Avoid changing an index's indcheckxmin horizon during REINDEX.

There can never be a need to push the indcheckxmin horizon forward, since
any HOT chains that are actually broken with respect to the index must
pre-date its original creation.  So we can just avoid changing pg_index
altogether during a REINDEX operation.

This offers a cleaner solution than my previous patch for the problem
found a few days ago that we mustn't try to update pg_index while we are
reindexing it.  System catalog indexes will always be created with
indcheckxmin = false during initdb, and with this modified code we should
never try to change their pg_index entries.  This avoids special-casing
system catalogs as the former patch did, and should provide a performance
benefit for many cases where REINDEX formerly caused an index to be
considered unusable for a short time.

Back-patch to 8.3 to cover all versions containing HOT.  Note that this
patch changes the API for index_build(), but I believe it is unlikely that
any add-on code is calling that directly.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/backend/bootstrap/bootstrap.c b/src/backend/bootstrap/bootstrap.c
index 5450313be9c..6183b475c59 100644
--- a/src/backend/bootstrap/bootstrap.c
+++ b/src/backend/bootstrap/bootstrap.c
@@ -1285,7 +1285,7 @@ build_indices(void)
 		heap = heap_open(ILHead->il_heap, NoLock);
 		ind = index_open(ILHead->il_ind, NoLock);
 
-		index_build(heap, ind, ILHead->il_info, false);
+		index_build(heap, ind, ILHead->il_info, false, false);
 
 		index_close(ind, NoLock);
 		heap_close(heap, NoLock);