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This prevents the LOCK table from "stealing" space that was originally calculated for the PROLOCK table, and vice versa. That was weirdly indeterministic so that if you e.g. took a lot of locks consuming all the available shared memory for the LOCK table, subsequent transactions that needed the more space for the PROCLOCK table would fail, but if you restarted the system then the space would be available for PROCLOCK again. Better to be strict and predictable, even though that means that in many cases you can acquire far fewer locks than before. This also prevents the lock hash tables from using up the general-purpose 100 kB reserve we set aside for "stuff that's too small to bother estimating" in CalculateShmemSize(). We are pretty good at accounting for everything nowadays, so we could probably make that reservation smaller, but I'll leave that for another commit. Reviewed-by: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com> Reviewed-by: Matthias van de Meent <boekewurm+postgres@gmail.com> Discussion: https://www.postgresql.org/message-id/e07be2ba-856b-4ff5-8313-8b58b6b4e4d0@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/.