Date: Wed, 24 Mar 2021 04:17:08 -0500
From: Justin Pryzby <pryzby@telsasoft.com>
To: Tomas Vondra <tomas.vondra@enterprisedb.com>
Cc: Dean Rasheed <dean.a.rasheed@gmail.com>, pgsql-hackers@postgresql.org
Subject: Re: PoC/WIP: Extended statistics on expressions
Message-ID: <20210324091708.GC28335@telsasoft.com>
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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