Fix amcheck's handling of incomplete root splits in B-tree

When the root page is being split, it's normal that root page
according to the metapage is not marked BTP_ROOT. Fix bogus error in
amcheck about that case.

Reviewed-by: Peter Geoghegan <pg@bowt.ie>
Discussion: https://www.postgresql.org/message-id/abd65090-5336-42cc-b768-2bdd66738404@iki.fi
Backpatch-through: 14

diff --git a/contrib/amcheck/verify_nbtree.c b/contrib/amcheck/verify_nbtree.c
index f11c43a0ed7974085a3007a3ecc696b5b078354b..434c562c5797a6a04010680a80eea1fe95fbf101 100644 (file)
--- a/contrib/amcheck/verify_nbtree.c
+++ b/contrib/amcheck/verify_nbtree.c
@@ -721,7 +721,7 @@ bt_check_level_from_leftmost(BtreeCheckState *state, BtreeLevel level)
                             errmsg("block %u is not leftmost in index \"%s\"",
                                    current, RelationGetRelationName(state->rel))));
 
-               if (level.istruerootlevel && !P_ISROOT(opaque))
+               if (level.istruerootlevel && (!P_ISROOT(opaque) && !P_INCOMPLETE_SPLIT(opaque)))
                    ereport(ERROR,
                            (errcode(ERRCODE_INDEX_CORRUPTED),
                             errmsg("block %u is not true root in index \"%s\"",