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Slip number -----: 19
Problem ---------: NOT IN clause performs badly
Opened by -------: Christian.Rudow@thinx.ch on 07/26/99 05:28
Assigned To -----: momjian
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Summary:
table a (id integer
any number/type of other attributes)
unique index on id.
holding 10'000 rows
table b (id integer)
holding a subset of 8'000 rows, that
exist in table a.
trying to select all id values from table a
that do nor exist in table b :
select id from a
where id not in (select id from b);
this takes hours to process, while a simple join
select id from a,b
where a.id = b.id
returns within seconds
explain says : sequential scan on a and b.
still 120 minutes for processing can't be.
system used :
PG 6.4 on SusE 6.0, PII/300mhz.
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History:
07/26/99 12:47 by scrappy:
Public setting changed to 1 from 0
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