When trying to understand queries in the slow log, an interesting metric to look at is rows examined. Also, when trying to understand CPU spikes on a MySQL instance, the InnoDB Metric dml_reads and the global status Innodb_rows_read are interesting to check. In a similar way, when trying to gather information about which queries are loading the system, SUM_ROWS_EXAMINED from the| J-F Gagné's MySQL Blog
If you ever wondered why a query that looks harmless is performing poorly despite having indexes in place, the answer could non-SARGable queries. First appeared on SQL SERVER – Catching Non-SARGable Queries in Action| SQL Authority with Pinal Dave