Re: Optimizing Query - Mailing list pgsql-sql

Have you tried VACUUM ANALYZE and CLUSTER?


> Any suggestions welcome!
> 
> Here is my query:
> 
> select k.*, c.category from knowledge k, kb_categories c , kbwords w0 , 
> kbwords w1 WHERE k.catid=c.catid AND ((k.kbid=w0.kbid and w0.wordid=42743) 
> AND (k.kbid=w1.kbid and w1.wordid=85369)) ORDER BY k.kbid DESC LIMIT 25;
> 
> Now for the details
> knowledge k = 3,150 records
> kbwords = 2-field database (kbid, wordid), 825,748 records
> 
> Each word in the knowledge base is stored in a database called wordindex, 
> which has 50,000 records or so. The system first explodes the query string 
> and pulls the word #s from this database, which is where we get 42743 and 
> 85369 above, "ASIA" and "CHILDREN" respectively.) The idea is then to pull 
> all the articles in the knowledge base which contain both of these words.
> 
> Here is the EXPLAIN for the query:
> 
> NOTICE:  QUERY PLAN:
> 
> Nested Loop  (cost=0.00..527690060.67 rows=2878549 width=308)
>    ->  Nested Loop  (cost=0.00..9472443.40 rows=52582 width=304)
>          ->  Nested Loop  (cost=0.00..6278.63 rows=960 width=300)
>                ->  Index Scan Backward using knowledge_kbid_key on 
> knowledge k  (cost=0.00..1292.51 rows=2825 width=284)
>                ->  Seq Scan on kb_categories c  (cost=0.00..1.34 rows=34 
> width=16)
>          ->  Seq Scan on kbwords w0  (cost=0.00..9787.02 rows=5474 width=4)
>    ->  Seq Scan on kbwords w1  (cost=0.00..9787.02 rows=5474 width=4)
> 
> This takes quite a while to return results... prohibitively long. There are 
> indexes on k.catid, c.catid, k.kbid, w0.kbid, w0.wordid. Any suggestions 
> for further optimization would be very welcome. We get about 3,000 searches 
> on our database daily...
> 
> Blessings,
> Justin Long
> 
> 
> 
> ____________________________________________________________________
> Justin Long                                     Network for Strategic Missions
> justinlong@strategicnetwork.org 1732 South Park Court
> http://www.strategicnetwork.org Chesapeake, VA 23320, USA
> Reality Check e-zine: reality-check-subscribe@yahoogroups.com
> ____________________________________________________________________
> Law: Never retreat. Never surrender. Never cut a deal with a dragon.
> Corollary: No armor? Unclean life? Then do not mess in the affairs
> of dragons, for you are crunchy and taste good with ketchup.
> 
> 
> ____________________________________________________________________
> Justin Long                                     Network for Strategic Missions
> justinlong@strategicnetwork.org 1732 South Park Court
> http://www.strategicnetwork.org Chesapeake, VA 23320, USA
> Reality Check e-zine: reality-check-subscribe@yahoogroups.com
> ____________________________________________________________________
> Law: Never retreat. Never surrender. Never cut a deal with a dragon.
> Corollary: No armor? Unclean life? Then do not mess in the affairs
> of dragons, for you are crunchy and taste good with ketchup.


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