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Need help with getting rid of filesort
Posted by: Marvin Herbold
Date: June 23, 2022 01:53PM

I have a pretty simple select query that the optimizer insists on using filesort for.

EXPLAIN SELECT
`id`, `displayName`, `order`
FROM
`someTable`
WHERE
`id` != 0
ORDER BY
`displayName`, `order`
LIMIT
123456, 1000

`id` is PK.

`displayName` and `order` have their own indexes.

I also have a ( `displayName`, `order` ) index as well as a ( `displayName`, `order`, `id` ) index.

The optimizer still insists on using filesort. If I add a FORCE INDEX to force it to use the ( `displayName`, `order` ) index, it works and runs much faster (50x faster). If I remove the WHERE clause, the filesort goes away. How can I properly set up this table / indexes so that I can have that where clause, and the optimizer would not use filesort?

Thanks for any help!

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