added e2e test for join with using in information_schema

Signed-off-by: Harshit Gangal <harshit@planetscale.com>

go/test/endtoend/vtgate/information_schema_test.go

@@ -114,3 +114,14 @@ func TestInformationSchemaQueryGetsRoutedToTheRightTableAndKeyspace(t *testing.T
 	result := exec(t, conn, "SELECT * FROM information_schema.tables WHERE table_schema = database() and table_name='t1000'")
 	assert.NotEmpty(t, result.Rows)
 }
+
+func TestFKConstraintUsingInformationSchema(t *testing.T) {
+	defer cluster.PanicHandler(t)
+	ctx := context.Background()
+	conn, err := mysql.Connect(ctx, &vtParams)
+	require.NoError(t, err)
+	defer conn.Close()
+
+	query := "select fk.referenced_table_name as to_table, fk.referenced_column_name as primary_key, fk.column_name as `column`, fk.constraint_name as name, rc.update_rule as on_update, rc.delete_rule as on_delete from information_schema.referential_constraints as rc join information_schema.key_column_usage as fk using (constraint_schema, constraint_name) where fk.referenced_column_name is not null and fk.table_schema = database() and fk.table_name = 't7_fk' and rc.constraint_schema = database() and rc.table_name = 't7_fk'"
+	assertMatches(t, conn, query, `[[VARCHAR("t7_xxhash") VARCHAR("uid") VARCHAR("t7_uid") VARCHAR("t7_fk_ibfk_1") VARCHAR("CASCADE") VARCHAR("SET NULL")]]`)
+}

go/test/endtoend/vtgate/main_test.go

@@ -127,7 +127,16 @@ create table t7_xxhash_idx(
 	phone bigint,
 	keyspace_id varbinary(50),
 	primary key(phone, keyspace_id)
-) Engine=InnoDB;`
+) Engine=InnoDB;
+
+create table t7_fk(
+	id bigint,
+	t7_uid varchar(50),
+    primary key(id),
+    CONSTRAINT t7_fk_ibfk_1 foreign key (t7_uid) references t7_xxhash(uid)
+    on delete set null on update cascade
+) Engine=InnoDB;
+`
 
 	VSchema = `
 {
@@ -353,6 +362,14 @@ create table t7_xxhash_idx(
           "name": "unicode_loose_xxhash"
         }
       ]
+    },
+	"t7_fk": {
+      "column_vindexes": [
+        {
+          "column": "t7_uid",
+          "name": "unicode_loose_xxhash"
+        }
+      ]
     }
   }
 }`