On 2018-06-13 16:35:58 +0900, Amit Langote wrote: > Hi. > > On 2018/06/13 14:55, Michael Paquier wrote: > > On Wed, Jun 13, 2018 at 11:08:38AM +0530, Rajkumar Raghuwanshi wrote: > >> postgres=# SELECT dense_rank(b) WITHIN GROUP (ORDER BY a) FROM pagg_tab > >> GROUP BY b ORDER BY 1; > >> server closed the connection unexpectedly > >> This probably means the server terminated abnormally > >> before or while processing the request. > >> The connection to the server was lost. Attempting reset: Failed. > > > > Indeed, thanks for the test case. This used to work in v10 but this is > > failing with v11 so I am adding an open item. The plans of the pre-10 > > query and the query on HEAD are rather similar, and the memory context > > at execution time looks messed up. > > Fwiw, I see that the crash can also occur even when using a > non-partitioned table in the query, as shown in the following example > which reuses Rajkumar's test data and query: > > create table foo (a int, b int, c text); > postgres=# insert into foo select i%20, i%30, to_char(i%12, 'FM0000') from > generate_series(0, 36) i; > > select dense_rank(b) within group (order by a) from foo group by b order by 1; > server closed the connection unexpectedly > This probably means the server terminated abnormally > before or while processing the request. > The connection to the server was lost. Attempting reset: Failed. > > Following query in the regression test suite can also be made to crash by > adding a group by clause: > > select dense_rank(3) within group (order by x) from (values > (1),(1),(2),(2),(3),(3),(4)) v(x) group by (x); > server closed the connection unexpectedly > This probably means the server terminated abnormally > before or while processing the request. > The connection to the server was lost. Attempting reset: Failed. > > Looking at the core dump of this, it seems the following commit may be > relevant: > > commit bf6c614a2f2c58312b3be34a47e7fb7362e07bcb > Author: Andres Freund <and...@anarazel.de> > Date: Thu Feb 15 21:55:31 2018 -0800 > > Do execGrouping.c via expression eval machinery, take two.
Andres, with RMT hat on: Andres, this needs looking at ASAP. Andres, without RMT hat on: Oh, I had first missed it, and then was distracted reviewing pluggable storage. Andres, with RMT hat on: that's not really an excuse Andres, without RMT hat on: sorry, will start looking now. Greetings, Andres Freund
