Re: Queries with Regular Expressions

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От Silas Justiniano
Тема Re: Queries with Regular Expressions
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Msg-id 58e3b9040604061352j55fd413cv8408f5ad0a809a65@mail.gmail.com
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Ответ на Re: Queries with Regular Expressions  ("John D. Burger" <john@mitre.org>)
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John, it worked completely fine! Thank you! I don't understand exactly
the difference between [] and () for REs, but I'm starting to study
them deeply.

Thank you very much! Pg is great!

On 4/6/06, John D. Burger <john@mitre.org> wrote:
> > But I just can't make it work correctly using brackets:
> > SELECT field FROM table WHERE field ~* 'ch[aã]o';
> >
> > It just returns tuples that have 'chao', but not 'chão'.
> >
> > My queries are utf-8 an the database is SQL_ASCII.
>
> I suspect the bracketed expression is turning into [aXY], where XY is
> the two-byte sequence corresponding to ã in UTF8.  So the regular
> expression is only going to match strings of the form chao, chXo and
> chYo.  To make sure that this is what's happening, try this:
>
>    select length('ã');
>
> I bet you get back 2, not 1.  I don't know if a UTF8 database will
> handle this correctly or not.  The safest thing to do may be to use
> queries like this:
>
>    SELECT field FROM table WHERE field ~* 'ch(a|ã)o';
>
> - John D. Burger
>    MITRE
>
> ---------------------------(end of broadcast)---------------------------
> TIP 6: explain analyze is your friend
>


--
Silas Justiniano - Brazil

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