diff --git a/internal/query/executor.go b/internal/query/executor.go
new file mode 100644
index 0000000..8224fb5
--- /dev/null
+++ b/internal/query/executor.go
@@ -0,0 +1,66 @@
+package query
+
+// Executor is a query executor.
+type Executor struct {
+	table Table
+}
+
+func NewExecutor(table Table) *Executor {
+	return &Executor{
+		table: table,
+	}
+}
+
+func (e *Executor) Execute(query Desc) error {
+	// Get a cursor
+	var cur Cursor
+	var err error
+	if len(query.Columns) == 0 && len(query.GroupBy) == 0 {
+		// No aggregations. Use a plain cursor.
+		cur, err = e.table.NewCursor()
+		if err != nil {
+			return err
+		}
+	} else {
+		fieldsMap := map[string]struct{}{}
+		for _, col := range query.Columns {
+			fieldsMap[col.Name] = struct{}{}
+		}
+		for _, col := range query.GroupBy {
+			fieldsMap[col.Name] = struct{}{}
+		}
+		fields := make([]string, 0, len(fieldsMap))
+		for field := range fieldsMap {
+			fields = append(fields, field)
+		}
+		cur, err = e.table.NewCursorForFields(fields)
+		if err != nil {
+			return err
+		}
+	}
+
+	// TODO
+	_ = cur
+
+	return nil
+}
+
+type Table interface {
+	NewCursor() (Cursor, error)
+	NewCursorForFields(fields []string) (Cursor, error)
+}
+
+type Cursor interface {
+	GetRow() (Row, error)
+	Next() bool
+	Err() error
+}
+
+type Seeker interface {
+	Seek(Row) error
+}
+
+type Row interface {
+	Fields() []string
+	Get(field string) (interface{}, error)
+}