Tweak indexscan and seqscan code to arrange that steps from one page to

the next are handled by ReleaseAndReadBuffer rather than separate
ReleaseBuffer and ReadBuffer calls.  This cuts the number of acquisitions
of the BufMgrLock by a factor of 2 (possibly more, if an indexscan happens
to pull successive rows from the same heap page).  Unfortunately this
doesn't seem enough to get us out of the recently discussed context-switch
storm problem, but it's surely worth doing anyway.

1 files changed, 4 insertions, 1 deletions

diff --git a/src/include/access/heapam.h b/src/include/access/heapam.h
index 9f91d81107d..9f138524155 100644
--- a/src/include/access/heapam.h
+++ b/src/include/access/heapam.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/access/heapam.h,v 1.88 2004/04/01 21:28:45 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/access/heapam.h,v 1.89 2004/04/21 18:24:26 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -150,6 +150,9 @@ extern HeapTuple heap_getnext(HeapScanDesc scan, ScanDirection direction);
 extern bool heap_fetch(Relation relation, Snapshot snapshot,
 		   HeapTuple tuple, Buffer *userbuf, bool keep_buf,
 		   PgStat_Info *pgstat_info);
+extern bool heap_release_fetch(Relation relation, Snapshot snapshot,
+		   HeapTuple tuple, Buffer *userbuf, bool keep_buf,
+		   PgStat_Info *pgstat_info);
 
 extern ItemPointer heap_get_latest_tid(Relation relation, Snapshot snapshot,
 					ItemPointer tid);