is it possible to specify DEFAULT value for PreparedStatements

Table DDL

CREATE TABLE EXAMPLE
(
    id     Int64,
    date   DateTime64,
    number Int64 DEFAULT -1
) ENGINE = MergeTree
      ORDER BY (id);

---

From ClickHouse’s documentation, looking to specify DEFAULT when inserting multiple values that should utilize the default value defined for the column.

INSERT INTO EXAMPLE (id, date, number)
VALUES (1, DEFAULT, DEFAULT) (2, DEFAULT, 2) (3, '2022-01-01 00:00:00.000', 3);

Is it possible to specify this using PreparedStatement?

...
preparedStatement.setObject(1, 1);
preparedStatement.setObject(2, DEFAULT);
preparedStatement.setObject(3, DEFAULT);
preparedStatement.addBatch();
...
preparedStatement.executeBatch();
...

---

Expected results

id	date	number
1	1970-01-01 00:00:00.000	-1
2	1970-01-01 00:00:00.000	2
3	2022-01-01 00:00:00.000	3

[zhicwu]

Turns out it’s not that simple 😦 First there’s no generic way to set null in RowBinary format. On the other hand, switching to TabSeparated works in some cases(see tests at here) but not all.

I think the best way as of now is to set default value by yourself, and you have to update application each time default value in DDL is changed… I’ll leave this issue open, and try again later by enhancing the parser to extract default value(constant only) from column/table definition.

[zhicwu]

Sorry I didn’t make it clear. You don’t have to deal with too many details of the data format , you just need to change connection property format to TabSeparatedWithNamesAndTypes. This way, the driver will use TabSeparatedWithNamesAndTypes for select queries and TabSeparated(without headers) for insert queries. It does not work in latest release(0.3.2-patch7), but I’ll fix that in these two days and then release another patch in weekend.

As to the workaround you mentioned above, it’s better to offload to the driver, so that nobody has to suffer. I’m thinking of a new connection property like nullAsDefault to control this - when it’s set to true, the driver will convert null value to default value based on target column data type(not column definition). Let me give it a shot tonight when I get home to see if it’s feasible.