Add compound predicate and radial+WHERE test coverage

- Unit test: compound AND predicate survives pushdown into bool.filter
- Integration test: compound WHERE (term + range) produces bool query
- Integration test: radial max_distance with WHERE produces bool query

Signed-off-by: Eric Wei <mengwei.eric@gmail.com>

Author: mengweieric

integ-test/src/test/java/org/opensearch/sql/sql/VectorSearchIT.java

@@ -256,6 +256,50 @@ public void testOrderByScoreAscRejects() throws IOException {
     assertThat(ex.getMessage(), containsString("_score ASC is not supported"));
   }
 
+  // ── Compound predicate and radial + WHERE ───────────────────────────────
+
+  @Test
+  public void testExplainCompoundPredicateProducesBoolQuery() throws IOException {
+    String explain =
+        explainQuery(
+            "SELECT v._id, v._score "
+                + "FROM vectorSearch(table='"
+                + TEST_INDEX
+                + "', field='embedding', "
+                + "vector='[1.0, 2.0, 3.0]', option='k=10') AS v "
+                + "WHERE v.state = 'TX' AND v.age > 30 "
+                + "LIMIT 10");
+
+    assertTrue("Explain should contain bool query:\n" + explain, explain.contains("bool"));
+    assertTrue(
+        "Explain should contain must clause (knn in scoring context):\n" + explain,
+        explain.contains("must"));
+    assertTrue(
+        "Explain should contain filter clause (compound WHERE in non-scoring context):\n" + explain,
+        explain.contains("filter"));
+  }
+
+  @Test
+  public void testExplainRadialWithWhereProducesBoolQuery() throws IOException {
+    String explain =
+        explainQuery(
+            "SELECT v._id, v._score "
+                + "FROM vectorSearch(table='"
+                + TEST_INDEX
+                + "', field='embedding', "
+                + "vector='[1.0, 2.0]', option='max_distance=10.5') AS v "
+                + "WHERE v.state = 'TX' "
+                + "LIMIT 100");
+
+    assertTrue("Explain should contain bool query:\n" + explain, explain.contains("bool"));
+    assertTrue(
+        "Explain should contain must clause (knn in scoring context):\n" + explain,
+        explain.contains("must"));
+    assertTrue(
+        "Explain should contain filter clause (WHERE in non-scoring context):\n" + explain,
+        explain.contains("filter"));
+  }
+
   // ── LIMIT validation ───────────────────────────────────────────────────
 
   @Test

opensearch/src/test/java/org/opensearch/sql/opensearch/storage/scan/VectorSearchQueryBuilderTest.java

@@ -243,6 +243,30 @@ void pushDownSortScoreAscRejected() {
     assertTrue(ex.getMessage().contains("_score ASC is not supported"));
   }
 
+  @Test
+  void pushDownFilterCompoundPredicateSurvives() {
+    var requestBuilder = createRequestBuilder();
+    var knnQuery = new WrapperQueryBuilder("{\"knn\":{}}");
+    var builder = new VectorSearchQueryBuilder(requestBuilder, knnQuery, Map.of("k", "5"));
+
+    // Simulate WHERE name = 'John' AND age > 30
+    var condition =
+        DSL.and(
+            DSL.equal(new ReferenceExpression("name", STRING), DSL.literal("John")),
+            DSL.greater(new ReferenceExpression("age", ExprCoreType.INTEGER), DSL.literal(30)));
+    var dummyChild = new LogicalValues(Collections.emptyList());
+    var filter = new LogicalFilter(dummyChild, condition);
+
+    boolean pushed = builder.pushDownFilter(filter);
+
+    assertTrue(pushed, "pushDownFilter with compound predicate should succeed");
+    QueryBuilder resultQuery = requestBuilder.getSourceBuilder().query();
+    assertTrue(resultQuery instanceof BoolQueryBuilder, "Result should be a BoolQuery");
+    BoolQueryBuilder boolQuery = (BoolQueryBuilder) resultQuery;
+    assertEquals(1, boolQuery.must().size(), "knn query should be in must (scoring context)");
+    assertEquals(1, boolQuery.filter().size(), "compound WHERE should be in filter (non-scoring)");
+  }
+
   private OpenSearchRequestBuilder createRequestBuilder() {
     return new OpenSearchRequestBuilder(
         mock(OpenSearchExprValueFactory.class), 10000, mock(Settings.class));