Re: Arg! PG not using index on an analyzed table

On Wed, 2 Feb 2005, Josh Berkus wrote:

> Reece,
>
> > Does anyone know what's going on here? I vaguely remember that
> > postgresql keeps frequency estimates of words... is the problem that the
> > new db doesn't have such estimates and therefore incorrectly guesses
> > that an index is better?
>
> What encoding does the new box have? Postgres is generally unable to use an
> index on "begins with" queries unless the database has "C" encoding. One of
> the differences between your old Red Hat and your new SuSE is that the
> default shell encoding will have changed from "C" to "en_US". You may need
> to re-initdb with --locale='C' .

You may also be able to get away with another index on the column using
text_pattern_ops as the operator class if you need/want other en_US
features.