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;