Fixed bug #27695.

Declaring an all space column name in the SELECT FROM DUAL or in a view
leads to misleading warning message:
"Leading spaces are removed from name ' '".

The Item::set_name method has been modified to raise warnings like
"Name ' ' has become ''" in case of the truncation of an all
space identifier to an empty string identifier instead of the
"Leading spaces are removed from name ' '" warning message.

1 files changed, 20 insertions, 0 deletions

diff --git a/mysql-test/t/select.test b/mysql-test/t/select.test
index abf55745080..851e8164c44 100644
--- a/mysql-test/t/select.test
+++ b/mysql-test/t/select.test
@@ -3460,4 +3460,24 @@ SHOW WARNINGS;
 
 DROP TABLE t1;
 
+#
+# Bug #27695: Misleading warning when declaring all space column names and
+#             truncation of one-space column names to zero length names.
+#
+
+SELECT 1 AS ` `;
+SELECT 1 AS `  `;
+SELECT 1 AS ` x`;
+
+CREATE VIEW v1 AS SELECT 1 AS ` `;
+SELECT `` FROM v1;
+
+CREATE VIEW v2 AS SELECT 1 AS `  `;
+SELECT `` FROM v2;
+
+CREATE VIEW v3 AS SELECT 1 AS ` x`;
+SELECT `x` FROM v3;
+
+DROP VIEW v1, v2, v3;
+
 --echo End of 5.0 tests