),
@@ -1050,7 +1050,7 @@ GetDefaultTablespace(bool forTemp)
 	 * to refer to an existing tablespace; we just silently return InvalidOid,
 	 * causing the new object to be created in the database's tablespace.
 	 */
-	result = get_tablespace_oid(default_tablespace);
+	result = get_tablespace_oid(default_tablespace, true);
 
 	/*
 	 * Allow explicit specification of database's default tablespace in
@@ -1117,21 +1117,13 @@ assign_temp_tablespaces(const char *newval, bool doit, GucSource source)
 				continue;
 			}
 
-			/* Else verify that name is a valid tablespace name */
-			curoid = get_tablespace_oid(curname);
+			/*
+			 * In an interactive SET command, we ereport for bad info.
+			 * Otherwise, silently ignore any bad list elements.
+			 */
+			curoid = get_tablespace_oid(curname, source < PGC_S_INTERACTIVE);
 			if (curoid == InvalidOid)
-			{
-				/*
-				 * In an interactive SET command, we ereport for bad info.
-				 * Otherwise, silently ignore any bad list elements.
-				 */
-				if (source >= PGC_S_INTERACTIVE)
-					ereport(ERROR,
-							(errcode(ERRCODE_UNDEFINED_OBJECT),
-							 errmsg("tablespace \"%s\" does not exist",
-									curname)));
 				continue;
-			}
 
 			/*
 			 * Allow explicit specification of database's default tablespace
@@ -1230,10 +1222,10 @@ PrepareTempTablespaces(void)
 		}
 
 		/* Else verify that name is a valid tablespace name */
-		curoid = get_tablespace_oid(curname);
+		curoid = get_tablespace_oid(curname, true);
 		if (curoid == InvalidOid)
 		{
-			/* Silently ignore any bad list elements */
+			/* Skip any bad list elements */
 			continue;
 		}
 
@@ -1266,10 +1258,11 @@ PrepareTempTablespaces(void)
 /*
  * get_tablespace_oid - given a tablespace name, look up the OID
  *
- * Returns InvalidOid if tablespace name not found.
+ * If missing_ok is false, throw an error if tablespace name not found.  If
+ * true, just return InvalidOid.
  */
 Oid
-get_tablespace_oid(const char *tablespacename)
+get_tablespace_oid(const char *tablespacename, bool missing_ok)
 {
 	Oid			result;
 	Relation	rel;
@@ -1300,6 +1293,12 @@ get_tablespace_oid(const char *tablespacename)
 	heap_endscan(scandesc);
 	heap_close(rel, AccessShareLock);
 
+	if (!OidIsValid(result) && !missing_ok)
+        ereport(ERROR,
+                (errcode(ERRCODE_UNDEFINED_OBJECT),
+                 errmsg("tablespace \"%s\" does not exist",
+                        tablespacename)));
+
 	return result;
 }
 
diff --git a/src/backend/commands/user.c b/src/backend/commands/user.c
index 2f0788e..1c73d9b 100644
--- a/src/backend/commands/user.c
+++ b/src/backend/commands/user.c
@@ -293,8 +293,7 @@ CreateRole(CreateRoleStmt *stmt)
 	pg_authid_rel = heap_open(AuthIdRelationId, RowExclusiveLock);
 	pg_authid_dsc = RelationGetDescr(pg_authid_rel);
 
-	tuple = SearchSysCache1(AUTHNAME, PointerGetDatum(stmt->role));
-	if (HeapTupleIsValid(tuple))
+	if (OidIsValid(get_role_oid(stmt->role, true)))
 		ereport(ERROR,
 				(errcode(ERRCODE_DUPLICATE_OBJECT),
 				 errmsg("role \"%s\" already exists",
@@ -384,7 +383,7 @@ CreateRole(CreateRoleStmt *stmt)
 	foreach(item, addroleto)
 	{
 		char	   *oldrolename = strVal(lfirst(item));
-		Oid			oldroleid = get_roleid_checked(oldrolename);
+		Oid			oldroleid = get_role_oid(oldrolename, false);
 
 		AddRoleMems(oldrolename, oldroleid,
 					list_make1(makeString(stmt->role)),
@@ -795,11 +794,7 @@ AlterRoleSet(AlterRoleSetStmt *stmt)
 	/* look up and lock the database, if specified */
 	if (stmt->database != NULL)
 	{
-		databaseid = get_database_oid(stmt->database);
-		if (!OidIsValid(databaseid))
-			ereport(ERROR,
-					(errcode(ERRCODE_UNDEFINED_OBJECT),
-					 errmsg("database \"%s\" not found", stmt->database)));
+		databaseid = get_database_oid(stmt->database, false);
 		shdepLockAndCheckObject(DatabaseRelationId, databaseid);
 	}
 
@@ -1099,7 +1094,7 @@ GrantRole(GrantRoleStmt *stmt)
 	ListCell   *item;
 
 	if (stmt->grantor)
-		grantor = get_roleid_checked(stmt->grantor);
+		grantor = get_role_oid(stmt->grantor, false);
 	else
 		grantor = GetUserId();
 
@@ -1127,7 +1122,7 @@ GrantRole(GrantRoleStmt *stmt)
 					(errcode(ERRCODE_INVALID_GRANT_OPERATION),
 			errmsg("column names cannot be included in GRANT/REVOKE ROLE")));
 
-		roleid = get_roleid_checked(rolename);
+		roleid = get_role_oid(rolename, false);
 		if (stmt->is_grant)
 			AddRoleMems(rolename, roleid,
 						stmt->grantee_roles, grantee_ids,
@@ -1194,7 +1189,7 @@ ReassignOwnedObjects(ReassignOwnedStmt *stmt)
 	}
 
 	/* Must have privileges on the receiving side too */
-	newrole = get_roleid_checked(stmt->newrole);
+	newrole = get_role_oid(stmt->newrole, false);
 
 	if (!has_privs_of_role(GetUserId(), newrole))
 		ereport(ERROR,
@@ -1220,7 +1215,7 @@ roleNamesToIds(List *memberNames)
 	foreach(l, memberNames)
 	{
 		char	   *rolename = strVal(lfirst(l));
-		Oid			roleid = get_roleid_checked(rolename);
+		Oid			roleid = get_role_oid(rolename, false);
 
 		result = lappend_oid(result, roleid);
 	}
diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
index d299310..857483a 100644
--- a/src/backend/executor/execMain.c
+++ b/src/backend/executor/execMain.c
@@ -2118,12 +2118,7 @@ OpenIntoRel(QueryDesc *queryDesc)
 	 */
 	if (into->tableSpaceName)
 	{
-		tablespaceId = get_tablespace_oid(into->tableSpaceName);
-		if (!OidIsValid(tablespaceId))
-			ereport(ERROR,
-					(errcode(ERRCODE_UNDEFINED_OBJECT),
-					 errmsg("tablespace \"%s\" does not exist",
-							into->tableSpaceName)));
+		tablespaceId = get_tablespace_oid(into->tableSpaceName, false);
 	}
 	else
 	{
diff --git a/src/backend/libpq/hba.c b/src/backend/libpq/hba.c
index c967364..7ee7842 100644
--- a/src/backend/libpq/hba.c
+++ b/src/backend/libpq/hba.c
@@ -459,7 +459,7 @@ is_member(Oid userid, const char *role)
 	if (!OidIsValid(userid))
 		return false;			/* if user not exist, say "no" */
 
-	roleid = get_roleid(role);
+	roleid = get_role_oid(role, true);
 
 	if (!OidIsValid(roleid))
 		return false;			/* if target role not exist, say "no" */
@@ -1327,7 +1327,7 @@ check_hba(hbaPort *port)
 	HbaLine    *hba;
 
 	/* Get the target role's OID.  Note we do not error out for bad role. */
-	roleid = get_roleid(port->user_name);
+	roleid = get_role_oid(port->user_name, true);
 
 	foreach(line, parsed_hba_lines)
 	{
diff --git a/src/backend/utils/adt/acl.c b/src/backend/utils/adt/acl.c
index faad11e..b320569 100644
--- a/src/backend/utils/adt/acl.c
+++ b/src/backend/utils/adt/acl.c
@@ -22,6 +22,7 @@
 #include "catalog/pg_type.h"
 #include "catalog/pg_class.h"
 #include "commands/dbcommands.h"
+#include "commands/proclang.h"
 #include "commands/tablespace.h"
 #include "foreign/foreign.h"
 #include "funcapi.h"
@@ -324,7 +325,7 @@ aclparse(const char *s, AclItem *aip)
 	if (name[0] == '\0')
 		aip->ai_grantee = ACL_ID_PUBLIC;
 	else
-		aip->ai_grantee = get_roleid_checked(name);
+		aip->ai_grantee = get_role_oid(name, false);
 
 	/*
 	 * XXX Allow a degree of backward compatibility by defaulting the grantor
@@ -337,7 +338,7 @@ aclparse(const char *s, AclItem *aip)
 			ereport(ERROR,
 					(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
 					 errmsg("a name must follow the \"/\" sign")));
-		aip->ai_grantor = get_roleid_checked(name2);
+		aip->ai_grantor = get_role_oid(name2, false);
 	}
 	else
 	{
@@ -1790,7 +1791,7 @@ has_table_privilege_name_name(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*rolename));
+	roleid = get_role_oid(NameStr(*rolename), false);
 	tableoid = convert_table_name(tablename);
 	mode = convert_table_priv_string(priv_type_text);
 
@@ -1839,7 +1840,7 @@ has_table_privilege_name_id(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	mode = convert_table_priv_string(priv_type_text);
 
 	if (!SearchSysCacheExists1(RELOID, ObjectIdGetDatum(tableoid)))
@@ -1997,7 +1998,7 @@ has_sequence_privilege_name_name(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*rolename));
+	roleid = get_role_oid(NameStr(*rolename), false);
 	mode = convert_sequence_priv_string(priv_type_text);
 	sequenceoid = convert_table_name(sequencename);
 	if (get_rel_relkind(sequenceoid) != RELKIND_SEQUENCE)
@@ -2057,7 +2058,7 @@ has_sequence_privilege_name_id(PG_FUNCTION_ARGS)
 	AclResult	aclresult;
 	char		relkind;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	mode = convert_sequence_priv_string(priv_type_text);
 	relkind = get_rel_relkind(sequenceoid);
 	if (relkind == '\0')
@@ -2208,7 +2209,7 @@ has_any_column_privilege_name_name(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*rolename));
+	roleid = get_role_oid(NameStr(*rolename), false);
 	tableoid = convert_table_name(tablename);
 	mode = convert_column_priv_string(priv_type_text);
 
@@ -2265,7 +2266,7 @@ has_any_column_privilege_name_id(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	mode = convert_column_priv_string(priv_type_text);
 
 	if (!SearchSysCacheExists1(RELOID, ObjectIdGetDatum(tableoid)))
@@ -2450,7 +2451,7 @@ has_column_privilege_name_name_name(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	int			privresult;
 
-	roleid = get_roleid_checked(NameStr(*rolename));
+	roleid = get_role_oid(NameStr(*rolename), false);
 	tableoid = convert_table_name(tablename);
 	colattnum = convert_column_name(tableoid, column);
 	mode = convert_column_priv_string(priv_type_text);
@@ -2478,7 +2479,7 @@ has_column_privilege_name_name_attnum(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	int			privresult;
 
-	roleid = get_roleid_checked(NameStr(*rolename));
+	roleid = get_role_oid(NameStr(*rolename), false);
 	tableoid = convert_table_name(tablename);
 	mode = convert_column_priv_string(priv_type_text);
 
@@ -2505,7 +2506,7 @@ has_column_privilege_name_id_name(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	int			privresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	colattnum = convert_column_name(tableoid, column);
 	mode = convert_column_priv_string(priv_type_text);
 
@@ -2531,7 +2532,7 @@ has_column_privilege_name_id_attnum(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	int			privresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	mode = convert_column_priv_string(priv_type_text);
 
 	privresult = column_privilege_check(tableoid, colattnum, roleid, mode);
@@ -2822,7 +2823,7 @@ has_database_privilege_name_name(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	databaseoid = convert_database_name(databasename);
 	mode = convert_database_priv_string(priv_type_text);
 
@@ -2871,7 +2872,7 @@ has_database_privilege_name_id(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	mode = convert_database_priv_string(priv_type_text);
 
 	if (!SearchSysCacheExists1(DATABASEOID, ObjectIdGetDatum(databaseoid)))
@@ -2966,15 +2967,8 @@ static Oid
 convert_database_name(text *databasename)
 {
 	char	   *dbname = text_to_cstring(databasename);
-	Oid			oid;
 
-	oid = get_database_oid(dbname);
-	if (!OidIsValid(oid))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_DATABASE),
-				 errmsg("database \"%s\" does not exist", dbname)));
-
-	return oid;
+	return get_database_oid(dbname, false);
 }
 
 /*
@@ -3027,7 +3021,7 @@ has_foreign_data_wrapper_privilege_name_name(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	fdwid = convert_foreign_data_wrapper_name(fdwname);
 	mode = convert_foreign_data_wrapper_priv_string(priv_type_text);
 
@@ -3076,7 +3070,7 @@ has_foreign_data_wrapper_privilege_name_id(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	mode = convert_foreign_data_wrapper_priv_string(priv_type_text);
 
 	aclresult = pg_foreign_data_wrapper_aclcheck(fdwid, roleid, mode);
@@ -3209,7 +3203,7 @@ has_function_privilege_name_name(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	functionoid = convert_function_name(functionname);
 	mode = convert_function_priv_string(priv_type_text);
 
@@ -3258,7 +3252,7 @@ has_function_privilege_name_id(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	mode = convert_function_priv_string(priv_type_text);
 
 	if (!SearchSysCacheExists1(PROCOID, ObjectIdGetDatum(functionoid)))
@@ -3409,7 +3403,7 @@ has_language_privilege_name_name(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	languageoid = convert_language_name(languagename);
 	mode = convert_language_priv_string(priv_type_text);
 
@@ -3458,7 +3452,7 @@ has_language_privilege_name_id(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	mode = convert_language_priv_string(priv_type_text);
 
 	if (!SearchSysCacheExists1(LANGOID, ObjectIdGetDatum(languageoid)))
@@ -3553,15 +3547,8 @@ static Oid
 convert_language_name(text *languagename)
 {
 	char	   *langname = text_to_cstring(languagename);
-	Oid			oid;
 
-	oid = GetSysCacheOid1(LANGNAME, CStringGetDatum(langname));
-	if (!OidIsValid(oid))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_OBJECT),
-				 errmsg("language \"%s\" does not exist", langname)));
-
-	return oid;
+	return get_language_oid(langname, false);
 }
 
 /*
@@ -3607,7 +3594,7 @@ has_schema_privilege_name_name(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	schemaoid = convert_schema_name(schemaname);
 	mode = convert_schema_priv_string(priv_type_text);
 
@@ -3656,7 +3643,7 @@ has_schema_privilege_name_id(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	mode = convert_schema_priv_string(priv_type_text);
 
 	if (!SearchSysCacheExists1(NAMESPACEOID, ObjectIdGetDatum(schemaoid)))
@@ -3751,15 +3738,8 @@ static Oid
 convert_schema_name(text *schemaname)
 {
 	char	   *nspname = text_to_cstring(schemaname);
-	Oid			oid;
-
-	oid = GetSysCacheOid1(NAMESPACENAME, CStringGetDatum(nspname));
-	if (!OidIsValid(oid))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_SCHEMA),
-				 errmsg("schema \"%s\" does not exist", nspname)));
 
-	return oid;
+	return get_namespace_oid(nspname, false);
 }
 
 /*
@@ -3807,7 +3787,7 @@ has_server_privilege_name_name(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	serverid = convert_server_name(servername);
 	mode = convert_server_priv_string(priv_type_text);
 
@@ -3856,7 +3836,7 @@ has_server_privilege_name_id(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	mode = convert_server_priv_string(priv_type_text);
 
 	aclresult = pg_foreign_server_aclcheck(serverid, roleid, mode);
@@ -3989,7 +3969,7 @@ has_tablespace_privilege_name_name(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	tablespaceoid = convert_tablespace_name(tablespacename);
 	mode = convert_tablespace_priv_string(priv_type_text);
 
@@ -4038,7 +4018,7 @@ has_tablespace_privilege_name_id(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	mode = convert_tablespace_priv_string(priv_type_text);
 
 	aclresult = pg_tablespace_aclcheck(tablespaceoid, roleid, mode);
@@ -4124,16 +4104,8 @@ static Oid
 convert_tablespace_name(text *tablespacename)
 {
 	char	   *spcname = text_to_cstring(tablespacename);
-	Oid			oid;
 
-	oid = get_tablespace_oid(spcname);
-
-	if (!OidIsValid(oid))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_OBJECT),
-				 errmsg("tablespace \"%s\" does not exist", spcname)));
-
-	return oid;
+	return get_tablespace_oid(spcname, false);
 }
 
 /*
@@ -4178,8 +4150,8 @@ pg_has_role_name_name(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
-	roleoid = get_roleid_checked(NameStr(*rolename));
+	roleid = get_role_oid(NameStr(*username), false);
+	roleoid = get_role_oid(NameStr(*rolename), false);
 	mode = convert_role_priv_string(priv_type_text);
 
 	aclresult = pg_role_aclcheck(roleoid, roleid, mode);
@@ -4204,7 +4176,7 @@ pg_has_role_name(PG_FUNCTION_ARGS)
 	AclResult	aclresult;
 
 	roleid = GetUserId();
-	roleoid = get_roleid_checked(NameStr(*rolename));
+	roleoid = get_role_oid(NameStr(*rolename), false);
 	mode = convert_role_priv_string(priv_type_text);
 
 	aclresult = pg_role_aclcheck(roleoid, roleid, mode);
@@ -4227,7 +4199,7 @@ pg_has_role_name_id(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleid = get_roleid_checked(NameStr(*username));
+	roleid = get_role_oid(NameStr(*username), false);
 	mode = convert_role_priv_string(priv_type_text);
 
 	aclresult = pg_role_aclcheck(roleoid, roleid, mode);
@@ -4273,7 +4245,7 @@ pg_has_role_id_name(PG_FUNCTION_ARGS)
 	AclMode		mode;
 	AclResult	aclresult;
 
-	roleoid = get_roleid_checked(NameStr(*rolename));
+	roleoid = get_role_oid(NameStr(*rolename), false);
 	mode = convert_role_priv_string(priv_type_text);
 
 	aclresult = pg_role_aclcheck(roleoid, roleid, mode);
@@ -4830,3 +4802,22 @@ select_best_grantor(Oid roleId, AclMode privileges,
 		}
 	}
 }
+
+/*
+ * get_role_oid - Given a role name, look up the role's OID.
+ *
+ * If missing_ok is false, throw an error if tablespace name not found.  If
+ * true, just return InvalidOid.
+ */
+Oid
+get_role_oid(const char *rolname, bool missing_ok)
+{
+	Oid			oid;
+
+	oid = GetSysCacheOid1(AUTHNAME, CStringGetDatum(rolname));
+	if (!OidIsValid(oid) && !missing_ok)
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("role \"%s\" does not exist", rolname)));
+	return oid;
+}
diff --git a/src/backend/utils/adt/dbsize.c b/src/backend/utils/adt/dbsize.c
index a4e0252..8ec6b71 100644
--- a/src/backend/utils/adt/dbsize.c
+++ b/src/backend/utils/adt/dbsize.c
@@ -141,13 +141,7 @@ Datum
 pg_database_size_name(PG_FUNCTION_ARGS)
 {
 	Name		dbName = PG_GETARG_NAME(0);
-	Oid			dbOid = get_database_oid(NameStr(*dbName));
-
-	if (!OidIsValid(dbOid))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_DATABASE),
-				 errmsg("database \"%s\" does not exist",
-						NameStr(*dbName))));
+	Oid			dbOid = get_database_oid(NameStr(*dbName), false);
 
 	PG_RETURN_INT64(calculate_database_size(dbOid));
 }
@@ -240,13 +234,7 @@ Datum
 pg_tablespace_size_name(PG_FUNCTION_ARGS)
 {
 	Name		tblspcName = PG_GETARG_NAME(0);
-	Oid			tblspcOid = get_tablespace_oid(NameStr(*tblspcName));
-
-	if (!OidIsValid(tblspcOid))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_OBJECT),
-				 errmsg("tablespace \"%s\" does not exist",
-						NameStr(*tblspcName))));
+	Oid			tblspcOid = get_tablespace_oid(NameStr(*tblspcName), false);
 
 	PG_RETURN_INT64(calculate_tablespace_size(tblspcOid));
 }
diff --git a/src/backend/utils/cache/lsyscache.c b/src/backend/utils/cache/lsyscache.c
index aad6c35..9932415 100644
--- a/src/backend/utils/cache/lsyscache.c
+++ b/src/backend/utils/cache/lsyscache.c
@@ -2626,34 +2626,3 @@ get_namespace_name(Oid nspid)
 	else
 		return NULL;
 }
-
-/*				---------- PG_AUTHID CACHE ----------					 */
-
-/*
- * get_roleid
- *	  Given a role name, look up the role's OID.
- *	  Returns InvalidOid if no such role.
- */
-Oid
-get_roleid(const char *rolname)
-{
-	return GetSysCacheOid1(AUTHNAME, PointerGetDatum(rolname));
-}
-
-/*
- * get_roleid_checked
- *	  Given a role name, look up the role's OID.
- *	  ereports if no such role.
- */
-Oid
-get_roleid_checked(const char *rolname)
-{
-	Oid			roleid;
-
-	roleid = get_roleid(rolname);
-	if (!OidIsValid(roleid))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_OBJECT),
-				 errmsg("role \"%s\" does not exist", rolname)));
-	return roleid;
-}
diff --git a/src/include/catalog/namespace.h b/src/include/catalog/namespace.h
index fe3b783..0fd61a9 100644
--- a/src/include/catalog/namespace.h
+++ b/src/include/catalog/namespace.h
@@ -91,6 +91,7 @@ extern void DeconstructQualifiedName(List *names,
 						 char **objname_p);
 extern Oid	LookupNamespaceNoError(const char *nspname);
 extern Oid	LookupExplicitNamespace(const char *nspname);
+extern Oid	get_namespace_oid(const char *nspname, bool missing_ok);
 
 extern Oid	LookupCreationNamespace(const char *nspname);
 extern Oid	QualifiedNameGetCreationNamespace(List *names, char **objname_p);
diff --git a/src/include/commands/dbcommands.h b/src/include/commands/dbcommands.h
index 542fc27..8c5ba1b 100644
--- a/src/include/commands/dbcommands.h
+++ b/src/include/commands/dbcommands.h
@@ -59,7 +59,7 @@ extern void AlterDatabase(AlterDatabaseStmt *stmt, bool isTopLevel);
 extern void AlterDatabaseSet(AlterDatabaseSetStmt *stmt);
 extern void AlterDatabaseOwner(const char *dbname, Oid newOwnerId);
 
-extern Oid	get_database_oid(const char *dbname);
+extern Oid	get_database_oid(const char *dbname, bool missingok);
 extern char *get_database_name(Oid dbid);
 
 extern void dbase_redo(XLogRecPtr lsn, XLogRecord *rptr);
diff --git a/src/include/commands/defrem.h b/src/include/commands/defrem.h
index 7edda97..76aff43 100644
--- a/src/include/commands/defrem.h
+++ b/src/include/commands/defrem.h
@@ -99,6 +99,7 @@ extern void AlterOpClassOwner(List *name, const char *access_method, Oid newOwne
 extern void AlterOpClassOwner_oid(Oid opclassOid, Oid newOwnerId);
 extern void AlterOpFamilyOwner(List *name, const char *access_method, Oid newOwnerId);
 extern void AlterOpFamilyOwner_oid(Oid opfamilyOid, Oid newOwnerId);
+extern Oid get_am_oid(const char *amname, bool missing_ok);
 
 /* commands/tsearchcmds.c */
 extern void DefineTSParser(List *names, List *parameters);
diff --git a/src/include/commands/proclang.h b/src/include/commands/proclang.h
index 5feff87..16c1d14 100644
--- a/src/include/commands/proclang.h
+++ b/src/include/commands/proclang.h
@@ -21,5 +21,6 @@ extern void RenameLanguage(const char *oldname, const char *newname);
 extern void AlterLanguageOwner(const char *name, Oid newOwnerId);
 extern void AlterLanguageOwner_oid(Oid oid, Oid newOwnerId);
 extern bool PLTemplateExists(const char *languageName);
+extern Oid get_language_oid(const char *langname, bool missing_ok);
 
 #endif   /* PROCLANG_H */
diff --git a/src/include/commands/tablespace.h b/src/include/commands/tablespace.h
index cf005ee..98a9b86 100644
--- a/src/include/commands/tablespace.h
+++ b/src/include/commands/tablespace.h
@@ -51,7 +51,7 @@ extern Oid	GetDefaultTablespace(bool forTemp);
 
 extern void PrepareTempTablespaces(void);
 
-extern Oid	get_tablespace_oid(const char *tablespacename);
+extern Oid	get_tablespace_oid(const char *tablespacename, bool missing_ok);
 extern char *get_tablespace_name(Oid spc_oid);
 
 extern bool directory_is_empty(const char *path);
diff --git a/src/include/utils/acl.h b/src/include/utils/acl.h
index 9c38bd1..d9921e8 100644
--- a/src/include/utils/acl.h
+++ b/src/include/utils/acl.h
@@ -223,6 +223,7 @@ extern bool is_member_of_role(Oid member, Oid role);
 extern bool is_member_of_role_nosuper(Oid member, Oid role);
 extern bool is_admin_of_role(Oid member, Oid role);
 extern void check_is_member_of_role(Oid member, Oid role);
+extern Oid get_role_oid(const char *rolname, bool missing_ok);
 
 extern void select_best_grantor(Oid roleId, AclMode privileges,
 					const Acl *acl, Oid ownerId,
diff --git a/src/include/utils/lsyscache.h b/src/include/utils/lsyscache.h
index 131acb7..066ad76 100644
--- a/src/include/utils/lsyscache.h
+++ b/src/include/utils/lsyscache.h
@@ -136,8 +136,6 @@ extern void free_attstatsslot(Oid atttype,
 				  Datum *values, int nvalues,
 				  float4 *numbers, int nnumbers);
 extern char *get_namespace_name(Oid nspid);
-extern Oid	get_roleid(const char *rolname);
-extern Oid	get_roleid_checked(const char *rolname);
 
 #define type_is_array(typid)  (get_element_type(typid) != InvalidOid)