Thread: (long) What's the problem?

Anybody have any ideas about a problem with this query?

urldb2=> EXPLAIN
urldb2-> SELECT
urldb2->   id,
urldb2->   source,
urldb2->   insertedby,
urldb2->   insertedon,
urldb2->   priority
urldb2-> FROM
urldb2->   indexscan
urldb2-> WHERE
urldb2->   lower(
urldb2->     substring(
urldb2->       urlhost( source ), rposition( 'www.', urlhost( source ) ) + 2
urldb2->     )
urldb2->   ) ~ '^q.*'
urldb2-> ORDER BY source;

QUERY PLAN

-------------------------------------------------------------------------------------------------------------------------------------------Sort
(cost=23.50..23.50 rows=3 width=48)  Sort Key: source  ->  Seq Scan on indexscan  (cost=0.00..23.47 rows=3 width=48)
   Filter: (lower("substring"(urlhost(source), (rposition('www.'::text, (urlhost(source))::character varying) + 2))) ~
'^q.*'::text)
(4 rows)

OK, cost=23.50..23.50, should be a quickie. I'll EXPLAIN ANALYZE just to be safe:

urldb2=> EXPLAIN ANALYZE
urldb2-> SELECT
urldb2->   id,
urldb2->   source,
urldb2->   insertedby,
urldb2->   insertedon,
urldb2->   priority
urldb2-> FROM
urldb2->   indexscan
urldb2-> WHERE
urldb2->   lower(
urldb2->     substring(
urldb2->       urlhost( source ), rposition( 'www.', urlhost( source ) ) + 2
urldb2->     )
urldb2->   ) ~ '^q.*'
urldb2-> ORDER BY source;

server closed the connection unexpectedly       This probably means the server terminated abnormally       before or
whileprocessing the request. 
The connection to the server was lost. Attempting reset: Failed.

Since EXPLAIN ANALYZE runs the query and then analyzes the results I haven't included that in this email because the
erroris the same. 

urlhost() is an immutable custom Pl/Perl function.
rposition() is a volatile custom C function.
indexscan has 614 tuples and only takes up 7 pages.
The load on this machine is zero when I attempt this, and no other processes are trying to use massive amounts of
resources.This is a P3 550 with 512MB of RAM. 

I can provide more information if needed.

Anybody have ideas about the problem?

--------------------------
David Olbersen
iGuard Engineer
11415 West Bernardo Court
San Diego, CA 92127
1-858-676-2277 x2152

David Olbersen wrote:
> Anybody have any ideas about a problem with this query?
> 
> urldb2=> EXPLAIN
> urldb2-> SELECT
> urldb2->   id,
> urldb2->   source,
> urldb2->   insertedby,
> urldb2->   insertedon,
> urldb2->   priority
> urldb2-> FROM
> urldb2->   indexscan
> urldb2-> WHERE
> urldb2->   lower(
> urldb2->     substring(
> urldb2->       urlhost( source ), rposition( 'www.', urlhost( source ) ) + 2
> urldb2->     )
> urldb2->   ) ~ '^q.*'
> urldb2-> ORDER BY source;                                                                
> 
> QUERY PLAN                                     
>
-------------------------------------------------------------------------------------------------------------------------------------------
>  Sort  (cost=23.50..23.50 rows=3 width=48)
>    Sort Key: source
>    ->  Seq Scan on indexscan  (cost=0.00..23.47 rows=3 width=48)
>          Filter: (lower("substring"(urlhost(source), (rposition('www.'::text, (urlhost(source))::character varying) +
2)))~ '^q.*'::text)
 
> (4 rows)
> 
> OK, cost=23.50..23.50, should be a quickie. I'll EXPLAIN ANALYZE just to be safe:
> 
> urldb2=> EXPLAIN ANALYZE
> urldb2-> SELECT
> urldb2->   id,
> urldb2->   source,
> urldb2->   insertedby,
> urldb2->   insertedon,
> urldb2->   priority
> urldb2-> FROM
> urldb2->   indexscan
> urldb2-> WHERE
> urldb2->   lower(
> urldb2->     substring(
> urldb2->       urlhost( source ), rposition( 'www.', urlhost( source ) ) + 2
> urldb2->     )
> urldb2->   ) ~ '^q.*'
> urldb2-> ORDER BY source;
> 
> 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.

If I would be you I would unlimit the coresize in the environment the 
postmaster is running, eventually recompile with debug symbols enabled 
and look at the stack backtrace of the coredump created when then 
backend crashes.


Jan

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