Re: exceeded MAX_ALLOCATED_DESCS while trying to open file

On Tue, May 28, 2013 at 11:28:02AM -0400, Steve(dot)Toutant(at)inspq(dot)qc(dot)ca wrote:
> Hi,
> Using postgres 9.2, I created a FOREIGN TABLE on a csv file. It works.
> But I need to change the structure of the data and I created several sql
> select using union, like
> select .... from .foreign table... where...
> union
> select .... from .foreign table... where...
> union
> ...
> It works for the first 10 select but then I get
> ERROR: exceeded MAX_ALLOCATED_DESCS while trying to open file
> "/srv/www/data/antidote/registre.csv"
>
> What is it MAX_ALLOCATED_DESCS? and how can I modify it without changing
> the code and re-compile? I tried using postgref.conf but this parameters
> is not recognize.
> thanks
> steve

Hi Steve,

Each SELECT opens your FOREIGN TABLE so you are opening it 10 times. This is
hardcoded by a #define in ./src/backend/storage/file/fd.c during the build so
you would need to recompile the software yourself to change it. Can you re-
write your query using a single SELECT or possibly read the data into a
temporary table for processing?

Regards,
Ken