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Re: Wrong estimation of Rows in explain
Posted by: Rick James
Date: August 02, 2016 06:23PM

Try innodb_buffer_pool_size = 2G -- if that leads to swapping, then it is too big.

EXPLAIN's row estimate is only approximate. There is no way to make it exact. It will even estimate the number of rows in the table.

For this:

a.col1 = b.col1 and a.col2 = b.col2

have both of these:

On a: INDEX(col1, col2)
On b: INDEX(col1, col2)

That is, a composite index is better (in this case) than an index on a single column.

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Re: Wrong estimation of Rows in explain
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August 02, 2016 06:23PM


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