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multi_reader_iterator.go
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/
multi_reader_iterator.go
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// Copyright (c) 2016 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package encoding
import (
"errors"
"time"
"github.com/m3db/m3/src/dbnode/namespace"
"github.com/m3db/m3/src/dbnode/ts"
"github.com/m3db/m3/src/dbnode/x/xio"
xtime "github.com/m3db/m3/src/x/time"
)
var (
errOutOfOrderIterator = errors.New("values are out of order from inner iterator")
)
// multiReaderIterator is an iterator that iterates in order over a list of sets of
// internally ordered but not collectively in order readers, it also deduplicates datapoints.
type multiReaderIterator struct {
schemaDesc namespace.SchemaDescr
iters iterators
slicesIter xio.ReaderSliceOfSlicesIterator
iteratorAlloc ReaderIteratorAllocate
singleSlicesIter singleSlicesOfSlicesIterator
pool MultiReaderIteratorPool
err error
firstNext bool
closed bool
}
// NewMultiReaderIterator creates a new multi-reader iterator.
func NewMultiReaderIterator(
iteratorAlloc ReaderIteratorAllocate,
pool MultiReaderIteratorPool,
) MultiReaderIterator {
it := &multiReaderIterator{pool: pool, iteratorAlloc: iteratorAlloc}
it.Reset(nil, time.Time{}, 0, nil)
return it
}
func (it *multiReaderIterator) Next() bool {
if !it.firstNext {
// When firstNext do not progress the first time
if !it.hasNext() {
return false
}
it.moveToNext()
}
it.firstNext = false
return it.hasNext()
}
func (it *multiReaderIterator) Current() (ts.Datapoint, xtime.Unit, ts.Annotation) {
return it.iters.current()
}
func (it *multiReaderIterator) hasError() bool {
return it.err != nil
}
func (it *multiReaderIterator) isClosed() bool {
return it.closed
}
func (it *multiReaderIterator) hasMore() bool {
return it.iters.len() > 0 || it.slicesIter != nil
}
func (it *multiReaderIterator) hasNext() bool {
return !it.hasError() && !it.isClosed() && it.hasMore()
}
func (it *multiReaderIterator) moveToNext() {
if it.iters.len() > 0 {
it.moveIteratorsToNext()
}
if it.iters.len() > 0 || it.hasError() {
// Still have valid iters or has error
return
}
// Move forward through slices of readers
if !it.slicesIter.Next() {
// No more readers, nil out so that hasMore reflects correctly
it.slicesIter.Close()
it.slicesIter = nil
return
}
// Add all readers to current iterators heap
currentLen, _, _ := it.slicesIter.CurrentReaders()
for i := 0; i < currentLen; i++ {
var (
reader = it.slicesIter.CurrentReaderAt(i)
iter = it.iteratorAlloc(reader, it.schemaDesc)
)
if iter.Next() {
// Only insert it if it has values
it.iters.push(iter)
} else {
err := iter.Err()
iter.Close()
if it.err == nil && err != nil {
it.err = err
}
}
}
if it.iters.len() == 0 && !it.hasError() {
// No iterators were added, move to next
it.moveToNext()
}
}
func (it *multiReaderIterator) moveIteratorsToNext() {
for {
prev := it.iters.at()
next, err := it.iters.moveToValidNext()
if it.err == nil && err != nil {
it.err = err
return
}
if err != nil || !next {
return
}
curr := it.iters.at()
if curr != prev {
return
}
// Dedupe by continuing
}
}
func (it *multiReaderIterator) Err() error {
return it.err
}
func (it *multiReaderIterator) Readers() xio.ReaderSliceOfSlicesIterator {
return it.slicesIter
}
func (it *multiReaderIterator) Reset(blocks []xio.SegmentReader, start time.Time, blockSize time.Duration, descr namespace.SchemaDescr) {
it.singleSlicesIter.readers = blocks
it.singleSlicesIter.firstNext = true
it.singleSlicesIter.closed = false
it.singleSlicesIter.start = start
it.singleSlicesIter.blockSize = blockSize
it.ResetSliceOfSlices(&it.singleSlicesIter, descr)
}
func (it *multiReaderIterator) ResetSliceOfSlices(slicesIter xio.ReaderSliceOfSlicesIterator, descr namespace.SchemaDescr) {
it.schemaDesc = descr
it.iters.reset()
it.slicesIter = slicesIter
it.err = nil
it.firstNext = true
it.closed = false
// Try moveToNext to load values for calls to Current before Next
it.moveToNext()
}
func (it *multiReaderIterator) Schema() namespace.SchemaDescr {
return it.schemaDesc
}
func (it *multiReaderIterator) Close() {
if it.isClosed() {
return
}
it.closed = true
it.iters.reset()
if it.slicesIter != nil {
it.slicesIter.Close()
}
it.slicesIter = nil
if it.pool != nil {
it.pool.Put(it)
}
}
type singleSlicesOfSlicesIterator struct {
readers []xio.SegmentReader
firstNext bool
closed bool
start time.Time
blockSize time.Duration
}
func (it *singleSlicesOfSlicesIterator) Next() bool {
if !it.firstNext || it.closed {
return false
}
it.firstNext = false
return true
}
func (it *singleSlicesOfSlicesIterator) CurrentReaders() (int, time.Time, time.Duration) {
return len(it.readers), it.start, it.blockSize
}
func (it *singleSlicesOfSlicesIterator) CurrentReaderAt(idx int) xio.BlockReader {
return xio.BlockReader{
SegmentReader: it.readers[idx],
Start: it.start,
BlockSize: it.blockSize,
}
}
func (it *singleSlicesOfSlicesIterator) Close() {
if it.closed {
return
}
it.closed = true
}
func (it *singleSlicesOfSlicesIterator) Size() (int, error) {
size := 0
for _, reader := range it.readers {
seg, err := reader.Segment()
if err != nil {
return 0, err
}
size += seg.Len()
}
return size, nil
}