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, 29 insertions, 15 deletions

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 10645b2b7fb..5f6c9df677a 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -10,7 +10,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.264 2008/05/12 20:01:58 alvherre Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.265 2008/08/11 11:05:10 heikki Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -819,7 +819,7 @@ RecordTransactionCommit(void)
 	bool		markXidCommitted = TransactionIdIsValid(xid);
 	TransactionId latestXid = InvalidTransactionId;
 	int			nrels;
-	RelFileNode *rels;
+	RelFileFork *rels;
 	bool		haveNonTemp;
 	int			nchildren;
 	TransactionId *children;
@@ -900,7 +900,7 @@ RecordTransactionCommit(void)
 		{
 			rdata[0].next = &(rdata[1]);
 			rdata[1].data = (char *) rels;
-			rdata[1].len = nrels * sizeof(RelFileNode);
+			rdata[1].len = nrels * sizeof(RelFileFork);
 			rdata[1].buffer = InvalidBuffer;
 			lastrdata = 1;
 		}
@@ -1203,7 +1203,7 @@ RecordTransactionAbort(bool isSubXact)
 	TransactionId xid = GetCurrentTransactionIdIfAny();
 	TransactionId latestXid;
 	int			nrels;
-	RelFileNode *rels;
+	RelFileFork *rels;
 	int			nchildren;
 	TransactionId *children;
 	XLogRecData rdata[3];
@@ -1264,7 +1264,7 @@ RecordTransactionAbort(bool isSubXact)
 	{
 		rdata[0].next = &(rdata[1]);
 		rdata[1].data = (char *) rels;
-		rdata[1].len = nrels * sizeof(RelFileNode);
+		rdata[1].len = nrels * sizeof(RelFileFork);
 		rdata[1].buffer = InvalidBuffer;
 		lastrdata = 1;
 	}
@@ -4282,8 +4282,13 @@ xact_redo_commit(xl_xact_commit *xlrec, TransactionId xid)
 	/* Make sure files supposed to be dropped are dropped */
 	for (i = 0; i < xlrec->nrels; i++)
 	{
-		XLogDropRelation(xlrec->xnodes[i]);
-		smgrdounlink(smgropen(xlrec->xnodes[i]), false, true);
+		SMgrRelation srel;
+
+		XLogDropRelation(xlrec->xnodes[i].rnode, xlrec->xnodes[i].forknum);
+
+		srel = smgropen(xlrec->xnodes[i].rnode);
+		smgrdounlink(srel, xlrec->xnodes[i].forknum, false, true);
+		smgrclose(srel);
 	}
 }
 
@@ -4317,8 +4322,13 @@ xact_redo_abort(xl_xact_abort *xlrec, TransactionId xid)
 	/* Make sure files supposed to be dropped are dropped */
 	for (i = 0; i < xlrec->nrels; i++)
 	{
-		XLogDropRelation(xlrec->xnodes[i]);
-		smgrdounlink(smgropen(xlrec->xnodes[i]), false, true);
+		SMgrRelation srel;
+
+		XLogDropRelation(xlrec->xnodes[i].rnode, xlrec->xnodes[i].forknum);
+
+		srel = smgropen(xlrec->xnodes[i].rnode);
+		smgrdounlink(srel, xlrec->xnodes[i].forknum, false, true);
+		smgrclose(srel);
 	}
 }
 
@@ -4374,10 +4384,12 @@ xact_desc_commit(StringInfo buf, xl_xact_commit *xlrec)
 		appendStringInfo(buf, "; rels:");
 		for (i = 0; i < xlrec->nrels; i++)
 		{
-			RelFileNode rnode = xlrec->xnodes[i];
+			RelFileNode rnode = xlrec->xnodes[i].rnode;
+			ForkNumber	forknum = xlrec->xnodes[i].forknum;
 
-			appendStringInfo(buf, " %u/%u/%u",
-							 rnode.spcNode, rnode.dbNode, rnode.relNode);
+			appendStringInfo(buf, " %u/%u/%u/%u",
+							 rnode.spcNode, rnode.dbNode, rnode.relNode,
+							 forknum);
 		}
 	}
 	if (xlrec->nsubxacts > 0)
@@ -4402,10 +4414,12 @@ xact_desc_abort(StringInfo buf, xl_xact_abort *xlrec)
 		appendStringInfo(buf, "; rels:");
 		for (i = 0; i < xlrec->nrels; i++)
 		{
-			RelFileNode rnode = xlrec->xnodes[i];
+			RelFileNode rnode = xlrec->xnodes[i].rnode;
+			ForkNumber	forknum = xlrec->xnodes[i].forknum;
 
-			appendStringInfo(buf, " %u/%u/%u",
-							 rnode.spcNode, rnode.dbNode, rnode.relNode);
+			appendStringInfo(buf, " %u/%u/%u/%u",
+							 rnode.spcNode, rnode.dbNode, rnode.relNode,
+							 forknum);
 		}
 	}
 	if (xlrec->nsubxacts > 0)