Tried to add posting list cache for single values

Author: Harshil Goel

posting/lists.go

@@ -111,6 +111,8 @@ type LocalCache struct {
 
 	// plists are posting lists in memory. They can be discarded to reclaim space.
 	plists map[string]*List
+
+	postings map[string]*pb.PostingList
 }
 
 // NewLocalCache returns a new LocalCache instance.
@@ -120,13 +122,17 @@ func NewLocalCache(startTs uint64) *LocalCache {
 		deltas:      make(map[string][]byte),
 		plists:      make(map[string]*List),
 		maxVersions: make(map[string]uint64),
+		postings:    make(map[string]*pb.PostingList),
 	}
 }
 
 // NoCache returns a new LocalCache instance, which won't cache anything. Useful to pass startTs
 // around.
 func NoCache(startTs uint64) *LocalCache {
-	return &LocalCache{startTs: startTs}
+	return &LocalCache{
+		startTs:  startTs,
+		postings: make(map[string]*pb.PostingList),
+	}
 }
 
 func (lc *LocalCache) getNoStore(key string) *List {
@@ -138,6 +144,20 @@ func (lc *LocalCache) getNoStore(key string) *List {
 	return nil
 }
 
+// SetIfAbsent adds the list for the specified key to the cache. If a list for the same
+// key already exists, the cache will not be modified and the existing list
+// will be returned instead. This behavior is meant to prevent the goroutines
+// using the cache from ending up with an orphaned version of a list.
+func (lc *LocalCache) SetPostingIfAbsent(key string, updated *pb.PostingList) *pb.PostingList {
+	lc.Lock()
+	defer lc.Unlock()
+	if pl, ok := lc.postings[key]; ok {
+		return pl
+	}
+	lc.postings[key] = updated
+	return updated
+}
+
 // SetIfAbsent adds the list for the specified key to the cache. If a list for the same
 // key already exists, the cache will not be modified and the existing list
 // will be returned instead. This behavior is meant to prevent the goroutines
@@ -200,8 +220,10 @@ func (lc *LocalCache) GetBatchSinglePosting(keys [][]byte) ([]*pb.PostingList, e
 	remaining_keys := make([][]byte, 0)
 	lc.RLock()
 	for i, key := range keys {
-		pl := &pb.PostingList{}
-		if delta, ok := lc.deltas[string(key)]; ok && len(delta) > 0 {
+		if pl, ok := lc.postings[string(key)]; ok && pl != nil {
+			results[i] = pl
+		} else if delta, ok := lc.deltas[string(key)]; ok && len(delta) > 0 {
+			pl := &pb.PostingList{}
 			err := pl.Unmarshal(delta)
 			if err != nil {
 				results[i] = pl
@@ -214,6 +236,10 @@ func (lc *LocalCache) GetBatchSinglePosting(keys [][]byte) ([]*pb.PostingList, e
 
 	txn := pstore.NewTransactionAt(lc.startTs, false)
 	items, err := txn.GetBatch(remaining_keys)
+	if err != nil {
+		fmt.Println(err, keys)
+		return nil, err
+	}
 	idx := 0
 
 	for i := 0; i < len(results); i++ {
@@ -245,6 +271,7 @@ func (lc *LocalCache) GetBatchSinglePosting(keys [][]byte) ([]*pb.PostingList, e
 		}
 		pl.Postings = pl.Postings[:idx]
 		results[i] = pl
+		lc.SetPostingIfAbsent(string(keys[i]), pl)
 	}
 
 	return results, err
@@ -311,6 +338,7 @@ func (lc *LocalCache) GetSinglePosting(key []byte) (*pb.PostingList, error) {
 		}
 	}
 	pl.Postings = pl.Postings[:idx]
+	lc.SetPostingIfAbsent(string(key), pl)
 	return pl, nil
 }
 

worker/sort.go

@@ -21,6 +21,7 @@ import (
 	"encoding/hex"
 	"sort"
 	"strings"
+	"time"
 
 	"github.com/golang/glog"
 	"github.com/pkg/errors"
@@ -511,7 +512,34 @@ func processSort(ctx context.Context, ts *pb.SortMessage) (*pb.SortResult, error
 	cctx, cancel := context.WithCancel(ctx)
 	defer cancel()
 
-	r := sortWithIndex(cctx, ts)
+	resCh := make(chan *sortresult, 2)
+	go func() {
+		select {
+		case <-time.After(3 * time.Millisecond):
+			// Wait between ctx chan and time chan.
+		case <-ctx.Done():
+			resCh <- &sortresult{err: ctx.Err()}
+			return
+		}
+		r := sortWithoutIndex(cctx, ts)
+		resCh <- r
+	}()
+
+	go func() {
+		sr := sortWithIndex(cctx, ts)
+		resCh <- sr
+	}()
+
+	r := <-resCh
+	if r.err == nil {
+		cancel()
+		// wait for other goroutine to get cancelled
+		<-resCh
+	} else {
+		span.Annotatef(nil, "processSort error: %v", r.err)
+		r = <-resCh
+	}
+
 	if r.err != nil {
 		return nil, r.err
 	}