Fix oversight in collecting values for cleanup_info records.

vacuum_log_cleanup_info() now generates log records with a valid
latestRemovedXid set in all cases. Also be careful not to zero the
value when we do a round of vacuuming part-way through lazy_scan_heap().
Incidentally, this reduces frequency of conflicts in Hot Standby.

src/backend/access/heap/pruneheap.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/heap/pruneheap.c,v 1.22 2010/02/26 02:00:33 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/heap/pruneheap.c,v 1.23 2010/04/21 17:20:56 sriggs Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -122,8 +122,10 @@ heap_page_prune_opt(Relation relation, Buffer buffer, TransactionId OldestXmin)
 		 */
 		if (PageIsFull(page) || PageGetHeapFreeSpace(page) < minfree)
 		{
+			TransactionId ignore = InvalidTransactionId;	/* return value not needed */
+
 			/* OK to prune */
-			(void) heap_page_prune(relation, buffer, OldestXmin, true);
+			(void) heap_page_prune(relation, buffer, OldestXmin, true, &ignore);
 		}
 
 		/* And release buffer lock */
@@ -145,11 +147,12 @@ heap_page_prune_opt(Relation relation, Buffer buffer, TransactionId OldestXmin)
  * send its own new total to pgstats, and we don't want this delta applied
  * on top of that.)
  *
- * Returns the number of tuples deleted from the page.
+ * Returns the number of tuples deleted from the page and sets
+ * latestRemovedXid.
  */
 int
 heap_page_prune(Relation relation, Buffer buffer, TransactionId OldestXmin,
-				bool report_stats)
+				bool report_stats, TransactionId *latestRemovedXid)
 {
 	int			ndeleted = 0;
 	Page		page = BufferGetPage(buffer);
@@ -273,6 +276,8 @@ heap_page_prune(Relation relation, Buffer buffer, TransactionId OldestXmin,
 	if (report_stats && ndeleted > prstate.ndead)
 		pgstat_update_heap_dead_tuples(relation, ndeleted - prstate.ndead);
 
+	*latestRemovedXid = prstate.latestRemovedXid;
+
 	/*
 	 * XXX Should we update the FSM information of this page ?
 	 *

src/backend/commands/vacuumlazy.c

@@ -29,7 +29,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/vacuumlazy.c,v 1.132 2010/02/26 02:00:40 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/vacuumlazy.c,v 1.133 2010/04/21 17:20:56 sriggs Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -274,6 +274,8 @@ vacuum_log_cleanup_info(Relation rel, LVRelStats *vacrelstats)
 	if (rel->rd_istemp || !XLogIsNeeded())
 		return;
 
+	Assert(TransactionIdIsValid(vacrelstats->latestRemovedXid));
+
 	(void) log_heap_cleanup_info(rel->rd_node, vacrelstats->latestRemovedXid);
 }
 
@@ -395,9 +397,11 @@ lazy_scan_heap(Relation onerel, LVRelStats *vacrelstats,
 								  vacrelstats);
 			/* Remove tuples from heap */
 			lazy_vacuum_heap(onerel, vacrelstats);
-			/* Forget the now-vacuumed tuples, and press on */
+			/*
+			 * Forget the now-vacuumed tuples, and press on, but be careful
+			 * not to reset latestRemovedXid since we want that value to be valid.
+			 */
 			vacrelstats->num_dead_tuples = 0;
-			vacrelstats->latestRemovedXid = InvalidTransactionId;
 			vacrelstats->num_index_scans++;
 		}
 
@@ -484,8 +488,8 @@ lazy_scan_heap(Relation onerel, LVRelStats *vacrelstats,
 		 *
 		 * We count tuples removed by the pruning step as removed by VACUUM.
 		 */
-		tups_vacuumed += heap_page_prune(onerel, buf, OldestXmin, false);
-
+		tups_vacuumed += heap_page_prune(onerel, buf, OldestXmin, false,
+													&vacrelstats->latestRemovedXid);
 		/*
 		 * Now scan the page to collect vacuumable items and check for tuples
 		 * requiring freezing.
@@ -676,9 +680,12 @@ lazy_scan_heap(Relation onerel, LVRelStats *vacrelstats,
 		{
 			/* Remove tuples from heap */
 			lazy_vacuum_page(onerel, blkno, buf, 0, vacrelstats);
-			/* Forget the now-vacuumed tuples, and press on */
+			/*
+			 * Forget the now-vacuumed tuples, and press on, but be careful
+			 * not to reset latestRemovedXid since we want that value to be valid.
+			 */
+			Assert(TransactionIdIsValid(vacrelstats->latestRemovedXid));
 			vacrelstats->num_dead_tuples = 0;
-			vacrelstats->latestRemovedXid = InvalidTransactionId;
 			vacuumed_pages++;
 		}
 

src/include/access/heapam.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/access/heapam.h,v 1.148 2010/02/26 02:01:20 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/access/heapam.h,v 1.149 2010/04/21 17:20:56 sriggs Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -144,7 +144,7 @@ extern void heap_page_prune_opt(Relation relation, Buffer buffer,
 					TransactionId OldestXmin);
 extern int heap_page_prune(Relation relation, Buffer buffer,
 				TransactionId OldestXmin,
-				bool report_stats);
+				bool report_stats, TransactionId *latestRemovedXid);
 extern void heap_page_prune_execute(Buffer buffer,
 						OffsetNumber *redirected, int nredirected,
 						OffsetNumber *nowdead, int ndead,