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MDEV-23983: Crash caused by query containing constant having clause

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Before this patch the crash occured when a single row dataset is used and
Item::remove_eq_conds() is called for HAVING. This function is not supposed
to be called after the elimination of multiple equalities.

To fix this problem instead of Item::remove_eq_conds() Item::val_int() is
used. In this case the optimizer tries to evaluate the condition for the
single row dataset and discovers impossible HAVING immediately. So, the
execution phase is skipped.

Approved by Igor Babaev <igor@maridb.com>
This commit is contained in:
Galina Shalygina
2024-07-24 13:55:55 +02:00
parent 001608de7e
commit d072a29601
3 changed files with 100 additions and 8 deletions
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19
sql/sql_select.cc
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@ -2971,19 +2971,22 @@ int JOIN::optimize_stage2()
which do not use aggregate functions. In such case
temporary table may not be used and const condition
elements may be lost during further having
condition transformation in JOIN::exec.
condition transformation.
*/
if (having && const_table_map && !having->with_sum_func())
{
having->update_used_tables();
having= having->remove_eq_conds(thd, &select_lex->having_value, true);
if (select_lex->having_value == Item::COND_FALSE)
if (having->const_item() && !having->is_expensive())
{
having= new (thd->mem_root) Item_bool(thd, false);
zero_result_cause= "Impossible HAVING noticed after reading const tables";
error= 0;
select_lex->mark_const_derived(zero_result_cause);
goto setup_subq_exit;
bool having_value= having->val_int();
having= new (thd->mem_root) Item_bool(thd, having_value);
if (!having_value)
{
zero_result_cause= "Impossible HAVING noticed after reading const tables";
error= 0;
select_lex->mark_const_derived(zero_result_cause);
goto setup_subq_exit;
}
}
}