Fixed bug #15917: unexpected complain for a NIST test case.

The problem was due to the fact that with --lower-case-table-names set to 1 
the function find_field_in_group did not convert the prefix 'HU' in
HU.PROJ.CITY into lower case when looking for it in the group list. Yet the
names in the group list were extended by the database name in lower case.

mysql-test/r/having.result

@@ -359,3 +359,38 @@ group by s1 collate latin1_swedish_ci having s1 = 'y';
 s1	count(s1)
 y	1
 drop table t1;
+DROP SCHEMA IF EXISTS HU;
+Warnings:
+Note	1008	Can't drop database 'HU'; database doesn't exist
+CREATE SCHEMA HU ;
+USE HU ;
+CREATE TABLE STAFF
+(EMPNUM   CHAR(3) NOT NULL UNIQUE,
+EMPNAME  CHAR(20),
+GRADE    DECIMAL(4),
+CITY     CHAR(15));
+CREATE TABLE PROJ
+(PNUM     CHAR(3) NOT NULL UNIQUE,
+PNAME    CHAR(20),
+PTYPE    CHAR(6),
+BUDGET   DECIMAL(9),
+CITY     CHAR(15));
+INSERT INTO STAFF VALUES ('E1','Alice',12,'Deale');
+INSERT INTO STAFF VALUES ('E2','Betty',10,'Vienna');
+INSERT INTO STAFF VALUES ('E3','Carmen',13,'Vienna');
+INSERT INTO STAFF VALUES ('E4','Don',12,'Deale');
+INSERT INTO STAFF VALUES ('E5','Ed',13,'Akron');
+INSERT INTO PROJ VALUES  ('P1','MXSS','Design',10000,'Deale');
+INSERT INTO PROJ VALUES  ('P2','CALM','Code',30000,'Vienna');
+INSERT INTO PROJ VALUES  ('P3','SDP','Test',30000,'Tampa');
+INSERT INTO PROJ VALUES  ('P4','SDP','Design',20000,'Deale');
+INSERT INTO PROJ VALUES  ('P5','IRM','Test',10000,'Vienna');
+INSERT INTO PROJ VALUES  ('P6','PAYR','Design',50000,'Deale');
+SELECT EMPNUM, GRADE*1000
+FROM HU.STAFF WHERE GRADE * 1000 > 
+ANY (SELECT SUM(BUDGET) FROM HU.PROJ
+GROUP BY CITY, PTYPE
+HAVING HU.PROJ.CITY = HU.STAFF.CITY);
+EMPNUM	GRADE*1000
+E3	13000
+DROP SCHEMA HU;

mysql-test/t/having.test

@@ -347,3 +347,47 @@ group by s1 collate latin1_swedish_ci having s1 = 'y';
 # MySQL returns: 1 row, with count(s1) = 1
 
 drop table t1;
+
+
+#
+# Bug #15917: unexpected complain for a name in having clause
+# when the server is run on Windows or with --lower-case-table-names=1
+#
+
+DROP SCHEMA IF EXISTS HU;
+CREATE SCHEMA HU ;
+USE HU ;
+
+CREATE TABLE STAFF
+ (EMPNUM   CHAR(3) NOT NULL UNIQUE,
+  EMPNAME  CHAR(20),
+  GRADE    DECIMAL(4),
+  CITY     CHAR(15));
+
+CREATE TABLE PROJ
+ (PNUM     CHAR(3) NOT NULL UNIQUE,
+  PNAME    CHAR(20),
+  PTYPE    CHAR(6),
+  BUDGET   DECIMAL(9),
+  CITY     CHAR(15));
+
+INSERT INTO STAFF VALUES ('E1','Alice',12,'Deale');
+INSERT INTO STAFF VALUES ('E2','Betty',10,'Vienna');
+INSERT INTO STAFF VALUES ('E3','Carmen',13,'Vienna');
+INSERT INTO STAFF VALUES ('E4','Don',12,'Deale');
+INSERT INTO STAFF VALUES ('E5','Ed',13,'Akron');
+
+INSERT INTO PROJ VALUES  ('P1','MXSS','Design',10000,'Deale');
+INSERT INTO PROJ VALUES  ('P2','CALM','Code',30000,'Vienna');
+INSERT INTO PROJ VALUES  ('P3','SDP','Test',30000,'Tampa');
+INSERT INTO PROJ VALUES  ('P4','SDP','Design',20000,'Deale');
+INSERT INTO PROJ VALUES  ('P5','IRM','Test',10000,'Vienna');
+INSERT INTO PROJ VALUES  ('P6','PAYR','Design',50000,'Deale');
+
+SELECT EMPNUM, GRADE*1000
+  FROM HU.STAFF WHERE GRADE * 1000 > 
+                  ANY (SELECT SUM(BUDGET) FROM HU.PROJ
+                         GROUP BY CITY, PTYPE
+                           HAVING HU.PROJ.CITY = HU.STAFF.CITY);
+
+DROP SCHEMA HU;

sql/item.cc

@@ -3054,6 +3054,7 @@ static Item** find_field_in_group_list(Item *find_item, ORDER *group_list)
   int         found_match_degree= 0;
   Item_ident *cur_field;
   int         cur_match_degree= 0;
+  char        name_buff[NAME_LEN+1];
 
   if (find_item->type() == Item::FIELD_ITEM ||
       find_item->type() == Item::REF_ITEM)
@@ -3065,6 +3066,14 @@ static Item** find_field_in_group_list(Item *find_item, ORDER *group_list)
   else
     return NULL;
 
+  if (db_name && lower_case_table_names)
+  {
+    /* Convert database to lower case for comparison */
+    strmake(name_buff, db_name, sizeof(name_buff)-1);
+    my_casedn_str(files_charset_info, name_buff);
+    db_name= name_buff;
+  }
+
   DBUG_ASSERT(field_name != 0);
 
   for (ORDER *cur_group= group_list ; cur_group ; cur_group= cur_group->next)