pgsql: Fix broken error check in _hash_doinsert.

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.

Branch
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REL9_5_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/aa04e5c3c1b1ba27d5e726d9afc291f475051ec0

Modified Files
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src/backend/access/hash/hashinsert.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)