Add a syscache for pg_resgroup

This commit makes access to pg_resgroup a little bit faster

src/backend/commands/resgroupcmds.c

@@ -380,7 +380,7 @@ AlterResourceGroup(AlterResourceGroupStmt *stmt)
 	 * Check the pg_resgroup relation to be certain the resource group already
 	 * exists.
 	 */
-	groupid = GetResGroupIdForName(stmt->name, RowExclusiveLock);
+	groupid = GetResGroupIdForName(stmt->name);
 	if (groupid == InvalidOid)
 		ereport(ERROR,
 				(errcode(ERRCODE_UNDEFINED_OBJECT),
@@ -612,32 +612,27 @@ GetResGroupIdForRole(Oid roleid)
  *	to Oid.
  */
 Oid
-GetResGroupIdForName(const char *name, LOCKMODE lockmode)
+GetResGroupIdForName(const char *name)
 {
-	Relation	rel;
-	ScanKeyData scankey;
-	SysScanDesc scan;
 	HeapTuple	tuple;
 	Oid			rsgid;
 
-	rel = heap_open(ResGroupRelationId, lockmode);
+	tuple = SearchSysCache1(RESGROUPNAME,
+							CStringGetDatum(name));
 
-	/* SELECT oid FROM pg_resgroup WHERE rsgname = :1 */
-	ScanKeyInit(&scankey,
-				Anum_pg_resgroup_rsgname,
-				BTEqualStrategyNumber, F_NAMEEQ,
-				CStringGetDatum(name));
-	scan = systable_beginscan(rel, ResGroupRsgnameIndexId, true,
-							  SnapshotNow, 1, &scankey);
-
-	tuple = systable_getnext(scan);
 	if (HeapTupleIsValid(tuple))
-		rsgid = HeapTupleGetOid(tuple);
+	{
+		bool isnull;
+		Datum oidDatum = SysCacheGetAttr(RESGROUPNAME, tuple,
+										  ObjectIdAttributeNumber,
+										  &isnull);
+		Assert (!isnull);
+		rsgid = DatumGetObjectId(oidDatum);
+	}
 	else
-		rsgid = InvalidOid;
+		return InvalidOid;
 
-	systable_endscan(scan);
-	heap_close(rel, lockmode);
+	ReleaseSysCache(tuple);
 
 	return rsgid;
 }
@@ -646,37 +641,28 @@ GetResGroupIdForName(const char *name, LOCKMODE lockmode)
  * GetResGroupNameForId -- Return the resource group name for an Oid
  */
 char *
-GetResGroupNameForId(Oid oid, LOCKMODE lockmode)
+GetResGroupNameForId(Oid oid)
 {
-	Relation	rel;
-	ScanKeyData scankey;
-	SysScanDesc scan;
 	HeapTuple	tuple;
 	char		*name = NULL;
 
-	rel = heap_open(ResGroupRelationId, lockmode);
-
-	/* SELECT rsgname FROM pg_resgroup WHERE oid = :1 */
-	ScanKeyInit(&scankey,
-				ObjectIdAttributeNumber,
-				BTEqualStrategyNumber, F_OIDEQ,
-				ObjectIdGetDatum(oid));
-	scan = systable_beginscan(rel, ResGroupOidIndexId, true,
-							  SnapshotNow, 1, &scankey);
+	tuple = SearchSysCache1(RESGROUPOID,
+							ObjectIdGetDatum(oid));
 
-	tuple = systable_getnext(scan);
 	if (HeapTupleIsValid(tuple))
 	{
 		bool isnull;
-		Datum nameDatum = heap_getattr(tuple, Anum_pg_resgroup_rsgname,
-									   rel->rd_att, &isnull);
+		Datum nameDatum = SysCacheGetAttr(RESGROUPOID, tuple,
+										  Anum_pg_resgroup_rsgname,
+										  &isnull);
 		Assert (!isnull);
 		Name resGroupName = DatumGetName(nameDatum);
 		name = pstrdup(NameStr(*resGroupName));
 	}
+	else
+		return "unknow";
 
-	systable_endscan(scan);
-	heap_close(rel, lockmode);
+	ReleaseSysCache(tuple);
 
 	return name;
 }

src/backend/commands/user.c

@@ -533,7 +533,7 @@ CreateRole(CreateRoleStmt *stmt)
 	{
 		Oid rsgid;
 
-		rsgid = GetResGroupIdForName(resgroup, ShareLock);
+		rsgid = GetResGroupIdForName(resgroup);
 		if (rsgid == InvalidOid)
 			ereport(ERROR,
 					(errcode(ERRCODE_UNDEFINED_OBJECT),
@@ -1195,7 +1195,7 @@ AlterRole(AlterRoleStmt *stmt)
 								resgroup)));
 		}
 
-		rsgid = GetResGroupIdForName(resgroup, ShareLock);
+		rsgid = GetResGroupIdForName(resgroup);
 		if (rsgid == InvalidOid)
 			ereport(ERROR,
 				(errcode(ERRCODE_UNDEFINED_OBJECT),

src/backend/utils/adt/pgstatfuncs.c

@@ -633,7 +633,7 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 			if (funcctx->tuple_desc->natts > 13)
 			{
 				Datum now = TimestampTzGetDatum(GetCurrentTimestamp());
-				char *groupName = GetResGroupNameForId(beentry->st_rsgid, AccessShareLock);
+				char *groupName = GetResGroupNameForId(beentry->st_rsgid);
 
 				values[13] = ObjectIdGetDatum(beentry->st_rsgid);
 

src/backend/utils/cache/syscache.c

@@ -54,6 +54,7 @@
 #include "catalog/pg_ts_template.h"
 #include "catalog/pg_type.h"
 #include "catalog/pg_window.h"
+#include "catalog/pg_resgroup.h"
 #include "utils/syscache.h"
 
 
@@ -509,6 +510,28 @@ static const struct cachedesc cacheinfo[] = {
 		},
 		1024
 	},
+	{ResGroupRelationId,		/* RESGROUPOID */
+		ResGroupOidIndexId,
+		1,
+		{
+			ObjectIdAttributeNumber,
+			0,
+			0,
+			0
+		},
+		128
+	},
+	{ResGroupRelationId,		/* RESGROUPNAME */
+		ResGroupRsgnameIndexId,
+		1,
+		{
+			Anum_pg_resgroup_rsgname,
+			0,
+			0,
+			0
+		},
+		128
+	},
 	{RewriteRelationId,			/* RULERELNAME */
 		RewriteRelRulenameIndexId,
 		2,

src/include/commands/resgroupcmds.h

@@ -32,8 +32,8 @@ extern void DropResourceGroup(DropResourceGroupStmt *stmt);
 extern void AlterResourceGroup(AlterResourceGroupStmt *stmt);
 
 /* catalog access function */
-extern Oid GetResGroupIdForName(const char *name, LOCKMODE lockmode);
-extern char *GetResGroupNameForId(Oid oid, LOCKMODE lockmode);
+extern Oid GetResGroupIdForName(const char *name);
+extern char *GetResGroupNameForId(Oid oid);
 extern Oid GetResGroupIdForRole(Oid roleid);
 extern void GetResGroupCapabilities(Relation rel,
 									Oid groupId,

src/include/utils/syscache.h

@@ -66,6 +66,8 @@ enum SysCacheIdentifier
 	PROCOID,
 	RELNAMENSP,
 	RELOID,
+	RESGROUPOID,
+	RESGROUPNAME,
 	RULERELNAME,
 	STATRELATT,
 	TSCONFIGMAP,