If the error happens during DELETE IGNORE, nothing could be send to the
client, thus leaving it frozen expecting the reply.
The problem was that if some error occurred, it wouldn't be reported to
the client because of IGNORE, but neither success would be reported.
MySQL 4.1 would not freeze the client, but will report
ERROR 1105 (HY000): Unknown error
instead, which is also a bug.
The solution is to report success if we are in DELETE IGNORE and some
non-fatal error has happened.
The bug is present only in 4.1, will be null-merged to 5.0
For InnoDB, check value of thd->transaction.all.innodb_active_trans instead of thd->transaction.stmt.innobase_tid to see if we really need to rollback.
Currently SQL_BIG_RESULT is checked only at compile time.
However, additional optimizations may take place after
this check that change the sort method from 'filesort'
to sorting via index. As a result the actual plan
executed is not the one specified by the SQL_BIG_RESULT
hint. Similarly, there is no such test when executing
EXPLAIN, resulting in incorrect output.
The patch corrects the problem by testing for
SQL_BIG_RESULT both during the explain and execution
phases.
The crash was caused by invalid sequence of handler::** calls:
ha_smth->index_init();
ha_smth->index_next_same(); (2)
(2) is an invalid call as it was not preceeded by any 'scan setup' call
like index_first() or index_read(). The cause was that QUICK_SELECT::reset()
didn't "fully reset" the quick select- current QUICK_RANGE wasn't forgotten,
and quick select might attempt to continue reading the range, which would
result in the above mentioned invalid sequence of handler calls.
5.x versions are not affected by the bug - they already have the missing
"range=NULL" clause.
* don't use join cache when the incoming data set is already ordered
for ORDER BY
This choice must be made because join cache will effectively
reverse the join order and the results will be sorted by the index
of the table that uses join cache.
The bug was as follows: When merge_key_fields() encounters "t.key=X OR t.key=Y" it will
try to join them into ref_or_null access via "t.key=X OR NULL". In order to make this
inference it checks if Y<=>NULL, ignoring the fact that value of Y may be not yet known.
The fix is that the check if Y<=>NULL is made only if value of Y is known (i.e. it is a
constant).
TODO: When merging to 5.0, replace used_tables() with const_item() everywhere in merge_key_fields().
