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Re: Query with GROUP BY not using Index
Posted by: Imran Akbar
Date: August 16, 2012 10:30AM

Hi Øystein,
thanks for the suggestion. The text field is 256 characters long, so the index of size 255 shouldn't be a prefix, should it? I tried to re-create the indexes without an explicit size, as you suggested:

ALTER TABLE `epi_iv` DROP INDEX `wafer_name`, ADD INDEX `wafer_name` (`wafer_name`)

ALTER TABLE `epi_iv` DROP INDEX `wafer_name_date`, ADD INDEX `wafer_name_date` (`wafer_name`,`date`)

but the wafer_name indexes still have size 255, and the query hasn't improved its speed as it's still not using the composite index.

Any other ideas?

imran

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