From 3450371910c00874743d9c98ab12bda38357f075 Mon Sep 17 00:00:00 2001
From: Anna Shaleva <shaleva.ann@nspcc.ru>
Date: Tue, 19 Oct 2021 18:03:47 +0300
Subject: [PATCH] core: split (*MemCachedStore) Seek and SeekAsync methods

Use SeekAsync for System.Storage.Find and Seek for the rest of cases.
---
 pkg/core/dao/dao.go                 |   9 +-
 pkg/core/storage/memcached_store.go | 160 ++++++++++++++--------------
 2 files changed, 84 insertions(+), 85 deletions(-)

diff --git a/pkg/core/dao/dao.go b/pkg/core/dao/dao.go
index bc3b90cbf..b15a36e97 100644
--- a/pkg/core/dao/dao.go
+++ b/pkg/core/dao/dao.go
@@ -338,10 +338,13 @@ func (dao *Simple) GetStorageItemsWithPrefix(id int32, prefix []byte) ([]state.S
 // Seek executes f for all items with a given prefix.
 // If key is to be used outside of f, they may not be copied.
 func (dao *Simple) Seek(id int32, prefix []byte, f func(k, v []byte)) {
-	res := dao.SeekAsync(context.Background(), id, prefix)
-	for r := range res {
-		f(r.Key, r.Value)
+	lookupKey := makeStorageItemKey(id, nil)
+	if prefix != nil {
+		lookupKey = append(lookupKey, prefix...)
 	}
+	dao.Store.Seek(lookupKey, func(k, v []byte) {
+		f(k[len(lookupKey):], v)
+	})
 }
 
 // SeekAsync sends all storage items matching given prefix to a channel and returns
diff --git a/pkg/core/storage/memcached_store.go b/pkg/core/storage/memcached_store.go
index ea137db8e..afe32481b 100644
--- a/pkg/core/storage/memcached_store.go
+++ b/pkg/core/storage/memcached_store.go
@@ -91,16 +91,28 @@ func (s *MemCachedStore) GetBatch() *MemBatch {
 
 // Seek implements the Store interface.
 func (s *MemCachedStore) Seek(key []byte, f func(k, v []byte)) {
-	seekres := s.SeekAsync(context.Background(), key, false)
-	for kv := range seekres {
-		f(kv.Key, kv.Value)
-	}
+	s.seek(context.Background(), key, false, f)
 }
 
 // SeekAsync returns non-buffered channel with matching KeyValue pairs. Key and
 // value slices may not be copied and may be modified. SeekAsync can guarantee
 // that key-value items are sorted by key in ascending way.
 func (s *MemCachedStore) SeekAsync(ctx context.Context, key []byte, cutPrefix bool) chan KeyValue {
+	res := make(chan KeyValue)
+	go func() {
+		s.seek(ctx, key, cutPrefix, func(k, v []byte) {
+			res <- KeyValue{
+				Key:   k,
+				Value: v,
+			}
+		})
+		close(res)
+	}()
+
+	return res
+}
+
+func (s *MemCachedStore) seek(ctx context.Context, key []byte, cutPrefix bool, f func(k, v []byte)) {
 	// Create memory store `mem` and `del` snapshot not to hold the lock.
 	var memRes []KeyValueExists
 	sk := string(key)
@@ -132,93 +144,77 @@ func (s *MemCachedStore) SeekAsync(ctx context.Context, key []byte, cutPrefix bo
 		return bytes.Compare(memRes[i].Key, memRes[j].Key) < 0
 	})
 
-	var seekres = make(chan KeyValue)
-
-	// Seek over persistent store.
-	go func() {
-		var (
-			done    bool
-			iMem    int
-			kvMem   KeyValueExists
-			haveMem bool
-		)
-		if iMem < len(memRes) {
-			kvMem = memRes[iMem]
-			haveMem = true
-			iMem++
+	var (
+		done    bool
+		iMem    int
+		kvMem   KeyValueExists
+		haveMem bool
+	)
+	if iMem < len(memRes) {
+		kvMem = memRes[iMem]
+		haveMem = true
+		iMem++
+	}
+	// Merge results of seek operations in ascending order.
+	ps.Seek(key, func(k, v []byte) {
+		if done {
+			return
 		}
-
-		// Merge results of seek operations in ascending order.
-		ps.Seek(key, func(k, v []byte) {
-			if done {
-				return
-			}
-			kvPs := KeyValue{
-				Key:   slice.Copy(k),
-				Value: slice.Copy(v),
-			}
-		loop:
-			for {
-				select {
-				case <-ctx.Done():
-					done = true
-					break loop
-				default:
-					var isMem = haveMem && (bytes.Compare(kvMem.Key, kvPs.Key) < 0)
-					if isMem {
-						if kvMem.Exists {
-							if cutPrefix {
-								kvMem.Key = kvMem.Key[len(key):]
-							}
-							seekres <- KeyValue{
-								Key:   kvMem.Key,
-								Value: kvMem.Value,
-							}
-						}
-						if iMem < len(memRes) {
-							kvMem = memRes[iMem]
-							haveMem = true
-							iMem++
-						} else {
-							haveMem = false
-						}
-					} else {
-						if !bytes.Equal(kvMem.Key, kvPs.Key) {
-							if cutPrefix {
-								kvPs.Key = kvPs.Key[len(key):]
-							}
-							seekres <- kvPs
-						}
-						break loop
-					}
-				}
-			}
-
-		})
-		if !done && haveMem {
-		loop:
-			for i := iMem - 1; i < len(memRes); i++ {
-				select {
-				case <-ctx.Done():
-					break loop
-				default:
-					kvMem = memRes[i]
+		kvPs := KeyValue{
+			Key:   slice.Copy(k),
+			Value: slice.Copy(v),
+		}
+	loop:
+		for {
+			select {
+			case <-ctx.Done():
+				done = true
+				break loop
+			default:
+				var isMem = haveMem && (bytes.Compare(kvMem.Key, kvPs.Key) < 0)
+				if isMem {
 					if kvMem.Exists {
 						if cutPrefix {
 							kvMem.Key = kvMem.Key[len(key):]
 						}
-						seekres <- KeyValue{
-							Key:   kvMem.Key,
-							Value: kvMem.Value,
-						}
+						f(kvMem.Key, kvMem.Value)
 					}
+					if iMem < len(memRes) {
+						kvMem = memRes[iMem]
+						haveMem = true
+						iMem++
+					} else {
+						haveMem = false
+					}
+				} else {
+					if !bytes.Equal(kvMem.Key, kvPs.Key) {
+						if cutPrefix {
+							kvPs.Key = kvPs.Key[len(key):]
+						}
+						f(kvPs.Key, kvPs.Value)
+					}
+					break loop
 				}
 			}
 		}
-		close(seekres)
-	}()
-
-	return seekres
+	})
+	if !done && haveMem {
+	loop:
+		for i := iMem - 1; i < len(memRes); i++ {
+			select {
+			case <-ctx.Done():
+				break loop
+			default:
+				kvMem = memRes[i]
+				if kvMem.Exists {
+					if cutPrefix {
+						kvMem.Key = kvMem.Key[len(key):]
+					}
+					f(kvMem.Key, kvMem.Value)
+				}
+			}
+		}
+	}
 }
 
 // Persist flushes all the MemoryStore contents into the (supposedly) persistent