prestodb/presto · error · SQLFeatureNotSupportedException

createNClob

Error message

createNClob

What it means

PrestoConnection.createNClob() unconditionally throws SQLFeatureNotSupportedException("createNClob"). National-character-set Clob objects (NClob) are not implemented by the driver; the method is a stub that always fails. Presto treats all text as UTF-8 VARCHAR, so NClob has no server-side counterpart.

Source

Thrown at presto-jdbc/src/main/java/com/facebook/presto/jdbc/PrestoConnection.java:519

    @Override
    public Clob createClob()
            throws SQLException
    {
        throw new SQLFeatureNotSupportedException("createClob");
    }

    @Override
    public Blob createBlob()
            throws SQLException
    {
        throw new SQLFeatureNotSupportedException("createBlob");
    }

    @Override
    public NClob createNClob()
            throws SQLException
    {
        throw new SQLFeatureNotSupportedException("createNClob");
    }

    @Override
    public SQLXML createSQLXML()
            throws SQLException
    {
        throw new SQLFeatureNotSupportedException("createSQLXML");
    }

    @Override
    public boolean isValid(int timeout)
            throws SQLException
    {
        if (timeout < 0) {
            throw new SQLException("Timeout is negative");
        }
        return !isClosed();
    }

View on GitHub (pinned to 55bb57d202)

Solutions

  1. Use setString/getString instead of NClob — Presto VARCHAR is already UTF-8
  2. Drop NClob-specific branches in generic data-binding code
  3. Fall back to string binding when SQLFeatureNotSupportedException is caught

Example fix

// before
NClob nclob = connection.createNClob();
nclob.setString(1, unicodeText);
ps.setNClob(1, nclob);
// after
ps.setString(1, unicodeText);
Defensive patterns

Strategy: try-catch

Validate before calling

DatabaseMetaData meta = connection.getMetaData();
if (meta.getDriverName().contains("Presto")) {
    // driver does not support createNClob — Presto text is UTF-8 VARCHAR
}

Type guard

static boolean supportsClientNClob(DatabaseMetaData meta) throws SQLException {
    return !meta.getDriverName().contains("Presto");
}

Try / catch

try {
    NClob nclob = connection.createNClob();
    // ... use nclob
} catch (SQLFeatureNotSupportedException e) {
    // fall back: ps.setString(...) for Unicode text
}

Prevention

When it happens

Trigger: Calling connection.createNClob(), or code paths that bind NCHAR/NVARCHAR parameters via setNClob using a created NClob.

Common situations: Migrating from SQL Server/Oracle where NClob is required for Unicode text; generic JDBC layers that distinguish Clob vs NClob types.

Related errors

AI-assisted analysis of prestodb/presto@55bb57d202 (2026-09-04). Data as JSON: /api/errors/f6e26854e5a297e7. Report an issue: GitHub.