Horton

Re: Issues with blocksize smaller than 8KB

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

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Casey Shobe <casey.allen.shobe@icloud.com>
Cc: pgsql-bugs@lists.postgresql.org
Date: 2025-10-18T16:45:45Z
Lists: pgsql-bugs

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Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Add static assertion that RELSEG_SIZE fits in an int.

Casey Shobe <casey.allen.shobe@icloud.com> writes:
> I have been comparing performance of postgresql (18.0) compiled for various block sizes etc., and found that while 8kb and 16kb builds work fine, a 4kb build does not, with identical configuration.  When I try to initialize pgbench, --scale=10 works fine, but the --scale=100 I was trying and even just --scale=20 result in a long delay on the vacuum analyze step followed by Postgres crashing due to a segmentation fault.
> I also found that initdb fails when I compile for a blocksize of either 1KB or 2KB build:

> 2025-10-17 15:39:13.182 UTC [97433] DETAIL:  The database cluster was initialized with RELSEG_SIZE 1895825408, but the server was compiled with RELSEG_SIZE 1895825408.
> 2025-10-17 15:39:13.182 UTC [97433] HINT:  It looks like you need to recompile or initdb.

I could not reproduce any of these misbehaviors here.  I suspect you
have a build process problem, ie failure to clean out all compilation
products when reconfiguring.  You need at least "make clean", and
personally I usually use "make distclean" or "git clean -dfxq".

(In theory, using --enable-depend would let you be sloppy about this,
but I've never particularly trusted that option.  It definitely will
not work to change configure settings without that.)

			regards, tom lane