Fix broken error check in _hash_doinsert.

You can't just cast a HashMetaPage to a Page, because the meta page
data is stored after the page header, not at offset 0.  Fortunately,
this didn't break anything because it happens to find hashm_bsize
at the offset at which it expects to find pd_pagesize_version, and
the values are close enough to the same that this works out.

Still, it's a bug, so back-patch to all supported versions.

Mithun Cy, revised a bit by me.

diff --git a/src/backend/access/hash/hashinsert.c b/src/backend/access/hash/hashinsert.c
index 59c4213f9c840816270a4abc2f3cd98e4a861e3f..4b022b5755a5390beaa712402412799f6c241eb3 100644 (file)
--- a/src/backend/access/hash/hashinsert.c
+++ b/src/backend/access/hash/hashinsert.c
@@ -35,6 +35,7 @@ _hash_doinsert(Relation rel, IndexTuple itup)
        BlockNumber blkno;
        BlockNumber oldblkno;
        bool            retry;
+       Page            metapage;
        Page            page;
        HashPageOpaque pageopaque;
        Size            itemsz;
@@ -58,7 +59,8 @@ _hash_doinsert(Relation rel, IndexTuple itup)
 restart_insert:
        /* Read the metapage */
        metabuf = _hash_getbuf(rel, HASH_METAPAGE, HASH_READ, LH_META_PAGE);
-       metap = HashPageGetMeta(BufferGetPage(metabuf));
+       metapage = BufferGetPage(metabuf);
+       metap = HashPageGetMeta(metapage);
 
        /*
         * Check whether the item can fit on a hash page at all. (Eventually, we
@@ -67,11 +69,11 @@ restart_insert:
         *
         * XXX this is useless code if we are only storing hash keys.
         */
-       if (itemsz > HashMaxItemSize((Page) metap))
+       if (itemsz > HashMaxItemSize(metapage))
                ereport(ERROR,
                                (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
                                 errmsg("index row size %zu exceeds hash maximum %zu",
-                                               itemsz, HashMaxItemSize((Page) metap)),
+                                               itemsz, HashMaxItemSize(metapage)),
                        errhint("Values larger than a buffer page cannot be indexed.")));
 
        oldblkno = InvalidBlockNumber;