Added simple verticalMergeChunkIterator implementation - no tests s…

…o far.

TODO: tests & splitting into 2.

Signed-off-by: Bartek Plotka <bwplotka@gmail.com>

querier.go

@@ -15,6 +15,7 @@ package tsdb
 
 import (
 	"fmt"
+	"math"
 	"sort"
 	"strings"
 	"unicode/utf8"
@@ -55,7 +56,7 @@ type Series interface {
 	// Iterator returns a new iterator of the data of the series.
 	Iterator() SeriesIterator
 
-	// ChunkIterator returns a new iterator of the chunks of the series.
+	// ChunkIterator returns a new iterator for the non-overlapping chunks of the series.
 	ChunkIterator() ChunkIterator
 }
 
@@ -990,13 +991,11 @@ func (s *verticalChainedSeries) Iterator() SeriesIterator {
 	return newVerticalMergeSeriesIterator(s.series...)
 }
 
-// ChunkIterator is currently not implemented.
-// TODO(bwplotka): Implement once we will want to use chunks in vertical compaction.
 func (s *verticalChainedSeries) ChunkIterator() ChunkIterator {
-	return errChunkIterator{err: errors.New("Not Implemented")}
+	return newVerticalMergeChunkIterator(s.series...)
 }
 
-// verticalMergeSeriesIterator implements a series iterater over a list
+// verticalMergeSeriesIterator implements a series iterator over a list
 // of time-sorted, time-overlapping iterators.
 type verticalMergeSeriesIterator struct {
 	a, b                  SeriesIterator
@@ -1076,6 +1075,141 @@ func (it *verticalMergeSeriesIterator) Err() error {
 	return it.b.Err()
 }
 
+type noSeekSeriesIterator struct {
+	chunkenc.Iterator
+	err error
+}
+
+func (it *noSeekSeriesIterator) Seek(t int64) bool {
+	it.err = errors.New("not implemented: Seek method invoked for noSeekSeriesIterator")
+	return false
+}
+
+func (it *noSeekSeriesIterator) Err() error {
+	if it.err != nil {
+		return it.err
+	}
+	return it.Iterator.Err()
+}
+
+// verticalMergeChunkIterator implements a ChunkIterator over a list
+// of time-sorted, time-overlapping chunk iterators for the same labels (same series).
+// Any overlap in chunks will be merged using verticalMergeSeriesIterator.
+type verticalMergeChunkIterator struct {
+	a, b                  ChunkIterator
+	aok, bok, initialized bool
+
+	curMeta chunks.Meta
+	err     error
+
+	aReuseIter, bReuseIter chunkenc.Iterator
+}
+
+func newVerticalMergeChunkIterator(s ...Series) ChunkIterator {
+	if len(s) == 1 {
+		return s[0].ChunkIterator()
+	} else if len(s) == 2 {
+		return &verticalMergeChunkIterator{
+			a: s[0].ChunkIterator(),
+			b: s[1].ChunkIterator(),
+		}
+	}
+	return &verticalMergeChunkIterator{
+		a: s[0].ChunkIterator(),
+		b: newVerticalMergeChunkIterator(s[1:]...),
+	}
+}
+
+func (it *verticalMergeChunkIterator) Next() bool {
+	if !it.initialized {
+		it.aok = it.a.Next()
+		it.bok = it.b.Next()
+		it.initialized = true
+	}
+
+	if !it.aok && !it.bok {
+		return false
+	}
+
+	if !it.aok {
+		it.curMeta = it.b.At()
+		it.bok = it.b.Next()
+		return true
+	}
+	if !it.bok {
+		it.curMeta = it.a.At()
+		it.aok = it.a.Next()
+		return true
+	}
+
+	aCurMeta := it.a.At()
+	bCurMeta := it.b.At()
+
+	if aCurMeta.MaxTime < bCurMeta.MinTime {
+		it.curMeta = aCurMeta
+		it.aok = it.a.Next()
+		return true
+	}
+
+	if bCurMeta.MaxTime < aCurMeta.MinTime {
+		it.curMeta = bCurMeta
+		it.bok = it.b.Next()
+		return true
+	}
+
+	chk := chunkenc.NewXORChunk()
+	app, err := chk.Appender()
+	if err != nil {
+		it.err = err
+		return false
+	}
+	seriesIter := &verticalMergeSeriesIterator{
+		a: &noSeekSeriesIterator{Iterator: aCurMeta.Chunk.Iterator(it.aReuseIter)},
+		b: &noSeekSeriesIterator{Iterator: bCurMeta.Chunk.Iterator(it.bReuseIter)},
+	}
+
+	mint := int64(math.MaxInt64)
+	maxt := int64(0)
+
+	// TODO: This can end up being up to 240 samples per chunk, so we need to have a case to split to two.
+	for seriesIter.Next() {
+		t, v := seriesIter.At()
+		app.Append(t, v)
+
+		maxt = t
+		if mint == math.MaxInt64 {
+			mint = t
+		}
+	}
+	if err := seriesIter.Err(); err != nil {
+		it.err = err
+		return false
+	}
+
+	it.curMeta = chunks.Meta{
+		MinTime: mint,
+		MaxTime: maxt,
+		Chunk:   chk,
+	}
+	it.aok = it.a.Next()
+	it.bok = it.b.Next()
+	return true
+}
+
+func (it *verticalMergeChunkIterator) At() chunks.Meta {
+	return it.curMeta
+}
+
+func (it *verticalMergeChunkIterator) Err() error {
+	if it.err != nil {
+		return it.err
+	}
+	if it.a.Err() != nil {
+		return it.a.Err()
+	}
+	return it.b.Err()
+}
+
 // chunkSeriesIterator implements a series iterator on top
 // of a list of time-sorted, non-overlapping chunks.
 type chunkSeriesIterator struct {