Fix bug #12537 UNION produces longtext instead of varchar

Item::tmp_table_field_from_field_type() and create_tmp_field_from_item()
was converting string field to blob depending on byte-wise length instead of
character length, which results in converting valid varchar string with
length == 86 to longtext.

Made that functions above take into account max width of character when
converting string fields to blobs.


sql/item.cc:
  Fix bug #12537 UNION produces longtext instead of varchar
  Item::tmp_table_field_from_field_type() now taking into account max char width when creating tmp field for string fields.
sql/sql_select.cc:
  Fix bug #12537 UNION produces longtext instead of varchar
   create_tmp_field_from_item()now taking into account max char width when creating tmp field for string fields.
mysql-test/r/create.result:
  Test case for bug #12537 UNION produces longtext instead of varchar
mysql-test/t/create.test:
  Test case for bug #12537 UNION produces longtext instead of varchar

1 files changed, 9 insertions, 0 deletions

diff --git a/mysql-test/t/create.test b/mysql-test/t/create.test
index 3b4b86a3df3..55321a81f5e 100644
--- a/mysql-test/t/create.test
+++ b/mysql-test/t/create.test
@@ -493,6 +493,15 @@ create table t2(test.t2.name int);
 drop table t1,t2;
 
 #
+# Bug #12537: UNION produces longtext instead of varchar
+#
+CREATE TABLE t1 (f1 VARCHAR(255) CHARACTER SET utf8);
+CREATE TABLE t2 AS SELECT LEFT(f1,86) AS f2 FROM t1 UNION SELECT LEFT(f1,86)
+AS f2 FROM t1;
+DESC t2;
+DROP TABLE t1,t2;
+
+#
 # Bug#11028: Crash on create table like
 #
 create database mysqltest;