Horton

Re: Large writable variables

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
Cc: pgsql-hackers@postgresql.org, Thomas Munro <thomas.munro@enterprisedb.com>
Date: 2018-10-16T14:16:33Z
Lists: pgsql-hackers 
Andres Freund <andres@anarazel.de> writes:
> On 2018-10-16 01:59:00 -0400, Tom Lane wrote:
>> Also, I noticed that the biggest part of those structs are arrays of
>> FormatNode, which has been designed with complete lack of thought about
>> size or padding issues.  We can very easily cut it in half on 64-bit
>> machines.

> Heh, neat. I feel like we've paid very little attention to that in a
> myriad of places :(

Most of the time, we probably *shouldn't* pay attention to it; logical
field ordering is worth a good deal IMO.  But in a case like this,
where there are large arrays of the things and it's not very painful
to avoid padding waste, it's worth the trouble.

			regards, tom lane

Commits

  1. Apply unconstify() in more places

  2. Improve unconstify() documentation

  3. Drop const cast from dlsym() calls

  4. Const-ify a few more large static tables.

  5. Improve tzparse's handling of TZDEFRULES ("posixrules") zone data.

  6. Avoid statically allocating statement cache in ecpglib/prepare.c.

  7. Reorder FmgrBuiltin members, saving 25% in size.

  8. Add macro to cast away const without allowing changes to underlying type.

  9. Mark constantly allocated dest receiver as const.

  10. Avoid statically allocating formatting.c's format string caches.

  11. Correct constness of system attributes in heap.c & prerequisites.

  12. Avoid statically allocating gmtsub()'s timezone workspace.

  13. Correct constness of a few variables.

  14. Move the replication lag tracker into heap memory.