Horton

Re: make MaxBackends available in _PG_init

Fujii Masao <masao.fujii@oss.nttdata.com>

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From: Fujii Masao <masao.fujii@oss.nttdata.com>
To: "Bossart, Nathan" <bossartn@amazon.com>, "wangsh.fnst@fujitsu.com" <wangsh.fnst@fujitsu.com>
Cc: Robert Haas <robertmhaas@gmail.com>, Andres Freund <andres@anarazel.de>, Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>, Greg Sabino Mullane <htamfids@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, "pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>
Date: 2022-01-07T16:53:52Z
Lists: pgsql-hackers 

On 2021/08/16 13:02, Bossart, Nathan wrote:
> On 8/15/21, 1:05 AM, "wangsh.fnst@fujitsu.com" <wangsh.fnst@fujitsu.com> wrote:
>> I don't think calling function GetMaxBackends() in the for loop is a good idea.
>> How about use a temp variable to save the return value of function GetMaxBackends() ?
> 
> I did this in v4.  There may be a couple of remaining places that call
> GetMaxBackends() several times, but the function should be relatively
> inexpensive.

The patch handles only MaxBackends. But isn't there other variable having the same issue?

It seems overkill to remove "extern" from MaxBackends and replace MaxBackends with GetMaxBackends() in the existing PostgreSQL codes. I'm not sure how much it's actually worth doing that.  Instead, isn't it enough to just add the comment like "Use GetMaxBackends() if you want to treat the lookup for uninitialized MaxBackends as an error" in the definition of MaxBackends?

Regards,

-- 
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION

Commits

  1. Add a new shmem_request_hook hook.

  2. Remove non-functional code for unloading loadable modules.

  3. Fix misleading comments about background worker registration.

  4. Revert the addition of GetMaxBackends() and related stuff.

  5. Fix typo in multixact.c

  6. Reduce more the number of calls to GetMaxBackends()

  7. Remove MaxBackends variable in favor of GetMaxBackends() function.

  8. Fix comments about bgworker registration before MaxBackends initialization

  9. Fix bogus assertion in BootstrapModeMain().

  10. Make sure MaxBackends is always set