diff options
Diffstat (limited to 'sql/lock.cc')
| -rw-r--r-- | sql/lock.cc | 20 |
1 files changed, 17 insertions, 3 deletions
diff --git a/sql/lock.cc b/sql/lock.cc index 29a07858bc1..ef4a0cc3d83 100644 --- a/sql/lock.cc +++ b/sql/lock.cc @@ -847,9 +847,6 @@ static MYSQL_LOCK *get_lock_data(THD *thd, TABLE **table_ptr, uint count, locks= locks_buf= sql_lock->locks= (THR_LOCK_DATA**) (sql_lock + 1); to= table_buf= sql_lock->table= (TABLE**) (locks + tables * 2); sql_lock->table_count=lock_count; - sql_lock->lock_count=tables; - DBUG_PRINT("info", ("sql_lock->table_count %d sql_lock->lock_count %d", - sql_lock->table_count, sql_lock->lock_count)); for (i=0 ; i < count ; i++) { @@ -889,6 +886,23 @@ static MYSQL_LOCK *get_lock_data(THD *thd, TABLE **table_ptr, uint count, for ( ; org_locks != locks ; org_locks++) (*org_locks)->debug_print_param= (void *) table; } + /* + We do not use 'tables', because there are cases where store_lock() + returns less locks than lock_count() claimed. This can happen when + a FLUSH TABLES tries to abort locks from a MERGE table of another + thread. When that thread has just opened the table, but not yet + attached its children, it cannot return the locks. lock_count() + always returns the number of locks that an attached table has. + This is done to avoid the reverse situation: If lock_count() would + return 0 for a non-attached MERGE table, and that table becomes + attached between the calls to lock_count() and store_lock(), then + we would have allocated too little memory for the lock data. Now + we may allocate too much, but better safe than memory overrun. + And in the FLUSH case, the memory is released quickly anyway. + */ + sql_lock->lock_count= locks - locks_buf; + DBUG_PRINT("info", ("sql_lock->table_count %d sql_lock->lock_count %d", + sql_lock->table_count, sql_lock->lock_count)); DBUG_RETURN(sql_lock); } |