le scoperte di monguz

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;

da https://mariadb.com/kb/en/mariadb/mysqlcolumn_stats-table/ CREATE TABLE mysql.column_stats (    db_name VARCHAR(64) NOT NULL COMMENT 'Database the table is in.',    table_name VARCHAR(64) NOT NULL COMMENT 'Table name.',    column_name VARCHAR(64) NOT NULL COMMENT 'Name of the column.',    min_value VARCHAR(64) DEFAULT NULL COMMENT 'Minimum value in the table (in text form).',    max_value VARCHAR(64) DEFAULT NULL COMMENT 'Maximum value in the table (in text form).',    nulls_ratio DECIMAL(12,4) DEFAULT NULL COMMENT 'Fraction of NULL values (0 - no NULLs, 0.5 - half values are NULLs, 1 - all values are NULLs).',    avg_length DECIMAL(12,4) DEFAULT NULL COMMENT 'Average length of column value, in bytes. Counted as if one ran SELECT AVG(LENGTH(col)). This doesn\'t count NULL bytes, assumes endspace removal for CHAR(n), etc.',    avg_frequency DECIMAL(12,4) DEFAULT NULL COMMENT 'Average number of records with the