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merge.go
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merge.go
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package reads
import (
"container/heap"
"github.com/influxdata/influxdb/models"
"github.com/influxdata/influxdb/tsdb/cursors"
)
type sequenceResultSet struct {
items []ResultSet
rs ResultSet
err error
stats cursors.CursorStats
}
// NewSequenceResultSet combines results into a single ResultSet,
// draining each ResultSet in order before moving to the next.
func NewSequenceResultSet(results []ResultSet) ResultSet {
if len(results) == 0 {
return nil
} else if len(results) == 1 {
return results[0]
}
rs := &sequenceResultSet{items: results}
rs.pop()
return rs
}
func (r *sequenceResultSet) Err() error { return r.err }
func (r *sequenceResultSet) Close() {
if r.rs != nil {
r.rs.Close()
r.rs = nil
}
for _, rs := range r.items {
rs.Close()
}
r.items = nil
}
func (r *sequenceResultSet) pop() bool {
if r.rs != nil {
r.rs.Close()
r.rs = nil
}
if len(r.items) > 0 {
r.rs = r.items[0]
r.items[0] = nil
r.items = r.items[1:]
return true
}
return false
}
func (r *sequenceResultSet) Next() bool {
RETRY:
if r.rs != nil {
if r.rs.Next() {
return true
}
err := r.rs.Err()
stats := r.rs.Stats()
if err != nil {
r.err = err
r.Close()
return false
}
r.stats.Add(stats)
if r.pop() {
goto RETRY
}
}
return false
}
func (r *sequenceResultSet) Cursor() cursors.Cursor {
return r.rs.Cursor()
}
func (r *sequenceResultSet) Tags() models.Tags {
return r.rs.Tags()
}
func (r *sequenceResultSet) Stats() cursors.CursorStats {
return r.stats
}
type mergedResultSet struct {
heap resultSetHeap
err error
first bool
stats cursors.CursorStats
}
// NewMergedResultSet combines the results into a single ResultSet,
// producing keys in ascending lexicographical order. It requires
// all input results are ordered.
func NewMergedResultSet(results []ResultSet) ResultSet {
if len(results) == 0 {
return nil
} else if len(results) == 1 {
return results[0]
}
mrs := &mergedResultSet{first: true}
mrs.heap.init(results)
return mrs
}
func (r *mergedResultSet) Err() error { return r.err }
func (r *mergedResultSet) Close() {
for _, rs := range r.heap.items {
rs.Close()
}
r.heap.items = nil
}
func (r *mergedResultSet) Next() bool {
if len(r.heap.items) == 0 {
return false
}
if !r.first {
top := r.heap.items[0]
if top.Next() {
heap.Fix(&r.heap, 0)
return true
}
err := top.Err()
stats := top.Stats()
top.Close()
heap.Pop(&r.heap)
if err != nil {
r.err = err
r.Close()
return false
}
r.stats.Add(stats)
return len(r.heap.items) > 0
}
r.first = false
return true
}
func (r *mergedResultSet) Cursor() cursors.Cursor {
return r.heap.items[0].Cursor()
}
func (r *mergedResultSet) Tags() models.Tags {
return r.heap.items[0].Tags()
}
func (r *mergedResultSet) Stats() cursors.CursorStats {
return r.stats
}
type resultSetHeap struct {
items []ResultSet
}
func (h *resultSetHeap) init(results []ResultSet) {
if cap(h.items) < len(results) {
h.items = make([]ResultSet, 0, len(results))
} else {
h.items = h.items[:0]
}
for _, rs := range results {
if rs.Next() {
h.items = append(h.items, rs)
} else {
rs.Close()
}
}
heap.Init(h)
}
func (h *resultSetHeap) Less(i, j int) bool {
return models.CompareTags(h.items[i].Tags(), h.items[j].Tags()) == -1
}
func (h *resultSetHeap) Len() int {
return len(h.items)
}
func (h *resultSetHeap) Swap(i, j int) {
h.items[i], h.items[j] = h.items[j], h.items[i]
}
func (h *resultSetHeap) Push(x interface{}) {
panic("not implemented")
}
func (h *resultSetHeap) Pop() interface{} {
n := len(h.items)
item := h.items[n-1]
h.items[n-1] = nil
h.items = h.items[:n-1]
return item
}
// MergedStringIterator merges multiple storage.StringIterators into one.
// It sorts and deduplicates adjacent values, so the output is sorted iff all inputs are sorted.
// If all inputs are not sorted, then output order and deduplication are undefined and unpleasant.
type MergedStringIterator struct {
heap stringIteratorHeap
nextValue string
stats cursors.CursorStats
}
// API compatibility
var _ cursors.StringIterator = (*MergedStringIterator)(nil)
func NewMergedStringIterator(iterators []cursors.StringIterator) *MergedStringIterator {
nonEmptyIterators := make([]cursors.StringIterator, 0, len(iterators))
var stats cursors.CursorStats
for _, iterator := range iterators {
// All iterators must be Next()'d so that their Value() methods return a meaningful value, and sort properly.
if iterator.Next() {
nonEmptyIterators = append(nonEmptyIterators, iterator)
} else {
stats.Add(iterator.Stats())
}
}
msi := &MergedStringIterator{
heap: stringIteratorHeap{iterators: nonEmptyIterators},
stats: stats,
}
heap.Init(&msi.heap)
return msi
}
func (msi *MergedStringIterator) Next() bool {
for msi.heap.Len() > 0 {
iterator := msi.heap.iterators[0]
haveNext := false
if proposedNextValue := iterator.Value(); proposedNextValue != msi.nextValue { // Skip dupes.
msi.nextValue = proposedNextValue
haveNext = true
}
if iterator.Next() {
// iterator.Value() has changed, so re-order that iterator within the heap
heap.Fix(&msi.heap, 0)
} else {
// iterator is drained, so count the stats and remove it from the heap
msi.stats.Add(iterator.Stats())
heap.Pop(&msi.heap)
}
if haveNext {
return true
}
}
return false
}
func (msi *MergedStringIterator) Value() string {
return msi.nextValue
}
func (msi *MergedStringIterator) Stats() cursors.CursorStats {
return msi.stats
}
type stringIteratorHeap struct {
iterators []cursors.StringIterator
}
func (h stringIteratorHeap) Len() int {
return len(h.iterators)
}
func (h stringIteratorHeap) Less(i, j int) bool {
return h.iterators[i].Value() < h.iterators[j].Value()
}
func (h *stringIteratorHeap) Swap(i, j int) {
h.iterators[i], h.iterators[j] = h.iterators[j], h.iterators[i]
}
func (h *stringIteratorHeap) Push(x interface{}) {
h.iterators = append(h.iterators, x.(cursors.StringIterator))
}
func (h *stringIteratorHeap) Pop() interface{} {
n := len(h.iterators)
item := h.iterators[n-1]
h.iterators[n-1] = nil
h.iterators = h.iterators[:n-1]
return item
}