moving row scanning into the data chunk api (#240)

data_chunk.go

@@ -16,13 +16,20 @@ type DataChunk struct {
 	data C.duckdb_data_chunk
 	// columns is a helper slice providing direct access to all columns.
 	columns []vector
+	// columnNames holds the column names, if known.
+	columnNames []string
 }
 
 // GetDataChunkCapacity returns the capacity of a data chunk.
 func GetDataChunkCapacity() int {
 	return int(C.duckdb_vector_size())
 }
 
+// GetSize returns the internal size of the data chunk.
+func (chunk *DataChunk) GetSize() int {
+	return int(C.duckdb_data_chunk_get_size(chunk.data))
+}
+
 // SetSize sets the internal size of the data chunk. Cannot exceed GetCapacity().
 func (chunk *DataChunk) SetSize(size int) error {
 	if size > GetDataChunkCapacity() {
@@ -32,6 +39,15 @@ func (chunk *DataChunk) SetSize(size int) error {
 	return nil
 }
 
+// GetValue returns a single value of a column.
+func (chunk *DataChunk) GetValue(colIdx int, rowIdx int) (any, error) {
+	if colIdx >= len(chunk.columns) {
+		return nil, getError(errAPI, columnCountError(colIdx, len(chunk.columns)))
+	}
+	column := &chunk.columns[colIdx]
+	return column.getFn(column, C.idx_t(rowIdx)), nil
+}
+
 // SetValue writes a single value to a column in a data chunk. Note that this requires casting the type for each invocation.
 // NOTE: Custom ENUM types must be passed as string.
 func (chunk *DataChunk) SetValue(colIdx int, rowIdx int, val any) error {
@@ -56,6 +72,7 @@ func (chunk *DataChunk) SetValue(colIdx int, rowIdx int, val any) error {
 }
 
 func (chunk *DataChunk) initFromTypes(ptr unsafe.Pointer, types []C.duckdb_logical_type) error {
+	// NOTE: initFromTypes does not initialize the column names.
 	columnCount := len(types)
 
 	// Initialize the callback functions to read and write values.
@@ -83,6 +100,30 @@ func (chunk *DataChunk) initFromTypes(ptr unsafe.Pointer, types []C.duckdb_logic
 	return nil
 }
 
+func (chunk *DataChunk) initFromDuckDataChunk(data C.duckdb_data_chunk) error {
+	columnCount := int(C.duckdb_data_chunk_get_column_count(data))
+	chunk.columns = make([]vector, columnCount)
+	chunk.data = data
+
+	var err error
+	for i := 0; i < columnCount; i++ {
+		duckdbVector := C.duckdb_data_chunk_get_vector(data, C.idx_t(i))
+
+		// Initialize the callback functions to read and write values.
+		logicalType := C.duckdb_vector_get_column_type(duckdbVector)
+		err = chunk.columns[i].init(logicalType, i)
+		C.duckdb_destroy_logical_type(&logicalType)
+		if err != nil {
+			break
+		}
+
+		// Initialize the vectors and their child vectors.
+		chunk.columns[i].duckdbVector = duckdbVector
+		chunk.columns[i].getChildVectors(duckdbVector)
+	}
+	return err
+}
+
 func (chunk *DataChunk) close() {
 	C.duckdb_destroy_data_chunk(&chunk.data)
 }