apache/shardingsphere · error · SQLFeatureNotSupportedException

getFetchSize

Error message

getFetchSize

What it means

getFetchSize() is rejected with SQLFeatureNotSupportedException("getFetchSize") by AbstractUnsupportedGeneratedKeysResultSet:187, the base class of ShardingSphere's GeneratedKeysResultSet. The key values live in an in-memory iterator, so there is no fetch size to report and the getter is part of the unsupported fetch-hint surface (setFetchDirection/getFetchDirection/setFetchSize/getFetchSize are all closed together).

Source

Thrown at jdbc/src/main/java/org/apache/shardingsphere/driver/jdbc/unsupported/AbstractUnsupportedGeneratedKeysResultSet.java:187

    
    @Override
    public final void setFetchDirection(final int direction) throws SQLException {
        throw new SQLFeatureNotSupportedException("setFetchDirection");
    }
    
    @Override
    public final int getFetchDirection() throws SQLException {
        throw new SQLFeatureNotSupportedException("getFetchDirection");
    }
    
    @Override
    public final void setFetchSize(final int rows) throws SQLException {
        throw new SQLFeatureNotSupportedException("setFetchSize");
    }
    
    @Override
    public final int getFetchSize() throws SQLException {
        throw new SQLFeatureNotSupportedException("getFetchSize");
    }
    
    @Override
    public final Blob getBlob(final int columnIndex) throws SQLException {
        throw new SQLFeatureNotSupportedException("getBlob");
    }
    
    @Override
    public final Blob getBlob(final String columnLabel) throws SQLException {
        throw new SQLFeatureNotSupportedException("getBlob");
    }
    
    @Override
    public final Clob getClob(final int columnIndex) throws SQLException {
        throw new SQLFeatureNotSupportedException("getClob");
    }
    
    @Override

View on GitHub (pinned to e952770a21)

Solutions

1. Do not read fetch size from generated-keys result sets; the concept does not apply.
2. In generic diagnostics, catch SQLFeatureNotSupportedException and log 'n/a' or fall back to the Statement's value.
3. Feature-probe per result-set class in wrapper libraries to avoid repeated exceptions.
4. Keep fetch-size accounting on the Statement or query result sets.

Example fix

// before
int size = rs.getFetchSize();

// after
int size;
try {
    size = rs.getFetchSize();
} catch (SQLFeatureNotSupportedException e) {
    size = -1; // not applicable to generated-keys result set
}

// read fetch size from the Statement instead of the generated-keys ResultSet
int size = stmt.getFetchSize();

private static boolean supportsFetchHints(ResultSet rs) {
    return !rs.getClass().getName().endsWith("GeneratedKeysResultSet");
}

int size;
try {
    size = rs.getFetchSize();
} catch (SQLFeatureNotSupportedException e) {
    size = -1; // n/a
}

When it happens

Trigger: Calling resultSet.getFetchSize() on the keys ResultSet — e.g. diagnostics that log result-set configuration, or generic iteration wrappers that choose processing strategy based on reported fetch size.

Common situations: Monitoring/audit tooling that records fetch size of every result set; pagination frameworks probing fetch size; behavior change after migrating INSERT-heavy services to ShardingSphere-JDBC where native drivers returned the driver default.

Related errors

• setFetchSize
• getUnicodeStream
• getBinaryStream
• getWarnings
• clearWarnings

AI-assisted analysis of apache/shardingsphere@e952770a21 (2026-08-14). Data as JSON: /api/errors/afd37192064a60da. Report an issue: GitHub.