9fe9ecd516
Previously, the shared header (HASHHDR) and the directory were
allocated by the caller, and passed to hash_create(), while the actual
elements were allocated separately with ShmemAlloc(). After this
commit, all the memory needed by the header, the directory, and all
the elements is allocated using a single ShmemInitStruct() call, and
the different parts are carved out of that allocation. This way the
ShmemIndex entries (and thus pg_shmem_allocations) reflect the size of
the whole hash table, rather than just the directories.
Commit f5930f9a98 attempted this earlier, but it had to be reverted.
The new strategy is to let dynahash.c perform all the allocations with
the alloc function, but have the alloc function carve out the parts
from the one larger allocation. The shared header and the directory
are now also allocated with alloc calls, instead of passing the area
for those directly from the caller.
Reviewed-by: Tomas Vondra <tomas@vondra.me>
Discussion: https://www.postgresql.org/message-id/01ab1d41-3eda-4705-8bbd-af898f5007f1@iki.fi
PostgreSQL Database Management System
This directory contains the source code distribution of the PostgreSQL database management system.
PostgreSQL is an advanced object-relational database management system that supports an extended subset of the SQL standard, including transactions, foreign keys, subqueries, triggers, user-defined types and functions. This distribution also contains C language bindings.
Copyright and license information can be found in the file COPYRIGHT.
General documentation about this version of PostgreSQL can be found at https://www.postgresql.org/docs/devel/. In particular, information about building PostgreSQL from the source code can be found at https://www.postgresql.org/docs/devel/installation.html.
The latest version of this software, and related software, may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.