apache/shardingsphere · error · SQLFeatureNotSupportedException

updateNClob

Error message

updateNClob

What it means

The SQL federation engine in ShardingSphere returns a read-only, forward-only ResultSet whose updater layer (AbstractUnsupportedUpdateOperationSQLFederationResultSet) deliberately rejects every JDBC row-update method. Calling updateNClob(int, NClob) throws SQLFeatureNotSupportedException because federation queries are computed in-memory from merged results and cannot be written back to the underlying shards. This mirrors how the JDBC driver reports an optional feature that is not implemented.

Solutions

  1. Do not use ResultSet updater methods on federation results; issue a separate UPDATE statement against the target table instead.
  2. Rewrite the query so it is not routed to the federation engine (e.g. make it a single-shard query) if you must use updatable ResultSets.
  3. Configure or exclude the SQL federation feature (sql_federation: false / remove SQLFederationRule) for statements where updater methods are required.
  4. Catch SQLFeatureNotSupportedException and fall back to a plain UPDATE via PreparedStatement in generic JDBC utility code.

Example fix

// before
ResultSet rs = stmt.executeQuery("SELECT t.*, u.name FROM t JOIN u ON ... federated");
rs.next();
rs.updateNClob(1, nclob); // SQLFeatureNotSupportedException
rs.updateRow();

// after
ResultSet rs = stmt.executeQuery("SELECT ... federated");
rs.next();
String sql = nclob == null ? "UPDATE t SET clob_col = NULL WHERE id = ?" : "UPDATE t SET clob_col = ? WHERE id = ?";
try (PreparedStatement ps = conn.prepareStatement(sql)) { ps.setNClob(1, nclob); ps.setLong(2, id); ps.executeUpdate(); }
Defensive patterns

Strategy: try-catch

Validate before calling

if (rs.getConcurrency() != ResultSet.CONCUR_UPDATABLE) { throw new IllegalStateException("ResultSet is not updatable; use UPDATE statement"); }

Try / catch

try { rs.updateNClob(1, nclob); } catch (final SQLFeatureNotSupportedException ex) { /* fall back to PreparedStatement UPDATE */ }

Prevention

When it happens

Trigger: Executing a federated query (cross-shard JOIN, subquery, or UNION routed through the SQL federation engine) and then calling rs.updateNClob(columnIndex, nClob) on the returned ResultSet, e.g. before rs.updateRow().

Common situations: ORM frameworks (Hibernate, MyBatis with updatable result maps, Spring Data JDBC) that auto-detect updatable ResultSets; code ported from a native MySQL/PostgreSQL driver where NClob updates worked; generic JDBC tooling that calls updateNClob when getConcurrency() is misreported.

Related errors

AI-assisted analysis of apache/shardingsphere@e952770a21 (2026-08-14). Data as JSON: /api/errors/1a7d1111a28518ab. Report an issue: GitHub.

Appendix: source

Thrown at kernel/sql-federation/core/src/main/java/org/apache/shardingsphere/sqlfederation/resultset/AbstractUnsupportedUpdateOperationSQLFederationResultSet.java:394

    
    @Override
    public final void updateClob(final String columnLabel, final Reader reader) throws SQLException {
        throw new SQLFeatureNotSupportedException("updateClob");
    }
    
    @Override
    public final void updateClob(final int columnIndex, final Reader reader, final long length) throws SQLException {
        throw new SQLFeatureNotSupportedException("updateClob");
    }
    
    @Override
    public final void updateClob(final String columnLabel, final Reader reader, final long length) throws SQLException {
        throw new SQLFeatureNotSupportedException("updateClob");
    }
    
    @Override
    public final void updateNClob(final int columnIndex, final NClob nClob) throws SQLException {
        throw new SQLFeatureNotSupportedException("updateNClob");
    }
    
    @Override
    public final void updateNClob(final String columnLabel, final NClob nClob) throws SQLException {
        throw new SQLFeatureNotSupportedException("updateNClob");
    }
    
    @Override
    public final void updateNClob(final int columnIndex, final Reader reader) throws SQLException {
        throw new SQLFeatureNotSupportedException("updateNClob");
    }
    
    @Override
    public final void updateNClob(final String columnLabel, final Reader reader) throws SQLException {
        throw new SQLFeatureNotSupportedException("updateNClob");
    }
    
    @Override

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