> Hello, > > I'm executing this query: > > SELECT x, y, another_field FROM generate_series(1, 10) x, > generate_series(1, 10) y, my_table
Well, do you realize this is a cartesian product that gives 10 x 10 x 360000 = 36.000.000 rows in the end. Not sure how wide is the third table (how many columns etc.) but this may occupy a lot of memory. > The field 'another_field' belongs to 'my_table'. And that table has > 360000 entries. In a 64 bits machine, with 4GB RAM, Ubuntu 10.10 and > postgres 8.4.7, the query works fine. But in a 32 bits machine, with > 1GB RAM, Ubuntu 9.10 and postgres 8.4.7, the query process is killed > after taking about 80% of available memory. In the 64 bits machine the > query takes about 60-70% of the available memory too, but it ends. > And this happens even if I simply get x and y: > > SELECT x, y FROM generate_series(1, 10) x, generate_series(1, 10) y, > my_table The result is still 36 million rows, so there's not a big difference I guess. > Is it normal? I mean, postgres has to deal with millions of rows, ok, > but shouldn't it start swapping memory instead of crashing? Is a > question of postgres configuration? I guess that's the OOM killer, killing one of the processes. See this http://en.wikipedia.org/wiki/Out_of_memory so it's a matter of the system, not PostgreSQL - the kernel decides there's not enough memory, chooses one of the processes and kills it. PostgreSQL is a victim in this case. Tomas -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
