amcheck: Sanitize metapage's allequalimage field.

This will be helpful if it ever proves necessary to revoke an opclass's
support for deduplication.

Backpatch: 13-, where nbtree deduplication was introduced.

diff --git a/contrib/amcheck/verify_nbtree.c b/contrib/amcheck/verify_nbtree.c
index c9f9e755dccc9cf9683397ed6bcb67afd5b3bd39..384a8ac747e13b87dbf6522d20b5c9b2237cddfb 100644 (file)
--- a/contrib/amcheck/verify_nbtree.c
+++ b/contrib/amcheck/verify_nbtree.c
@@ -305,8 +305,20 @@ bt_index_check_internal(Oid indrelid, bool parentcheck, bool heapallindexed,
                     errmsg("index \"%s\" lacks a main relation fork",
                            RelationGetRelationName(indrel))));
 
-       /* Check index, possibly against table it is an index on */
+       /* Extract metadata from metapage, and sanitize it in passing */
        _bt_metaversion(indrel, &heapkeyspace, &allequalimage);
+       if (allequalimage && !heapkeyspace)
+           ereport(ERROR,
+                   (errcode(ERRCODE_INDEX_CORRUPTED),
+                    errmsg("index \"%s\" metapage has equalimage field set on unsupported nbtree version",
+                           RelationGetRelationName(indrel))));
+       if (allequalimage && !_bt_allequalimage(indrel, false))
+           ereport(ERROR,
+                   (errcode(ERRCODE_INDEX_CORRUPTED),
+                    errmsg("index \"%s\" metapage incorrectly indicates that deduplication is safe",
+                           RelationGetRelationName(indrel))));
+
+       /* Check index, possibly against table it is an index on */
        bt_check_every_level(indrel, heaprel, heapkeyspace, parentcheck,
                             heapallindexed, rootdescend);
    }