From: | Vadim Mikheev <vadim(at)krs(dot)ru> |
---|---|
To: | Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us> |
Cc: | bamby(at)marka(dot)net(dot)ua, hackers(at)postgreSQL(dot)org |
Subject: | Re: [HACKERS] Re: [BUGS] General Bug Report: Bug in optimizer |
Date: | 1999-03-18 18:42:12 |
Message-ID: | 36F14904.87062929@krs.ru |
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Lists: | pgsql-bugs pgsql-hackers |
Bruce Momjian wrote:
>
> Let me tell you why I don't think this is a bug. The optimizer will
> choose ordered results over unordered results if the costs are the same.
> In this case, the cost of the query is zero, so it chose to use the
> index because the index produces an ordered result.
>
> This works well for un-vacuumed tables, because it thinks everything is
> zero cost, and chooses the index.
Agreed, this is ok as long as
vac=> create table table1 (field1 int);
CREATE
vac=> insert into table1 values (1);
INSERT 1583349 1
vac=> create index i_table1__field1 on table1 (field1);
CREATE
vac=> explain select * from table1 where field1 = 1;
NOTICE: QUERY PLAN:
Seq Scan on table1 (cost=1.03 size=1 width=4)
- SeqScan is used for small tables.
So, only bug reported is left.
Vadim
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