Condition pushdown is not a new kind of wrestling move but a special optimization in the MySQL server. It allows the Storage Engine and Information Schema plugins to use the
WHERE condition to filter the rows returned to MySQL, as opposed to letting MySQL process the
WHERE condition internally after the rows have been received. So it is effectively pushing down the
WHERE condition into the plugin. This optimization is not always meaningful to use. However, if the total number of rows is large, while the number of rows that satisfy the
WHERE clause is small, and generating rows is relatively expensive—in such a case this optimization can bring huge performance benefits. For example, the
INFORMATION_SCHEMA.COLUMNS table uses it, ...