Teach pgstat_vacuum_stat to not bother scanning pg_proc in the common case

where no function stats entries exist.  Partial response to Pavel's
observation that small VACUUM operations are noticeably slower in CVS HEAD
than 8.3.

diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index 85c4313cca31d4aab652fbc49d527fe8951336f9..0526d169f7e16029b01a2dd186ef614485ae55c9 100644 (file)
--- a/src/backend/postmaster/pgstat.c
+++ b/src/backend/postmaster/pgstat.c
@@ -13,7 +13,7 @@
  *
  *     Copyright (c) 2001-2008, PostgreSQL Global Development Group
  *
- *     $PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.184 2008/11/04 11:04:06 petere Exp $
+ *     $PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.185 2008/12/08 15:44:54 tgl Exp $
  * ----------
  */
 #include "postgres.h"
@@ -967,55 +967,60 @@ pgstat_vacuum_stat(void)
        hash_destroy(htab);
 
        /*
-        * Now repeat the above steps for functions.
+        * Now repeat the above steps for functions.  However, we needn't bother
+        * in the common case where no function stats are being collected.
         */
-       htab = pgstat_collect_oids(ProcedureRelationId);
+       if (dbentry->functions != NULL &&
+               hash_get_num_entries(dbentry->functions) > 0)
+       {
+               htab = pgstat_collect_oids(ProcedureRelationId);
 
-       pgstat_setheader(&f_msg.m_hdr, PGSTAT_MTYPE_FUNCPURGE);
-       f_msg.m_databaseid = MyDatabaseId;
-       f_msg.m_nentries = 0;
+               pgstat_setheader(&f_msg.m_hdr, PGSTAT_MTYPE_FUNCPURGE);
+               f_msg.m_databaseid = MyDatabaseId;
+               f_msg.m_nentries = 0;
 
-       hash_seq_init(&hstat, dbentry->functions);
-       while ((funcentry = (PgStat_StatFuncEntry *) hash_seq_search(&hstat)) != NULL)
-       {
-               Oid                     funcid = funcentry->functionid;
+               hash_seq_init(&hstat, dbentry->functions);
+               while ((funcentry = (PgStat_StatFuncEntry *) hash_seq_search(&hstat)) != NULL)
+               {
+                       Oid                     funcid = funcentry->functionid;
 
-               CHECK_FOR_INTERRUPTS();
+                       CHECK_FOR_INTERRUPTS();
 
-               if (hash_search(htab, (void *) &funcid, HASH_FIND, NULL) != NULL)
-                       continue;
+                       if (hash_search(htab, (void *) &funcid, HASH_FIND, NULL) != NULL)
+                               continue;
 
-               /*
-                * Not there, so add this function's Oid to the message
-                */
-               f_msg.m_functionid[f_msg.m_nentries++] = funcid;
+                       /*
+                        * Not there, so add this function's Oid to the message
+                        */
+                       f_msg.m_functionid[f_msg.m_nentries++] = funcid;
+
+                       /*
+                        * If the message is full, send it out and reinitialize to empty
+                        */
+                       if (f_msg.m_nentries >= PGSTAT_NUM_FUNCPURGE)
+                       {
+                               len = offsetof(PgStat_MsgFuncpurge, m_functionid[0])
+                                       +f_msg.m_nentries * sizeof(Oid);
+
+                               pgstat_send(&f_msg, len);
+
+                               f_msg.m_nentries = 0;
+                       }
+               }
 
                /*
-                * If the message is full, send it out and reinitialize to empty
+                * Send the rest
                 */
-               if (f_msg.m_nentries >= PGSTAT_NUM_FUNCPURGE)
+               if (f_msg.m_nentries > 0)
                {
                        len = offsetof(PgStat_MsgFuncpurge, m_functionid[0])
                                +f_msg.m_nentries * sizeof(Oid);
 
                        pgstat_send(&f_msg, len);
-
-                       f_msg.m_nentries = 0;
                }
-       }
 
-       /*
-        * Send the rest
-        */
-       if (f_msg.m_nentries > 0)
-       {
-               len = offsetof(PgStat_MsgFuncpurge, m_functionid[0])
-                       +f_msg.m_nentries * sizeof(Oid);
-
-               pgstat_send(&f_msg, len);
+               hash_destroy(htab);
        }
-
-       hash_destroy(htab);
 }