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, 37 insertions, 22 deletions

diff --git a/src/backend/access/transam/xlogutils.c b/src/backend/access/transam/xlogutils.c
index 3e2d5046da6..59124e349e4 100644
--- a/src/backend/access/transam/xlogutils.c
+++ b/src/backend/access/transam/xlogutils.c
@@ -11,7 +11,7 @@
  * 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/xlogutils.c,v 1.57 2008/07/13 20:45:47 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/access/transam/xlogutils.c,v 1.58 2008/08/11 11:05:10 heikki Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -37,6 +37,7 @@
 typedef struct xl_invalid_page_key
 {
 	RelFileNode node;			/* the relation */
+	ForkNumber	forkno;			/* the fork number */
 	BlockNumber blkno;			/* the page */
 } xl_invalid_page_key;
 
@@ -51,7 +52,8 @@ static HTAB *invalid_page_tab = NULL;
 
 /* Log a reference to an invalid page */
 static void
-log_invalid_page(RelFileNode node, BlockNumber blkno, bool present)
+log_invalid_page(RelFileNode node, ForkNumber forkno, BlockNumber blkno,
+				 bool present)
 {
 	xl_invalid_page_key key;
 	xl_invalid_page *hentry;
@@ -63,11 +65,11 @@ log_invalid_page(RelFileNode node, BlockNumber blkno, bool present)
 	 * something about the XLOG record that generated the reference).
 	 */
 	if (present)
-		elog(DEBUG1, "page %u of relation %u/%u/%u is uninitialized",
-			 blkno, node.spcNode, node.dbNode, node.relNode);
+		elog(DEBUG1, "page %u of relation %u/%u/%u/%u is uninitialized",
+			 blkno, node.spcNode, node.dbNode, node.relNode, forkno);
 	else
-		elog(DEBUG1, "page %u of relation %u/%u/%u does not exist",
-			 blkno, node.spcNode, node.dbNode, node.relNode);
+		elog(DEBUG1, "page %u of relation %u/%u/%u/%u does not exist",
+			 blkno, node.spcNode, node.dbNode, node.relNode, forkno);
 
 	if (invalid_page_tab == NULL)
 	{
@@ -87,6 +89,7 @@ log_invalid_page(RelFileNode node, BlockNumber blkno, bool present)
 
 	/* we currently assume xl_invalid_page_key contains no padding */
 	key.node = node;
+	key.forkno = forkno;
 	key.blkno = blkno;
 	hentry = (xl_invalid_page *)
 		hash_search(invalid_page_tab, (void *) &key, HASH_ENTER, &found);
@@ -104,7 +107,7 @@ log_invalid_page(RelFileNode node, BlockNumber blkno, bool present)
 
 /* Forget any invalid pages >= minblkno, because they've been dropped */
 static void
-forget_invalid_pages(RelFileNode node, BlockNumber minblkno)
+forget_invalid_pages(RelFileNode node, ForkNumber forkno, BlockNumber minblkno)
 {
 	HASH_SEQ_STATUS status;
 	xl_invalid_page *hentry;
@@ -117,11 +120,12 @@ forget_invalid_pages(RelFileNode node, BlockNumber minblkno)
 	while ((hentry = (xl_invalid_page *) hash_seq_search(&status)) != NULL)
 	{
 		if (RelFileNodeEquals(hentry->key.node, node) &&
+			hentry->key.forkno == forkno &&
 			hentry->key.blkno >= minblkno)
 		{
-			elog(DEBUG2, "page %u of relation %u/%u/%u has been dropped",
+			elog(DEBUG2, "page %u of relation %u/%u/%u/%u has been dropped",
 				 hentry->key.blkno, hentry->key.node.spcNode,
-				 hentry->key.node.dbNode, hentry->key.node.relNode);
+				 hentry->key.node.dbNode, hentry->key.node.relNode, forkno);
 
 			if (hash_search(invalid_page_tab,
 							(void *) &hentry->key,
@@ -224,6 +228,18 @@ XLogCheckInvalidPages(void)
 Buffer
 XLogReadBuffer(RelFileNode rnode, BlockNumber blkno, bool init)
 {
+	return XLogReadBufferWithFork(rnode, MAIN_FORKNUM, blkno, init);
+}
+
+/*
+ * XLogReadBufferWithFork
+ *		Like XLogReadBuffer, but for reading other relation forks than
+ *		the main one.
+ */
+Buffer
+XLogReadBufferWithFork(RelFileNode rnode, ForkNumber forknum,
+					   BlockNumber blkno, bool init)
+{
 	BlockNumber lastblock;
 	Buffer		buffer;
 	SMgrRelation smgr;
@@ -241,21 +257,21 @@ XLogReadBuffer(RelFileNode rnode, BlockNumber blkno, bool init)
 	 * filesystem loses an inode during a crash.  Better to write the data
 	 * until we are actually told to delete the file.)
 	 */
-	smgrcreate(smgr, false, true);
+	smgrcreate(smgr, forknum, false, true);
 
-	lastblock = smgrnblocks(smgr);
+	lastblock = smgrnblocks(smgr, forknum);
 
 	if (blkno < lastblock)
 	{
 		/* page exists in file */
-		buffer = ReadBufferWithoutRelcache(rnode, false, blkno, init);
+		buffer = ReadBufferWithoutRelcache(rnode, false, forknum, blkno, init);
 	}
 	else
 	{
 		/* hm, page doesn't exist in file */
 		if (!init)
 		{
-			log_invalid_page(rnode, blkno, false);
+			log_invalid_page(rnode, forknum, blkno, false);
 			return InvalidBuffer;
 		}
 		/* OK to extend the file */
@@ -266,7 +282,8 @@ XLogReadBuffer(RelFileNode rnode, BlockNumber blkno, bool init)
 		{
 			if (buffer != InvalidBuffer)
 				ReleaseBuffer(buffer);
-			buffer = ReadBufferWithoutRelcache(rnode, false, P_NEW, false);
+			buffer = ReadBufferWithoutRelcache(rnode, false, forknum,
+											   P_NEW, false);
 			lastblock++;
 		}
 		Assert(BufferGetBlockNumber(buffer) == blkno);
@@ -282,7 +299,7 @@ XLogReadBuffer(RelFileNode rnode, BlockNumber blkno, bool init)
 		if (PageIsNew(page))
 		{
 			UnlockReleaseBuffer(buffer);
-			log_invalid_page(rnode, blkno, true);
+			log_invalid_page(rnode, forknum, blkno, true);
 			return InvalidBuffer;
 		}
 	}
@@ -363,12 +380,9 @@ FreeFakeRelcacheEntry(Relation fakerel)
  * any open "invalid-page" records for the relation.
  */
 void
-XLogDropRelation(RelFileNode rnode)
+XLogDropRelation(RelFileNode rnode, ForkNumber forknum)
 {
-	/* Tell smgr to forget about this relation as well */
-	smgrclosenode(rnode);
-
-	forget_invalid_pages(rnode, 0);
+	forget_invalid_pages(rnode, forknum, 0);
 }
 
 /*
@@ -397,7 +411,8 @@ XLogDropDatabase(Oid dbid)
  * We need to clean up any open "invalid-page" records for the dropped pages.
  */
 void
-XLogTruncateRelation(RelFileNode rnode, BlockNumber nblocks)
+XLogTruncateRelation(RelFileNode rnode, ForkNumber forkNum,
+					 BlockNumber nblocks)
 {
-	forget_invalid_pages(rnode, nblocks);
+	forget_invalid_pages(rnode, forkNum, nblocks);
 }