Fix bug introduced by microvacuum for GiST

Commit 013ebc0a7b7ea9c1b1ab7a3d4dd75ea121ea8ba7 introduces microvacuum for
GiST, deletetion of tuple marked LP_DEAD uses IndexPageMultiDelete while
recovery code uses IndexPageTupleDelete in loop. This causes a difference
in offset numbers of tuples to delete. Patch introduces usage of
IndexPageMultiDelete in GiST except gistplacetopage() where only one tuple is
deleted at once. That also slightly improve performance, because
IndexPageMultiDelete is more effective.

Patch changes WAL format, so bump wal page magic.

Bug report from Jeff Janes
Diagnostic and patch by Anastasia Lubennikova and me

4 files changed, 11 insertions, 11 deletions

diff --git a/src/backend/access/gist/gist.c b/src/backend/access/gist/gist.c
index 4edc5a75f2..53bccf6d18 100644
--- a/src/backend/access/gist/gist.c
+++ b/src/backend/access/gist/gist.c
@@ -466,6 +466,11 @@ gistplacetopage(Relation rel, Size freespace, GISTSTATE *giststate,
 		 */
 		START_CRIT_SECTION();
 
+		/*
+		 * While we delete only one tuple at once we could mix calls
+		 * PageIndexTupleDelete() here and PageIndexMultiDelete() in
+		 * gistRedoPageUpdateRecord()
+		 */
 		if (OffsetNumberIsValid(oldoffnum))
 			PageIndexTupleDelete(page, oldoffnum);
 		gistfillbuffer(page, itup, ntup, InvalidOffsetNumber);
diff --git a/src/backend/access/gist/gistvacuum.c b/src/backend/access/gist/gistvacuum.c
index 2337dbd7f9..a0b0eebed3 100644
--- a/src/backend/access/gist/gistvacuum.c
+++ b/src/backend/access/gist/gistvacuum.c
@@ -208,23 +208,20 @@ gistbulkdelete(PG_FUNCTION_ARGS)
 				idxtuple = (IndexTuple) PageGetItem(page, iid);
 
 				if (callback(&(idxtuple->t_tid), callback_state))
-				{
-					todelete[ntodelete] = i - ntodelete;
-					ntodelete++;
-					stats->tuples_removed += 1;
-				}
+					todelete[ntodelete++] = i;
 				else
 					stats->num_index_tuples += 1;
 			}
 
+			stats->tuples_removed += ntodelete;
+
 			if (ntodelete)
 			{
 				START_CRIT_SECTION();
 
 				MarkBufferDirty(buffer);
 
-				for (i = 0; i < ntodelete; i++)
-					PageIndexTupleDelete(page, todelete[i]);
+				PageIndexMultiDelete(page, todelete, ntodelete);
 				GistMarkTuplesDeleted(page);
 
 				if (RelationNeedsWAL(rel))
diff --git a/src/backend/access/gist/gistxlog.c b/src/backend/access/gist/gistxlog.c
index fbdbb3c51f..c63cc8190c 100644
--- a/src/backend/access/gist/gistxlog.c
+++ b/src/backend/access/gist/gistxlog.c
@@ -83,13 +83,11 @@ gistRedoPageUpdateRecord(XLogReaderState *record)
 		/* Delete old tuples */
 		if (xldata->ntodelete > 0)
 		{
-			int			i;
 			OffsetNumber *todelete = (OffsetNumber *) data;
 
 			data += sizeof(OffsetNumber) * xldata->ntodelete;
 
-			for (i = 0; i < xldata->ntodelete; i++)
-				PageIndexTupleDelete(page, todelete[i]);
+			PageIndexMultiDelete(page, todelete, xldata->ntodelete);
 			if (GistPageIsLeaf(page))
 				GistMarkTuplesDeleted(page);
 		}
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index 5ebaa5f69c..590bf1729a 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -31,7 +31,7 @@
 /*
  * Each page of XLOG file has a header like this:
  */
-#define XLOG_PAGE_MAGIC 0xD085	/* can be used as WAL version indicator */
+#define XLOG_PAGE_MAGIC 0xD086	/* can be used as WAL version indicator */
 
 typedef struct XLogPageHeaderData
 {