add workaround for SQLNULL

data_chunk.go

@@ -47,6 +47,9 @@ func (chunk *DataChunk) GetValue(colIdx int, rowIdx int) (any, error) {
 		return nil, getError(errAPI, columnCountError(colIdx, len(chunk.columns)))
 	}
 	column := &chunk.columns[colIdx]
+	if column.isSQLNull {
+		return nil, nil
+	}
 	return column.getFn(column, C.idx_t(rowIdx)), nil
 }
 
@@ -58,6 +61,10 @@ func (chunk *DataChunk) SetValue(colIdx int, rowIdx int, val any) error {
 	}
 	column := &chunk.columns[colIdx]
 
+	if column.isSQLNull {
+		return getError(errAPI, errSetSQLNULLValue)
+	}
+
 	// Ensure that the types match before attempting to set anything.
 	// This is done to prevent failures 'halfway through' writing column values,
 	// potentially corrupting data in that column.

errors.go

@@ -107,6 +107,8 @@ var (
 	errScalarUDFResultTypeIsNil = fmt.Errorf("%w: result type is nil", errScalarUDFCreate)
 	errScalarUDFResultTypeIsANY = fmt.Errorf("%w: result type is ANY", errScalarUDFCreate)
 
+	errSetSQLNULLValue = errors.New("cannot write to a NULL column")
+
 	// Errors not covered in tests.
 	errConnect      = errors.New("could not connect to database")
 	errCreateConfig = errors.New("could not create config for database")

scalar_udf_test.go

@@ -265,9 +265,6 @@ func (*anyScalarUDF) ExecuteRow(args []driver.Value) (any, error) {
 }
 
 func TestANYScalarUDF(t *testing.T) {
-	// TODO: once DuckDB has SQLNull type.
-	return
-
 	db, err := sql.Open("duckdb", "")
 	require.NoError(t, err)
 

vector.go

@@ -28,6 +28,9 @@ type vector struct {
 	// The child vectors of nested data types.
 	childVectors []vector
 
+	// FIXME: this is a workaround until the C API exposes SQLNULL.
+	isSQLNull bool
+
 	// The vector's type information.
 	vectorTypeInfo
 }
@@ -253,6 +256,11 @@ func (vec *vector) tryCastUUID(val any) (UUID, error) {
 func (vec *vector) init(logicalType C.duckdb_logical_type, colIdx int) error {
 	t := Type(C.duckdb_get_type_id(logicalType))
 
+	if t == TYPE_INVALID {
+		vec.isSQLNull = true
+		return nil
+	}
+
 	name, inMap := unsupportedTypeToStringMap[t]
 	if inMap {
 		return addIndexToError(unsupportedTypeError(name), colIdx)
@@ -312,6 +320,10 @@ func (vec *vector) init(logicalType C.duckdb_logical_type, colIdx int) error {
 }
 
 func (vec *vector) initVectors(v C.duckdb_vector, writable bool) {
+	if vec.isSQLNull {
+		return
+	}
+
 	vec.duckdbVector = v
 	vec.ptr = C.duckdb_vector_get_data(v)
 	if writable {