From: | Hannu Krosing <hannu(at)trust(dot)ee> |
---|---|
To: | Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us> |
Cc: | David Hartwig <daveh(at)insightdist(dot)com>, pgsql-interfaces(at)postgreSQL(dot)org, hackers(at)postgreSQL(dot)org |
Subject: | Re: [INTERFACES] Re: [HACKERS] changes in 6.4 |
Date: | 1998-07-16 08:41:47 |
Message-ID: | 35ADBCCB.3B1FB91B@trust.ee |
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Lists: | pgsql-general pgsql-hackers pgsql-interfaces |
Bruce Momjian wrote:
>
> > The results are profound. Queries that used to scan tables because of the
>
> How about if instead of doing:
>
> select * from tab1 where val = 3
> union
> select * from tab1 where val = 4
> ...
>
> you change it to:
>
> select * from tab1 where val in (
> select 3
> union
> select 4
> )
>
the explosion happens for ORs of multiple ANDs that get rewritten to:
select * from tabl wehere val1=1 and val2=1 and val3=1
union
select * from tabl wehere val1=1 and val2=1 and val3=2
union
...
And there is no way of doing (at least presently):
select * from table where (val1,val2,val3) in (select 1,1,1 union select
1,1,2);
Hannu
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