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, 10 insertions, 0 deletions

diff --git a/mysql-test/t/func_concat.test b/mysql-test/t/func_concat.test
index 5487ad9c56b..f2aa0d004e5 100644
--- a/mysql-test/t/func_concat.test
+++ b/mysql-test/t/func_concat.test
@@ -68,3 +68,13 @@ create table t1(f1 varchar(6)) charset=utf8;
 insert into t1 values ("123456");
 select concat(f1, 2) a from t1 union select 'x' a from t1;
 drop table t1;
+
+#
+# Bug #36488: regexp returns false matches, concatenating with previous rows
+#
+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.*';
+DROP TABLE t1;
+
+--echo # End of 5.0 tests