pre_get_col_charset

Filter Hook: Filters the column charset value before the DB is checked.

Source: wp-includes/wp-db.php:2556

wpdb::check_safe_collation()

Method: Check if the query is accessing a collation considered safe on the current version of MySQL.

Source: wp-includes/wp-db.php:2717

wpdb::strip_invalid_text()

Method: Strips any invalid characters based on value/charset pairs.

Source: wp-includes/wp-db.php:2780