Re: Accent-insensitive

On Fri, Dec 06, 2002 at 09:33:10PM +0100, Cédric Dufour (public) wrote:
> Use the 'to_ascii' function to convert your string to the "no accent" ASCII
> equivalent before accomplishing your comparison
> 
> SELECT foo FROM table WHERE ( to_ascii(foo) ILIKE to_ascii('caractères
> accentués') );
> 
> This does not work with all database locale (LATIN1 is OK, but LATIN9 is
> not).
> 
> I was actually wondering if this is efficient enough or if there is any more
> efficient method to accomplish this...

I'd think that something like:

CREATE FUNCTION lower_ascii (text) RETURNS text AS ' BEGIN   RETURN lower(to_ascii($1)); END
' language 'plpgsql';

CREATE INDEX table_lower_ascii ON table(lower_ascii(field));

would perform better, since we can now use this index, whereas we
couldn't do this with ILIKE to_ascii(...).

Also, not sure it's a good idea to use ILIKE simply to get
lower-case-matching. If the user string ends with '%', for instance, it
will match everything-starting-with, which is probably not what the user
meant. Better the check against lower().

There might be a better way specifically-oriented toward
de-accentuation; this is just generic PG advice.

- J.
-- 

Joel BURTON  |  joel@joelburton.com  |  joelburton.com  |  aim: wjoelburton
Independent Knowledge Management Consultant