Re: pg_trgm comparison bug on cross-architecture replication due to different char implementation

"Guo, Adam" <adamguo(at)amazon(dot)com> writes:
> I would like to report an issue with the pg_trgm extension on
> cross-architecture replication scenarios. When an x86_64 standby
> server is replicating from an aarch64 primary server or vice versa,
> the gist_trgm_ops opclass returns different results on the primary
> and standby.

I do not think that is a supported scenario. Hash functions and
suchlike are not guaranteed to produce the same results on different
CPU architectures. As a quick example, I get

regression=# select hashfloat8(34);
hashfloat8
------------
21570837
(1 row)

on x86_64 but

postgres=# select hashfloat8(34);
hashfloat8
------------
-602898821
(1 row)

on ppc32 thanks to the endianness difference.

> Given that this has problem has come up before and seems likely to
> come up again, I'm curious what other broad solutions there might be
> to resolve it?

Reject as not a bug. Discourage people from thinking that physical
replication will work across architectures.

regards, tom lane