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, 31 insertions, 23 deletions

diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c
index 57eb7eeea4..b86bdc3667 100644
--- a/src/backend/access/transam/twophase.c
+++ b/src/backend/access/transam/twophase.c
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *		$PostgreSQL: pgsql/src/backend/access/transam/twophase.c,v 1.44 2008/08/01 13:16:08 alvherre Exp $
+ *		$PostgreSQL: pgsql/src/backend/access/transam/twophase.c,v 1.45 2008/08/11 11:05:10 heikki Exp $
  *
  * NOTES
  *		Each global transaction is associated with a global transaction
@@ -141,12 +141,12 @@ static void RecordTransactionCommitPrepared(TransactionId xid,
 								int nchildren,
 								TransactionId *children,
 								int nrels,
-								RelFileNode *rels);
+								RelFileFork *rels);
 static void RecordTransactionAbortPrepared(TransactionId xid,
 							   int nchildren,
 							   TransactionId *children,
 							   int nrels,
-							   RelFileNode *rels);
+							   RelFileFork *rels);
 static void ProcessRecords(char *bufptr, TransactionId xid,
 			   const TwoPhaseCallback callbacks[]);
 
@@ -694,8 +694,8 @@ TwoPhaseGetDummyProc(TransactionId xid)
  *
  *	1. TwoPhaseFileHeader
  *	2. TransactionId[] (subtransactions)
- *	3. RelFileNode[] (files to be deleted at commit)
- *	4. RelFileNode[] (files to be deleted at abort)
+ *	3. RelFileFork[] (files to be deleted at commit)
+ *	4. RelFileFork[] (files to be deleted at abort)
  *	5. TwoPhaseRecordOnDisk
  *	6. ...
  *	7. TwoPhaseRecordOnDisk (end sentinel, rmid == TWOPHASE_RM_END_ID)
@@ -793,8 +793,8 @@ StartPrepare(GlobalTransaction gxact)
 	TransactionId xid = gxact->proc.xid;
 	TwoPhaseFileHeader hdr;
 	TransactionId *children;
-	RelFileNode *commitrels;
-	RelFileNode *abortrels;
+	RelFileFork *commitrels;
+	RelFileFork *abortrels;
 
 	/* Initialize linked list */
 	records.head = palloc0(sizeof(XLogRecData));
@@ -832,12 +832,12 @@ StartPrepare(GlobalTransaction gxact)
 	}
 	if (hdr.ncommitrels > 0)
 	{
-		save_state_data(commitrels, hdr.ncommitrels * sizeof(RelFileNode));
+		save_state_data(commitrels, hdr.ncommitrels * sizeof(RelFileFork));
 		pfree(commitrels);
 	}
 	if (hdr.nabortrels > 0)
 	{
-		save_state_data(abortrels, hdr.nabortrels * sizeof(RelFileNode));
+		save_state_data(abortrels, hdr.nabortrels * sizeof(RelFileFork));
 		pfree(abortrels);
 	}
 }
@@ -1140,8 +1140,8 @@ FinishPreparedTransaction(const char *gid, bool isCommit)
 	TwoPhaseFileHeader *hdr;
 	TransactionId latestXid;
 	TransactionId *children;
-	RelFileNode *commitrels;
-	RelFileNode *abortrels;
+	RelFileFork *commitrels;
+	RelFileFork *abortrels;
 	int			i;
 
 	/*
@@ -1169,10 +1169,10 @@ FinishPreparedTransaction(const char *gid, bool isCommit)
 	bufptr = buf + MAXALIGN(sizeof(TwoPhaseFileHeader));
 	children = (TransactionId *) bufptr;
 	bufptr += MAXALIGN(hdr->nsubxacts * sizeof(TransactionId));
-	commitrels = (RelFileNode *) bufptr;
-	bufptr += MAXALIGN(hdr->ncommitrels * sizeof(RelFileNode));
-	abortrels = (RelFileNode *) bufptr;
-	bufptr += MAXALIGN(hdr->nabortrels * sizeof(RelFileNode));
+	commitrels = (RelFileFork *) bufptr;
+	bufptr += MAXALIGN(hdr->ncommitrels * sizeof(RelFileFork));
+	abortrels = (RelFileFork *) bufptr;
+	bufptr += MAXALIGN(hdr->nabortrels * sizeof(RelFileFork));
 
 	/* compute latestXid among all children */
 	latestXid = TransactionIdLatest(xid, hdr->nsubxacts, children);
@@ -1215,12 +1215,20 @@ FinishPreparedTransaction(const char *gid, bool isCommit)
 	if (isCommit)
 	{
 		for (i = 0; i < hdr->ncommitrels; i++)
-			smgrdounlink(smgropen(commitrels[i]), false, false);
+		{
+			SMgrRelation srel = smgropen(commitrels[i].rnode);
+			smgrdounlink(srel, commitrels[i].forknum, false, false);
+			smgrclose(srel);
+		}
 	}
 	else
 	{
 		for (i = 0; i < hdr->nabortrels; i++)
-			smgrdounlink(smgropen(abortrels[i]), false, false);
+		{
+			SMgrRelation srel = smgropen(abortrels[i].rnode);
+			smgrdounlink(srel, abortrels[i].forknum, false, false);
+			smgrclose(srel);
+		}
 	}
 
 	/* And now do the callbacks */
@@ -1631,8 +1639,8 @@ RecoverPreparedTransactions(void)
 			bufptr = buf + MAXALIGN(sizeof(TwoPhaseFileHeader));
 			subxids = (TransactionId *) bufptr;
 			bufptr += MAXALIGN(hdr->nsubxacts * sizeof(TransactionId));
-			bufptr += MAXALIGN(hdr->ncommitrels * sizeof(RelFileNode));
-			bufptr += MAXALIGN(hdr->nabortrels * sizeof(RelFileNode));
+			bufptr += MAXALIGN(hdr->ncommitrels * sizeof(RelFileFork));
+			bufptr += MAXALIGN(hdr->nabortrels * sizeof(RelFileFork));
 
 			/*
 			 * Reconstruct subtrans state for the transaction --- needed
@@ -1685,7 +1693,7 @@ RecordTransactionCommitPrepared(TransactionId xid,
 								int nchildren,
 								TransactionId *children,
 								int nrels,
-								RelFileNode *rels)
+								RelFileFork *rels)
 {
 	XLogRecData rdata[3];
 	int			lastrdata = 0;
@@ -1710,7 +1718,7 @@ RecordTransactionCommitPrepared(TransactionId xid,
 	{
 		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;
 	}
@@ -1760,7 +1768,7 @@ RecordTransactionAbortPrepared(TransactionId xid,
 							   int nchildren,
 							   TransactionId *children,
 							   int nrels,
-							   RelFileNode *rels)
+							   RelFileFork *rels)
 {
 	XLogRecData rdata[3];
 	int			lastrdata = 0;
@@ -1790,7 +1798,7 @@ RecordTransactionAbortPrepared(TransactionId xid,
 	{
 		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;
 	}