da https://mariadb.com/kb/en/mariadb/mysqlindex_stats-table/
CREATE TABLE mysql.index_stats (
db_name VARCHAR(64) COMMENT 'Database the table is in.',
table_name VARCHAR(64) COMMENT 'Table name',
index_name VARCHAR(64) COMMENT 'Name of the index',
prefix_arity INT(11) UNSIGNED COMMENT 'Index prefix length. 1 for the first keypart, 2 for the first two, and so on. InnoDB\'s extended keys are supported.',
avg_frequency DECIMAL(12,4) DEFAULT NULL COMMENT 'Average number of records one will find for given values of (keypart1, keypart2, ..), provided the values will be found in the table.',
PRIMARY KEY (db_name, table_name, index_name, prefix_arity)
) ENGINE = InnoDB ROW_FORMAT = DEFAULT;
CREATE TABLE mysql.index_stats (
db_name VARCHAR(64) COMMENT 'Database the table is in.',
table_name VARCHAR(64) COMMENT 'Table name',
index_name VARCHAR(64) COMMENT 'Name of the index',
prefix_arity INT(11) UNSIGNED COMMENT 'Index prefix length. 1 for the first keypart, 2 for the first two, and so on. InnoDB\'s extended keys are supported.',
avg_frequency DECIMAL(12,4) DEFAULT NULL COMMENT 'Average number of records one will find for given values of (keypart1, keypart2, ..), provided the values will be found in the table.',
PRIMARY KEY (db_name, table_name, index_name, prefix_arity)
) ENGINE = InnoDB ROW_FORMAT = DEFAULT;
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