Re: AllocSetReset improvement

Tom Lane wrote:
> Bruce Momjian <pgman@candle.pha.pa.us> writes:
> > Patch applied.  Thanks.  (The first if == NULL test was already in CVS).
>
> The first if == NULL test was the only part I wanted to apply ...
> I do not think this patch is a performance win in general.

Attached is the part I backed out of CVS.

--
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073
Index: aset.c
===================================================================
RCS file: /cvsroot/pgsql/src/backend/utils/mmgr/aset.c,v
retrieving revision 1.60
retrieving revision 1.61
diff -c -c -r1.60 -r1.61
*** aset.c    14 May 2005 20:29:13 -0000    1.60
--- aset.c    4 Jun 2005 20:14:12 -0000    1.61
***************
*** 399,404 ****
--- 399,415 ----
      if (block == NULL)
          return;

+     /*
+      * When blocks list has only "keeper" block and freeptr of the block
+      * is initial value, the context is not used from last reset.
+      */
+     if (block == set->keeper && block->next == NULL)
+     {
+         char       *datastart = ((char *) block) + ALLOC_BLOCKHDRSZ;
+         if (block->freeptr == datastart)
+             return;
+     }
+
      /* Clear chunk freelists */
      MemSetAligned(set->freelist, 0, sizeof(set->freelist));