Forum: Ruby on Rails Optimizing OR Queries in Rails and MySQL

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Moodang (Guest)
on 2009-05-01 14:14
(Received via mailing list)
According to MySQL doc, I must use union and temporary tables.

It seems I have to do something along the line of this:

http://www.ricroberts.com/articles/2007/09/25/mysq...

There are cases where I use OR queries quite often. I am talking about
queries like this "where column_1 = 123 OR column_2 = 123". It seems
MySQL indices cannot properly optimize this.

Are there plugins or snippets out there that automagically hide the
complexity of using temporary tables for such queries?
Frederick C. (Guest)
on 2009-05-01 14:16
(Received via mailing list)
On May 1, 10:38 am, Moodang <removed_email_address@domain.invalid> wrote:
> According to MySQL doc, I must use union and temporary tables.
>
> It seems I have to do something along the line of this:
>
> http://www.ricroberts.com/articles/2007/09/25/mysq......
>
> There are cases where I use OR queries quite often. I am talking about
> queries like this "where column_1 = 123 OR column_2 = 123". It seems
> MySQL indices cannot properly optimize this.

I don't think that's quite true - on mysql5 it should be able to do an
index merge:
http://dev.mysql.com/doc/refman/5.0/en/index-merge...

Fred
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