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
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