Regression: DatabaseMetaData.getColumns returns IS_NULLABLE="true"/"false" instead of JDBC spec "YES"/"NO"

[wdroste]

Summary

In duckdb_jdbc 1.5.2.0, DatabaseMetaData.getColumns(...) returns values of "true" / "false" for the IS_NULLABLE column. The JDBC specification mandates "YES" / "NO" / "" (empty). 1.5.1.0 returned "YES" as expected; this is a regression.

This breaks consumers that parse IS_NULLABLE per spec — notably jOOQ's generic MetaImpl under SQLDialect.DEFAULT, whose getTables(...) then returns tables with an empty field list.

Reproduction

import java.sql.*;
import java.util.Properties;

public class Repro {
  public static void main(String[] a) throws Exception {
    var c = new org.duckdb.DuckDBDriver().connect("jdbc:duckdb:", new Properties());
    try (var s = c.createStatement()) {
      s.execute("CREATE TABLE \"t\" (\"id\" BIGINT, \"v\" VARCHAR)");
    }
    try (var rs = c.getMetaData().getColumns(null, null, "t", null)) {
      while (rs.next()) {
        System.out.println(rs.getString("COLUMN_NAME") + " -> IS_NULLABLE=" + rs.getString("IS_NULLABLE"));
      }
    }
  }
}

Observed

1.5.2.0

id -> IS_NULLABLE=true
v  -> IS_NULLABLE=true

1.5.1.0 (expected / spec-compliant)

id -> IS_NULLABLE=YES
v  -> IS_NULLABLE=YES

Spec reference

java.sql.DatabaseMetaData#getColumns, column 18 IS_NULLABLE:

String => ISO rules are used to determine the nullability for a column.

• YES --- if the column can include NULLs
• NO --- if the column cannot include NULLs
• empty string --- if the nullability for the column is unknown

Boolean literals "true" / "false" are not valid per the spec.

Impact

• Any JDBC consumer that does "YES".equals(isNullable) / "NO".equals(isNullable) will misinterpret column nullability.
• jOOQ 3.21.x generic Meta with SQLDialect.DEFAULT returns tables with zero fields against DuckDB 1.5.2.0, whereas SQLDialect.DUCKDB (dialect-specific path) still works. This surfaces in downstream test suites that use DSL.using(conn, SQLDialect.DEFAULT).meta() for inspection.

Environment

• duckdb_jdbc: 1.5.2.0 (regression) vs 1.5.1.0 (OK)
• JDK: Zulu 11.0.29
• OS: Linux x86_64

[staticlibs]

Thanks for the report! This should be fixed in #665, the following 1.5 snapshot build with the fix can be used:

  <dependency>
    <groupId>org.duckdb</groupId>
    <artifactId>duckdb_jdbc</artifactId>
    <version>1.5.3.0-083033b8-SNAPSHOT</version>
  </dependency>

  <repository>
    <id>central-snapshots</id>
    <url>https://central.sonatype.com/repository/maven-snapshots/</url>
    <snapshots><enabled>true</enabled></snapshots>
  </repository>

[wdroste]

I'll have answers for you tomorrow, I'm deploying it tonight.