Bug#15949 union + illegal mix of collations (IMPLICIT + COERCIBLE)

union.result, union.test:
  Adding test case.
item.cc:
  Allow safe character set conversion in UNION
  - string constant to column's charset
  - to unicode
  Thus, UNION now works the same with CONCAT (and other string functions)
  in respect of aggregating arguments with different character sets.


sql/item.cc:
  Allow character set conversion in UNION
  - string to column's charset
  - to unicode
  Bug#15949 union + illegal mix of collations (IMPLICIT + COERCIBLE)
mysql-test/t/union.test:
  Adding test case.
mysql-test/r/union.result:
  Adding test case.

1 files changed, 10 insertions, 1 deletions

diff --git a/mysql-test/t/union.test b/mysql-test/t/union.test
index 1f6fc2c8d3b..994546e9d97 100644
--- a/mysql-test/t/union.test
+++ b/mysql-test/t/union.test
@@ -711,6 +711,15 @@ set @val:=6;
 select concat('value is: ', @val) union select 'some text';
 
 #
+# Bug#15949 union + illegal mix of collations (IMPLICIT + COERCIBLE)
+#
+select concat(_latin1'a', _ascii'b' collate ascii_bin);
+create table t1 (foo varchar(100)) collate ascii_bin;
+insert into t1 (foo) values ("foo");
+select foo from t1 union select 'bar' as foo from dual;
+drop table t1;
+
+#
 # Enum merging test
 #
 CREATE TABLE t1 (
@@ -729,8 +738,8 @@ drop table t2;
 create table t2 select a from t1 union select a from t1;
 show columns from t2;
 drop table t2;
--- error 1267
 create table t2 select a from t1 union select c from t1;
+drop table t2;
 create table t2 select a from t1 union select b from t1;
 show columns from t2;
 drop table t2, t1;