Support join on bases of query match with $foo(id: *).

src/filter.cpp

@@ -418,7 +418,11 @@ Option<bool> toFilter(const std::string expression,
         filter_exp = {field_name, {}, {}};
         NUM_COMPARATOR id_comparator = EQUALS;
         size_t filter_value_index = 0;
-        if (raw_value[0] == '=') {
+        if (raw_value == "*") { // Match all.
+            // NOT_EQUALS comparator with no id match will get all the ids.
+            id_comparator = NOT_EQUALS;
+            filter_exp.apply_not_equals = true;
+        } else if (raw_value[0] == '=') {
             id_comparator = EQUALS;
             while (++filter_value_index < raw_value.size() && raw_value[filter_value_index] == ' ');
         } else if (raw_value.size() >= 2 && raw_value[0] == '!' && raw_value[1] == '=') {

src/filter_result_iterator.cpp

@@ -659,7 +659,8 @@ void filter_result_iterator_t::init() {
                 values.push_back(std::to_string(result.docs[i]));
             }
 
-            filter filter_exp = {get_reference_field_op.get(), std::move(values), {EQUALS}};
+            filter filter_exp = {get_reference_field_op.get(), std::move(values),
+                                 std::vector<NUM_COMPARATOR>(result.count, EQUALS)};
 
             auto filter_tree_root = new filter_node_t(filter_exp);
             std::unique_ptr<filter_node_t> filter_tree_root_guard(filter_tree_root);

test/collection_filtering_test.cpp

@@ -1327,6 +1327,13 @@ TEST_F(CollectionFilteringTest, FilteringViaDocumentIds) {
 
     ASSERT_EQ(0, results["found"].get<size_t>());
 
+    // match all IDs
+    results = coll1->search("*",
+                            {}, "id: *",
+                            {}, sort_fields, {0}, 10, 1, FREQUENCY, {true}).get();
+
+    ASSERT_EQ(4, results["found"].get<size_t>());
+
     collectionManager.drop_collection("coll1");
 }
 

test/collection_join_test.cpp

@@ -482,6 +482,21 @@ TEST_F(CollectionJoinTest, FilterByReference_SingleMatch) {
     ASSERT_EQ(1, res_obj["hits"].size());
     ASSERT_EQ("soap", result["hits"][0]["document"]["product_name"].get<std::string>());
 
+    req_params = {
+            {"collection", "Customers"},
+            {"q", "Dan"},
+            {"query_by", "customer_name"},
+            {"filter_by", "$Products(id:*) && product_price:<100"},
+    };
+
+    search_op_bool = collectionManager.do_search(req_params, embedded_params, json_res, now_ts);
+    ASSERT_TRUE(search_op_bool.ok());
+
+    res_obj = nlohmann::json::parse(json_res);
+    ASSERT_EQ(1, res_obj["found"].get<size_t>());
+    ASSERT_EQ(1, res_obj["hits"].size());
+    ASSERT_EQ("soap", result["hits"][0]["document"]["product_name"].get<std::string>());
+
     collectionManager.drop_collection("Customers");
     collectionManager.drop_collection("Products");
 }