JDBC: Undefined behavior when reading from a returned java.sql.Blob outside of a closed result set

[ShadelessFox]

What happens?

Blobs retrieved from a result set before it's closed might return random values between GC calls.

To Reproduce

import java.sql.*;
import java.util.HexFormat;

public class DuckDBBlobTest {
    public static void main(String[] args) throws Exception {
        try (Connection connection = DriverManager.getConnection("jdbc:duckdb:")) {
            try (Statement stmt = connection.createStatement()) {
                Blob blob;

                try (ResultSet resultSet = stmt.executeQuery("select 'AAAA'::blob")) {
                    resultSet.next();
                    blob = resultSet.getBlob(1);
                }

                String expected = HexFormat.of().formatHex(new byte[]{'A', 'A', 'A', 'A'});
                for (int i = 0; i < 5000; i++) {
                    System.gc();
                    String actual = HexFormat.of().formatHex(blob.getBytes(0, Math.toIntExact(blob.length())));
                    if (!expected.equals(actual)) {
                        throw new SQLException("expected != actual: " + expected + " != " + actual);
                    }
                }
            }
        }
    }
}

Please note that this is a floating issue and might not reproduce immediately. Try running the sample multiple times. Eventually, you will see something like this:

expected != actual: 41414141 != 00000000

OS:

Windows 11 x64

DuckDB Version:

1.1.1

DuckDB Client:

Java JDBC / DBeaver 24.2.3

Hardware:

No response

Full Name:

Ian Vinogradov

Affiliation:

DBeaver

What is the latest build you tested with? If possible, we recommend testing with the latest nightly build.

I have tested with a stable release

Did you include all relevant data sets for reproducing the issue?

Yes

Did you include all code required to reproduce the issue?

• Yes, I have

Did you include all relevant configuration (e.g., CPU architecture, Python version, Linux distribution) to reproduce the issue?

• Yes, I have

[Tishj]

@szarnyasg can we move this to https://github.com/duckdb/duckdb-java ?

[EastLord]

#79

[Mause]

Going to assume this is resolved by #103