Clean up code associated with updating pg_class statistics columns

(relpages/reltuples).  To do this, create formal support in heapam.c for
"overwrite" tuple updates (including xlog replay capability) and use that
instead of the ad-hoc overwrites we'd been using in VACUUM and CREATE INDEX.
Take the responsibility for updating stats during CREATE INDEX out of the
individual index AMs, and do it where it belongs, in catalog/index.c.  Aside
from being more modular, this avoids having to update the same tuple twice in
some paths through CREATE INDEX.  It's probably not measurably faster, but
for sure it's a lot cleaner than before.

1 files changed, 154 insertions, 1 deletions

diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index 779e86a3894..dcb9fc8fb64 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/heap/heapam.c,v 1.211 2006/03/31 23:32:05 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/heap/heapam.c,v 1.212 2006/05/10 23:18:39 tgl Exp $
  *
  *
  * INTERFACE ROUTINES
@@ -2673,6 +2673,97 @@ l3:
 	return HeapTupleMayBeUpdated;
 }
 
+
+/*
+ * heap_inplace_update - update a tuple "in place" (ie, overwrite it)
+ *
+ * Overwriting violates both MVCC and transactional safety, so the uses
+ * of this function in Postgres are extremely limited.  Nonetheless we
+ * find some places to use it.
+ *
+ * The tuple cannot change size, and therefore it's reasonable to assume
+ * that its null bitmap (if any) doesn't change either.  So we just
+ * overwrite the data portion of the tuple without touching the null
+ * bitmap or any of the header fields.
+ *
+ * tuple is an in-memory tuple structure containing the data to be written
+ * over the target tuple.  Also, tuple->t_self identifies the target tuple.
+ */
+void
+heap_inplace_update(Relation relation, HeapTuple tuple)
+{
+	Buffer		buffer;
+	Page		page;
+	OffsetNumber offnum;
+	ItemId		lp = NULL;
+	HeapTupleHeader htup;
+	uint32		oldlen;
+	uint32		newlen;
+
+	buffer = ReadBuffer(relation, ItemPointerGetBlockNumber(&(tuple->t_self)));
+	LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
+	page = (Page) BufferGetPage(buffer);
+
+	offnum = ItemPointerGetOffsetNumber(&(tuple->t_self));
+	if (PageGetMaxOffsetNumber(page) >= offnum)
+		lp = PageGetItemId(page, offnum);
+
+	if (PageGetMaxOffsetNumber(page) < offnum || !ItemIdIsUsed(lp))
+		elog(ERROR, "heap_inplace_update: invalid lp");
+
+	htup = (HeapTupleHeader) PageGetItem(page, lp);
+
+	oldlen = ItemIdGetLength(lp) - htup->t_hoff;
+	newlen = tuple->t_len - tuple->t_data->t_hoff;
+	if (oldlen != newlen || htup->t_hoff != tuple->t_data->t_hoff)
+		elog(ERROR, "heap_inplace_update: wrong tuple length");
+
+	/* NO EREPORT(ERROR) from here till changes are logged */
+	START_CRIT_SECTION();
+
+	memcpy((char *) htup + htup->t_hoff,
+		   (char *) tuple->t_data + tuple->t_data->t_hoff,
+		   newlen);
+
+	MarkBufferDirty(buffer);
+
+	/* XLOG stuff */
+	if (!relation->rd_istemp)
+	{
+		xl_heap_inplace xlrec;
+		XLogRecPtr	recptr;
+		XLogRecData rdata[2];
+
+		xlrec.target.node = relation->rd_node;
+		xlrec.target.tid = tuple->t_self;
+
+		rdata[0].data = (char *) &xlrec;
+		rdata[0].len = SizeOfHeapInplace;
+		rdata[0].buffer = InvalidBuffer;
+		rdata[0].next = &(rdata[1]);
+
+		rdata[1].data = (char *) htup + htup->t_hoff;
+		rdata[1].len = newlen;
+		rdata[1].buffer = buffer;
+		rdata[1].buffer_std = true;
+		rdata[1].next = NULL;
+
+		recptr = XLogInsert(RM_HEAP_ID, XLOG_HEAP_INPLACE, rdata);
+
+		PageSetLSN(page, recptr);
+		PageSetTLI(page, ThisTimeLineID);
+	}
+
+	END_CRIT_SECTION();
+
+	UnlockReleaseBuffer(buffer);
+
+	/* Send out shared cache inval if necessary */
+	if (!IsBootstrapProcessingMode())
+		CacheInvalidateHeapTuple(relation, tuple);
+}
+
+
 /* ----------------
  *		heap_markpos	- mark scan position
  * ----------------
@@ -3329,6 +3420,59 @@ heap_xlog_lock(XLogRecPtr lsn, XLogRecord *record)
 	UnlockReleaseBuffer(buffer);
 }
 
+static void
+heap_xlog_inplace(XLogRecPtr lsn, XLogRecord *record)
+{
+	xl_heap_inplace *xlrec = (xl_heap_inplace *) XLogRecGetData(record);
+	Relation	reln = XLogOpenRelation(xlrec->target.node);
+	Buffer		buffer;
+	Page		page;
+	OffsetNumber offnum;
+	ItemId		lp = NULL;
+	HeapTupleHeader htup;
+	uint32		oldlen;
+	uint32		newlen;
+
+	if (record->xl_info & XLR_BKP_BLOCK_1)
+		return;
+
+	buffer = XLogReadBuffer(reln,
+							ItemPointerGetBlockNumber(&(xlrec->target.tid)),
+							false);
+	if (!BufferIsValid(buffer))
+		return;
+	page = (Page) BufferGetPage(buffer);
+
+	if (XLByteLE(lsn, PageGetLSN(page)))		/* changes are applied */
+	{
+		UnlockReleaseBuffer(buffer);
+		return;
+	}
+
+	offnum = ItemPointerGetOffsetNumber(&(xlrec->target.tid));
+	if (PageGetMaxOffsetNumber(page) >= offnum)
+		lp = PageGetItemId(page, offnum);
+
+	if (PageGetMaxOffsetNumber(page) < offnum || !ItemIdIsUsed(lp))
+		elog(PANIC, "heap_inplace_redo: invalid lp");
+
+	htup = (HeapTupleHeader) PageGetItem(page, lp);
+
+	oldlen = ItemIdGetLength(lp) - htup->t_hoff;
+	newlen = record->xl_len - SizeOfHeapInplace;
+	if (oldlen != newlen)
+		elog(PANIC, "heap_inplace_redo: wrong tuple length");
+
+	memcpy((char *) htup + htup->t_hoff,
+		   (char *) xlrec + SizeOfHeapInplace,
+		   newlen);
+
+	PageSetLSN(page, lsn);
+	PageSetTLI(page, ThisTimeLineID);
+	MarkBufferDirty(buffer);
+	UnlockReleaseBuffer(buffer);
+}
+
 void
 heap_redo(XLogRecPtr lsn, XLogRecord *record)
 {
@@ -3349,6 +3493,8 @@ heap_redo(XLogRecPtr lsn, XLogRecord *record)
 		heap_xlog_newpage(lsn, record);
 	else if (info == XLOG_HEAP_LOCK)
 		heap_xlog_lock(lsn, record);
+	else if (info == XLOG_HEAP_INPLACE)
+		heap_xlog_inplace(lsn, record);
 	else
 		elog(PANIC, "heap_redo: unknown op code %u", info);
 }
@@ -3442,6 +3588,13 @@ heap_desc(StringInfo buf, uint8 xl_info, char *rec)
 		appendStringInfo(buf, "%u ", xlrec->locking_xid);
 		out_target(buf, &(xlrec->target));
 	}
+	else if (info == XLOG_HEAP_INPLACE)
+	{
+		xl_heap_inplace *xlrec = (xl_heap_inplace *) rec;
+
+		appendStringInfo(buf, "inplace: ");
+		out_target(buf, &(xlrec->target));
+	}
 	else
 		appendStringInfo(buf, "UNKNOWN");
 }