In ReadOrZeroBuffer (and related entry points), don't bother to call

PageHeaderIsValid when we zero the buffer instead of reading the page in.
The actual performance improvement is probably marginal since this function
isn't very heavily used, but a cycle saved is a cycle earned.

Zdenek Kotala

diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index e40a815b5dd1e70f260c01441a6037ca5876099a..456dc4233604e7f49e13b0c532f02c10c27ea8c4 100644 (file)
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *       $PostgreSQL: pgsql/src/backend/storage/buffer/bufmgr.c,v 1.235 2008/08/01 13:16:08 alvherre Exp $
+ *       $PostgreSQL: pgsql/src/backend/storage/buffer/bufmgr.c,v 1.236 2008/08/05 15:09:04 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -352,28 +352,31 @@ ReadBuffer_common(SMgrRelation smgr, bool isLocalBuf, BlockNumber blockNum,
                if (zeroPage)
                        MemSet((char *) bufBlock, 0, BLCKSZ);
                else
-                       smgrread(smgr, blockNum, (char *) bufBlock);
-               /* check for garbage data */
-               if (!PageHeaderIsValid((PageHeader) bufBlock))
                {
-                       if (zero_damaged_pages)
+                       smgrread(smgr, blockNum, (char *) bufBlock);
+
+                       /* check for garbage data */
+                       if (!PageHeaderIsValid((PageHeader) bufBlock))
                        {
-                               ereport(WARNING,
-                                               (errcode(ERRCODE_DATA_CORRUPTED),
-                                                errmsg("invalid page header in block %u of relation %u/%u/%u; zeroing out page",
-                                                               blockNum, 
-                                                               smgr->smgr_rnode.spcNode,
-                                                               smgr->smgr_rnode.dbNode,
-                                                               smgr->smgr_rnode.relNode)));
-                               MemSet((char *) bufBlock, 0, BLCKSZ);
+                               if (zero_damaged_pages)
+                               {
+                                       ereport(WARNING,
+                                                       (errcode(ERRCODE_DATA_CORRUPTED),
+                                                        errmsg("invalid page header in block %u of relation %u/%u/%u; zeroing out page",
+                                                                       blockNum, 
+                                                                       smgr->smgr_rnode.spcNode,
+                                                                       smgr->smgr_rnode.dbNode,
+                                                                       smgr->smgr_rnode.relNode)));
+                                       MemSet((char *) bufBlock, 0, BLCKSZ);
+                               }
+                               else
+                                       ereport(ERROR,
+                                                       (errcode(ERRCODE_DATA_CORRUPTED),
+                                                        errmsg("invalid page header in block %u of relation %u/%u/%u",
+                                                                       blockNum, smgr->smgr_rnode.spcNode,
+                                                                       smgr->smgr_rnode.dbNode,
+                                                                       smgr->smgr_rnode.relNode)));
                        }
-                       else
-                               ereport(ERROR,
-                                               (errcode(ERRCODE_DATA_CORRUPTED),
-                                errmsg("invalid page header in block %u of relation %u/%u/%u",
-                                               blockNum, smgr->smgr_rnode.spcNode,
-                                               smgr->smgr_rnode.dbNode,
-                                               smgr->smgr_rnode.relNode)));
                }
        }