If a table is already in the table cache but without data from persistent
statistical tables then the function open_and_process_table should not
only allocate memory for this statistical data in the corresponding
TABLE_SHARE object, but also should copy the references to the data into
certain fields of the TABLE data structure: for each key of the table 
KEY::read_stats should be copied, and for each column of the table
Field::read_stats should be copied.