Tweak OpernameGetCandidates() to reduce palloc overhead --- profiling

showed that for common operator names such as '=', the pallocs done by
this routine occupied a surprisingly large fraction of the total time
for the parser to process an operator.

diff --git a/src/backend/catalog/namespace.c b/src/backend/catalog/namespace.c
index 397a7517f95f4508a457ae1db04a2991c58c4ebc..1d7e21e31951ac612cbf3777ebaca1cab9d250f5 100644 (file)
--- a/src/backend/catalog/namespace.c
+++ b/src/backend/catalog/namespace.c
@@ -13,7 +13,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *       $PostgreSQL: pgsql/src/backend/catalog/namespace.c,v 1.60 2003/12/12 18:45:08 petere Exp $
+ *       $PostgreSQL: pgsql/src/backend/catalog/namespace.c,v 1.61 2003/12/29 21:33:09 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -659,6 +659,8 @@ FuncCandidateList
 OpernameGetCandidates(List *names, char oprkind)
 {
        FuncCandidateList resultList = NULL;
+       char       *resultSpace = NULL;
+       int                     nextResult = 0;
        char       *schemaname;
        char       *opername;
        Oid                     namespaceId;
@@ -685,6 +687,20 @@ OpernameGetCandidates(List *names, char oprkind)
                                                                 CStringGetDatum(opername),
                                                                 0, 0, 0);
 
+       /*
+        * In typical scenarios, most if not all of the operators found by the
+        * catcache search will end up getting returned; and there can be quite
+        * a few, for common operator names such as '=' or '+'.  To reduce the
+        * time spent in palloc, we allocate the result space as an array large
+        * enough to hold all the operators.  The original coding of this routine
+        * did a separate palloc for each operator, but profiling revealed that
+        * the pallocs used an unreasonably large fraction of parsing time.
+        */
+#define SPACE_PER_OP MAXALIGN(sizeof(struct _FuncCandidateList) + sizeof(Oid))
+
+       if (catlist->n_members > 0)
+               resultSpace = palloc(catlist->n_members * SPACE_PER_OP);
+
        for (i = 0; i < catlist->n_members; i++)
        {
                HeapTuple       opertup = &catlist->members[i]->tuple;
@@ -768,8 +784,9 @@ OpernameGetCandidates(List *names, char oprkind)
                /*
                 * Okay to add it to result list
                 */
-               newResult = (FuncCandidateList)
-                       palloc(sizeof(struct _FuncCandidateList) + sizeof(Oid));
+               newResult = (FuncCandidateList) (resultSpace + nextResult);
+               nextResult += SPACE_PER_OP;
+
                newResult->pathpos = pathpos;
                newResult->oid = HeapTupleGetOid(opertup);
                newResult->nargs = 2;