From: | Raymond O'Donnell <rod(at)iol(dot)ie> |
---|---|
To: | Dan Halbert <halbert(at)halwitz(dot)org> |
Cc: | pgsql-general(at)postgresql(dot)org |
Subject: | Re: select distinct in a subquery bug/problem |
Date: | 2012-08-11 18:21:02 |
Message-ID: | 5026A28E.6000502@iol.ie |
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Lists: | pgsql-general |
On 11/08/2012 04:32, Dan Halbert wrote:
> In version 9.1.4-0ubuntu12.04:
>
>
>
> Hi - I am getting wrong answers from a certain kind of query, and have
> narrowed it down to a change in the query plan between two similar
> queries. The two queries below use different query plans, and generate
> different results, one of which is completely wrong.
>
>
>
> 1. select count(t1_id) from t1 where t1_id not in (select distinct t1_id
> from t2 limit 1103) ==> 13357 [CORRECT result]
>
> 2. select count(t1_id) from t1 where t1_id not in (select distinct t1_id
> from t2 limit 1104) ==> 0 [WRONG result; should be close to 13357]
Does it make a difference if you include an ORDER BY in the subquery?
AIUI, the particular result set from the subquery is indeterminate (in
theory anyway) without it.
Ray.
--
Raymond O'Donnell :: Galway :: Ireland
rod(at)iol(dot)ie
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