Re: [GENERAL] Re: can't seem to use index

From: admin <admin(at)wtbwts(dot)com>
To: tesio(at)easynet(dot)fr
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: [GENERAL] Re: can't seem to use index
Date: 2000-01-11 11:38:02
Message-ID: Pine.BSF.4.10.10001111128360.58707-100000@server.b0x.com
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I have changed the name field to a char(32) NOT NULL, and I still get a
sequential scan. I have added the 2500 records and I did "vacuumdb
database" from the command-line. Unfortunately, "vacuum analyze" from the
psql prompt returns a pqReadData() error, loses the connection to the
backend and returns me to the shell. After reconnecting to the database,
explain still returns a sequential scan when trying something like:
explain select * from manufacturer where name='3COM';

Thanks anyways for the tip, I've been using varchar() all over the place,
I think I'll change a few to char(). What are the advantages of using
char() instead of varchar(). For a sequential scan, explain returned a
cost of 105.44 for a char() field as opposed to 95.44 for a varchar().

Thanks again,
Marc

> --- admin <admin(at)wtbwts(dot)com> wrote:
> > > I'm trying to use an index on a varchar(32) field, but explain
> > keeps
> > > retuning a sequential scan. This is my table and index:
> > >
> > > CREATE TABLE manufacturer (
> > > id int2,
> > > name varchar(32)
> > > );
> > >
> > > CREATE INDEX manu_name_idx ON "manufacturer" using btree ( "name"
> > > "text_ops" );
>
> Do you really need a varchar ? I've got similar queries on a char
> column which use the index. Maybe it's a problem about text_ops,
> it may not be compatible with varchar.
>
> Alain
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