1st

atree/select.go

@@ -0,0 +1,129 @@
+package atree
+
+import (
+	"fmt"
+
+	diploma "gordenko.dev/dima/qb"
+)
+
+type ContinueFullScanReq struct {
+	FracDigits     byte
+	ResponseWriter AtreeMeasureConsumer
+	LastPageNo     uint32
+}
+
+func (s *Atree) ContinueFullScan(req ContinueFullScanReq) error {
+	buf, err := s.fetchDataPage(req.LastPageNo)
+	if err != nil {
+		return fmt.Errorf("fetchDataPage(%d): %s", req.LastPageNo, err)
+	}
+
+	treeCursor, err := NewBackwardCursor(BackwardCursorOptions{
+		PageNo:     req.LastPageNo,
+		PageData:   buf,
+		Atree:      s,
+		FracDigits: req.FracDigits,
+		MetricType: diploma.Instant,
+	})
+	if err != nil {
+		return err
+	}
+	defer treeCursor.Close()
+
+	for {
+		timestamp, value, done, err := treeCursor.Prev()
+		if err != nil {
+			return err
+		}
+		if done {
+			return nil
+		}
+		req.ResponseWriter.Feed(timestamp, value)
+	}
+}
+
+type ContinueRangeScanReq struct {
+	FracDigits     byte
+	ResponseWriter AtreeMeasureConsumer
+	LastPageNo     uint32
+	Since          uint32
+}
+
+func (s *Atree) ContinueRangeScan(req ContinueRangeScanReq) error {
+	buf, err := s.fetchDataPage(req.LastPageNo)
+	if err != nil {
+		return fmt.Errorf("fetchDataPage(%d): %s", req.LastPageNo, err)
+	}
+
+	treeCursor, err := NewBackwardCursor(BackwardCursorOptions{
+		PageNo:     req.LastPageNo,
+		PageData:   buf,
+		Atree:      s,
+		FracDigits: req.FracDigits,
+		MetricType: diploma.Instant,
+	})
+	if err != nil {
+		return err
+	}
+	defer treeCursor.Close()
+
+	for {
+		timestamp, value, done, err := treeCursor.Prev()
+		if err != nil {
+			return err
+		}
+		if done {
+			return nil
+		}
+		req.ResponseWriter.Feed(timestamp, value)
+		if timestamp < req.Since {
+			return nil
+		}
+	}
+}
+
+type RangeScanReq struct {
+	FracDigits     byte
+	ResponseWriter AtreeMeasureConsumer
+	RootPageNo     uint32
+	Since          uint32
+	Until          uint32
+}
+
+func (s *Atree) RangeScan(req RangeScanReq) error {
+	pageNo, buf, err := s.findDataPage(req.RootPageNo, req.Until)
+	if err != nil {
+		return err
+	}
+
+	cursor, err := NewBackwardCursor(BackwardCursorOptions{
+		PageNo:     pageNo,
+		PageData:   buf,
+		Atree:      s,
+		FracDigits: req.FracDigits,
+		MetricType: diploma.Instant,
+	})
+	if err != nil {
+		return err
+	}
+	defer cursor.Close()
+
+	for {
+		timestamp, value, done, err := cursor.Prev()
+		if err != nil {
+			return err
+		}
+		if done {
+			return nil
+		}
+
+		if timestamp <= req.Until {
+			req.ResponseWriter.Feed(timestamp, value)
+
+			if timestamp < req.Since {
+				// - записи, удовлетворяющие временным рамкам, закончились.
+				return nil
+			}
+		}
+	}
+}