diff --git a/hugegraph-api/src/main/java/com/baidu/hugegraph/auth/HugeGraphAuthProxy.java b/hugegraph-api/src/main/java/com/baidu/hugegraph/auth/HugeGraphAuthProxy.java
index 34fcc6d495..807d3c4f71 100644
--- a/hugegraph-api/src/main/java/com/baidu/hugegraph/auth/HugeGraphAuthProxy.java
+++ b/hugegraph-api/src/main/java/com/baidu/hugegraph/auth/HugeGraphAuthProxy.java
@@ -65,6 +65,7 @@
 import com.baidu.hugegraph.backend.store.raft.RaftGroupManager;
 import com.baidu.hugegraph.config.ConfigOption;
 import com.baidu.hugegraph.config.HugeConfig;
+import com.baidu.hugegraph.config.TypedOption;
 import com.baidu.hugegraph.exception.NotSupportException;
 import com.baidu.hugegraph.iterator.FilterIterator;
 import com.baidu.hugegraph.rpc.RpcServiceConfig4Client;
@@ -552,7 +553,7 @@ public long now() {
     }
 
     @Override
-    public <V> V option(ConfigOption<V> option) {
+    public <K, V> V option(TypedOption<K, V> option) {
         this.verifyAnyPermission();
         return this.hugegraph.option(option);
     }
diff --git a/hugegraph-core/src/main/java/com/baidu/hugegraph/HugeGraph.java b/hugegraph-core/src/main/java/com/baidu/hugegraph/HugeGraph.java
index ed26bbb5d0..e9b93f4d86 100644
--- a/hugegraph-core/src/main/java/com/baidu/hugegraph/HugeGraph.java
+++ b/hugegraph-core/src/main/java/com/baidu/hugegraph/HugeGraph.java
@@ -38,6 +38,7 @@
 import com.baidu.hugegraph.backend.store.BackendStoreSystemInfo;
 import com.baidu.hugegraph.backend.store.raft.RaftGroupManager;
 import com.baidu.hugegraph.config.ConfigOption;
+import com.baidu.hugegraph.config.TypedOption;
 import com.baidu.hugegraph.rpc.RpcServiceConfig4Client;
 import com.baidu.hugegraph.rpc.RpcServiceConfig4Server;
 import com.baidu.hugegraph.schema.EdgeLabel;
@@ -170,7 +171,7 @@ public interface HugeGraph extends Graph {
 
     public long now();
 
-    public <V> V option(ConfigOption<V> option);
+    public <K, V> V option(TypedOption<K, V> option);
 
     public void registerRpcServices(RpcServiceConfig4Server serverConfig,
                                     RpcServiceConfig4Client clientConfig);
diff --git a/hugegraph-core/src/main/java/com/baidu/hugegraph/StandardHugeGraph.java b/hugegraph-core/src/main/java/com/baidu/hugegraph/StandardHugeGraph.java
index 1a3e87547c..a45aeb7664 100644
--- a/hugegraph-core/src/main/java/com/baidu/hugegraph/StandardHugeGraph.java
+++ b/hugegraph-core/src/main/java/com/baidu/hugegraph/StandardHugeGraph.java
@@ -67,6 +67,7 @@
 import com.baidu.hugegraph.config.ConfigOption;
 import com.baidu.hugegraph.config.CoreOptions;
 import com.baidu.hugegraph.config.HugeConfig;
+import com.baidu.hugegraph.config.TypedOption;
 import com.baidu.hugegraph.event.EventHub;
 import com.baidu.hugegraph.event.EventListener;
 import com.baidu.hugegraph.exception.NotAllowException;
@@ -116,7 +117,7 @@ public class StandardHugeGraph implements HugeGraph {
            StandardHugeGraph.SysTransaction.class
     };
 
-    public static final Set<ConfigOption<?>> ALLOWED_CONFIGS = ImmutableSet.of(
+    public static final Set<TypedOption<?, ?>> ALLOWED_CONFIGS = ImmutableSet.of(
            CoreOptions.TASK_WAIT_TIMEOUT,
            CoreOptions.TASK_SYNC_DELETION,
            CoreOptions.TASK_TTL_DELETE_BATCH,
@@ -978,7 +979,7 @@ public long now() {
     }
 
     @Override
-    public <V> V option(ConfigOption<V> option) {
+    public <K, V> V option(TypedOption<K, V> option) {
         HugeConfig config = this.configuration();
         if (!ALLOWED_CONFIGS.contains(option)) {
             throw new NotAllowException("Not allowed to access config: %s",
diff --git a/hugegraph-core/src/main/java/com/baidu/hugegraph/config/CoreOptions.java b/hugegraph-core/src/main/java/com/baidu/hugegraph/config/CoreOptions.java
index 60eede09a8..4c90d4db0d 100644
--- a/hugegraph-core/src/main/java/com/baidu/hugegraph/config/CoreOptions.java
+++ b/hugegraph-core/src/main/java/com/baidu/hugegraph/config/CoreOptions.java
@@ -26,6 +26,7 @@
 import static com.baidu.hugegraph.config.OptionChecker.rangeInt;
 
 import com.baidu.hugegraph.backend.query.Query;
+import com.baidu.hugegraph.type.define.CollectionType;
 import com.baidu.hugegraph.util.Bytes;
 
 public class CoreOptions extends OptionHolder {
@@ -624,12 +625,13 @@ public static synchronized CoreOptions instance() {
                     10
             );
 
-    public static final ConfigOption<String> OLTP_COLLECTION_IMPL_TYPE =
-            new ConfigOption<>(
+    public static final ConfigConvOption<String, CollectionType> OLTP_COLLECTION_IMPL_TYPE =
+            new ConfigConvOption<>(
                     "oltp.collection_impl_type",
                     "The implementation type of collections " +
                     "used in oltp algorithm.",
                     allowValues("jcf", "ec", "fu"),
+                    CollectionType::valueOf,
                     "ec"
             );
 }
diff --git a/hugegraph-core/src/main/java/com/baidu/hugegraph/structure/HugeVertex.java b/hugegraph-core/src/main/java/com/baidu/hugegraph/structure/HugeVertex.java
index c707983d8d..63ae52b5e3 100644
--- a/hugegraph-core/src/main/java/com/baidu/hugegraph/structure/HugeVertex.java
+++ b/hugegraph-core/src/main/java/com/baidu/hugegraph/structure/HugeVertex.java
@@ -53,7 +53,7 @@
 import com.baidu.hugegraph.schema.VertexLabel;
 import com.baidu.hugegraph.type.HugeType;
 import com.baidu.hugegraph.type.define.Cardinality;
-import com.baidu.hugegraph.type.define.CollectionImplType;
+import com.baidu.hugegraph.type.define.CollectionType;
 import com.baidu.hugegraph.type.define.Directions;
 import com.baidu.hugegraph.type.define.HugeKeys;
 import com.baidu.hugegraph.type.define.IdStrategy;
@@ -223,7 +223,11 @@ public Collection<HugeEdge> getEdges() {
     }
 
     public void resetEdges() {
-        this.edges = CollectionFactory.newList(CollectionImplType.EC);
+        /*
+         * Use list to hold edges for vertices to reduce memory usage and
+         * add operation time.
+         */
+        this.edges = newList();
     }
 
     public void removeEdge(HugeEdge edge) {
@@ -232,7 +236,7 @@ public void removeEdge(HugeEdge edge) {
 
     public void addEdge(HugeEdge edge) {
         if (this.edges == EMPTY_LIST) {
-            this.edges = CollectionFactory.newList(CollectionImplType.EC);
+            this.edges = CollectionFactory.newList(CollectionType.EC);
         }
         this.edges.add(edge);
     }
@@ -642,6 +646,14 @@ public static HugeVertex create(final GraphTransaction tx,
         return new HugeVertex4Insert(tx, id, label);
     }
 
+    private static <V> Set<V> newSet() {
+        return CollectionFactory.newSet(CollectionType.EC);
+    }
+
+    private static <V> List<V> newList() {
+        return CollectionFactory.newList(CollectionType.EC);
+    }
+
     private static final class HugeVertex4Insert extends HugeVertex {
 
         private GraphTransaction tx;
@@ -649,6 +661,10 @@ private static final class HugeVertex4Insert extends HugeVertex {
         public HugeVertex4Insert(final GraphTransaction tx,
                                  Id id, VertexLabel label) {
             super(tx.graph(), id, label);
+            /*
+             * Use set to hold edges for inserted vertex
+             * to avoid duplicated edges
+             */
             this.edges = newSet();
             this.tx = tx;
             this.fresh(true);
@@ -679,9 +695,5 @@ protected GraphTransaction tx() {
             }
             return null;
         }
-
-        private static <V> Set<V> newSet() {
-            return CollectionFactory.newSet(CollectionImplType.EC);
-        }
     }
 }
diff --git a/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/HugeTraverser.java b/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/HugeTraverser.java
index a9129e8df8..797e97cf49 100644
--- a/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/HugeTraverser.java
+++ b/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/HugeTraverser.java
@@ -54,7 +54,7 @@
 import com.baidu.hugegraph.traversal.algorithm.steps.EdgeStep;
 import com.baidu.hugegraph.traversal.optimize.TraversalUtil;
 import com.baidu.hugegraph.type.HugeType;
-import com.baidu.hugegraph.type.define.CollectionImplType;
+import com.baidu.hugegraph.type.define.CollectionType;
 import com.baidu.hugegraph.type.define.Directions;
 import com.baidu.hugegraph.type.define.HugeKeys;
 import com.baidu.hugegraph.util.CollectionUtil;
@@ -103,9 +103,8 @@ protected int concurrentDepth() {
         return this.graph.option(CoreOptions.OLTP_CONCURRENT_DEPTH);
     }
 
-    private CollectionImplType collectionImplType() {
-        return CollectionImplType.valueOf(this.graph.option(
-               CoreOptions.OLTP_COLLECTION_IMPL_TYPE).toUpperCase());
+    private CollectionType collectionImplType() {
+        return this.graph.option(CoreOptions.OLTP_COLLECTION_IMPL_TYPE);
     }
 
     protected Set<Id> adjacentVertices(Set<Id> vertices, Directions dir,
@@ -549,22 +548,6 @@ public String toString() {
         }
     }
 
-    public static class KNode extends Node {
-
-        public KNode(Id id, KNode parent) {
-            super(id, parent);
-        }
-
-        @Override
-        public boolean equals(Object object) {
-            if (!(object instanceof KNode)) {
-                return false;
-            }
-            KNode other = (KNode) object;
-            return Objects.equals(this.id(), other.id());
-        }
-    }
-
     public static class Path {
 
         public static final Path EMPTY_PATH = new Path(ImmutableList.of());
@@ -585,7 +568,7 @@ public Id crosspoint() {
             return this.crosspoint;
         }
 
-        public void addToEnd(Id id) {
+        public void addToLast(Id id) {
             this.vertices.add(id);
         }
 
diff --git a/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/KneighborTraverser.java b/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/KneighborTraverser.java
index 6846ae8f7a..543070f7cd 100644
--- a/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/KneighborTraverser.java
+++ b/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/KneighborTraverser.java
@@ -36,8 +36,6 @@
 
 public class KneighborTraverser extends OltpTraverser {
 
-    private volatile boolean stop;
-
     public KneighborTraverser(HugeGraph graph) {
         super(graph);
     }
@@ -88,14 +86,13 @@ public KneighborRecords customizedKneighbor(Id source, EdgeStep step,
                                                         source, true);
 
         Consumer<Id> consumer = v -> {
-            if (this.stop) {
+            if (this.reachLimit(limit, records.size())) {
                 return;
             }
             Iterator<Edge> edges = edgesOfVertex(v, step);
-            while (!this.stop && edges.hasNext()) {
+            while (!this.reachLimit(limit, records.size()) && edges.hasNext()) {
                 Id target = ((HugeEdge) edges.next()).id().otherVertexId();
                 records.addPath(v, target);
-                this.reachLimit(limit, records.size());
             }
         };
 
@@ -108,10 +105,6 @@ public KneighborRecords customizedKneighbor(Id source, EdgeStep step,
     }
 
     private boolean reachLimit(long limit, int size) {
-        if (limit == NO_LIMIT || size < limit) {
-            return false;
-        }
-        this.stop = true;
-        return true;
+        return limit != NO_LIMIT && size >= limit;
     }
 }
diff --git a/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/KoutTraverser.java b/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/KoutTraverser.java
index edc0399de0..afcf9dc32d 100644
--- a/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/KoutTraverser.java
+++ b/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/KoutTraverser.java
@@ -38,7 +38,6 @@
 public class KoutTraverser extends OltpTraverser {
 
     private int depth;
-    private volatile boolean stop = false;
 
     public KoutTraverser(HugeGraph graph) {
         super(graph);
@@ -117,16 +116,15 @@ public KoutRecords customizedKout(Id source, EdgeStep step,
                                               source, nearest);
 
         Consumer<Id> consumer = v -> {
-            if (this.stop) {
+            if (this.reachLimit(limit, this.depth, records.size())) {
                 return;
             }
             Iterator<Edge> edges = edgesOfVertex(v, step);
-            while (!this.stop && edges.hasNext()) {
+            while (!this.reachLimit(limit, this.depth, records.size()) &&
+                   edges.hasNext()) {
                 Id target = ((HugeEdge) edges.next()).id().otherVertexId();
                 records.addPath(v, target);
-
                 this.checkCapacity(capacity, records.accessed(), this.depth);
-                this.checkLimit(limit, this.depth, records.size());
             }
         };
 
@@ -149,12 +147,7 @@ private void checkCapacity(long capacity, long accessed, int depth) {
         }
     }
 
-    private void checkLimit(long limit, long depth, int size) {
-        if (limit == NO_LIMIT || depth > 0) {
-            return;
-        }
-        if (size >= limit) {
-            this.stop = true;
-        }
+    private boolean reachLimit(long limit, long depth, int size) {
+        return limit != NO_LIMIT && depth <= 0 && size >= limit;
     }
 }
diff --git a/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/OltpTraverser.java b/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/OltpTraverser.java
index 0837ff5604..af4a73cc39 100644
--- a/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/OltpTraverser.java
+++ b/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/OltpTraverser.java
@@ -21,14 +21,11 @@
 
 import java.util.Iterator;
 import java.util.List;
-import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.CopyOnWriteArrayList;
-import java.util.concurrent.atomic.AtomicLong;
 import java.util.function.Consumer;
 
 import org.apache.commons.lang3.tuple.Pair;
-import org.apache.tinkerpop.gremlin.structure.Edge;
 import org.apache.tinkerpop.gremlin.structure.Element;
 import org.apache.tinkerpop.gremlin.structure.Property;
 import org.apache.tinkerpop.gremlin.structure.Vertex;
@@ -38,8 +35,6 @@
 import com.baidu.hugegraph.backend.id.Id;
 import com.baidu.hugegraph.config.CoreOptions;
 import com.baidu.hugegraph.iterator.FilterIterator;
-import com.baidu.hugegraph.structure.HugeEdge;
-import com.baidu.hugegraph.traversal.algorithm.steps.EdgeStep;
 import com.baidu.hugegraph.util.Consumers;
 
 import jersey.repackaged.com.google.common.base.Objects;
@@ -81,63 +76,6 @@ public static void destroy() {
         }
     }
 
-    protected Set<Node> adjacentVertices(Set<Node> latest, EdgeStep step,
-                                         Set<Node> all, long remaining,
-                                         boolean single) {
-        if (single) {
-            return this.adjacentVertices(latest, step, all, remaining);
-        } else {
-            AtomicLong remain = new AtomicLong(remaining);
-            return this.adjacentVertices(latest, step, all, remain);
-        }
-    }
-
-    protected Set<Node> adjacentVertices(Set<Node> vertices, EdgeStep step,
-                                         Set<Node> excluded, long remaining) {
-        Set<Node> neighbors = newSet();
-        for (Node source : vertices) {
-            Iterator<Edge> edges = this.edgesOfVertex(source.id(), step);
-            while (edges.hasNext()) {
-                Id target = ((HugeEdge) edges.next()).id().otherVertexId();
-                KNode kNode = new KNode(target, (KNode) source);
-                if (excluded != null && excluded.contains(kNode)) {
-                    continue;
-                }
-                neighbors.add(kNode);
-                if (remaining != NO_LIMIT && --remaining <= 0L) {
-                    return neighbors;
-                }
-            }
-        }
-        return neighbors;
-    }
-
-    protected Set<Node> adjacentVertices(Set<Node> vertices, EdgeStep step,
-                                         Set<Node> excluded,
-                                         AtomicLong remaining) {
-        Set<Node> neighbors = ConcurrentHashMap.newKeySet();
-        this.traverseNodes(vertices.iterator(), v -> {
-            Iterator<Edge> edges = this.edgesOfVertex(v.id(), step);
-            while (edges.hasNext()) {
-                Id target = ((HugeEdge) edges.next()).id().otherVertexId();
-                KNode kNode = new KNode(target, (KNode) v);
-                if (excluded != null && excluded.contains(kNode)) {
-                    continue;
-                }
-                neighbors.add(kNode);
-                if (remaining.decrementAndGet() <= 0L) {
-                    return;
-                }
-            }
-        });
-        return neighbors;
-    }
-
-    protected long traverseNodes(Iterator<Node> vertices,
-                                 Consumer<Node> consumer) {
-        return this.traverse(vertices, consumer, "traverse-nodes");
-    }
-
     protected long traversePairs(Iterator<Pair<Id, Id>> pairs,
                                  Consumer<Pair<Id, Id>> consumer) {
         return this.traverse(pairs, consumer, "traverse-pairs");
diff --git a/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/records/DoubleWayMultiPathsRecords.java b/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/records/DoubleWayMultiPathsRecords.java
index a6bc4b7a73..bae50817fe 100644
--- a/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/records/DoubleWayMultiPathsRecords.java
+++ b/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/records/DoubleWayMultiPathsRecords.java
@@ -178,7 +178,7 @@ private PathSet linkPath(Stack<Record> all, int id, int layerIndex) {
                     iter.remove();
                     continue;
                 }
-                path.addToEnd(sid);
+                path.addToLast(sid);
             }
 
             results.addAll(paths);
diff --git a/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/records/KneighborRecords.java b/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/records/KneighborRecords.java
index 5302719b09..24762006b6 100644
--- a/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/records/KneighborRecords.java
+++ b/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/records/KneighborRecords.java
@@ -24,34 +24,29 @@
 import java.util.Set;
 
 import com.baidu.hugegraph.backend.id.Id;
-import com.baidu.hugegraph.traversal.algorithm.HugeTraverser;
 import com.baidu.hugegraph.traversal.algorithm.HugeTraverser.PathSet;
 import com.baidu.hugegraph.traversal.algorithm.records.record.IntIterator;
 import com.baidu.hugegraph.traversal.algorithm.records.record.RecordType;
-import com.baidu.hugegraph.type.define.CollectionImplType;
+import com.baidu.hugegraph.type.define.CollectionType;
 import com.baidu.hugegraph.util.collection.CollectionFactory;
-import com.google.common.collect.ImmutableList;
 
 public class KneighborRecords extends SingleWayMultiPathsRecords {
 
-    private final Id source;
-
     public KneighborRecords(RecordType type, boolean concurrent,
                             Id source, boolean nearest) {
         super(type, concurrent, source, nearest);
-        this.source = source;
     }
 
+    @Override
     public int size() {
         return (int) this.accessed();
     }
 
     public Set<Id> ids(long limit) {
-        Set<Id> ids = CollectionFactory.newIdSet(CollectionImplType.EC);
-        ids.add(this.source);
+        Set<Id> ids = CollectionFactory.newIdSet(CollectionType.EC);
         for (int i = 1; i < this.records.size(); i++) {
             IntIterator iterator = this.records.get(i).keys();
-            while ((limit == NO_LIMIT || limit > 1L) && iterator.hasNext()) {
+            while ((limit == NO_LIMIT || limit > 0L) && iterator.hasNext()) {
                 ids.add(this.id(iterator.next()));
                 limit--;
             }
@@ -61,10 +56,9 @@ public Set<Id> ids(long limit) {
 
     public PathSet paths(long limit) {
         PathSet paths = new PathSet();
-        paths.add(new HugeTraverser.Path(ImmutableList.of(this.source)));
         for (int i = 1; i < this.records.size(); i++) {
             IntIterator iterator = this.records.get(i).keys();
-            while ((limit == NO_LIMIT || limit > 1L) && iterator.hasNext()) {
+            while ((limit == NO_LIMIT || limit > 0L) && iterator.hasNext()) {
                 paths.add(this.getPath(i, iterator.next()));
                 limit--;
             }
diff --git a/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/records/KoutRecords.java b/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/records/KoutRecords.java
index 41d6a44086..1302e9612a 100644
--- a/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/records/KoutRecords.java
+++ b/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/records/KoutRecords.java
@@ -27,7 +27,7 @@
 import com.baidu.hugegraph.traversal.algorithm.HugeTraverser.PathSet;
 import com.baidu.hugegraph.traversal.algorithm.records.record.IntIterator;
 import com.baidu.hugegraph.traversal.algorithm.records.record.RecordType;
-import com.baidu.hugegraph.type.define.CollectionImplType;
+import com.baidu.hugegraph.type.define.CollectionType;
 import com.baidu.hugegraph.util.collection.CollectionFactory;
 
 public class KoutRecords extends SingleWayMultiPathsRecords {
@@ -44,7 +44,7 @@ public int size() {
 
     public Set<Id> ids(long limit) {
         IntIterator iterator = this.records.peek().keys();
-        Set<Id> ids = CollectionFactory.newIdSet(CollectionImplType.EC);
+        Set<Id> ids = CollectionFactory.newIdSet(CollectionType.EC);
         while ((limit == NO_LIMIT || limit-- > 0L) && iterator.hasNext()) {
             ids.add(this.id(iterator.next()));
         }
diff --git a/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/records/SingleWayMultiPathsRecords.java b/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/records/SingleWayMultiPathsRecords.java
index e9185d874f..2b53d9ed0c 100644
--- a/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/records/SingleWayMultiPathsRecords.java
+++ b/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/records/SingleWayMultiPathsRecords.java
@@ -41,7 +41,7 @@
 import com.baidu.hugegraph.traversal.algorithm.records.record.Record;
 import com.baidu.hugegraph.traversal.algorithm.records.record.RecordType;
 
-public class SingleWayMultiPathsRecords extends AbstractRecords {
+public abstract class SingleWayMultiPathsRecords extends AbstractRecords {
 
     protected final Stack<Record> records;
 
@@ -127,9 +127,7 @@ public void addPath(Id source, Id target) {
         this.accessedVertices.add(targetCode);
     }
 
-    public int size() {
-        return 0;
-    }
+    public abstract int size();
 
     public Path getPath(int target) {
         List<Id> ids = new ArrayList<>();
diff --git a/hugegraph-core/src/main/java/com/baidu/hugegraph/type/define/CollectionImplType.java b/hugegraph-core/src/main/java/com/baidu/hugegraph/type/define/CollectionType.java
similarity index 88%
rename from hugegraph-core/src/main/java/com/baidu/hugegraph/type/define/CollectionImplType.java
rename to hugegraph-core/src/main/java/com/baidu/hugegraph/type/define/CollectionType.java
index db2bcfc27e..0d02fbb517 100644
--- a/hugegraph-core/src/main/java/com/baidu/hugegraph/type/define/CollectionImplType.java
+++ b/hugegraph-core/src/main/java/com/baidu/hugegraph/type/define/CollectionType.java
@@ -19,7 +19,7 @@
 
 package com.baidu.hugegraph.type.define;
 
-public enum CollectionImplType implements SerialEnum {
+public enum CollectionType implements SerialEnum {
 
     // Java Collection Framework
     JCF(1, "jcf"),
@@ -34,10 +34,10 @@ public enum CollectionImplType implements SerialEnum {
     private final String name;
 
     static {
-        SerialEnum.register(CollectionImplType.class);
+        SerialEnum.register(CollectionType.class);
     }
 
-    CollectionImplType(int code, String name) {
+    CollectionType(int code, String name) {
         assert code < 256;
         this.code = (byte) code;
         this.name = name;
@@ -51,7 +51,7 @@ public String string() {
         return this.name;
     }
 
-    public static CollectionImplType fromCode(byte code) {
+    public static CollectionType fromCode(byte code) {
         switch (code) {
             case 1:
                 return JCF;
diff --git a/hugegraph-core/src/main/java/com/baidu/hugegraph/util/collection/CollectionFactory.java b/hugegraph-core/src/main/java/com/baidu/hugegraph/util/collection/CollectionFactory.java
index 54b928af69..f3aaaf1a62 100644
--- a/hugegraph-core/src/main/java/com/baidu/hugegraph/util/collection/CollectionFactory.java
+++ b/hugegraph-core/src/main/java/com/baidu/hugegraph/util/collection/CollectionFactory.java
@@ -35,7 +35,7 @@
 import org.eclipse.collections.impl.set.mutable.UnifiedSet;
 
 import com.baidu.hugegraph.backend.id.Id;
-import com.baidu.hugegraph.type.define.CollectionImplType;
+import com.baidu.hugegraph.type.define.CollectionType;
 import com.baidu.hugegraph.util.E;
 
 import it.unimi.dsi.fastutil.objects.Object2ObjectOpenHashMap;
@@ -44,13 +44,13 @@
 
 public class CollectionFactory {
 
-    private CollectionImplType type;
+    private CollectionType type;
 
     public CollectionFactory() {
-        this.type = CollectionImplType.EC;
+        this.type = CollectionType.EC;
     }
 
-    public CollectionFactory(CollectionImplType type) {
+    public CollectionFactory(CollectionType type) {
         this.type = type;
     }
 
@@ -66,7 +66,7 @@ public <V> List<V> newList(Collection<V> collection) {
         return newList(this.type, collection);
     }
 
-    public static <V> List<V> newList(CollectionImplType type) {
+    public static <V> List<V> newList(CollectionType type) {
         switch (type) {
             case EC:
                 return new FastList<>();
@@ -80,7 +80,7 @@ public static <V> List<V> newList(CollectionImplType type) {
         }
     }
 
-    public static <V> List<V> newList(CollectionImplType type,
+    public static <V> List<V> newList(CollectionType type,
                                       int initialCapacity) {
         switch (type) {
             case EC:
@@ -95,7 +95,7 @@ public static <V> List<V> newList(CollectionImplType type,
         }
     }
 
-    public static <V> List<V> newList(CollectionImplType type,
+    public static <V> List<V> newList(CollectionType type,
                                       Collection<V> collection) {
         switch (type) {
             case EC:
@@ -122,7 +122,7 @@ public <V> Set<V> newSet(Collection<V> collection) {
         return newSet(this.type, collection);
     }
 
-    public static <V> Set<V> newSet(CollectionImplType type) {
+    public static <V> Set<V> newSet(CollectionType type) {
         switch (type) {
             case EC:
                 return new UnifiedSet<>();
@@ -136,7 +136,7 @@ public static <V> Set<V> newSet(CollectionImplType type) {
         }
     }
 
-    public static <V> Set<V> newSet(CollectionImplType type,
+    public static <V> Set<V> newSet(CollectionType type,
                                     int initialCapacity) {
         switch (type) {
             case EC:
@@ -151,7 +151,7 @@ public static <V> Set<V> newSet(CollectionImplType type,
         }
     }
 
-    public static <V> Set<V> newSet(CollectionImplType type,
+    public static <V> Set<V> newSet(CollectionType type,
                                     Collection<V> collection) {
         switch (type) {
             case EC:
@@ -174,7 +174,11 @@ public <K, V> Map<K, V> newMap(int initialCapacity) {
         return newMap(this.type, initialCapacity);
     }
 
-    public static <K, V> Map<K, V> newMap(CollectionImplType type) {
+    public static <K, V> Map<K, V> newMap(CollectionType type) {
+        /*
+         * EC is faster 10%-20% than JCF, and it's more stable & less
+         * memory cost(size is bigger, EC is better).
+         */
         switch (type) {
             case EC:
                 return new UnifiedMap<>();
@@ -188,7 +192,7 @@ public static <K, V> Map<K, V> newMap(CollectionImplType type) {
         }
     }
 
-    public static <K, V> Map<K, V> newMap(CollectionImplType type,
+    public static <K, V> Map<K, V> newMap(CollectionType type,
                                           int initialCapacity) {
         switch (type) {
             case EC:
@@ -256,7 +260,7 @@ public Set<Id> newIdSet() {
         return newIdSet(this.type);
     }
 
-    public static Set<Id> newIdSet(CollectionImplType type) {
+    public static Set<Id> newIdSet(CollectionType type) {
         return new IdSet(type);
     }
 }
diff --git a/hugegraph-core/src/main/java/com/baidu/hugegraph/util/collection/IdSet.java b/hugegraph-core/src/main/java/com/baidu/hugegraph/util/collection/IdSet.java
index d1c38f429a..ea1860691c 100644
--- a/hugegraph-core/src/main/java/com/baidu/hugegraph/util/collection/IdSet.java
+++ b/hugegraph-core/src/main/java/com/baidu/hugegraph/util/collection/IdSet.java
@@ -31,7 +31,7 @@
 import com.baidu.hugegraph.backend.id.Id;
 import com.baidu.hugegraph.backend.id.IdGenerator;
 import com.baidu.hugegraph.iterator.ExtendableIterator;
-import com.baidu.hugegraph.type.define.CollectionImplType;
+import com.baidu.hugegraph.type.define.CollectionType;
 
 import it.unimi.dsi.fastutil.objects.ObjectOpenHashSet;
 
@@ -40,7 +40,7 @@ public class IdSet extends AbstractSet<Id> {
     private LongHashSet numberIds;
     private Set<Id> nonNumberIds;
 
-    public IdSet(CollectionImplType type) {
+    public IdSet(CollectionType type) {
         this.numberIds = new LongHashSet();
         switch (type) {
             case JCF: