From: js (ebgssthgmail.com)
Date: Sat Oct 27 2007 - 07:57:50 CDT

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Hello,

I encountered weird problem.

I upgraded MySQL on my database on my app from 5.0 to the latest 5.1.22.
After the upgrade, the app suddenly got very slow.
A query, which was executed within about 0.1 sec, now took longer than
a few minutes.
(Actually, I don't know exactly how long it would take
 because the time executing the query is so long, I Ctrl-C'd the query)

Some explain showed that on 5.1.22, when I include a certain
column(VARCHAR(300))
in select list, MySQL ignore the index that should be used.
The query has force index to use the right index, but that seems to be ignored.

After downgrading to 5.0, MySQL picks the right index.

Unfortunately, I cannot connect to the system now,
cannot show any explain result, table defijnition, show index etc,
but the query that's got slow is a two innodb table joined query with order by.
order by column is datetime field and correctly indexed.
eacy table contains 2,3 million rows.

Is there anybody that has the same experience like this?
are there known issues that causes slow query when selecting some columns?

Any suggestions would be appreciated.
Thank you.

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