[client-v2] NativeFormatReader fails for non-null values of Nullable(String)

[donats11]

I am using client-v2 0.10.0 with ClickHouseFormat.Native.

Given a table:

CREATE TABLE test_table
(
    id String,
    optionalValue Nullable(String)
)
ENGINE = MergeTree
ORDER BY id;

Working query

This works:

SELECT optionalValue
FROM test_table
WHERE optionalValue IS NULL;

Failing query

This fails:

SELECT optionalValue
FROM test_table
WHERE optionalValue IS NOT NULL;

with:

ClientException: Failed to read block
Caused by: EOFException: End of stream reached before reading all data
    at NativeFormatReader.readBlock(...)

Workaround

Casting the column to String works:

SELECT CAST(optionalValue AS String) AS optionalValue
FROM test_table;

Java code

QuerySettings settings =
        new QuerySettings().setFormat(ClickHouseFormat.Native);

try (QueryResponse response =
             client.query(sqlQuery, settings).get()) {

    NativeFormatReader reader =
            (NativeFormatReader) client.newBinaryFormatReader(response);
}

Environment

• client-v2: 0.10.0
• ClickHouse server: 25.9.3.48
• Java: 21

[chernser]

Thank you for reporting @donats11 !