Re: limit clause breaks query planner?
От | Russell Smith |
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Тема | Re: limit clause breaks query planner? |
Дата | |
Msg-id | 48BCB90D.8090606@pws.com.au обсуждение исходный текст |
Ответ на | Re: limit clause breaks query planner? ("Pavel Stehule" <pavel.stehule@gmail.com>) |
Ответы |
Re: limit clause breaks query planner?
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Список | pgsql-performance |
Pavel Stehule wrote: > Hello > > 2008/9/1 David West <david.west@cusppoint.com>: > >> Thanks for your suggestion but the result is the same. >> >> Here is the explain analyse output from different queries. >> Select * from my_table where A is null and B = '21' limit 15 >> >> "Limit (cost=0.00..3.68 rows=15 width=128) (actual time=85837.043..85896.140 rows=15 loops=1)" >> " -> Seq Scan on my_table this_ (cost=0.00..258789.88 rows=1055580 width=128) (actual time=85837.038..85896.091 rows=15loops=1)" >> " Filter: ((A IS NULL) AND ((B)::text = '21'::text))" >> "Total runtime: 85896.214 ms" >> >> [snip] Further to Pavel's comments; (actual time=85837.038..85896.091 rows=15 loops=1) That's 85 seconds on a sequence scan to return the first tuple. The table is not bloated by any chance is it? Regards Russell
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