apache/shardingsphere · error · UnsupportedSQLOperationException

Unsupported segment type

Error message

Unsupported segment type: %s

What it means

TableConverter.convert dispatches on the FROM-clause table segment type: SimpleTableSegment, JoinTableSegment, SubqueryTableSegment, and DeleteMultiTableSegment are handled; any other TableSegment subclass throws UnsupportedSQLOperationException with the class name. Federation compilation only supports these table reference shapes.

Solutions

1. Restructure the query so FROM items are plain tables, joins of tables, or subqueries with aliases.
2. Replace table-valued functions / LATERAL references with subqueries the converter supports.
3. Disable federation for this query so it executes on the storage directly.

Example fix

-- before
SELECT * FROM GENERATE_SERIES(1, 10) AS g(n);
-- after
SELECT * FROM (SELECT 1 AS n UNION ALL SELECT 2) AS g;

try {
    rs = executeFederated(sql);
} catch (final SQLFederationUnsupportedSQLException ex) {
    if (ex.getMessage().contains("Unsupported segment type")) { rs = executeOnSingleStorage(sql); } else { throw ex; }
}

When it happens

Trigger: A federated query's FROM clause contains a table reference the converter does not model — e.g. a VALUES clause table, LATERAL table, function table (unnest/generate_series), or a newer parser segment type — reaching convert() during compilation.

Common situations: Queries with table-valued functions or CTE-only shapes; parser versions that produce distinct segment classes for exotic FROM items; dialect-specific joins.

Related errors

• unsupported CommonExpressionSegment
• unsupported TableSegment type
• unsupported TextOrderByItemSegment
• SQL federation does not support SQL
• Unsupported interval unit

AI-assisted analysis of apache/shardingsphere@e952770a21 (2026-08-14). Data as JSON: /api/errors/1ac9a51f560a0bfa. Report an issue: GitHub.

Appendix: source

Thrown at kernel/sql-federation/compiler/src/main/java/org/apache/shardingsphere/sqlfederation/compiler/sql/ast/converter/segment/from/TableConverter.java:65

     * @throws UnsupportedSQLOperationException unsupported SQL operation exception
     */
    public static Optional<SqlNode> convert(final TableSegment segment) {
        if (null == segment) {
            return Optional.empty();
        }
        if (segment instanceof SimpleTableSegment) {
            return SimpleTableConverter.convert((SimpleTableSegment) segment);
        }
        if (segment instanceof JoinTableSegment) {
            return JoinTableConverter.convert((JoinTableSegment) segment);
        }
        if (segment instanceof SubqueryTableSegment) {
            return SubqueryTableConverter.convert((SubqueryTableSegment) segment);
        }
        if (segment instanceof DeleteMultiTableSegment) {
            return DeleteMultiTableConverter.convert((DeleteMultiTableSegment) segment);
        }
        throw new UnsupportedSQLOperationException("Unsupported segment type: " + segment.getClass());
    }
}

View on GitHub (pinned to e952770a21)