make MaxBackends available in _PG_init

From: "Wang, Shenhao" <wangsh(dot)fnst(at)cn(dot)fujitsu(dot)com>
To: "pgsql-hackers(at)lists(dot)postgresql(dot)org" <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: make MaxBackends available in _PG_init
Date: 2020-09-21 03:43:41
Views: Raw Message | Whole Thread | Download mbox | Resend email
Lists: pgsql-hackers

Hi Hackers:

I find the value in function _PG_init, the value of MaxBackends is 0.
In source, I find that the postmaster will first load library, and then calculate the value of MaxBackends.

In the old version, the MaxBackends was calculated by:
MaxBackends = MaxConnections + autovacuum_max_workers + 1 +
Because any extension can register workers which will affect the return value of GetNumShmemAttachedBgworkers.
InitializeMaxBackends must be called after shared_preload_libraries. This is also mentioned in comments.

Now, function GetNumShmemAttachedBgworkers was deleted and replaced by guc max_worker_processes,
so if we changed the calling order like:
Step1: calling InitializeMaxBackends.
Step2: calling process_shared_preload_libraries

In this order extension can get the correct value of MaxBackends in _PG_init.

Any thoughts?


Attachment Content-Type Size
0001-Make-MaxBackends-available-in-_PG_init.patch application/octet-stream 2.2 KB


Browse pgsql-hackers by date

  From Date Subject
Next Message Bharath Rupireddy 2020-09-21 03:44:30 Re: Retry Cached Remote Connections for postgres_fdw in case remote backend gets killed/goes away
Previous Message Andy Fan 2020-09-21 03:41:09 Re: Dynamic gathering the values for seq_page_cost/xxx_cost