ERROR: out of memory DETAIL: Failed on request of size ???

[Brian Wong <bwong64@xxxxxxxxxxx>]

We'd like to seek out your expertise on postgresql regarding this error that we're getting in an analytical database.

Some specs:
proc: Intel Xeon X5650 @ 2.67Ghz dual procs 6-core, hyperthreading on.
memory: 48GB
OS: Oracle Enterprise Linux 6.3

postgresql version: 9.1.9

shared_buffers: 18GB

We're doing a grouping query like this:

create table test as

select col1, max(col2), max(col3), max(col4), max(col5)

from view

where ...

and ...

and ...

group by col1;

The view queries another view that does a lot of UNION ALLs of tables.  This particular case I'm dealing with about 60 tables unioned together.

The resulting error is:

ERROR: out of memory
DETAIL: Failed on request of size ???

The issue seems a straight match with this link I found online: http://stackoverflow.com/questions/11878035/postgresql-9-1-out-of-memory-during-create-table-as-select

After doing a lot of googling, I've tried setting FETCH_COUNT on psql AND/OR setting work_mem.  I'm just not able to work around this issue, unless if I take most of the MAX() functions out but just one.

Would anyone give me some hints on how to resolve this issue?

Brian