Re: BUG #15324: Non-deterministic behaviour from parallelised sub-query

Andres Freund <andres@anarazel.de>

From: Andres Freund <andres@anarazel.de>

To: andy@prestigedigital.com, pgsql-bugs@lists.postgresql.org

Date: 2018-08-13T16:35:18Z

Lists: pgsql-bugs

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

Don't allow LIMIT/OFFSET clause within sub-selects to be pushed to workers.
- 568b4e1fdeb3 9.6.11 landed
- 1ceb103e7d1e 10.6 landed
- 830d7565902f 11.0 landed
- 75f9c4ca5a80 12.0 landed
Back-patch "Fix parallel hash join path search."
- 271b678436ce 9.6.11 landed
Prohibit pushing subqueries containing window function calculation to
- f658235a448a 9.6.11 landed
- bf61873ae3b6 10.6 landed
- 14e9b2a752ef 12.0 landed
- 2ce253cf57b1 11.0 landed
Fix parallel hash join path search.
- 655393a022bd 10.0 cited

Hi,

On 2018-08-13 16:14:03 +0000, PG Bug reporting form wrote:
> Execute this query (multiple times!)
> 
> select * from events where account in (select account from events where
> data->>'page' = 'success.html' limit 3);

Well, the subselect with thelimit going to return different results from
run to run. Unless you add an ORDER BY there's no guaranteed order in
which tuples are returned.  So I don't think it's surprising that you're
getting results that differ between runs.

Greetings,

Andres Freund