Introduce the concept of relation forks. An smgr relation can now consist

of multiple forks, and each fork can be created and grown separately.

The bulk of this patch is about changing the smgr API to include an extra
ForkNumber argument in every smgr function. Also, smgrscheduleunlink and
smgrdounlink no longer implicitly call smgrclose, because other forks might
still exist after unlinking one. The callers of those functions have been
modified to call smgrclose instead.

This patch in itself doesn't have any user-visible effect, but provides the
infrastructure needed for upcoming patches. The additional forks envisioned
are a rewritten FSM implementation that doesn't rely on a fixed-size shared
memory block, and a visibility map to allow skipping portions of a table in
VACUUM that have no dead tuples.

1 files changed, 4 insertions, 4 deletions

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 72e531d3dc3..709836f2be7 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.316 2008/07/13 20:45:47 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.317 2008/08/11 11:05:10 heikki Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1034,8 +1034,7 @@ XLogCheckBuffer(XLogRecData *rdata, bool doPageWrites,
 		/*
 		 * The page needs to be backed up, so set up *bkpb
 		 */
-		bkpb->node = BufferGetFileNode(rdata->buffer);
-		bkpb->block = BufferGetBlockNumber(rdata->buffer);
+		BufferGetTag(rdata->buffer, &bkpb->node, &bkpb->fork, &bkpb->block);
 
 		if (rdata->buffer_std)
 		{
@@ -2855,7 +2854,8 @@ RestoreBkpBlocks(XLogRecord *record, XLogRecPtr lsn)
 		memcpy(&bkpb, blk, sizeof(BkpBlock));
 		blk += sizeof(BkpBlock);
 
-		buffer = XLogReadBuffer(bkpb.node, bkpb.block, true);
+		buffer = XLogReadBufferWithFork(bkpb.node, bkpb.fork, bkpb.block,
+										true);
 		Assert(BufferIsValid(buffer));
 		page = (Page) BufferGetPage(buffer);