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Bug #29717 INSERT INTO SELECT inserts values even if

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SELECT statement itself returns empty.

As a result of this bug 'SELECT AGGREGATE_FUNCTION(fld) ... GROUP BY'
can return one row instead of an empty result set.

When GROUP BY only has fields of constant tables
(with a single row), the optimizer deletes the group_list.
After that we lose the information about whether we had an
GROUP BY statement. Though it's important
as SELECT min(x) from empty_table; and
   SELECT min(x) from empty_table GROUP BY y; have to return
different results - the first query should return one row,
second - an empty result set.
So here we add the 'group_optimized_away' flag to remember this case
when GROUP BY exists in the query and is removed
by the optimizer, and check this flag in end_send_group()
This commit is contained in:
holyfoot/hf@mysql.com/hfmain.(none)
2007-07-31 10:46:04 +05:00
parent 40fb6443ce
commit f1ee2d0687
6 changed files with 106 additions and 1 deletions
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4
sql/sql_select.cc
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@ -777,6 +777,7 @@ JOIN::optimize()
order=0; // The output has only one row
simple_order=1;
select_distinct= 0; // No need in distinct for 1 row
group_optimized_away= 1;
}
calc_group_buffer(this, group_list);
@ -6896,7 +6897,8 @@ end_send_group(JOIN *join, JOIN_TAB *join_tab __attribute__((unused)),
if (!join->first_record || end_of_records ||
(idx=test_if_group_changed(join->group_fields)) >= 0)
{
if (join->first_record || (end_of_records && !join->group))
if (join->first_record ||
(end_of_records && !join->group && !join->group_optimized_away))
{
if (join->procedure)
join->procedure->end_group();