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 63be2f37872cb799af2833cc9fc57fd7c44374b9..c8598facd44cbb8b3a92ab300aabf08412e1b3ad 100644 (file)
--- a/src/backend/access/hash/hashinsert.c
+++ b/src/backend/access/hash/hashinsert.c
@@ -34,6 +34,7 @@ _hash_doinsert(Relation rel, IndexTuple itup)
    BlockNumber blkno;
    BlockNumber oldblkno = InvalidBlockNumber;
    bool        retry = false;
+   Page        metapage;
    Page        page;
    HashPageOpaque pageopaque;
    Size        itemsz;
@@ -53,7 +54,8 @@ _hash_doinsert(Relation rel, IndexTuple itup)
 
    /* 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
@@ -62,12 +64,12 @@ _hash_doinsert(Relation rel, IndexTuple itup)
     *
     * 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 %lu exceeds hash maximum %lu",
                        (unsigned long) itemsz,
-                       (unsigned long) HashMaxItemSize((Page) metap)),
+                       (unsigned long) HashMaxItemSize(metapage)),
            errhint("Values larger than a buffer page cannot be indexed.")));
 
    /*