From: Robert Haas <rhaas@postgresql.org>
Date: Thu, 22 Dec 2016 18:54:40 +0000 (-0500)
Subject: Fix broken error check in _hash_doinsert.
X-Git-Tag: REL9_2_20~37
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=de651a6e5db25d462bde0a47cb4f8f45c45a6a6d;p=postgresql

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 66084f4a6f..9ce4c18608 100644
--- a/src/backend/access/hash/hashinsert.c
+++ b/src/backend/access/hash/hashinsert.c
@@ -32,6 +32,7 @@ _hash_doinsert(Relation rel, IndexTuple itup)
 	Buffer		metabuf;
 	HashMetaPage metap;
 	BlockNumber blkno;
+	Page		metapage;
 	Page		page;
 	HashPageOpaque pageopaque;
 	Size		itemsz;
@@ -57,7 +58,8 @@ _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
@@ -66,12 +68,12 @@ _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.")));
 
 	/*