MySQL 8 Administrator???s Guide

InnoDB and MyISAM index statistics collection

MySQL 8 will consider table statistics based on the value group, which is nothing but a set of rows with the same prefix values. The storage engine collects statistics related to the table, which are used by the optimizer. From the optimization perspective, average value group size is an important statistic. If the average value of the group size increases, then the index is not meaningful. So, it's better to target a small number of rows for each index. This can be achieved by table cardinality, which is nothing but a number of value group. For InnoDB and MyISAM tables, MySQL 8 provides control on statistics by the myisam_stats_method and the innodb_stats_method system variables. The following ...