pgsql: simplehash: preserve consistency in case of OOM.

simplehash: preserve consistency in case of OOM.

Compute size first, then allocate, then update the structure.

Previously, an out-of-memory when growing could leave the hashtable in
an inconsistent state.

Discussion: https://postgr.es/m/20231117201334.eyb542qr5yk4gilq@awork3.anarazel.de
Reviewed-by: Andres Freund
Reviewed-by: Gurjeet Singh

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/b282fa88df78a05643d2df84a2b8e81cd9c1705d

Modified Files
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src/include/lib/simplehash.h | 42 +++++++++++++++++++++++++++++++-----------
1 file changed, 31 insertions(+), 11 deletions(-)