… making it unusable to check the optimizer performance. Solution for this problem was to use set optimizer_search_depth=0, rarely used option which as per manual will chose best value automatically. Making this change I could bring optimization… makes Timour explanation somewhat conflicting though as if we assume MySQL users do not join lots of tables (less than 7…

… benefits and drawbacks. Benefit being you can get extra optimizations by optimizer knowing index is UNIQUE the drawback is insert buffer will… key significantly fragmented. I also would note there are some MySQL optimizer restrictions in how well it can deal with primary key… comparison as a search condition WHERE A=5 ORDER BY B will use index (A,B) for sorting optimization, for more complicated…

… to the amazing MySQL manual, especially the option and variable reference …definitionsblogpercona.commanual Opened_tablesblogpercona.commanual optimizer_prune_levelblogpercona.commanual optimizer_search_depthblogpercona.commanual optimizer_switchblogpercona.commanual partitionblogpercona.commanual…