Re: PoC/WIP: Extended statistics on expressions

On Wed, Mar 24, 2021 at 09:54:22AM +0100, Tomas Vondra wrote:
> Hi Justin,
>
> Unfortunately the query is incomplete, so I can't quite determine what
> went wrong. Can you extract the full query causing the crash, either
> from the server log or from a core file?

Oh, shoot, I didn't realize it was truncated, and I already destroyed the core
and moved on to something else...

But this fails well enough, and may be much shorter than the original :)

select distinct
pg_catalog.variance(
cast(pg_catalog.pg_stat_get_bgwriter_timed_checkpoints() as int8)) over (partition by subq_0.c2 order by subq_0.c0) as c0,
subq_0.c2 as c1, subq_0.c0 as c2, subq_0.c2 as c3, subq_0.c1 as c4, subq_0.c1 as c5, subq_0.c0 as c6
from
(select
ref_1.foreign_server_catalog as c0,
ref_1.authorization_identifier as c1,
sample_2.tgname as c2,
ref_1.foreign_server_catalog as c3
from
pg_catalog.pg_stat_database_conflicts as ref_0
left join information_schema._pg_user_mappings as ref_1
on (ref_0.datname < ref_0.datname)
inner join pg_catalog.pg_amproc as sample_0 tablesample system (5)
on (cast(null as uuid) < cast(null as uuid))
left join pg_catalog.pg_aggregate as sample_1 tablesample system (2.9)
on (sample_0.amprocnum = sample_1.aggnumdirectargs )
inner join pg_catalog.pg_trigger as sample_2 tablesample system (1) on true )subq_0;

TRAP: FailedAssertion("bms_num_members(varnos) == 1", File: "selfuncs.c", Line: 3332, PID: 16422)

Also ... with this patch CREATE STATISTIC is no longer rejecting multiple
tables, and instead does this:

postgres=# CREATE STATISTICS xt ON a FROM t JOIN t ON true;
ERROR: schema "i" does not exist

--
Justin