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* INDEX PROBLEMS ?
@ 2002-11-16 18:04 PostgreSQL Server <postgres@rsd.it>
0 siblings, 1 reply; 2+ messages in thread
From: PostgreSQL Server @ 2002-11-16 18:04 UTC (permalink / raw)
To: pgsql-sql
On postgres 7.2.3 I have found what follows:
explain select * from documents where iddoc>1;
Seq Scan on lotti (cost=0.00..831.79 rows=26783 width=98)
EXPLAIN
explain select * from documents where iddoc=1;
Index Scan using lotti_pkey on lotti (cost=0.00..2.26 rows=1 width=98)
Why index is not used for operators > and < ????
Alex
^ permalink raw reply [nested|flat] 2+ messages in thread
* Re: INDEX PROBLEMS ?
@ 2002-11-16 19:06 Josh Berkus <josh@agliodbs.com>
parent: PostgreSQL Server <postgres@rsd.it>
0 siblings, 0 replies; 2+ messages in thread
From: Josh Berkus @ 2002-11-16 19:06 UTC (permalink / raw)
To: PostgreSQL Server <postgres@rsd.it>; pgsql-sql
Alex,
> On postgres 7.2.3 I have found what follows:
>
> explain select * from documents where iddoc>1;
>
> Seq Scan on lotti (cost=0.00..831.79 rows=26783 width=98)
>
> EXPLAIN
> explain select * from documents where iddoc=1;
>
> Index Scan using lotti_pkey on lotti (cost=0.00..2.26 rows=1
> width=98)
>
> Why index is not used for operators > and < ????
Because ">" is returning 26,000 rows. When you return that many rows,
a Seq Scan is faster.
-Josh
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2002-11-16 18:04 INDEX PROBLEMS ? PostgreSQL Server <postgres@rsd.it>
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