feat: Expose LogicalType(s) for columns in QueryResult, fix #24

Author: ovr

lib/duckdb.d.ts

@@ -108,7 +108,13 @@ export class Connection {
   unregister_buffer(name: string, callback?: Callback<void>): void;
 }
 
+export type LogicalType = {
+  id: number,
+  name: string,
+}
+
 export class QueryResult implements AsyncIterable<RowData> {
+  getColumns(): Record<string, LogicalType>;
   [Symbol.asyncIterator](): AsyncIterator<RowData>;
 }
 

lib/duckdb.js

@@ -84,6 +84,13 @@ QueryResult.prototype.nextChunk;
  */
 QueryResult.prototype.nextIpcBuffer;
 
+/**
+ * Function to return logical types for columns
+ *
+ * @method
+ */
+QueryResult.prototype.getColumns;
+
 /**
  * @name asyncIterator
  * @memberof module:duckdb~QueryResult
@@ -218,12 +225,9 @@ Connection.prototype.each = function (sql) {
  * @param {...*} params
  * @yields row chunks
  */
-Connection.prototype.stream = async function* (sql) {
+Connection.prototype.stream = async function (sql) {
     const statement = new Statement(this, sql);
-    const queryResult = await statement.stream.apply(statement, arguments);
-    for await (const result of queryResult) {
-        yield result;
-    }
+    return statement.stream.apply(statement, arguments);
 }
 
 /**

src/duckdb_node.hpp

@@ -208,6 +208,7 @@ class QueryResult : public Napi::ObjectWrap<QueryResult> {
 public:
 	Napi::Value NextChunk(const Napi::CallbackInfo &info);
 	Napi::Value NextIpcBuffer(const Napi::CallbackInfo &info);
+	Napi::Value GetColumns(const Napi::CallbackInfo &info);
 	duckdb::shared_ptr<ArrowSchema> cschema;
 
 private:

src/statement.cpp

@@ -636,7 +636,8 @@ Napi::FunctionReference QueryResult::Init(Napi::Env env, Napi::Object exports) {
 
 	Napi::Function t = DefineClass(env, "QueryResult",
 	                               {InstanceMethod("nextChunk", &QueryResult::NextChunk),
-	                                InstanceMethod("nextIpcBuffer", &QueryResult::NextIpcBuffer)});
+	                                InstanceMethod("nextIpcBuffer", &QueryResult::NextIpcBuffer),
+	                                InstanceMethod("getColumns", &QueryResult::GetColumns)});
 
 	exports.Set("QueryResult", t);
 
@@ -742,6 +743,26 @@ Napi::Value QueryResult::NextIpcBuffer(const Napi::CallbackInfo &info) {
 	return deferred.Promise();
 }
 
+Napi::Value QueryResult::GetColumns(const Napi::CallbackInfo &info)
+{
+	auto env = info.Env();
+	auto result = Napi::Object::New(env);
+
+	for (duckdb::idx_t column_idx = 0; column_idx < this->result->ColumnCount(); column_idx++)
+	{
+		auto column_name = this->result->ColumnName(column_idx);
+		auto column_type = this->result->types[column_idx];
+
+		auto logic_type = Napi::Object::New(env);
+		logic_type.Set("id", Napi::Number::New(env, (double)column_type.id()));
+		logic_type.Set("name", Napi::String::New(env, column_type.ToString()));
+
+		result.Set(column_name, logic_type);
+	}
+
+	return result;
+}
+
 Napi::Object QueryResult::NewInstance(const Napi::Object &db) {
 	return NodeDuckDB::GetData(db.Env())->query_result_constructor.New({db});
 }

test/query_result.test.ts

@@ -14,7 +14,15 @@ describe('QueryResult', () => {
 
     it('streams results', async () => {
         let retrieved = 0;
-        const stream = conn.stream('SELECT * FROM range(0, ?)', total);
+
+        const stream = await conn.stream("SELECT * FROM range(0, ?)", total);
+        assert.deepEqual(stream.getColumns(), {
+          range: {
+            id: 14,
+            name: "1",
+          },
+        });
+
         for await (const row of stream) {
             retrieved++;
         }

test/typescript_decls.test.ts

@@ -222,7 +222,7 @@ describe("typescript: stream and QueryResult", function () {
 
   it("streams results", async () => {
     let retrieved = 0;
-    const stream = conn.stream("SELECT * FROM range(0, ?)", total);
+    const stream = await conn.stream("SELECT * FROM range(0, ?)", total);
     for await (const row of stream) {
       retrieved++;
     }