Re: "could not find pathkey item to sort" for TPC-DS queries 94-96

On 4/12/21 2:24 PM, Luc Vlaming wrote:
> Hi,
>
> When trying to run on master (but afaik also PG-13) TPC-DS queries 94,
> 95 and 96 on a SF10 I get the error "could not find pathkey item to sort".
> When I disable enable_gathermerge the problem goes away and then the
> plan for query 94 looks like below. I tried figuring out what the
> problem is but to be honest I would need some pointers as the code that
> tries to matching equivalence members in prepare_sort_from_pathkeys is
> something i'm really not familiar with.
>

Could be related to incremental sort, which allowed some gather merge
paths that were impossible before. We had a couple issues related to
that fixed in November, IIRC.

> To reproduce you can either ingest and test using the toolkit I used too
> (see https://github.com/swarm64/s64da-benchmark-toolkit/) or
> alternatively just use the schema (see
> https://github.com/swarm64/s64da-benchmark-toolkit/tree/master/benchmarks/tpcds/schemas/psql_native)
>

Thanks, I'll see if I can reproduce that with your schema.

regards

--
Tomas Vondra
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company