…low depending on your scenario. You can read more about the MRR … are incremented when index lookup is performed. As I explained at the …wrong choice. It looks like that there is still improvement and changes needed in the optimizer’s cost estimation… Algorithms. So I am not going to cover it here, but…
Post: When EXPLAIN estimates can go wrong!
October 13, 2011 By 7 Comments
…EXPLAIN. Now this can be a real pain as MySQL uses “the number of rows” estimation to pick and choose indexes and it could really be picking up a wrong index simply because of the wrong estimate…can happen in all cases, but there are two scenarios when this can happen: when…
Post: MySQL EXPLAIN limits and errors.
July 24, 2006 By 6 Comments
…EXPLAIN can be wrong – this does not happen very often but it does. EXPLAIN…are still cases when it may …EXPLAIN might never complete. Solution is to run EXPLAIN for statements in FROM clause separately before looking at main query. Estimated…going to be used in particular sort is not seen in explain…
