Re: Sequential scan being used despite indexes

>
> Explaining:
> Hash Join (cost=337.93..1267.54 rows=180 width=35)
> Hash Cond: ("outer".message_id = "inner".message_id)
> -> Seq Scan on message_meta_data (cost=0.00..739.19 rows=37719 width=30)
> -> Hash (cost=337.79..337.79 rows=57 width=13)
> -> Nested Loop (cost=0.00..337.79 rows=57 width=13)
> -> Index Scan using thread_forum_id_idx on thread
> (cost=0.00..41.61 rows=13 width=4)
> Index Cond: (forum_id = 6)
> -> Index Scan using message_thread_id_idx on message
> (cost=0.00..22.72 rows=5 width=17)
> Index Cond: ("outer".thread_id = message.thread_id)
>
> As you can see, the message and message_meta_data tables use a Seq
> Scan. The only way I can think of forcing it to use the Index Scan in
> all cases would be to use two separate nested queries: The outer query
> would retrieve the list of messages in the forum, and the inner query
> would retrieve the list of metadata for an individual message.
> Obviously I want to avoid having to do that if possible.
>
> Any ideas?
What does explain analyze say?

Joshua D. Drake

>
> Many thanks if you can help.
>
> James

--
The PostgreSQL Company - Command Prompt, Inc. 1.503.667.4564
PostgreSQL Replication, Consulting, Custom Development, 24x7 support
Managed Services, Shared and Dedicated Hosting
Co-Authors: PLphp, PLperl - http://www.commandprompt.com/