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Displaying posts with tag: in clause (reset)
Gigantic IN Clauses

Over the last few weeks I’ve been looking at several customers’ slow query logs, and I found in many of them an odd type of query. These are SELECT statements that contain an IN clause that includes dozens, sometimes hundreds of values. These statements often end in the slow query log. I’m not sure if these queries are this way by design or if they are generated by a specific database development tool.

I did some tests in one of my own databases, one with only around 10K rows in its largest table. The database corresponds to the Amarok media player. For example, I queried for songs by B. B. King (spelled “BB King”, “B.B. King”, etc. or with other artists: “B. B. King & Eric Clapton”).

The first query used a JOIN and an IN clause with all the …

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