feat(query): support SELECT REDUCED solution modifier in query pipeline (#593)

src/main/java/fr/inria/corese/core/next/query/impl/sparql/bridge/CoreseAstQueryBuilder.java

@@ -103,7 +103,6 @@ public Query toNextQuery(AskQueryAst askQueryAst) {
      */
     public Query toNextQuery(SelectQueryAst selectQueryAst) {
         Objects.requireNonNull(selectQueryAst, "selectQueryAst");
-        rejectUnsupportedSelectClauses(selectQueryAst);
 
         WhereCompiler compiler = whereCompiler.withPrologue(selectQueryAst.prologue());
         Query query = createQuery(
@@ -114,6 +113,7 @@ public Query toNextQuery(SelectQueryAst selectQueryAst) {
                 compiler);
         applyGroupBy(query, selectQueryAst.solutionModifier(), compiler);
         applyProjection(query, selectQueryAst.projection(), compiler);
+        // Full deduplication or preserving cardinality is permitted by SELECT REDUCED.
         query.setDistinct(selectQueryAst.solutionModifier().distinct());
         applyOrderBy(query, selectQueryAst.solutionModifier(), compiler);
         applyHaving(query, selectQueryAst.solutionModifier(), compiler);
@@ -220,23 +220,6 @@ private static void rejectUnsupportedAskClauses(AskQueryAst askQueryAst) {
         }
     }
 
-    /**
-     * Rejects unsupported clauses for {@code SELECT} queries.
-     *
-     * <p>Planned roadmap items:
-     * <ul>
-     *   <li>Issue #387: {@code GROUP BY} / {@code HAVING} require aggregate semantics, not only AST field propagation.</li>
-     *   <li>Issue #387: {@code REDUCED} support aligned with next-pipeline query-form policy.</li>
-     * </ul>
-     * </p>
-     */
-    private static void rejectUnsupportedSelectClauses(SelectQueryAst selectQueryAst) {
-        SolutionModifierAst solutionModifier = selectQueryAst.solutionModifier();
-        if (solutionModifier.reduced()) {
-            throw new UnsupportedQueryFeatureException("REDUCED is not supported yet by the next pipeline for SELECT");
-        }
-    }
-
     /**
      * Rejects unsupported clauses for {@code DESCRIBE} queries.
      *

src/test/java/fr/inria/corese/core/next/query/impl/sparql/execution/NextSparqlPipelineExecutorTest.java

@@ -90,6 +90,36 @@ void selectJoinRunsEndToEnd() {
         assertFalse(result.hasNext());
     }
 
+    @Test
+    @DisplayName("SELECT REDUCED executes and returns projected bindings")
+    void selectReducedExecutesAndReturnsBindings() {
+        try (var result = executor.evaluateTuple("""
+                SELECT REDUCED ?name WHERE {
+                  VALUES (?name ?id) { ("Alice" 1) ("Bob" 3) }
+                } ORDER BY ?name
+                """)) {
+            assertEquals(List.of("name"), result.getBindingNames());
+            assertTrue(result.hasNext());
+            assertEquals(valueFactory.createLiteral("Alice"), result.next().getValue("name"));
+            assertTrue(result.hasNext());
+            assertEquals(valueFactory.createLiteral("Bob"), result.next().getValue("name"));
+            assertFalse(result.hasNext());
+        }
+    }
+
+    @Test
+    @DisplayName("SELECT REDUCED * executes without error")
+    void selectReducedStarExecutes() {
+        try (var result = executor.evaluateTuple("""
+                SELECT REDUCED * WHERE { VALUES ?name { "Alice" } }
+                """)) {
+            assertEquals(List.of("name"), result.getBindingNames());
+            assertTrue(result.hasNext());
+            assertEquals(valueFactory.createLiteral("Alice"), result.next().getValue("name"));
+            assertFalse(result.hasNext());
+        }
+    }
+
     @Test
     @DisplayName("FILTER evaluates native numeric expressions")
     void filterRunsThroughNativeExpressionEvaluator() {