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Re: Question on bad execution plan
Posted by: Rick James
Date: June 22, 2010 09:09AM

Eh? Each "row" in the EXPLAINs you have shown is either
type: ALL
key: NULL
meaning table scan, or
type: eq_ref (or other)
key: PRIMARY (or other)
except when you said FORCE INDEX(), which confused things. In that case, it needed to read ALL the rows, but told it to do things a slower way by using a particular index.

No, I don't know whether it is ignoring the FORCE and simply doing a table scan, or whether it is using the index. The only way I can see to figure out which it is actually doing is to have enough data so that you can see a difference in performance. And, I will state that using the index will be slower.

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