Fix Bug #16290 Unclear error message when adding foreign key constraint

rb://502 approved by Sunny Bains

storage/innobase/dict/dict0dict.c

@@ -3483,7 +3483,7 @@ col_loop1:
 			start_of_latest_foreign);
 		mutex_exit(&dict_foreign_err_mutex);
 
-		return(DB_CANNOT_ADD_CONSTRAINT);
+		return(DB_CHILD_NO_INDEX);
 	}
 	ptr = dict_accept(cs, ptr, "REFERENCES", &success);
 
@@ -3764,7 +3764,7 @@ try_find_index:
 				start_of_latest_foreign);
 			mutex_exit(&dict_foreign_err_mutex);
 
-			return(DB_CANNOT_ADD_CONSTRAINT);
+			return(DB_PARENT_NO_INDEX);
 		}
 	} else {
 		ut_a(trx->check_foreigns == FALSE);

storage/innobase/handler/ha_innodb.cc

@@ -960,6 +960,8 @@ convert_error_code_to_mysql(
 		return(HA_ERR_ROW_IS_REFERENCED);
 
 	case DB_CANNOT_ADD_CONSTRAINT:
+	case DB_CHILD_NO_INDEX:
+	case DB_PARENT_NO_INDEX:
 		return(HA_ERR_CANNOT_ADD_FOREIGN);
 
 	case DB_CANNOT_DROP_CONSTRAINT:
@@ -6977,6 +6979,29 @@ ha_innobase::create(
 			trx, stmt, stmt_len, norm_name,
 			create_info->options & HA_LEX_CREATE_TMP_TABLE);
 
+		switch (error) {
+
+		case DB_PARENT_NO_INDEX:
+			push_warning_printf(
+				thd, MYSQL_ERROR::WARN_LEVEL_WARN,
+				HA_ERR_CANNOT_ADD_FOREIGN,
+				"Create table '%s' with foreign key constraint"
+				" failed. There is no index in the referenced"
+				" table where the referenced columns appear"
+				" as the first columns.\n", norm_name);
+			break;
+
+		case DB_CHILD_NO_INDEX:
+			push_warning_printf(
+				thd, MYSQL_ERROR::WARN_LEVEL_WARN,
+				HA_ERR_CANNOT_ADD_FOREIGN,
+				"Create table '%s' with foreign key constraint"
+				" failed. There is no index in the referencing"
+				" table where referencing columns appear"
+				" as the first columns.\n", norm_name);
+			break;
+                }
+
 		error = convert_error_code_to_mysql(error, flags, NULL);
 
 		if (error) {

storage/innobase/include/db0err.h

@@ -104,6 +104,12 @@ enum db_err {
 	DB_FOREIGN_EXCEED_MAX_CASCADE,	/* Foreign key constraint related
 					cascading delete/update exceeds
 					maximum allowed depth */
+	DB_CHILD_NO_INDEX,		/* the child (foreign) table does not
+					have an index that contains the
+					foreign keys as its prefix columns */
+	DB_PARENT_NO_INDEX,		/* the parent table does not
+					have an index that contains the
+					foreign keys as its prefix columns */
 
 	/* The following are partial failure codes */
 	DB_FAIL = 1000,

storage/innobase/ut/ut0ut.c

@@ -715,6 +715,10 @@ ut_strerr(
 		return("Zip overflow");
 	case DB_RECORD_NOT_FOUND:
 		return("Record not found");
+	case DB_CHILD_NO_INDEX:
+		return("No index on referencing keys in referencing table");
+	case DB_PARENT_NO_INDEX:
+		return("No index on referenced keys in referenced table");
 	case DB_END_OF_INDEX:
 		return("End of index");
 	/* do not add default: in order to produce a warning if new code