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Fix bug lp:1002079

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Analysis:
  The optimizer detects an empty result through constant table optimization.
  Then it calls return_zero_rows(), which in turns calls inderctly
  Item_maxmin_subselect::no_rows_in_result(). The latter method set "value=0",
  however "value" is pointer to Item_cache, and not just an integer value.
  
  All of the Item_[maxmin | singlerow]_subselect::val_XXX methods does:
    if (forced_const)
      return value->val_real();
  which of course crashes when value is a NULL pointer.
  
  Solution:
  When the optimizer discovers an empty result set, set
  Item_singlerow_subselect::value to a FALSE constant Item instead of NULL.
This commit is contained in:
unknown
2012-05-22 15:22:55 +03:00
parent b87ccfdfbc
commit 02bdc608b5
8 changed files with 115 additions and 2 deletions
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15
mysql-test/t/subselect.test
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@ -5174,6 +5174,21 @@ SELECT COUNT(f1), f2 IN (SELECT f1 FROM t1 WHERE f2 > 0) AS f4 FROM t2, t1 WHERE
drop table t1,t2;
--echo #
--echo # LP BUG#1002079 Server crashes in Item_singlerow_subselect::val_int with constant table,
--echo # HAVING, UNION in subquery
--echo #
CREATE TABLE t1 (a INT);
INSERT INTO t1 VALUES (7),(0);
CREATE TABLE t2 (b INT);
EXPLAIN
SELECT SUM(a) AS f1, a AS f2 FROM (t1, t2) HAVING f2 >= ALL (SELECT 4 UNION SELECT 5) AND f1 = 7;
SELECT SUM(a) AS f1, a AS f2 FROM (t1, t2) HAVING f2 >= ALL (SELECT 4 UNION SELECT 5) AND f1 = 7;
drop table t1,t2;
--echo # return optimizer switch changed in the beginning of this test
set optimizer_switch=@subselect_tmp;