ResultSet getObject with class return null values filled as it was not null

[FDoKE]

When selecting values from table with getObject(index, Class)
simple types (like float/int/boolean) return 0/false as result (when null is expected).

CREATE TABLE db.tbl
   (
   id int not null,
   double_col double,
   float_col float,
   varchar_col varchar(36),
   boolean_col boolean,
   int_col int,
   bigint_col bigint,
   char_col char(10),
   int32_col int32
   primary key (id)
   )
   distributed by (id)

Expected: [1, null, null, null, null, null, null, null, null]
Actual: [1, 0.0, 0.0, null, false, 0, 0, null, 0]

getObject(int columnIndex) returns null as expected.

Is that expected behaivor? (it breaks Vertx jdbc client as it always uses getObject with expected class)

[zhicwu]

Hi @FDoKE, it's not expected. Which version of the driver you're using? Are you using com.clickhouse.jdbc.Driver?

[FDoKE]

@zhicwu on 0.3.2-patch10, yes, from com.clickhouse.jdbc
I traced down problem to ClickHouseFloatValue
asFloat return value, which is initilized with 0.0, but actual value is null.
(same with other simple types)
called from :

    @Override
    public <T> T getObject(int columnIndex, Class<T> type) throws SQLException {
        return getValue(columnIndex).asObject(type);
    }

[zhicwu]

Thanks for the details information @FDoKE. Is that possible that you set nullAsDefault to 2? Or, it's related to the distributed tables?

Just tried below case in DBeaver using patch10 driver and it works fine.

drop table tbl if exists;
create table tbl(a Int8, b Nullable(Int32))engine=Memory;
insert into tbl values(1, null);
select * from tbl;

[FDoKE]

@zhicwu dbeaver probably using getObject(index) to retrieve column values
simple reproducer:

Connection connection = DriverManager.getConnection("jdbc:clickhouse://clickhouse:8123/default");
Statement statement = connection.createStatement();
statement.execute("select double_col from db.table");
ResultSet resultSet = statement.getResultSet();
resultSet.next();
Object object1 = resultSet.getObject(1); // returns null
Double object2 = resultSet.getObject(1, Double.class); // returns 0.0

[zhicwu]

it breaks Vertx jdbc client as it always uses getObject with expected class

Not sure if it's a good idea to use getObject(int, Class), because it's always the slowest mainly for two reasons: 1) autoboxing; and 2) type conversion.

[FDoKE]

Yeah, that seems strange to me too, why would they do that if it perfectly worked with getObject(int), I made an issue for them too to get their idea behind this change.