pgsql: Remove HASH_DIRSIZE, always use the default algorithm to select

Remove HASH_DIRSIZE, always use the default algorithm to select it

It's not very useful to specify a non-standard directory size. The
HASH_DIRSIZE option was only used for shared memory hash tables, and
those always used hash_select_dirsize() to choose the size, which in
turn just uses the default algorithm anyway. That assumption was
ingrained in hash_estimate_size(), too.

Reviewed-by: Tomas Vondra <tomas(at)vondra(dot)me>
Discussion: https://www.postgresql.org/message-id/01ab1d41-3eda-4705-8bbd-af898f5007f1@iki.fi

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/4953a25b7f3bb5a555342764231157c76e6acbac

Modified Files
--------------
src/backend/storage/ipc/shmem.c | 3 +-
src/backend/utils/hash/dynahash.c | 63 ++++++++-------------------------------
src/include/utils/hsearch.h | 6 +---
3 files changed, 15 insertions(+), 57 deletions(-)