early-out, if provided arguments don't match the expected column count (marcboeker#211)

Author: taniabogatsch

appender.go

@@ -139,11 +139,6 @@ func (a *Appender) AppendRow(args ...driver.Value) error {
 		return getError(errAppenderAppendAfterClose, nil)
 	}
 
-	// Create a new data chunk if the current chunk is full, or if this is the first row.
-	if a.currSize == C.duckdb_vector_size() || len(a.chunks) == 0 {
-		a.newDataChunk(len(args))
-	}
-
 	err := a.appendRowSlice(args)
 	if err != nil {
 		return getError(errAppenderAppendRow, err)
@@ -186,6 +181,16 @@ func (a *Appender) newDataChunk(colCount int) {
 }
 
 func (a *Appender) appendRowSlice(args []driver.Value) error {
+	// early-out, if the number of args does not match the column count
+	if len(args) != len(a.vectors) {
+		return columnCountError(len(args), len(a.vectors))
+	}
+
+	// Create a new data chunk if the current chunk is full, or if this is the first row.
+	if a.currSize == C.duckdb_vector_size() || len(a.chunks) == 0 {
+		a.newDataChunk(len(args))
+	}
+
 	for i, val := range args {
 		vec := a.vectors[i]
 

errors.go

@@ -29,6 +29,10 @@ func columnError(err error, colIdx int) error {
 	return fmt.Errorf("%w: %s: %d", err, columnErrMsg, colIdx)
 }
 
+func columnCountError(actual int, expected int) error {
+	return fmt.Errorf("%s: expected %d, got %d", columnCountErrMsg, expected, actual)
+}
+
 func unsupportedTypeError(name string) error {
 	return fmt.Errorf("%s: %s", unsupportedTypeErrMsg, name)
 }
@@ -46,6 +50,7 @@ const (
 	castErrMsg             = "cast error"
 	structFieldErrMsg      = "invalid STRUCT field"
 	columnErrMsg           = "column index"
+	columnCountErrMsg      = "invalid column count"
 	unsupportedTypeErrMsg  = "unsupported data type"
 	invalidatedAppenderMsg = "appended data has been invalidated due to corrupt row"
 )
@@ -63,8 +68,10 @@ var (
 	errAppenderDoubleClose      = errors.New("could not close appender: already closed")
 	errAppenderAppendRow        = errors.New("could not append row")
 	errAppenderAppendAfterClose = errors.New("could not append row: appender already closed")
-	errAppenderClose            = errors.New("could not close appender")
-	errAppenderFlush            = errors.New("could not flush appender")
+	// FIXME: not covered by tests. Should be triggered by appending a constraint violation, see #210.
+	errAppenderClose = errors.New("could not close appender")
+	// FIXME: not covered by tests. Should be triggered by appending a constraint violation, see #210.
+	errAppenderFlush = errors.New("could not flush appender")
 
 	// Errors not covered in tests.
 	errConnect      = errors.New("could not connect to database")

errors_test.go

@@ -113,22 +113,10 @@ func TestErrAppender(t *testing.T) {
 		require.NoError(t, c.Close())
 	})
 
-	t.Run(errAppenderClose.Error(), func(t *testing.T) {
+	t.Run(columnCountErrMsg, func(t *testing.T) {
 		c, con, a := prepareAppender(t, `CREATE TABLE test (a VARCHAR, b VARCHAR)`)
-		require.NoError(t, a.AppendRow("hello"))
-		err := a.Close()
-
-		testError(t, err, errAppenderClose.Error(), duckdbErrMsg, invalidatedAppenderMsg)
-		require.NoError(t, con.Close())
-		require.NoError(t, c.Close())
-	})
-
-	t.Run(errAppenderFlush.Error(), func(t *testing.T) {
-		c, con, a := prepareAppender(t, `CREATE TABLE test (a VARCHAR, b VARCHAR)`)
-		require.NoError(t, a.AppendRow("hello"))
-		err := a.Flush()
-
-		testError(t, err, errAppenderFlush.Error(), duckdbErrMsg, invalidatedAppenderMsg)
+		err := a.AppendRow("hello")
+		testError(t, err, errAppenderAppendRow.Error(), columnCountErrMsg)
 		cleanupAppender(t, c, con, a)
 	})