• dlenev@mockturtle.local's avatar
    Fix for bug#20390 "SELECT FOR UPDATE does not release locks · ab98cbc8
    dlenev@mockturtle.local authored
    of untouched rows in full table scans".
    
    SELECT ... FOR UPDATE/LOCK IN SHARE MODE statements as well as
    UPDATE/DELETE statements which were executed using full table
    scan were not releasing locks on rows which didn't satisfy
    WHERE condition.
    This bug surfaced in 5.0 and affected NDB tables. (InnoDB tables
    intentionally don't support such unlocking in default mode).
    
    This problem occured because code implementing join didn't call
    handler::unlock_row() for rows which didn't satisfy part of condition
    attached to this particular table/level of nested loop. So we solve
    the problem adding this call.
    Note that we already had this call in place in 4.1 but it was lost
    (actually not quite correctly placed) when we have introduced nested 
    joins.
    
    Also note that additional QA should be requested once this patch is
    pushed as interaction between handler::unlock_row() and many recent
    MySQL features such as subqueries, unions, views is not tested enough.
    ab98cbc8
ndb_lock.result 3.92 KB