Hello
these queries are different. I checked a string_agg and it working
with me. So I am expecting, so your query has a performance problem
when aggregate function is used.
please, recheck so indexes are used
you can try "set enable_seqscan" to off, maybe set hashagg to off
please, send a execute plans - see statement EXPLAIN
Regards
Pavel Stehule
2011/2/21 Joel Reed <joelreed@openarc.net>:
> Hoping someone will be kind enough to share how to write a query that uses
> 9.0's string_agg with a subselect, something like...
>
> select m.id,m.subject,m.from_address,m.date_sent,m.size,string_agg((select
> address as to_address from recipient r inner join message_recipient mr on
> r.id=mr.recipient_id and mr.message_id=m.id and mr.recipient_type='To'), ',
> ') from message m, recipient r group by m.id, m.subject, m.from_address,
> m.date_sent, m.size limit 20;
>
> Unforunately, that just seems to hang. So I'm using...
>
> select
> m.id,m.subject,m.from_address,m.date_sent,m.size,array_to_string(ARRAY(select
> r.address from recipient r inner join message_recipient mr on
> r.id=mr.recipient_id and message_id=m.id and mr.recipient_type='To'), ',')
> as to_addresses from message m, recipient r limit 20;
>
> Which returns in under 4 seconds. Am I doing something wrong with the
> string_agg query to make it hang?
>
> Thanks in advance - I greatly appreciate any help you can offer.
>
> jr
>
>
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