Re: Issues with blocksize smaller than 8KB

Hi Tom,

I was also setting the relation segment size to something high like 1000 or 10000 - I found that when I changed that back to the default, the smaller blocksizes work fine without segfaulting. So the problem is apparently with that option being set too high, or maybe an incompatibility with smaller block sizes...

> On Oct 18, 2025, at 12:45 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> Casey Shobe <casey(dot)allen(dot)shobe(at)icloud(dot)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