The earlier pushed fix for the bug was incomplete. It did not remove
the main cause of the problem: the function remove_eq_conds()
removed always true multiple equalities from any conjunct, but did not
adjust the list of them stored in Item_cond_and::cond_equal.current_level.
Simplified the test case for the bug and moved it to another test file.
The fix triggered changes in EXPLAIN EXTENDED for some queries.
Applied a patch from Philip Hazel implementing the non-standard
syntax for word boundaries in PCRE, for compatibility with the
old Henry Spencer's regex library.
- Don't pull out a table out of a semi-join if it is on the inner side of an outer join.
- Make join->sort_by_table= get_sort_by_table(...) call after const table detection
is done. That way, the value of join->sort_by_table will match the actual execution.
Which will allow the code in setup_semijoin_dups_elimination() (search for
"Make sure that possible sorting of rows from the head table is not to be employed."
to see that "Using filesort" is going to be used together with Duplicate Elimination (
and change it to Using temporary + Using filesort)
- make_join_readinfo() has the code that forces use of "Using temporary;
Using filesort" when join buffering is in use.
That code didn't handle all cases, in particular it didn't hande the case
where ORDER BY originally has tables from multiple columns, but the
optimizer eventually figures out that doing filesort() on one table
will be sufficient. Adjusted the code to handle that case.
Apply fix suggested by Igor:
- When eliminate_item_equal() generates pair-wise equalities from a
multi-equality, do generate a "bridge" equality between the first
field inside SJM nest and the field that's first in the overall multi-equality.
When setting Item_func_not_all::test_sum_item or Item_func_not_all::test_sub_item,
reset the other one to NULL - they can never be set both. When a PS is reexecuted,
different executions might be optimized differently and a wrong test_su*_item
might stay set from the previous execution.
- MIN/MAX optimizer does a check whether a "field CMP const" comparison uses a constant
that's longer than the field it is compared to. Make this check only for string columns,
also compare character lengths, not byte lengths.
