pgsql: Accommodate very large dshash tables.

Accommodate very large dshash tables.

If a dshash table grows very large (e.g., the dshash table for
cumulative statistics when there are millions of tables), resizing
it may fail with an error like:

        ERROR: invalid DSA memory alloc request size 1073741824

To fix, permit dshash resizing to allocate more than 1 GB by
providing the DSA_ALLOC_HUGE flag.

Reported-by: Andreas Scherbaum
Author: Matthias van de Meent
Reviewed-by: Cédric Villemain, Michael Paquier, Andres Freund
Discussion: https://postgr.es/m/80a12d59-0d5e-4c54-866c-e69cd6536471%40pgug.de
Backpatch-through: 13

Branch
------
REL_16_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/2a74023221f9b9e484611581542c14fc6ef6d239

Modified Files
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src/backend/lib/dshash.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)