Fixed bug #36488: regexp returns false matches, concatenating

                  with previous rows.

The WHERE clause containing expression:
  CONCAT(empty_field1, empty_field2, ..., 'literal constant', ...)
    REGEXP 'regular expression'
may return wrong matches.

Optimization of the CONCAT function has been fixed.



mysql-test/r/func_concat.result:
  Added test case for bug #36488.
mysql-test/t/func_concat.test:
  Added test case for bug #36488.
sql/item_strfunc.cc:
  Fixed bug #36488.
  The Item_func_concat::val_str method is optimized to
  use first non-empty argument of the CONCAT function for in-place
  result accumulation. This optimization is acceptable if that
  first argument is not a constant.
  However, current implementation checks this condition only for
  the first actual argument of the CONCAT function.
  So, the Item_func_concat::val_str method can corrupt values
  of, for example, literal strings by appending random data.
  
  The Item_func_concat::val_str method has been modified to take
  into account the ability to be modified in-place for the first
  non-empty argument.

1 files changed, 7 insertions, 0 deletions

diff --git a/mysql-test/r/func_concat.result b/mysql-test/r/func_concat.result
index 66808afd4e9..7e7c163716e 100644
--- a/mysql-test/r/func_concat.result
+++ b/mysql-test/r/func_concat.result
@@ -82,3 +82,10 @@ a
 1234562
 x
 drop table t1;
+CREATE TABLE t1 (c1 varchar(100), c2 varchar(100));
+INSERT INTO t1 VALUES ('',''), ('','First'), ('Random','Random');
+SELECT * FROM t1 WHERE CONCAT(c1,' ',c2) REGEXP 'First.*';
+c1	c2
+	First
+DROP TABLE t1;
+# End of 5.0 tests