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Fix LP BUG#613029

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Analysis:
There are two code paths through which JOIN::exec may produce
an all-NULL row for an empty result set. One goes via the
function return_zero_rows(), when query processing detectes
early that the where clause is false, the other one is via
do_select() in the case of join execution.

In the case of do_select(), the problem was that the executioner
didn't set TABLE::null_row to 1. As result when sending the only
result row, the evaluation of each field didn't detect that all
non-aggregated fields are NULL, because Field::is_null returned
true, after checking that field->table->null_row was false.

Given that the each non-aggregated field was not considered NULL,
select_result::send_data sent whatever was in the buffer of each
field. However, since there was no actual data in the field buffer,
send_data() accessed and sent whatever junk was in the field's
data buffer.

Solution:
Similar to the analogous case in return_zero_rows() mark all
tables that their current row is NULL before sending the
artificailly created NULL row.
This commit is contained in:
unknown
2011-03-28 12:55:36 +03:00
parent ec23949158
commit 7999f40a99
4 changed files with 118 additions and 2 deletions
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4
sql/sql_select.h
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@ -954,8 +954,8 @@ public:
bool init_save_join_tab();
bool send_row_on_empty_set()
{
return (do_send_rows && tmp_table_param.sum_func_count != 0 &&
!group_list && having_value != Item::COND_FALSE);
return (do_send_rows && implicit_grouping &&
having_value != Item::COND_FALSE);
}
bool change_result(select_result *result);
bool is_top_level_join() const