Re: slow queries and blob fields

[Jay Pipes]

Erin,

Remove the index on active if it only has a cardinality of 2. That's a waste of space, since the index has very low selectivity. It would be better to see the news_date index used, and the Using WHERE be referring to the active column, instead of vice versa.

However, MySQL will choose to do a table scan versus an index range operation if the number of records in news meeting the criteria news_date <= 1120337337 is greater than a certain (say 35%) of the total rows in the table.

You're going to get the filesort appear in either case: it refers to the ORDER BY clause. As long as it doesn't say "Using temporary; using filesort", you're fine.

Jay Pipes
Community Relations Manager, North America, MySQL Inc.

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