Update extension lookup routines to use the syscache

The following routines are changed to use the syscache entries added for
pg_extension in 490f869d92e5:
- get_extension_oid()
- get_extension_name()
- get_extension_schema()

A catalog scan is costly and could easily lead to a noticeable
performance impact when called once or more per query, so this is going
to be helpful for developers for extension data lookups.

Author: Andrei Lepikhov
Reviewed-by: Jelte Fennema-Nio
Discussion: https://postgr.es/m/529295b2-6ba9-4dae-acd1-20a9c6fb8f9a@gmail.com

diff --git a/src/backend/commands/extension.c b/src/backend/commands/extension.c
index 1643c8c69a0d816390b265762fc1a123b4131b5a..fab59ad5f66245c41efe21cf98ab99f46efe590a 100644 (file)
--- a/src/backend/commands/extension.c
+++ b/src/backend/commands/extension.c
@@ -64,6 +64,7 @@
 #include "utils/memutils.h"
 #include "utils/rel.h"
 #include "utils/snapmgr.h"
+#include "utils/syscache.h"
 #include "utils/varlena.h"
 
 
@@ -145,32 +146,9 @@ Oid
 get_extension_oid(const char *extname, bool missing_ok)
 {
        Oid                     result;
-       Relation        rel;
-       SysScanDesc scandesc;
-       HeapTuple       tuple;
-       ScanKeyData entry[1];
-
-       rel = table_open(ExtensionRelationId, AccessShareLock);
-
-       ScanKeyInit(&entry[0],
-                               Anum_pg_extension_extname,
-                               BTEqualStrategyNumber, F_NAMEEQ,
-                               CStringGetDatum(extname));
 
-       scandesc = systable_beginscan(rel, ExtensionNameIndexId, true,
-                                                                 NULL, 1, entry);
-
-       tuple = systable_getnext(scandesc);
-
-       /* We assume that there can be at most one matching tuple */
-       if (HeapTupleIsValid(tuple))
-               result = ((Form_pg_extension) GETSTRUCT(tuple))->oid;
-       else
-               result = InvalidOid;
-
-       systable_endscan(scandesc);
-
-       table_close(rel, AccessShareLock);
+       result = GetSysCacheOid1(EXTENSIONNAME, Anum_pg_extension_oid,
+                                                        CStringGetDatum(extname));
 
        if (!OidIsValid(result) && !missing_ok)
                ereport(ERROR,
@@ -190,32 +168,15 @@ char *
 get_extension_name(Oid ext_oid)
 {
        char       *result;
-       Relation        rel;
-       SysScanDesc scandesc;
        HeapTuple       tuple;
-       ScanKeyData entry[1];
 
-       rel = table_open(ExtensionRelationId, AccessShareLock);
+       tuple = SearchSysCache1(EXTENSIONOID, ObjectIdGetDatum(ext_oid));
 
-       ScanKeyInit(&entry[0],
-                               Anum_pg_extension_oid,
-                               BTEqualStrategyNumber, F_OIDEQ,
-                               ObjectIdGetDatum(ext_oid));
+       if (!HeapTupleIsValid(tuple))
+               return NULL;
 
-       scandesc = systable_beginscan(rel, ExtensionOidIndexId, true,
-                                                                 NULL, 1, entry);
-
-       tuple = systable_getnext(scandesc);
-
-       /* We assume that there can be at most one matching tuple */
-       if (HeapTupleIsValid(tuple))
-               result = pstrdup(NameStr(((Form_pg_extension) GETSTRUCT(tuple))->extname));
-       else
-               result = NULL;
-
-       systable_endscan(scandesc);
-
-       table_close(rel, AccessShareLock);
+       result = pstrdup(NameStr(((Form_pg_extension) GETSTRUCT(tuple))->extname));
+       ReleaseSysCache(tuple);
 
        return result;
 }
@@ -229,32 +190,15 @@ Oid
 get_extension_schema(Oid ext_oid)
 {
        Oid                     result;
-       Relation        rel;
-       SysScanDesc scandesc;
        HeapTuple       tuple;
-       ScanKeyData entry[1];
-
-       rel = table_open(ExtensionRelationId, AccessShareLock);
 
-       ScanKeyInit(&entry[0],
-                               Anum_pg_extension_oid,
-                               BTEqualStrategyNumber, F_OIDEQ,
-                               ObjectIdGetDatum(ext_oid));
+       tuple = SearchSysCache1(EXTENSIONOID, ObjectIdGetDatum(ext_oid));
 
-       scandesc = systable_beginscan(rel, ExtensionOidIndexId, true,
-                                                                 NULL, 1, entry);
-
-       tuple = systable_getnext(scandesc);
-
-       /* We assume that there can be at most one matching tuple */
-       if (HeapTupleIsValid(tuple))
-               result = ((Form_pg_extension) GETSTRUCT(tuple))->extnamespace;
-       else
-               result = InvalidOid;
-
-       systable_endscan(scandesc);
+       if (!HeapTupleIsValid(tuple))
+               return InvalidOid;
 
-       table_close(rel, AccessShareLock);
+       result = ((Form_pg_extension) GETSTRUCT(tuple))->extnamespace;
+       ReleaseSysCache(tuple);
 
        return result;
 }