MDEV-33460 select '123' 'x'; unexpected result

Queries that select concatenated constant strings now have
colname and value that match.  For example,
  SELECT '123' 'x';
will return a result where the column name and value both
are '123x'.

Review: Daniel Black

mysql-test/main/empty_string_literal.result

@@ -64,7 +64,7 @@ SET sql_mode=@mode;
 # Test litteral concat
 #
 SELECT 'a' 'b';
-a
+ab
 ab
 SELECT 'a' '';
 a
@@ -76,13 +76,13 @@ SELECT '' '';
 NULL
 NULL
 SELECT '' 'b' 'c';
-b
+bc
 bc
 SELECT '' '' 'c';
 c
 c
 SELECT 'a' '' 'c';
-a
+ac
 ac
 SELECT 'a' '' '';
 a
@@ -208,3 +208,22 @@ t1	CREATE TABLE `t1` (
   KEY `a` (`a`,`b`)
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci
 drop table t1;
+#
+# MDEV-33460 select '123' 'x'; unexpected result
+#
+SELECT '';
+NULL
+NULL
+SELECT '' 'b' 'c';
+bc
+bc
+SELECT '' '' 'c';
+c
+c
+SELECT 'a' '' 'c';
+ac
+ac
+SELECT 'a' '' '';
+a
+a
+# End of 10.5 test

mysql-test/main/empty_string_literal.test

@@ -25,3 +25,15 @@ flush tables;
 update t1 set a = 2;
 show create table t1;
 drop table t1;
+
+--echo #
+--echo # MDEV-33460 select '123' 'x'; unexpected result
+--echo #
+
+SELECT '';
+SELECT '' 'b' 'c';
+SELECT '' '' 'c';
+SELECT 'a' '' 'c';
+SELECT 'a' '' '';
+
+--echo # End of 10.5 test

mysql-test/main/func_str.result

@@ -8,7 +8,7 @@ select 'hello',"'hello'",'""hello""','''h''e''l''l''o''',"hel""lo",'hel\'lo';
 hello	'hello'	""hello""	'h'e'l'l'o'	hel"lo	hel'lo
 hello	'hello'	""hello""	'h'e'l'l'o'	hel"lo	hel'lo
 select 'hello' 'monty';
-hello
+hellomonty
 hellomonty
 select length('\n\t\r\b\0\_\%\\');
 length('\n\t\r\b\0\_\%\\')

mysql-test/main/join.result

@@ -894,7 +894,7 @@ show status like '%cost%';
 Variable_name	Value
 Last_query_cost	4.016090
 select 'The cost of accessing t1 (dont care if it changes' '^';
-The cost of accessing t1 (dont care if it changes
+The cost of accessing t1 (dont care if it changes^
 The cost of accessing t1 (dont care if it changes^
 select 'vv: Following query must use ALL(t1), eq_ref(A), eq_ref(B): vv' Z;
 Z

mysql-test/suite/compat/oracle/r/empty_string_literal.result

@@ -64,7 +64,7 @@ SET sql_mode=@mode;
 # Test litteral concat
 #
 SELECT 'a' 'b';
-a
+ab
 ab
 SELECT 'a' '';
 a
@@ -76,13 +76,13 @@ SELECT '' '';
 NULL
 NULL
 SELECT '' 'b' 'c';
-b
+bc
 bc
 SELECT '' '' 'c';
 c
 c
 SELECT 'a' '' 'c';
-a
+ac
 ac
 SELECT 'a' '' '';
 a

sql/item.cc

@@ -6943,6 +6943,7 @@ Item_basic_constant *
 Item_string::make_string_literal_concat(THD *thd, const LEX_CSTRING *str)
 {
   append(str->str, (uint32) str->length);
+  set_name(thd, &str_value);
   if (!(collation.repertoire & MY_REPERTOIRE_EXTENDED))
   {
     // If the string has been pure ASCII so far, check the new part.