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 de8950c92bb405ce75cb8e4fbab02e5961c69073..52474d07e0010ddc64e79d297846ebc92cc4bfe2 100644 (file)
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -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)));
                }
        }