why sequential scan
От | newsreader@mediaone.net |
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Тема | why sequential scan |
Дата | |
Msg-id | 20010816085011.A2208@dragon.universe обсуждение исходный текст |
Ответы |
Re: why sequential scan
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Список | pgsql-general |
Can someone explain why pg is doing a sequential scan on table item with the following statement ----- q=> explain select distinct h.id,i.item,i.heading,i.finish from item i ,body_index h where h.id=i.item and (h.string='book')order by finish; NOTICE: QUERY PLAN: Unique (cost=6591.46..6606.51 rows=150 width=24) -> Sort (cost=6591.46..6591.46 rows=1505 width=24) -> Hash Join (cost=5323.27..6512.04 rows=1505 width=24) -> Seq Scan on item i (cost=0.00..964.39 rows=5139 width=20) -> Hash (cost=5319.51..5319.51 rows=1505 width=4) -> Index Scan using body_index_string on body_index h (cost=0.00..5319.51 rows=1505 width=4) --------- "item" table has integer primary key "item". It has 15 or so other columns. The performance is not very impressive with about 5000 records in item table and 1.5 million record in body_index and both are supposed to get much bigger in the real life situation Is the performance bottle neck that particular sequential scan? The database has just been vacuumed. Thanks in advance
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