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chunk_merge_iterator.go
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/
chunk_merge_iterator.go
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package iterators
import (
"container/heap"
"sort"
"github.com/prometheus/common/model"
"github.com/prometheus/prometheus/tsdb/chunkenc"
"github.com/cortexproject/cortex/pkg/chunk"
)
type chunkMergeIterator struct {
its []*nonOverlappingIterator
h seriesIteratorHeap
currTime int64
currValue float64
currErr error
}
// NewChunkMergeIterator creates a chunkenc.Iterator for a set of chunks.
func NewChunkMergeIterator(cs []chunk.Chunk, _, _ model.Time) chunkenc.Iterator {
its := buildIterators(cs)
c := &chunkMergeIterator{
currTime: -1,
its: its,
h: make(seriesIteratorHeap, 0, len(its)),
}
for _, iter := range c.its {
if iter.Next() {
c.h = append(c.h, iter)
continue
}
if err := iter.Err(); err != nil {
c.currErr = err
}
}
heap.Init(&c.h)
return c
}
// Build a list of lists of non-overlapping chunk iterators.
func buildIterators(cs []chunk.Chunk) []*nonOverlappingIterator {
chunks := make([]*chunkIterator, len(cs))
for i := range cs {
chunks[i] = &chunkIterator{
Chunk: cs[i],
it: cs[i].Data.NewIterator(nil),
}
}
sort.Sort(byFrom(chunks))
chunkLists := [][]*chunkIterator{}
outer:
for _, chunk := range chunks {
for i, chunkList := range chunkLists {
if chunkList[len(chunkList)-1].Through.Before(chunk.From) {
chunkLists[i] = append(chunkLists[i], chunk)
continue outer
}
}
chunkLists = append(chunkLists, []*chunkIterator{chunk})
}
its := make([]*nonOverlappingIterator, 0, len(chunkLists))
for _, chunkList := range chunkLists {
its = append(its, newNonOverlappingIterator(chunkList))
}
return its
}
func (c *chunkMergeIterator) Seek(t int64) bool {
c.h = c.h[:0]
for _, iter := range c.its {
if iter.Seek(t) {
c.h = append(c.h, iter)
continue
}
if err := iter.Err(); err != nil {
c.currErr = err
return false
}
}
heap.Init(&c.h)
if len(c.h) > 0 {
c.currTime, c.currValue = c.h[0].At()
return true
}
return false
}
func (c *chunkMergeIterator) Next() bool {
if len(c.h) == 0 {
return false
}
lastTime := c.currTime
for c.currTime == lastTime && len(c.h) > 0 {
c.currTime, c.currValue = c.h[0].At()
if c.h[0].Next() {
heap.Fix(&c.h, 0)
continue
}
iter := heap.Pop(&c.h).(chunkenc.Iterator)
if err := iter.Err(); err != nil {
c.currErr = err
return false
}
}
return c.currTime != lastTime
}
func (c *chunkMergeIterator) At() (t int64, v float64) {
return c.currTime, c.currValue
}
func (c *chunkMergeIterator) Err() error {
return c.currErr
}
type extraIterator interface {
chunkenc.Iterator
AtTime() int64
}
type seriesIteratorHeap []extraIterator
func (h *seriesIteratorHeap) Len() int { return len(*h) }
func (h *seriesIteratorHeap) Swap(i, j int) { (*h)[i], (*h)[j] = (*h)[j], (*h)[i] }
func (h *seriesIteratorHeap) Less(i, j int) bool {
iT := (*h)[i].AtTime()
jT := (*h)[j].AtTime()
return iT < jT
}
func (h *seriesIteratorHeap) Push(x interface{}) {
*h = append(*h, x.(extraIterator))
}
func (h *seriesIteratorHeap) Pop() interface{} {
old := *h
n := len(old)
x := old[n-1]
*h = old[0 : n-1]
return x
}
type byFrom []*chunkIterator
func (b byFrom) Len() int { return len(b) }
func (b byFrom) Swap(i, j int) { b[i], b[j] = b[j], b[i] }
func (b byFrom) Less(i, j int) bool { return b[i].From < b[j].From }
type nonOverlappingIterator struct {
curr int
chunks []*chunkIterator
}
// newNonOverlappingIterator returns a single iterator over an slice of sorted,
// non-overlapping iterators.
func newNonOverlappingIterator(chunks []*chunkIterator) *nonOverlappingIterator {
return &nonOverlappingIterator{
chunks: chunks,
}
}
func (it *nonOverlappingIterator) Seek(t int64) bool {
for ; it.curr < len(it.chunks); it.curr++ {
if it.chunks[it.curr].Seek(t) {
return true
}
}
return false
}
func (it *nonOverlappingIterator) Next() bool {
for it.curr < len(it.chunks) && !it.chunks[it.curr].Next() {
it.curr++
}
return it.curr < len(it.chunks)
}
func (it *nonOverlappingIterator) AtTime() int64 {
return it.chunks[it.curr].AtTime()
}
func (it *nonOverlappingIterator) At() (int64, float64) {
return it.chunks[it.curr].At()
}
func (it *nonOverlappingIterator) Err() error {
return nil
}