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Bug#22331: Wrong WHERE in EXPLAIN EXTENDED when all expressions were optimized

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away.

During optimization stage the WHERE conditions can be changed or even
be removed at all if they know for sure to be true of false. Thus they aren't
showed in the EXPLAIN EXTENDED which prints conditions after optimization.

Now if all elements of an Item_cond were removed this Item_cond is substituted
for an Item_int with the int value of the Item_cond.
If there were conditions that were totally optimized away then values of the
saved cond_value and having_value will be printed instead.
This commit is contained in:
evgen@moonbone.local
2007-03-07 21:44:58 +03:00
parent 0461228a70
commit 7afa5f1c5a
8 changed files with 74 additions and 15 deletions
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23
sql/sql_select.cc
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@ -681,7 +681,6 @@ JOIN::optimize()
}
{
Item::cond_result having_value;
having= optimize_cond(this, having, join_list, &having_value);
if (thd->net.report_error)
{
@ -689,6 +688,10 @@ JOIN::optimize()
DBUG_PRINT("error",("Error from optimize_cond"));
DBUG_RETURN(1);
}
if (select_lex->where)
select_lex->cond_value= cond_value;
if (select_lex->having)
select_lex->having_value= having_value;
if (cond_value == Item::COND_FALSE || having_value == Item::COND_FALSE ||
(!unit->select_limit_cnt && !(select_options & OPTION_FOUND_ROWS)))
@ -829,6 +832,7 @@ JOIN::optimize()
conds->update_used_tables();
DBUG_EXECUTE("where", print_where(conds, "after substitute_best_equal"););
}
/*
Permorm the the optimization on fields evaluation mentioned above
for all on expressions.
@ -7535,6 +7539,9 @@ static COND* substitute_for_best_equal_field(COND *cond,
break;
}
}
if (!((Item_cond*)cond)->argument_list()->elements)
cond= new Item_int(cond->val_bool());
}
else if (cond->type() == Item::FUNC_ITEM &&
((Item_cond*) cond)->functype() == Item_func::MULT_EQUAL_FUNC)
@ -15259,10 +15266,13 @@ void st_select_lex::print(THD *thd, String *str)
Item *cur_where= where;
if (join)
cur_where= join->conds;
if (cur_where)
if (cur_where || cond_value != Item::COND_UNDEF)
{
str->append(STRING_WITH_LEN(" where "));
cur_where->print(str);
if (cur_where)
cur_where->print(str);
else
str->append(cond_value != Item::COND_FALSE ? "1" : "0");
}
// group by & olap
@ -15288,10 +15298,13 @@ void st_select_lex::print(THD *thd, String *str)
if (join)
cur_having= join->having;
if (cur_having)
if (cur_having || having_value != Item::COND_UNDEF)
{
str->append(STRING_WITH_LEN(" having "));
cur_having->print(str);
if (cur_having)
cur_having->print(str);
else
str->append(having_value != Item::COND_FALSE ? "1" : "0");
}
if (order_list.elements)