fix: shell parameters are not counted correctly (#1178)

Due to the lack of "", the empty param is not considered a legal parameter

PS: After the modification, it seems there are at least five params. Should also adjust the logic in `hugegraph-server.sh`? Keep it unchanged now, maybe adjust them on master/0,11 branch is better.

Fix #1172

README.md

@@ -1,8 +1,8 @@
 # HugeGraph
 
 [![License](https://img.shields.io/badge/license-Apache%202-0E78BA.svg)](https://www.apache.org/licenses/LICENSE-2.0.html)
-[![Build Status](https://travis-ci.org/hugegraph/hugegraph.svg?branch=master)](https://travis-ci.org/hugegraph/hugegraph)
-[![codecov](https://codecov.io/gh/hugegraph/hugegraph/branch/master/graph/badge.svg)](https://codecov.io/gh/hugegraph/hugegraph)
+[![Build Status](https://travis-ci.org/hugegraph/hugegraph.svg?branch=release-0.10)](https://travis-ci.org/hugegraph/hugegraph)
+[![codecov](https://codecov.io/gh/hugegraph/hugegraph/branch/release-0.10/graph/badge.svg)](https://codecov.io/gh/hugegraph/hugegraph)
 
 HugeGraph is a fast-speed and highly-scalable [graph database](https://en.wikipedia.org/wiki/Graph_database). Billions of vertices and edges can be easily stored into and queried from HugeGraph due to its excellent OLTP ability. As compliance to [Apache TinkerPop 3](https://tinkerpop.apache.org/) framework, various complicated graph queries can be accomplished through [Gremlin](https://tinkerpop.apache.org/gremlin.html)(a powerful graph traversal language).
 

hugegraph-api/src/main/java/com/baidu/hugegraph/api/API.java

@@ -39,9 +39,9 @@ import com.baidu.hugegraph.metrics.MetricsUtil;
 import com.baidu.hugegraph.server.RestServer;
 import com.baidu.hugegraph.type.HugeType;
 import com.baidu.hugegraph.util.E;
+import com.baidu.hugegraph.util.JsonUtil;
 import com.baidu.hugegraph.util.Log;
 import com.codahale.metrics.Meter;
-import com.fasterxml.jackson.databind.ObjectMapper;
 import com.google.common.collect.ImmutableMap;
 
 public class API {
@@ -172,13 +172,15 @@ public class API {
         if (properties == null || properties.isEmpty()) {
             return ImmutableMap.of();
         }
-        ObjectMapper mapper = new ObjectMapper();
+
         Map<String, Object> props = null;
         try {
-            props = mapper.readValue(properties, Map.class);
+            props = JsonUtil.fromJson(properties, Map.class);
         } catch (Exception ignored) {}
+
         // If properties is the string "null", props will be null
-        E.checkArgument(props != null, "Invalid request with none properties");
+        E.checkArgument(props != null,
+                        "Invalid request with properties: %s", properties);
         return props;
     }
 

hugegraph-api/src/main/java/com/baidu/hugegraph/api/graph/EdgeAPI.java

@@ -276,13 +276,9 @@ public class EdgeAPI extends BatchAPI {
 
         Map<String, Object> props = parseProperties(properties);
         if (page != null) {
-            E.checkArgument(vertexId == null && direction == null &&
-                            offset == 0,
+            E.checkArgument(offset == 0,
                             "Not support querying edges based on paging " +
-                            "and [vertex, direction, offset] together");
-            E.checkArgument(props.size() <= 1,
-                            "Not support querying edges based on paging " +
-                            "and more than one property");
+                            "and offset together");
         }
 
         Id vertex = VertexAPI.checkAndParseVertexId(vertexId);

hugegraph-api/src/main/java/com/baidu/hugegraph/api/graph/VertexAPI.java

@@ -230,9 +230,6 @@ public class VertexAPI extends BatchAPI {
             E.checkArgument(offset == 0,
                             "Not support querying vertices based on paging " +
                             "and offset together");
-            E.checkArgument(props.size() <= 1,
-                            "Not support querying vertices based on paging " +
-                            "and more than one property");
         }
 
         HugeGraph g = graph(manager, graph);

hugegraph-cassandra/src/main/java/com/baidu/hugegraph/backend/store/cassandra/CassandraSessionPool.java

@@ -209,21 +209,27 @@ public class CassandraSessionPool extends BackendSessionPool {
             } catch (InvalidQueryException ignored) {}
         }
 
+        @Override
         public void open() {
             assert this.session == null;
             this.session = cluster().connect(keyspace());
+            this.opened = true;
         }
 
+        @Override
         public boolean opened() {
-            return this.session != null;
+            if (this.opened && this.session == null) {
+                this.tryOpen();
+            }
+            return this.opened && this.session != null;
         }
 
         @Override
         public boolean closed() {
-            if (this.session == null) {
-                this.tryOpen();
+            if (!this.opened || this.session == null) {
+                return true;
             }
-            return this.session == null ? true : this.session.isClosed();
+            return this.session.isClosed();
         }
 
         @Override
@@ -233,6 +239,7 @@ public class CassandraSessionPool extends BackendSessionPool {
                 return;
             }
             this.session.close();
+            this.session = null;
         }
 
         @Override

hugegraph-cassandra/src/main/java/com/baidu/hugegraph/backend/store/cassandra/CassandraStore.java

@@ -123,7 +123,8 @@ public abstract class CassandraStore
                                                      this.store);
         }
 
-        if (this.sessions.opened()) {
+        assert this.sessions != null;
+        if (!this.sessions.closed()) {
             // TODO: maybe we should throw an exception here instead of ignore
             LOG.debug("Store {} has been opened before", this.store);
             this.sessions.useSession();
@@ -169,7 +170,7 @@ public abstract class CassandraStore
     @Override
     public boolean opened() {
         this.checkClusterConnected();
-        return !this.sessions.session().closed();
+        return this.sessions.session().opened();
     }
 
     @Override
@@ -259,15 +260,16 @@ public abstract class CassandraStore
     public void init() {
         this.checkClusterConnected();
 
+        // Create keyspace if needed
+        if (!this.existsKeyspace()) {
+            this.initKeyspace();
+        }
+
         if (this.sessions.session().opened()) {
             // Session has ever been opened.
             LOG.warn("Session has ever been opened(exist keyspace '{}' before)",
                      this.keyspace);
         } else {
-            // Create keyspace if needed
-            if (!this.existsKeyspace()) {
-                this.initKeyspace();
-            }
             // Open session explicitly to get the exception when it fails
             this.sessions.session().open();
         }
@@ -280,13 +282,16 @@ public abstract class CassandraStore
     }
 
     @Override
-    public void clear() {
+    public void clear(boolean clearSpace) {
         this.checkClusterConnected();
 
         if (this.existsKeyspace()) {
-            this.checkOpened();
-            this.clearTables();
-            this.clearKeyspace();
+            if (!clearSpace) {
+                this.checkOpened();
+                this.clearTables();
+            } else {
+                this.clearKeyspace();
+            }
         }
 
         LOG.debug("Store cleared: {}", this.store);

hugegraph-cassandra/src/main/java/com/baidu/hugegraph/backend/store/cassandra/CassandraTable.java

@@ -96,7 +96,7 @@ public abstract class CassandraTable
                                         Query query) {
         ExtendableIterator<BackendEntry> rs = new ExtendableIterator<>();
 
-        if (query.limit() == 0 && query.limit() != Query.NO_LIMIT) {
+        if (query.limit() == 0L && !query.nolimit()) {
             LOG.debug("Return empty result(limit=0) for query {}", query);
             return rs;
         }
@@ -159,7 +159,7 @@ public abstract class CassandraTable
     }
 
     protected void setPageState(Query query, List<Select> selects) {
-        if (query.limit() == Query.NO_LIMIT) {
+        if (query.nolimit()) {
             return;
         }
         for (Select select : selects) {

hugegraph-core/src/main/java/com/baidu/hugegraph/backend/cache/CachedBackendStore.java

@@ -82,8 +82,8 @@ public class CachedBackendStore implements BackendStore {
     }
 
     @Override
-    public void clear() {
-        this.store.clear();
+    public void clear(boolean clearSpace) {
+        this.store.clear(clearSpace);
     }
 
     @Override

hugegraph-core/src/main/java/com/baidu/hugegraph/backend/page/IdHolderList.java

@@ -26,18 +26,42 @@ import com.baidu.hugegraph.util.E;
 
 public class IdHolderList extends ArrayList<IdHolder> {
 
+    private static final IdHolderList EMPTY_P = new IdHolderList(true);
+    private static final IdHolderList EMPTY_NP = new IdHolderList(false);
+
     private static final long serialVersionUID = -738694176552424990L;
 
     private final boolean paging;
+    private final boolean needSkipOffset;
+
+    public static IdHolderList empty(boolean paging) {
+        IdHolderList empty = paging ? EMPTY_P : EMPTY_NP;
+        empty.clear();
+        return empty;
+    }
 
     public IdHolderList(boolean paging) {
+        this(paging, true);
+    }
+
+    public IdHolderList(boolean paging, boolean needSkipOffset) {
         this.paging = paging;
+        this.needSkipOffset = needSkipOffset;
     }
 
     public boolean paging() {
         return this.paging;
     }
 
+    public boolean needSkipOffset() {
+        return this.needSkipOffset;
+    }
+
+    public boolean sameParameters(IdHolderList other) {
+        return this.paging == other.paging &&
+               this.needSkipOffset == other.needSkipOffset;
+    }
+
     @Override
     public boolean add(IdHolder holder) {
         E.checkArgument(this.paging == holder.paging(),

hugegraph-core/src/main/java/com/baidu/hugegraph/backend/page/QueryList.java

@@ -62,11 +62,12 @@ public final class QueryList {
         return this.fetcher;
     }
 
-    public void add(List<IdHolder> holders) {
+    public void add(IdHolderList holders) {
+        // IdHolderList is results of one index query, the query is flattened
         if (!this.parent.paging()) {
             for (QueryHolder q : this.queries) {
                 if (q instanceof IndexQuery) {
-                    ((IndexQuery) q).holders.addAll(holders);
+                    ((IndexQuery) q).merge(holders);
                     return;
                 }
             }
@@ -124,7 +125,6 @@ public final class QueryList {
         return query.iterator(offset - current, pageInfo.page(), pageSize);
     }
 
-    @SuppressWarnings("unused")
     private static Set<Id> limit(Set<Id> ids, Query query) {
         long fromIndex = query.offset();
         E.checkArgument(fromIndex <= Integer.MAX_VALUE,
@@ -134,11 +134,11 @@ public final class QueryList {
         if (query.offset() >= ids.size()) {
             return ImmutableSet.of();
         }
-        if (query.limit() == Query.NO_LIMIT && query.offset() == 0) {
+        if (query.nolimit() && query.offset() == 0) {
             return ids;
         }
-        long toIndex = query.offset() + query.limit();
-        if (query.limit() == Query.NO_LIMIT || toIndex > ids.size()) {
+        long toIndex = query.total();
+        if (query.nolimit() || toIndex > ids.size()) {
             toIndex = ids.size();
         }
         assert fromIndex < ids.size();
@@ -191,14 +191,13 @@ public final class QueryList {
             Query query = this.query.copy();
             query.page(page);
             // Not set limit to pageSize due to PageEntryIterator.remaining
-            if (this.query.limit() == Query.NO_LIMIT) {
+            if (this.query.nolimit()) {
                 query.limit(pageSize);
             }
-            QueryResults results = fetcher().apply(query);
+            QueryResults rs = fetcher().apply(query);
             // Must iterate all entries before get the next page
-            return new PageIterator(results.list().iterator(),
-                                    results.queries(),
-                                    PageInfo.pageState(results.iterator()));
+            return new PageIterator(rs.list().iterator(), rs.queries(),
+                                    PageInfo.pageState(rs.iterator()));
         }
 
         @Override
@@ -212,11 +211,21 @@ public final class QueryList {
      */
     private class IndexQuery implements QueryHolder {
 
-        // Actual is an instance of IdHolderList
-        private final List<IdHolder> holders;
+        // An IdHolder each sub-query
+        private final IdHolderList holders;
+        // To skip the offset in parent query
+        private long offsetToSkip;
 
-        public IndexQuery(List<IdHolder> holders) {
+        public IndexQuery(IdHolderList holders) {
             this.holders = holders;
+            this.offsetToSkip = this.holders.needSkipOffset() ?
+                                parent().offset() : -1L;
+        }
+
+        public void merge(IdHolderList holders) {
+            E.checkState(holders.sameParameters(this.holders),
+                         "Can't merge IdHolderList with different parameters");
+            this.holders.addAll(holders);
         }
 
         @Override
@@ -229,18 +238,23 @@ public final class QueryList {
 
         private QueryResults each(IdHolder holder) {
             Set<Id> ids = holder.ids();
-            if (ids.isEmpty()) {
-                return null;
-            }
-            if (parent().limit() != Query.NO_LIMIT &&
-                ids.size() > parent().limit()) {
+            Query parent = parent();
+            if (this.offsetToSkip > 0L) {
+                // Skip offset when needed
+                this.offsetToSkip -= ids.size();
+                ids = limit(ids, parent);
+            } else if (!parent.nolimit() && ids.size() > parent.total()) {
                 /*
                  * Avoid too many ids in one time query,
                  * Assume it will get one result by each id
                  */
-                ids = CollectionUtil.subSet(ids, 0, (int) parent().limit());
+                ids = CollectionUtil.subSet(ids, 0, (int) parent.total());
             }
-            IdQuery query = new IdQuery(parent(), ids);
+
+            if (ids.isEmpty()) {
+                return null;
+            }
+            IdQuery query = new IdQuery(parent, ids);
             return fetcher().apply(query);
         }
 
@@ -252,8 +266,8 @@ public final class QueryList {
                 return PageIterator.EMPTY;
             }
             IdQuery query = new IdQuery(parent(), pageIds.ids());
-            QueryResults results = fetcher().apply(query);
-            return new PageIterator(results.iterator(), results.queries(),
+            QueryResults rs = fetcher().apply(query);
+            return new PageIterator(rs.iterator(), rs.queries(),
                                     pageIds.pageState());
         }
 

hugegraph-core/src/main/java/com/baidu/hugegraph/backend/query/Query.java

@@ -156,6 +156,10 @@ public class Query implements Cloneable {
         this.limit = limit;
     }
 
+    public boolean nolimit() {
+        return this.limit() == NO_LIMIT;
+    }
+
     public boolean reachLimit(long count) {
         long limit = this.limit();
         if (limit == NO_LIMIT) {
@@ -170,7 +174,7 @@ public class Query implements Cloneable {
      * @param start the range start, include it
      * @param end   the range end, exclude it
      */
-    public void range(long start, long end) {
+    public long range(long start, long end) {
         // Update offset
         long offset = this.offset();
         start = Math.max(start, offset);
@@ -178,7 +182,7 @@ public class Query implements Cloneable {
 
         // Update limit
         if (end != -1L) {
-            if (this.limit() != Query.NO_LIMIT) {
+            if (!this.nolimit()) {
                 end = Math.min(end, offset + this.limit());
             } else {
                 assert end < Query.NO_LIMIT;
@@ -190,6 +194,7 @@ public class Query implements Cloneable {
             // Keep the origin limit
             assert this.limit() <= Query.NO_LIMIT;
         }
+        return this.limit;
     }
 
     public String page() {

hugegraph-core/src/main/java/com/baidu/hugegraph/backend/query/QueryResults.java

@@ -178,8 +178,8 @@ public class QueryResults {
         return (Iterator<T>) EMPTY_ITERATOR;
     }
 
-    private static class EmptyIterator<T> implements Iterator<T>,
-                                                     Metadatable {
+    private static class EmptyIterator<T> implements Iterator<T>, Metadatable {
+
         @Override
         public Object metadata(String meta, Object... args) {
             return null;

hugegraph-core/src/main/java/com/baidu/hugegraph/backend/store/AbstractBackendStoreProvider.java

@@ -112,7 +112,12 @@ public abstract class AbstractBackendStoreProvider
     public void clear() throws BackendException {
         this.checkOpened();
         for (BackendStore store : this.stores.values()) {
-            store.clear();
+            // Just clear tables of store, not clear space
+            store.clear(false);
+        }
+        for (BackendStore store : this.stores.values()) {
+            // Only clear space of store
+            store.clear(true);
         }
         this.notifyAndWaitEvent(Events.STORE_CLEAR);
 

hugegraph-core/src/main/java/com/baidu/hugegraph/backend/store/BackendSession.java

@@ -26,12 +26,14 @@ import com.baidu.hugegraph.backend.store.BackendStore.TxState;
  */
 public abstract class BackendSession {
 
+    protected boolean opened;
     private int refs;
     private TxState txState;
     private final long created;
     private long updated;
 
     public BackendSession() {
+        this.opened = true;
         this.refs = 1;
         this.txState = TxState.CLEAN;
         this.created = System.currentTimeMillis();
@@ -50,10 +52,9 @@ public abstract class BackendSession {
         this.updated = System.currentTimeMillis();
     }
 
+    public abstract void open();
     public abstract void close();
 
-    public abstract boolean closed();
-
     public abstract Object commit();
 
     public abstract void rollback();
@@ -64,6 +65,18 @@ public abstract class BackendSession {
         // pass
     }
 
+    protected void reset() {
+        // pass
+    }
+
+    public boolean opened() {
+        return this.opened;
+    }
+
+    public boolean closed() {
+        return !this.opened;
+    }
+
     protected int attach() {
         return ++this.refs;
     }

hugegraph-core/src/main/java/com/baidu/hugegraph/backend/store/BackendSessionPool.java

@@ -19,6 +19,8 @@
 
 package com.baidu.hugegraph.backend.store;
 
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicInteger;
 
@@ -37,12 +39,14 @@ public abstract class BackendSessionPool {
     private final String name;
     private final ThreadLocal<BackendSession> threadLocalSession;
     private final AtomicInteger sessionCount;
+    private final Map<Long, BackendSession> sessions;
 
     public BackendSessionPool(HugeConfig config, String name) {
         this.config = config;
         this.name = name;
         this.threadLocalSession = new ThreadLocal<>();
         this.sessionCount = new AtomicInteger(0);
+        this.sessions = new ConcurrentHashMap<>();
     }
 
     public HugeConfig config() {
@@ -55,6 +59,8 @@ public abstract class BackendSessionPool {
             session = this.newSession();
             assert session != null;
             this.threadLocalSession.set(session);
+            assert !this.sessions.containsKey(Thread.currentThread().getId());
+            this.sessions.put(Thread.currentThread().getId(), session);
             int sessionCount = this.sessionCount.incrementAndGet();
             LOG.debug("Now(after connect({})) session count is: {}",
                       this, sessionCount);
@@ -113,9 +119,18 @@ public abstract class BackendSessionPool {
             throw e;
         }
         this.threadLocalSession.remove();
+        assert this.sessions.containsKey(Thread.currentThread().getId());
+        this.sessions.remove(Thread.currentThread().getId());
+
         return Pair.of(this.sessionCount.decrementAndGet(), ref);
     }
 
+    protected void forceResetSessions() {
+        for (BackendSession session : this.sessions.values()) {
+            session.reset();
+        }
+    }
+
     public void close() {
         Pair<Integer, Integer> result = Pair.of(-1, -1);
         try {

hugegraph-core/src/main/java/com/baidu/hugegraph/backend/store/BackendStore.java

@@ -46,7 +46,7 @@ public interface BackendStore {
 
     // Initialize/clear database
     public void init();
-    public void clear();
+    public void clear(boolean clearSpace);
     public boolean initialized();
 
     // Delete all data of database (keep table structure)

hugegraph-core/src/main/java/com/baidu/hugegraph/backend/store/memory/InMemoryDBStore.java

@@ -177,7 +177,7 @@ public abstract class InMemoryDBStore
     }
 
     @Override
-    public void clear() {
+    public void clear(boolean clearSpace) {
         for (InMemoryDBTable table : this.tables()) {
             table.clear(null);
         }
@@ -263,9 +263,9 @@ public abstract class InMemoryDBStore
         }
 
         @Override
-        public void clear() {
+        public void clear(boolean clearSpace) {
             this.counter.reset();
-            super.clear();
+            super.clear(clearSpace);
         }
 
         @Override

hugegraph-core/src/main/java/com/baidu/hugegraph/backend/store/memory/InMemoryDBTable.java

@@ -147,8 +147,7 @@ public class InMemoryDBTable extends BackendTable<BackendSession,
         }
         iterator = this.skipOffset(iterator, query.offset());
 
-        if (query.limit() != Query.NO_LIMIT &&
-            query.offset() + query.limit() < rs.size()) {
+        if (!query.nolimit() && query.total() < rs.size()) {
             iterator = this.dropTails(iterator, query.limit());
         }
         return iterator;

hugegraph-core/src/main/java/com/baidu/hugegraph/backend/tx/AbstractTransaction.java

@@ -154,8 +154,7 @@ public abstract class AbstractTransaction implements Transaction {
         RateLimiter rateLimiter = this.graph.rateLimiter();
         if (rateLimiter != null) {
             int size = this.mutationSize();
-            assert size > 0;
-            double time = rateLimiter.acquire(size);
+            double time = size > 0 ? rateLimiter.acquire(size) : 0.0;
             if (time > 0) {
                 LOG.debug("Waited for {}s to mutate {} item(s)", time, size);
             }

hugegraph-core/src/main/java/com/baidu/hugegraph/backend/tx/GraphIndexTransaction.java

@@ -325,7 +325,7 @@ public class GraphIndexTransaction extends AbstractTransaction {
      * @return      converted id query
      */
     @Watched(prefix = "index")
-    public List<IdHolder> queryIndex(ConditionQuery query) {
+    public IdHolderList queryIndex(ConditionQuery query) {
         // Index query must have been flattened in Graph tx
         query.checkFlattened();
 
@@ -355,7 +355,7 @@ public class GraphIndexTransaction extends AbstractTransaction {
     }
 
     @Watched(prefix = "index")
-    private List<IdHolder> queryByLabel(ConditionQuery query) {
+    private IdHolderList queryByLabel(ConditionQuery query) {
         HugeType queryType = query.resultType();
         IndexLabel il = IndexLabel.label(queryType);
         Id label = query.condition(HugeKeys.LABEL);
@@ -390,13 +390,15 @@ public class GraphIndexTransaction extends AbstractTransaction {
         indexQuery.capacity(query.capacity());
 
         IdHolder idHolder = this.doIndexQuery(il, indexQuery);
-        List<IdHolder> holders = new IdHolderList(query.paging());
+
+        // NOTE: the backend itself will skip the offset
+        IdHolderList holders = new IdHolderList(query.paging(), false);
         holders.add(idHolder);
         return holders;
     }
 
     @Watched(prefix = "index")
-    private List<IdHolder> queryByUserprop(ConditionQuery query) {
+    private IdHolderList queryByUserprop(ConditionQuery query) {
         // Get user applied label or collect all qualified labels with
         // related index labels
         Set<MatchedIndex> indexes = this.collectMatchedIndexes(query);
@@ -406,12 +408,12 @@ public class GraphIndexTransaction extends AbstractTransaction {
         }
 
         // Value type of Condition not matched
+        boolean paging = query.paging();
         if (!validQueryConditionValues(this.graph(), query)) {
-            return ImmutableList.of();
+            return IdHolderList.empty(paging);
         }
 
         // Do index query
-        boolean paging = query.paging();
         IdHolderList holders = new IdHolderList(paging);
         long idsSize = 0;
         for (MatchedIndex index : indexes) {
@@ -430,6 +432,12 @@ public class GraphIndexTransaction extends AbstractTransaction {
                 holders.add(holder);
             }
 
+            /*
+             * Finish early if records exceeds required.
+             * NOTE: need to skip the offset if offset > 0, but can't handle
+             * it here because the query may a sub-query after flatten,
+             * so the offset will be handle in QueryList.IndexQuery
+             */
             idsSize += holders.idsSize();
             if (query.reachLimit(idsSize)) {
                 break;

hugegraph-core/src/main/java/com/baidu/hugegraph/backend/tx/GraphTransaction.java

@@ -45,7 +45,7 @@ import com.baidu.hugegraph.backend.BackendException;
 import com.baidu.hugegraph.backend.id.EdgeId;
 import com.baidu.hugegraph.backend.id.Id;
 import com.baidu.hugegraph.backend.id.SplicingIdGenerator;
-import com.baidu.hugegraph.backend.page.IdHolder;
+import com.baidu.hugegraph.backend.page.IdHolderList;
 import com.baidu.hugegraph.backend.page.PageInfo;
 import com.baidu.hugegraph.backend.page.QueryList;
 import com.baidu.hugegraph.backend.query.Condition;
@@ -553,8 +553,7 @@ public class GraphTransaction extends IndexableTransaction {
     }
 
     public Iterator<Vertex> queryVertices(Query query) {
-        E.checkArgument(this.removedVertices.isEmpty() ||
-                        query.limit() == Query.NO_LIMIT,
+        E.checkArgument(this.removedVertices.isEmpty() || query.nolimit(),
                         "It's not allowed to query with limit when " +
                         "there are uncommitted delete records.");
 
@@ -700,8 +699,7 @@ public class GraphTransaction extends IndexableTransaction {
     }
 
     public Iterator<Edge> queryEdges(Query query) {
-        E.checkArgument(this.removedEdges.isEmpty() ||
-                        query.limit() == Query.NO_LIMIT,
+        E.checkArgument(this.removedEdges.isEmpty() || query.nolimit(),
                         "It's not allowed to query with limit when " +
                         "there are uncommitted delete records.");
 
@@ -1103,7 +1101,7 @@ public class GraphTransaction extends IndexableTransaction {
         return null;
     }
 
-    private List<IdHolder> indexQuery(ConditionQuery query) {
+    private IdHolderList indexQuery(ConditionQuery query) {
         /*
          * Optimize by index-query
          * It will return a list of id (maybe empty) if success,

hugegraph-core/src/main/java/com/baidu/hugegraph/io/HugeGraphSONModule.java

@@ -409,6 +409,17 @@ public class HugeGraphSONModule extends TinkerPopJacksonModule {
 
             generator.writeEndObject();
         }
+
+        @Override
+        public void serializeWithType(HugeVertex value, JsonGenerator generator,
+                                      SerializerProvider provider,
+                                      TypeSerializer typeSer)
+                                      throws IOException {
+            WritableTypeId typeId = typeSer.typeId(value, JsonToken.VALUE_STRING);
+            typeSer.writeTypePrefix(generator, typeId);
+            this.serialize(value, generator, provider);
+            typeSer.writeTypeSuffix(generator, typeId);
+        }
     }
 
     private static class HugeEdgeSerializer
@@ -441,6 +452,17 @@ public class HugeGraphSONModule extends TinkerPopJacksonModule {
 
             generator.writeEndObject();
         }
+
+        @Override
+        public void serializeWithType(HugeEdge value, JsonGenerator generator,
+                                      SerializerProvider provider,
+                                      TypeSerializer typeSer)
+                                      throws IOException {
+            WritableTypeId typeId = typeSer.typeId(value, JsonToken.VALUE_STRING);
+            typeSer.writeTypePrefix(generator, typeId);
+            this.serialize(value, generator, provider);
+            typeSer.writeTypeSuffix(generator, typeId);
+        }
     }
 
     private static class ShardSerializer extends StdSerializer<Shard> {

hugegraph-core/src/main/java/com/baidu/hugegraph/plugin/HugeGraphGremlinPlugin.java

@@ -29,13 +29,14 @@ import org.apache.tinkerpop.gremlin.jsr223.DefaultImportCustomizer;
 import org.apache.tinkerpop.gremlin.jsr223.ImportCustomizer;
 
 import com.baidu.hugegraph.HugeException;
+import com.baidu.hugegraph.HugeFactory;
 import com.baidu.hugegraph.util.ReflectionUtil;
 import com.google.common.reflect.ClassPath;
 
 public class HugeGraphGremlinPlugin extends AbstractGremlinPlugin {
 
-    private static final String PACKAGE = "com.baidu.hugegraph";
-    private static final String NAME = "com.baidu.hugegraph";
+    private static final String PACKAGE = "com.baidu.hugegraph.type.define";
+    private static final String NAME = "HugeGraph";
 
     private static final HugeGraphGremlinPlugin instance;
     private static final ImportCustomizer imports;
@@ -54,6 +55,9 @@ public class HugeGraphGremlinPlugin extends AbstractGremlinPlugin {
         @SuppressWarnings("rawtypes")
         Set<Class> classes = new HashSet<>();
         classInfos.forEachRemaining(classInfo -> classes.add(classInfo.load()));
+        // Add entrance class: graph = HugeFactory.open("hugegraph.properties")
+        classes.add(HugeFactory.class);
+
         imports = DefaultImportCustomizer.build()
                                          .addClassImports(classes)
                                          .create();

hugegraph-core/src/main/java/com/baidu/hugegraph/security/HugeSecurityManager.java

@@ -22,12 +22,19 @@ package com.baidu.hugegraph.security;
 import java.io.FileDescriptor;
 import java.net.InetAddress;
 import java.security.Permission;
+import java.util.Map;
 import java.util.Set;
 
+import org.slf4j.Logger;
+
+import com.baidu.hugegraph.util.Log;
+import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableSet;
 
 public class HugeSecurityManager extends SecurityManager {
 
+    private static final String USER_DIR = System.getProperty("user.dir");
+
     private static final String GREMLIN_SERVER_WORKER = "gremlin-server-exec";
     private static final String TASK_WORKER = "task-worker";
     private static final Set<String> GREMLIN_EXECUTOR_CLASS = ImmutableSet.of(
@@ -42,7 +49,8 @@ public class HugeSecurityManager extends SecurityManager {
             "groovy.lang.GroovyClassLoader",
             "sun.reflect.DelegatingClassLoader",
             "org.codehaus.groovy.reflection.SunClassLoader",
-            "org.codehaus.groovy.runtime.callsite.CallSiteClassLoader"
+            "org.codehaus.groovy.runtime.callsite.CallSiteClassLoader",
+            "org.apache.hadoop.hbase.util.DynamicClassLoader"
     );
 
     private static final Set<String> CAFFEINE_CLASSES = ImmutableSet.of(
@@ -51,15 +59,49 @@ public class HugeSecurityManager extends SecurityManager {
 
     private static final Set<String> WHITE_SYSTEM_PROPERTYS = ImmutableSet.of(
             "line.separator",
-            "file.separator"
+            "file.separator",
+            "socksProxyHost", // MySQL
+            "file.encoding" // PostgreSQL
+    );
+
+    private static final Map<String, Set<String>> ASYNC_TASKS = ImmutableMap.of(
+            // Fixed https://github.com/hugegraph/hugegraph/pull/892#issue-387202362
+            "com.baidu.hugegraph.backend.tx.SchemaTransaction",
+            ImmutableSet.of("removeVertexLabel", "removeEdgeLabel",
+                            "removeIndexLabel", "rebuildIndex"),
+            "com.baidu.hugegraph.backend.tx.GraphIndexTransaction",
+            ImmutableSet.of("asyncRemoveIndexLeft")
+    );
+
+    private static final Map<String, Set<String>> BACKEND_SOCKET = ImmutableMap.of(
+            // Fixed #758
+            "com.baidu.hugegraph.backend.store.mysql.MysqlStore",
+            ImmutableSet.of("open", "init", "clear", "opened", "initialized")
+    );
+
+    private static final Map<String, Set<String>> BACKEND_THREAD = ImmutableMap.of(
+            // Fixed #758
+            "com.baidu.hugegraph.backend.store.cassandra.CassandraStore",
+            ImmutableSet.of("open", "opened", "init"),
+            // Fixed https://github.com/hugegraph/hugegraph/pull/892#issuecomment-598545072
+            "com.datastax.driver.core.AbstractSession",
+            ImmutableSet.of("execute")
+    );
+
+    private static final Set<String> HBASE_CLASSES = ImmutableSet.of(
+            // Fixed #758
+            "com.baidu.hugegraph.backend.store.hbase.HbaseStore",
+            "com.baidu.hugegraph.backend.store.hbase.HbaseStore$HbaseSchemaStore",
+            "com.baidu.hugegraph.backend.store.hbase.HbaseStore$HbaseGraphStore",
+            "com.baidu.hugegraph.backend.store.hbase.HbaseSessions$RowIterator"
     );
 
     @Override
     public void checkPermission(Permission permission) {
         if (DENIED_PERMISSIONS.contains(permission.getName()) &&
             callFromGremlin()) {
-            throw new SecurityException(
-                      "Not allowed to access denied permission via Gremlin");
+            throw newSecurityException(
+                  "Not allowed to access denied permission via Gremlin");
         }
     }
 
@@ -67,16 +109,16 @@ public class HugeSecurityManager extends SecurityManager {
     public void checkPermission(Permission permission, Object context) {
         if (DENIED_PERMISSIONS.contains(permission.getName()) &&
             callFromGremlin()) {
-            throw new SecurityException(
-                      "Not allowed to access denied permission via Gremlin");
+            throw newSecurityException(
+                  "Not allowed to access denied permission via Gremlin");
         }
     }
 
     @Override
     public void checkCreateClassLoader() {
         if (!callFromAcceptClassLoaders() && callFromGremlin()) {
-            throw new SecurityException(
-                      "Not allowed to create class loader via Gremlin");
+            throw newSecurityException(
+                  "Not allowed to create class loader via Gremlin");
         }
         super.checkCreateClassLoader();
     }
@@ -84,26 +126,30 @@ public class HugeSecurityManager extends SecurityManager {
     @Override
     public void checkLink(String lib) {
         if (callFromGremlin()) {
-            throw new SecurityException(
-                      "Not allowed to link library via Gremlin");
+            throw newSecurityException(
+                  "Not allowed to link library via Gremlin");
         }
         super.checkLink(lib);
     }
 
     @Override
     public void checkAccess(Thread thread) {
-        if (callFromGremlin() && !callFromCaffeine()) {
-            throw new SecurityException(
-                      "Not allowed to access thread via Gremlin");
+        if (callFromGremlin() && !callFromCaffeine() &&
+            !callFromAsyncTasks() && !callFromEventHubNotify() &&
+            !callFromBackendThread() && !callFromBackendHbase()) {
+            throw newSecurityException(
+                  "Not allowed to access thread via Gremlin");
         }
         super.checkAccess(thread);
     }
 
     @Override
     public void checkAccess(ThreadGroup threadGroup) {
-        if (callFromGremlin() && !callFromCaffeine()) {
-            throw new SecurityException(
-                      "Not allowed to access thread group via Gremlin");
+        if (callFromGremlin() && !callFromCaffeine() &&
+            !callFromAsyncTasks() && !callFromEventHubNotify() &&
+            !callFromBackendThread() && !callFromBackendHbase()) {
+            throw newSecurityException(
+                  "Not allowed to access thread group via Gremlin");
         }
         super.checkAccess(threadGroup);
     }
@@ -111,8 +157,8 @@ public class HugeSecurityManager extends SecurityManager {
     @Override
     public void checkExit(int status) {
         if (callFromGremlin()) {
-            throw new SecurityException(
-                      "Not allowed to call System.exit() via Gremlin");
+            throw newSecurityException(
+                  "Not allowed to call System.exit() via Gremlin");
         }
         super.checkExit(status);
     }
@@ -120,24 +166,26 @@ public class HugeSecurityManager extends SecurityManager {
     @Override
     public void checkExec(String cmd) {
         if (callFromGremlin()) {
-            throw new SecurityException(
-                      "Not allowed to execute command via Gremlin");
+            throw newSecurityException(
+                  "Not allowed to execute command via Gremlin");
         }
         super.checkExec(cmd);
     }
 
     @Override
     public void checkRead(FileDescriptor fd) {
-        if (callFromGremlin()) {
-            throw new SecurityException("Not allowed to read fd via Gremlin");
+        if (callFromGremlin() && !callFromBackendSocket()) {
+            throw newSecurityException("Not allowed to read fd via Gremlin");
         }
         super.checkRead(fd);
     }
 
     @Override
     public void checkRead(String file) {
-        if (callFromGremlin() && !callFromCaffeine()) {
-            throw new SecurityException("Not allowed to read file via Gremlin");
+        if (callFromGremlin() && !callFromCaffeine() &&
+            !readGroovyInCurrentDir(file) && !callFromBackendHbase()) {
+            throw newSecurityException(
+                  "Not allowed to read file via Gremlin: %s", file);
         }
         super.checkRead(file);
     }
@@ -145,15 +193,16 @@ public class HugeSecurityManager extends SecurityManager {
     @Override
     public void checkRead(String file, Object context) {
         if (callFromGremlin()) {
-            throw new SecurityException("Not allowed to read file via Gremlin");
+            throw newSecurityException(
+                  "Not allowed to read file via Gremlin: %s", file);
         }
         super.checkRead(file, context);
     }
 
     @Override
     public void checkWrite(FileDescriptor fd) {
-        if (callFromGremlin()) {
-            throw new SecurityException("Not allowed to write fd via Gremlin");
+        if (callFromGremlin() && !callFromBackendSocket()) {
+            throw newSecurityException("Not allowed to write fd via Gremlin");
         }
         super.checkWrite(fd);
     }
@@ -161,8 +210,7 @@ public class HugeSecurityManager extends SecurityManager {
     @Override
     public void checkWrite(String file) {
         if (callFromGremlin()) {
-            throw new SecurityException(
-                      "Not allowed to write file via Gremlin");
+            throw newSecurityException("Not allowed to write file via Gremlin");
         }
         super.checkWrite(file);
     }
@@ -170,8 +218,8 @@ public class HugeSecurityManager extends SecurityManager {
     @Override
     public void checkDelete(String file) {
         if (callFromGremlin()) {
-            throw new SecurityException(
-                      "Not allowed to delete file via Gremlin");
+            throw newSecurityException(
+                  "Not allowed to delete file via Gremlin");
         }
         super.checkDelete(file);
     }
@@ -179,8 +227,8 @@ public class HugeSecurityManager extends SecurityManager {
     @Override
     public void checkListen(int port) {
         if (callFromGremlin()) {
-            throw new SecurityException(
-                      "Not allowed to listen socket via Gremlin");
+            throw newSecurityException(
+                  "Not allowed to listen socket via Gremlin");
         }
         super.checkListen(port);
     }
@@ -188,17 +236,18 @@ public class HugeSecurityManager extends SecurityManager {
     @Override
     public void checkAccept(String host, int port) {
         if (callFromGremlin()) {
-            throw new SecurityException(
-                      "Not allowed to accept socket via Gremlin");
+            throw newSecurityException(
+                  "Not allowed to accept socket via Gremlin");
         }
         super.checkAccept(host, port);
     }
 
     @Override
     public void checkConnect(String host, int port) {
-        if (callFromGremlin()) {
-            throw new SecurityException(
-                      "Not allowed to connect socket via Gremlin");
+        if (callFromGremlin() && !callFromBackendSocket() &&
+            !callFromBackendHbase()) {
+            throw newSecurityException(
+                  "Not allowed to connect socket via Gremlin");
         }
         super.checkConnect(host, port);
     }
@@ -206,8 +255,8 @@ public class HugeSecurityManager extends SecurityManager {
     @Override
     public void checkConnect(String host, int port, Object context) {
         if (callFromGremlin()) {
-            throw new SecurityException(
-                      "Not allowed to connect socket via Gremlin");
+            throw newSecurityException(
+                  "Not allowed to connect socket via Gremlin");
         }
         super.checkConnect(host, port, context);
     }
@@ -215,7 +264,7 @@ public class HugeSecurityManager extends SecurityManager {
     @Override
     public void checkMulticast(InetAddress maddr) {
         if (callFromGremlin()) {
-            throw new SecurityException("Not allowed to multicast via Gremlin");
+            throw newSecurityException("Not allowed to multicast via Gremlin");
         }
         super.checkMulticast(maddr);
     }
@@ -224,7 +273,7 @@ public class HugeSecurityManager extends SecurityManager {
     @SuppressWarnings("deprecation")
     public void checkMulticast(InetAddress maddr, byte ttl) {
         if (callFromGremlin()) {
-            throw new SecurityException("Not allowed to multicast via Gremlin");
+            throw newSecurityException("Not allowed to multicast via Gremlin");
         }
         super.checkMulticast(maddr, ttl);
     }
@@ -232,8 +281,8 @@ public class HugeSecurityManager extends SecurityManager {
     @Override
     public void checkSetFactory() {
         if (callFromGremlin()) {
-            throw new SecurityException(
-                      "Not allowed to set socket factory via Gremlin");
+            throw newSecurityException(
+                  "Not allowed to set socket factory via Gremlin");
         }
         super.checkSetFactory();
     }
@@ -241,8 +290,8 @@ public class HugeSecurityManager extends SecurityManager {
     @Override
     public void checkPropertiesAccess() {
         if (callFromGremlin()) {
-            throw new SecurityException(
-                      "Not allowed to access system properties via Gremlin");
+            throw newSecurityException(
+                  "Not allowed to access system properties via Gremlin");
         }
         super.checkPropertiesAccess();
     }
@@ -250,10 +299,9 @@ public class HugeSecurityManager extends SecurityManager {
     @Override
     public void checkPropertyAccess(String key) {
         if (!callFromAcceptClassLoaders() && callFromGremlin() &&
-            !WHITE_SYSTEM_PROPERTYS.contains(key)) {
-            throw new SecurityException(String.format(
-                      "Not allowed to access system property(%s) via Gremlin",
-                      key));
+            !WHITE_SYSTEM_PROPERTYS.contains(key) && !callFromBackendHbase()) {
+            throw newSecurityException(
+                  "Not allowed to access system property(%s) via Gremlin", key);
         }
         super.checkPropertyAccess(key);
     }
@@ -261,7 +309,7 @@ public class HugeSecurityManager extends SecurityManager {
     @Override
     public void checkPrintJobAccess() {
         if (callFromGremlin()) {
-            throw new SecurityException("Not allowed to print job via Gremlin");
+            throw newSecurityException("Not allowed to print job via Gremlin");
         }
         super.checkPrintJobAccess();
     }
@@ -270,8 +318,8 @@ public class HugeSecurityManager extends SecurityManager {
     @SuppressWarnings("deprecation")
     public void checkSystemClipboardAccess() {
         if (callFromGremlin()) {
-            throw new SecurityException(
-                      "Not allowed to access system clipboard via Gremlin");
+            throw newSecurityException(
+                  "Not allowed to access system clipboard via Gremlin");
         }
         super.checkSystemClipboardAccess();
     }
@@ -309,6 +357,29 @@ public class HugeSecurityManager extends SecurityManager {
         super.checkAwtEventQueueAccess();
     }
 
+    private static SecurityException newSecurityException(String message,
+                                                          Object... args) {
+        if (args.length > 0) {
+            message = String.format(message, args);
+        }
+        /*
+         * use dynamic logger here because "static final logger" can't be
+         * initialized: the logger is not initialized when HugeSecurityManager
+         * class is loaded
+         */
+        Logger log = Log.logger(HugeSecurityManager.class);
+        log.warn("SecurityException: {}", message);
+        return new SecurityException(message);
+    }
+
+    private static boolean readGroovyInCurrentDir(String file) {
+        if (USER_DIR != null && file != null && file.startsWith(USER_DIR)
+            && (file.endsWith(".class") || file.endsWith(".groovy"))) {
+            return true;
+        }
+        return false;
+    }
+
     private static boolean callFromGremlin() {
         return callFromWorkerWithClass(GREMLIN_EXECUTOR_CLASS);
     }
@@ -321,6 +392,32 @@ public class HugeSecurityManager extends SecurityManager {
         return callFromWorkerWithClass(CAFFEINE_CLASSES);
     }
 
+    private static boolean callFromBackendSocket() {
+        // Fixed issue #758
+        return callFromMethods(BACKEND_SOCKET);
+    }
+
+    private static boolean callFromBackendThread() {
+        // Fixed issue #758
+        return callFromMethods(BACKEND_THREAD);
+    }
+
+    private static boolean callFromEventHubNotify() {
+        // Fixed issue #758
+        // notify() will create thread when submit task to executor
+        return callFromMethod("com.baidu.hugegraph.event.EventHub", "notify");
+    }
+
+    private static boolean callFromAsyncTasks() {
+        // Async tasks will create thread when submitted to executor
+        return callFromMethods(ASYNC_TASKS);
+    }
+
+    private static boolean callFromBackendHbase() {
+        // TODO: remove this unsafe entrance
+        return callFromWorkerWithClass(HBASE_CLASSES);
+    }
+
     private static boolean callFromWorkerWithClass(Set<String> classes) {
         Thread curThread = Thread.currentThread();
         if (curThread.getName().startsWith(GREMLIN_SERVER_WORKER) ||
@@ -336,7 +433,19 @@ public class HugeSecurityManager extends SecurityManager {
         return false;
     }
 
-    @SuppressWarnings("unused")
+    private static boolean callFromMethods(Map<String, Set<String>> methods) {
+        Thread curThread = Thread.currentThread();
+        StackTraceElement[] elements = curThread.getStackTrace();
+        for (StackTraceElement element : elements) {
+            Set<String> clazzMethods = methods.get(element.getClassName());
+            if (clazzMethods != null &&
+                clazzMethods.contains(element.getMethodName())) {
+                return true;
+            }
+        }
+        return false;
+    }
+
     private static boolean callFromMethod(String clazz, String method) {
         Thread curThread = Thread.currentThread();
         StackTraceElement[] elements = curThread.getStackTrace();

hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/optimize/HugeGraphStep.java

@@ -50,7 +50,7 @@ public final class HugeGraphStep<S, E extends Element>
     // Store limit/order-by
     private final Query queryInfo = new Query(HugeType.UNKNOWN);
 
-    private Iterator<E> lastTimeResults = null;
+    private Iterator<E> lastTimeResults = QueryResults.emptyIterator();
 
     public HugeGraphStep(final GraphStep<S, E> originGraphStep) {
         super(originGraphStep.getTraversal(),

hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/optimize/HugeVertexStep.java

@@ -38,6 +38,7 @@ import com.baidu.hugegraph.HugeGraph;
 import com.baidu.hugegraph.backend.id.Id;
 import com.baidu.hugegraph.backend.query.ConditionQuery;
 import com.baidu.hugegraph.backend.query.Query;
+import com.baidu.hugegraph.backend.query.QueryResults;
 import com.baidu.hugegraph.backend.tx.GraphTransaction;
 import com.baidu.hugegraph.type.define.Directions;
 import com.baidu.hugegraph.util.Log;
@@ -54,7 +55,7 @@ public final class HugeVertexStep<E extends Element>
     // Store limit/order-by
     private final Query queryInfo = new Query(null);
 
-    private Iterator<E> lastTimeResults = null;
+    private Iterator<E> lastTimeResults = QueryResults.emptyIterator();
 
     public HugeVertexStep(final VertexStep<E> originVertexStep) {
         super(originVertexStep.getTraversal(),

hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/optimize/QueryHolder.java

@@ -50,8 +50,7 @@ public interface QueryHolder extends HasContainerHolder, Metadatable {
     }
 
     public default long setRange(long start, long end) {
-        this.queryInfo().range(start, end);
-        return this.queryInfo().limit();
+        return this.queryInfo().range(start, end);
     }
 
     public default void setPage(String page) {

hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/optimize/TraversalUtil.java

@@ -570,9 +570,9 @@ public final class TraversalUtil {
     private static <V> V validPredicateValue(V value, PropertyKey pkey) {
         V validValue = pkey.convValue(value, false);
         E.checkArgumentNotNull(validValue,
-                               "Invalid data type of query value, " +
-                               "expect '%s', actual '%s'",
-                               pkey.dataType().clazz(),
+                               "Invalid data type of query value '%s', " +
+                               "expect '%s' for '%s', actual '%s'",
+                               value, pkey.dataType().clazz(), pkey.name(),
                                value == null ? null : value.getClass());
         return validValue;
     }

hugegraph-dist/src/assembly/static/bin/start-hugegraph.sh

@@ -57,10 +57,10 @@ check_port "$REST_SERVER_URL"
 echo "Starting HugeGraphServer..."
 if [ -n "$VERBOSE" ]; then
     "$BIN"/hugegraph-server.sh "$TOP"/conf/gremlin-server.yaml \
-    "$TOP"/conf/rest-server.properties "$OPEN_SECURITY_CHECK" $USER_OPTION $GC_OPTION &
+    "$TOP"/conf/rest-server.properties "$OPEN_SECURITY_CHECK" "$USER_OPTION" "$GC_OPTION" &
 else
     "$BIN"/hugegraph-server.sh "$TOP"/conf/gremlin-server.yaml \
-    "$TOP"/conf/rest-server.properties "$OPEN_SECURITY_CHECK" $USER_OPTION $GC_OPTION >/dev/null 2>&1 &
+    "$TOP"/conf/rest-server.properties "$OPEN_SECURITY_CHECK" "$USER_OPTION" "$GC_OPTION" >/dev/null 2>&1 &
 fi
 
 PID="$!"
@@ -69,7 +69,7 @@ echo "$PID" > $PID_FILE
 
 trap 'kill $PID; exit' SIGHUP SIGINT SIGQUIT SIGTERM
 
-wait_for_startup 'HugeGraphServer' "$REST_SERVER_URL/graphs" $SERVER_STARTUP_TIMEOUT_S || {
+wait_for_startup ${PID} 'HugeGraphServer' "$REST_SERVER_URL/graphs" ${SERVER_STARTUP_TIMEOUT_S} || {
     echo "See $TOP/logs/hugegraph-server.log for HugeGraphServer log output." >&2
     exit 1
 }

hugegraph-dist/src/assembly/static/bin/util.sh

@@ -107,9 +107,10 @@ function crontab_remove() {
 
 # wait_for_startup friendly_name host port timeout_s
 function wait_for_startup() {
-    local server_name="$1"
-    local server_url="$2"
-    local timeout_s="$3"
+    local pid="$1"
+    local server_name="$2"
+    local server_url="$3"
+    local timeout_s="$4"
 
     local now_s=`date '+%s'`
     local stop_s=$(( $now_s + $timeout_s ))
@@ -119,8 +120,14 @@ function wait_for_startup() {
     echo -n "Connecting to $server_name ($server_url)"
     while [ $now_s -le $stop_s ]; do
         echo -n .
+        process_status "$server_name" "$pid" >/dev/null
+        if [ $? -eq 1 ]; then
+            echo "Starting $server_name failed"
+            return 1
+        fi
+
         status=`curl -o /dev/null -s -w %{http_code} $server_url`
-        if [ $status -eq 200 ]; then
+        if [[ $status -eq 200 || $status -eq 401 ]]; then
             echo "OK"
             return 0
         fi

hugegraph-dist/src/assembly/static/conf/gremlin-driver-settings.yaml

@@ -1,8 +1,9 @@
 hosts: [localhost]
 port: 8182
 serializer: {
-  className: org.apache.tinkerpop.gremlin.driver.ser.GryoMessageSerializerV1d0,
+  className: org.apache.tinkerpop.gremlin.driver.ser.GraphSONMessageSerializerV1d0,
   config: {
-    serializeResultToString: false
+    serializeResultToString: false,
+    ioRegistries: [com.baidu.hugegraph.io.HugeGraphIoRegistry]
   }
 }

hugegraph-dist/src/assembly/static/conf/gremlin-server.yaml

@@ -1,4 +1,4 @@
-# host and port of gremlin server
+# host and port of gremlin server, need to be consistent with host and port in rest-server.properties
 #host: 127.0.0.1
 #port: 8182
 
@@ -31,12 +31,6 @@ scriptEngines: {
   }
 }
 serializers:
-  - { className: org.apache.tinkerpop.gremlin.driver.ser.GryoLiteMessageSerializerV1d0,
-      config: {
-        serializeResultToString: false,
-        ioRegistries: [com.baidu.hugegraph.io.HugeGraphIoRegistry]
-      }
-  }
   - { className: org.apache.tinkerpop.gremlin.driver.ser.GraphBinaryMessageSerializerV1,
       config: {
         serializeResultToString: false,

hugegraph-dist/src/assembly/static/conf/hugegraph.properties

@@ -21,6 +21,9 @@ serializer=binary
 
 store=hugegraph
 
+search.text_analyzer=jieba
+search.text_analyzer_mode=INDEX
+
 # rocksdb backend config
 #rocksdb.data_path=/path/to/disk
 #rocksdb.wal_path=/path/to/disk

hugegraph-dist/src/assembly/static/conf/remote-objects.yaml

@@ -1,3 +1,9 @@
 hosts: [localhost]
 port: 8182
-serializer: { className: org.apache.tinkerpop.gremlin.driver.ser.GryoMessageSerializerV1d0, config: { ioRegistries: [com.baidu.hugegraph.graphdb.tinkerpop.hugegraphIoRegistry] }}
+serializer: {
+  className: org.apache.tinkerpop.gremlin.driver.ser.GraphSONMessageSerializerV1d0,
+  config: {
+    serializeResultToString: false,
+    ioRegistries: [com.baidu.hugegraph.io.HugeGraphIoRegistry]
+  }
+}

hugegraph-dist/src/assembly/static/conf/remote.yaml

@@ -1,9 +1,9 @@
 hosts: [localhost]
 port: 8182
 serializer: {
-  className: org.apache.tinkerpop.gremlin.driver.ser.GryoMessageSerializerV1d0,
+  className: org.apache.tinkerpop.gremlin.driver.ser.GraphSONMessageSerializerV1d0,
   config: {
-    serializeResultToString: true,
+    serializeResultToString: false,
     ioRegistries: [com.baidu.hugegraph.io.HugeGraphIoRegistry]
   }
-}
+}

hugegraph-dist/src/assembly/static/conf/rest-server.properties

@@ -1,5 +1,7 @@
 # bind url
 restserver.url=http://127.0.0.1:8080
+# gremlin server url, need to be consistent with host and port in gremlin-server.yaml
+#gremlinserver.url=http://127.0.0.1:8182
 
 # graphs list with pair NAME:CONF_PATH
 graphs=[hugegraph:conf/hugegraph.properties]

hugegraph-dist/src/assembly/static/ext/plugins.txt

@@ -1,8 +1,4 @@
 com.baidu.hugegraph.plugin.HugeGraphGremlinPlugin
-org.apache.tinkerpop.gremlin.console.plugin.DriverGremlinPlugin
-org.apache.tinkerpop.gremlin.console.groovy.plugin.DriverGremlinPlugin
-org.apache.tinkerpop.gremlin.tinkergraph.groovy.plugin.TinkerGraphGremlinPlugin
-org.apache.tinkerpop.gremlin.hadoop.groovy.plugin.HadoopGremlinPlugin
-org.apache.tinkerpop.gremlin.giraph.groovy.plugin.GiraphGremlinPlugin
-org.apache.tinkerpop.gremlin.spark.groovy.plugin.SparkGremlinPlugin
-org.apache.tinkerpop.gremlin.console.groovy.plugin.UtilitiesGremlinPlugin
+org.apache.tinkerpop.gremlin.console.jsr223.DriverGremlinPlugin
+org.apache.tinkerpop.gremlin.console.jsr223.UtilitiesGremlinPlugin
+org.apache.tinkerpop.gremlin.tinkergraph.jsr223.TinkerGraphGremlinPlugin

hugegraph-dist/src/assembly/travis/install-backend.sh

@@ -4,6 +4,10 @@ set -ev
 
 TRAVIS_DIR=`dirname $0`
 
+if [ ! -d $HOME/downloads ]; then
+    mkdir $HOME/downloads
+fi
+
 if [[ "$BACKEND" == "cassandra" || "$BACKEND" == "scylladb" ]]; then
     $TRAVIS_DIR/install-cassandra.sh
 elif [ "$BACKEND" == "hbase" ]; then

hugegraph-dist/src/assembly/travis/run-api-test.sh

@@ -3,9 +3,11 @@
 set -ev
 
 TRAVIS_DIR=`dirname $0`
+VERSION=`mvn help:evaluate -Dexpression=project.version -q -DforceStdout`
+SERVER_DIR=hugegraph-$VERSION
 
 mvn package -DskipTests
-$TRAVIS_DIR/start-server.sh
-mvn test -P api-test,$BACKEND
+$TRAVIS_DIR/start-server.sh $SERVER_DIR
+mvn test -P api-test,$BACKEND || (cat $SERVER_DIR/logs/hugegraph-server.log && exit 1)
 $TRAVIS_DIR/build-report.sh
 $TRAVIS_DIR/stop-server.sh

hugegraph-dist/src/assembly/travis/start-server.sh

@@ -4,10 +4,11 @@ set -ev
 
 HOME_DIR=`pwd`
 TRAVIS_DIR=`dirname $0`
-VERSION=`mvn help:evaluate -Dexpression=project.version -q -DforceStdout`
-BASE_DIR=hugegraph-$VERSION
+BASE_DIR=$1
 BIN=$BASE_DIR/bin
 CONF=$BASE_DIR/conf/hugegraph.properties
+REST_CONF=$BASE_DIR/conf/rest-server.properties
+GREMLIN_CONF=$BASE_DIR/conf/gremlin-server.yaml
 
 # PostgreSQL configurations
 POSTGRESQL_DRIVER=org.postgresql.Driver
@@ -32,6 +33,13 @@ if [ "$BACKEND" == "postgresql" ]; then
     sed -i "s/#jdbc.username=.*/jdbc.username=$POSTGRESQL_USERNAME/" $CONF
 fi
 
+# Set timeout for hbase
+if [ "$BACKEND" == "hbase" ]; then
+    sed -i '$arestserver.request_timeout=200' $REST_CONF
+    sed -i '$agremlinserver.timeout=200' $REST_CONF
+    sed -i 's/scriptEvaluationTimeout.*/scriptEvaluationTimeout: 200000/' $GREMLIN_CONF
+fi
+
 # Append schema.sync_deletion=true to config file
 echo "schema.sync_deletion=true" >> $CONF
 

hugegraph-hbase/src/main/java/com/baidu/hugegraph/backend/store/hbase/HbaseOptions.java

@@ -20,6 +20,7 @@
 package com.baidu.hugegraph.backend.store.hbase;
 
 import static com.baidu.hugegraph.config.OptionChecker.disallowEmpty;
+import static com.baidu.hugegraph.config.OptionChecker.positiveInt;
 import static com.baidu.hugegraph.config.OptionChecker.rangeInt;
 
 import com.baidu.hugegraph.config.ConfigOption;
@@ -80,4 +81,12 @@ public class HbaseOptions extends OptionHolder {
                     rangeInt(1, 1000),
                     64
             );
+
+    public static final ConfigOption<Long> TRUNCATE_TIMEOUT =
+            new ConfigOption<>(
+                    "hbase.truncate_timeout",
+                    "The timeout in seconds of waiting for store truncate.",
+                    positiveInt(),
+                    30L
+            );
 }

hugegraph-hbase/src/main/java/com/baidu/hugegraph/backend/store/hbase/HbaseSessions.java

@@ -115,6 +115,7 @@ public class HbaseSessions extends BackendSessionPool {
 
     @Override
     protected synchronized boolean opened() {
+        // NOTE: isClosed() seems to always return true even if not connected
         return this.hbase != null && !this.hbase.isClosed();
     }
 
@@ -205,7 +206,7 @@ public class HbaseSessions extends BackendSessionPool {
             } catch (TableNotEnabledException ignored) {
                 // pass
             }
-            return admin.truncateTableAsync(tableName, false);
+            return admin.truncateTableAsync(tableName, true);
         }
     }
 
@@ -232,11 +233,9 @@ public class HbaseSessions extends BackendSessionPool {
      */
     public final class Session extends BackendSession {
 
-        private boolean closed;
         private final Map<String, List<Row>> batch;
 
         public Session() {
-            this.closed = false;
             this.batch = new HashMap<>();
         }
 
@@ -272,15 +271,20 @@ public class HbaseSessions extends BackendSessionPool {
             }
         }
 
+        @Override
+        public void open() {
+            this.opened = true;
+        }
+
         @Override
         public void close() {
             assert this.closeable();
-            this.closed = true;
+            this.opened = false;
         }
 
         @Override
         public boolean closed() {
-            return this.closed;
+            return !this.opened || !HbaseSessions.this.opened();
         }
 
         /**

hugegraph-hbase/src/main/java/com/baidu/hugegraph/backend/store/hbase/HbaseStore.java

@@ -24,6 +24,10 @@ import java.util.HashMap;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
 import java.util.stream.Collectors;
 
 import org.apache.hadoop.hbase.NamespaceExistException;
@@ -128,8 +132,8 @@ public abstract class HbaseStore extends AbstractBackendStore<Session> {
             this.sessions = new HbaseSessions(config, this.namespace, this.store);
         }
 
-        // NOTE: seems to always return true even if not connected
-        if (this.sessions.opened()) {
+        assert this.sessions != null;
+        if (!this.sessions.closed()) {
             LOG.debug("Store {} has been opened before", this.store);
             this.sessions.useSession();
             return;
@@ -162,7 +166,7 @@ public abstract class HbaseStore extends AbstractBackendStore<Session> {
     @Override
     public boolean opened() {
         this.checkConnectionOpened();
-        return !this.sessions.session().closed();
+        return this.sessions.session().opened();
     }
 
     @Override
@@ -243,7 +247,7 @@ public abstract class HbaseStore extends AbstractBackendStore<Session> {
     }
 
     @Override
-    public void clear() {
+    public void clear(boolean clearSpace) {
         this.checkConnectionOpened();
 
         // Return if not exists namespace
@@ -257,29 +261,34 @@ public abstract class HbaseStore extends AbstractBackendStore<Session> {
                       e, this.namespace);
         }
 
-        // Drop tables
-        for (String table : this.tableNames()) {
-            try {
-                this.sessions.dropTable(table);
-            } catch (TableNotFoundException e) {
-                continue;
-            } catch (IOException e) {
-                throw new BackendException("Failed to drop table '%s' for '%s'",
-                                           e, table, this.store);
+        if (!clearSpace) {
+            // Drop tables
+            for (String table : this.tableNames()) {
+                try {
+                    this.sessions.dropTable(table);
+                } catch (TableNotFoundException e) {
+                    LOG.warn("The table '{}' for '{}' does not exist " +
+                             "when trying to drop", table, this.store);
+                } catch (IOException e) {
+                    throw new BackendException(
+                              "Failed to drop table '%s' for '%s'",
+                              e, table, this.store);
+                }
             }
-        }
-
-        // Drop namespace
-        try {
-            this.sessions.dropNamespace();
-        } catch (IOException e) {
-            String notEmpty = "Only empty namespaces can be removed";
-            if (e.getCause().getMessage().contains(notEmpty)) {
-                LOG.debug("Can't drop namespace '{}': {}", this.namespace, e);
-            } else {
-                throw new BackendException(
-                          "Failed to drop namespace '%s' for '%s'",
-                          e, this.namespace, this.store);
+        } else {
+            // Drop namespace
+            try {
+                this.sessions.dropNamespace();
+            } catch (IOException e) {
+                String notEmpty = "Only empty namespaces can be removed";
+                if (e.getCause().getMessage().contains(notEmpty)) {
+                    LOG.debug("Can't drop namespace '{}': {}",
+                              this.namespace, e);
+                } else {
+                    throw new BackendException(
+                              "Failed to drop namespace '%s' for '%s'",
+                              e, this.namespace, this.store);
+                }
             }
         }
 
@@ -310,14 +319,25 @@ public abstract class HbaseStore extends AbstractBackendStore<Session> {
         this.checkOpened();
 
         // Truncate tables
-        for (String table : this.tableNames()) {
-            try {
-                this.sessions.truncateTable(table);
-            } catch (IOException e) {
-                throw new BackendException(
-                          "Failed to truncate table '%s' for '%s'",
-                          e, table, this.store);
+        List<String> tables = this.tableNames();
+        Map<String, Future<Void>> futures = new HashMap<>(tables.size());
+        String currentTable = null;
+        try {
+            for (String table : tables) {
+                currentTable = table;
+                futures.put(table, this.sessions.truncateTable(table));
             }
+            long timeout = this.sessions.config()
+                                        .get(HbaseOptions.TRUNCATE_TIMEOUT);
+            for (Map.Entry<String, Future<Void>> entry : futures.entrySet()) {
+                currentTable = entry.getKey();
+                entry.getValue().get(timeout, TimeUnit.SECONDS);
+            }
+        } catch (IOException | InterruptedException |
+                 ExecutionException | TimeoutException e) {
+            throw new BackendException(
+                      "Failed to truncate table '%s' for '%s'",
+                      e, currentTable, this.store);
         }
 
         LOG.debug("Store truncated: {}", this.store);

hugegraph-hbase/src/main/java/com/baidu/hugegraph/backend/store/hbase/HbaseTable.java

@@ -123,7 +123,7 @@ public class HbaseTable extends BackendTable<Session, BackendEntry> {
 
     @Override
     public Iterator<BackendEntry> query(Session session, Query query) {
-        if (query.limit() == 0 && query.limit() != Query.NO_LIMIT) {
+        if (query.limit() == 0L && !query.nolimit()) {
             LOG.debug("Return empty result(limit=0) for query {}", query);
             return ImmutableList.<BackendEntry>of().iterator();
         }

hugegraph-mysql/src/main/java/com/baidu/hugegraph/backend/store/mysql/MysqlSessions.java

@@ -125,7 +125,7 @@ public class MysqlSessions extends BackendSessionPool {
             if (e.getCause() instanceof SocketTimeoutException) {
                 LOG.warn("Drop database '{}' timeout", this.database());
             } else {
-                throw new BackendException("Failed to drop database '%s'",
+                throw new BackendException("Failed to drop database '%s'", e,
                                            this.database());
             }
         }
@@ -156,6 +156,11 @@ public class MysqlSessions extends BackendSessionPool {
         }
     }
 
+    public void resetConnections() {
+        // Close the under layer connections owned by each thread
+        this.forceResetSessions();
+    }
+
     protected String buildCreateDatabase(String database) {
         return String.format("CREATE DATABASE IF NOT EXISTS %s " +
                              "DEFAULT CHARSET utf8 COLLATE utf8_bin;",
@@ -178,15 +183,11 @@ public class MysqlSessions extends BackendSessionPool {
      * Connect DB without specified database
      */
     protected Connection openWithoutDB(int timeout) {
-        String jdbcUrl = this.config.get(MysqlOptions.JDBC_URL);
-        String url = new URIBuilder().setPath(jdbcUrl)
-                                     .setParameter("socketTimeout",
-                                                   String.valueOf(timeout))
-                                     .toString();
+        String url = this.buildUri(false, false, false, timeout);
         try {
             return this.connect(url);
         } catch (SQLException e) {
-            throw new BackendException("Failed to access %s", jdbcUrl);
+            throw new BackendException("Failed to access %s", e, url);
         }
     }
 
@@ -194,20 +195,11 @@ public class MysqlSessions extends BackendSessionPool {
      * Connect DB with specified database, but won't auto reconnect
      */
     protected Connection openWithDB(int timeout) {
-        String jdbcUrl = this.config.get(MysqlOptions.JDBC_URL);
-        if (jdbcUrl.endsWith("/")) {
-            jdbcUrl = String.format("%s%s", jdbcUrl, this.database());
-        } else {
-            jdbcUrl = String.format("%s/%s", jdbcUrl, this.database());
-        }
-        String url = new URIBuilder().setPath(jdbcUrl)
-                                     .setParameter("socketTimeout",
-                                                   String.valueOf(timeout))
-                                     .toString();
+        String url = this.buildUri(false, true, false, timeout);
         try {
             return this.connect(url);
         } catch (SQLException e) {
-            throw new BackendException("Failed to access %s", jdbcUrl);
+            throw new BackendException("Failed to access %s", e, url);
         }
     }
 
@@ -215,27 +207,39 @@ public class MysqlSessions extends BackendSessionPool {
      * Connect DB with specified database
      */
     private Connection open(boolean autoReconnect) throws SQLException {
+        String url = this.buildUri(true, true, autoReconnect, null);
+        return this.connect(url);
+    }
+
+    protected String buildUri(boolean withConnParams, boolean withDB,
+                              boolean autoReconnect, Integer timeout) {
         String url = this.config.get(MysqlOptions.JDBC_URL);
-        if (url.endsWith("/")) {
-            url = String.format("%s%s", url, this.database());
-        } else {
-            url = String.format("%s/%s", url, this.database());
+        if (withDB) {
+            if (url.endsWith("/")) {
+                url = String.format("%s%s", url, this.database());
+            } else {
+                url = String.format("%s/%s", url, this.database());
+            }
         }
 
         int maxTimes = this.config.get(MysqlOptions.JDBC_RECONNECT_MAX_TIMES);
         int interval = this.config.get(MysqlOptions.JDBC_RECONNECT_INTERVAL);
         String sslMode = this.config.get(MysqlOptions.JDBC_SSL_MODE);
 
-        URIBuilder uriBuilder = this.newConnectionURIBuilder();
-        uriBuilder.setPath(url)
-                  .setParameter("useSSL", sslMode)
-                  .setParameter("characterEncoding", "utf-8")
-                  .setParameter("rewriteBatchedStatements", "true")
-                  .setParameter("useServerPrepStmts", "false")
-                  .setParameter("autoReconnect", String.valueOf(autoReconnect))
-                  .setParameter("maxReconnects", String.valueOf(maxTimes))
-                  .setParameter("initialTimeout", String.valueOf(interval));
-        return this.connect(uriBuilder.toString());
+        URIBuilder builder = this.newConnectionURIBuilder();
+        builder.setPath(url).setParameter("useSSL", sslMode);
+        if (withConnParams) {
+            builder.setParameter("characterEncoding", "utf-8")
+                   .setParameter("rewriteBatchedStatements", "true")
+                   .setParameter("useServerPrepStmts", "false")
+                   .setParameter("autoReconnect", String.valueOf(autoReconnect))
+                   .setParameter("maxReconnects", String.valueOf(maxTimes))
+                   .setParameter("initialTimeout", String.valueOf(interval));
+        }
+        if (timeout != null) {
+            builder.setParameter("socketTimeout", String.valueOf(timeout));
+        }
+        return builder.toString();
     }
 
     protected URIBuilder newConnectionURIBuilder() {
@@ -260,26 +264,36 @@ public class MysqlSessions extends BackendSessionPool {
 
         private Connection conn;
         private Map<String, PreparedStatement> statements;
-        private boolean opened;
         private int count;
 
         public Session() {
             this.conn = null;
             this.statements = new HashMap<>();
-            this.opened = false;
             this.count = 0;
-            try {
-                this.open();
-            } catch (SQLException ignored) {
-                // Ignore
-            }
         }
 
         public HugeConfig config() {
             return MysqlSessions.this.config();
         }
 
-        public void open() throws SQLException {
+        @Override
+        public void open() {
+            try {
+                this.doOpen();
+            } catch (SQLException e) {
+                throw new BackendException("Failed to open connection", e);
+            }
+        }
+
+        private void tryOpen() {
+            try {
+                this.doOpen();
+            } catch (SQLException ignored) {
+                // Ignore
+            }
+        }
+
+        private void doOpen() throws SQLException {
             if (this.conn != null && !this.conn.isClosed()) {
                 return;
             }
@@ -294,6 +308,11 @@ public class MysqlSessions extends BackendSessionPool {
                 return;
             }
 
+            this.opened = false;
+            this.doClose();
+        }
+
+        private void doClose() {
             SQLException exception = null;
             for (PreparedStatement statement : this.statements.values()) {
                 try {
@@ -302,23 +321,42 @@ public class MysqlSessions extends BackendSessionPool {
                     exception = e;
                 }
             }
+            this.statements.clear();
 
             try {
                 this.conn.close();
             } catch (SQLException e) {
                 exception = e;
+            } finally {
+                this.conn = null;
             }
 
-            this.opened = false;
             if (exception != null) {
                 throw new BackendException("Failed to close connection",
                                            exception);
             }
         }
 
+        @Override
+        public boolean opened() {
+            if (this.opened && this.conn == null) {
+                // Reconnect if the connection is reset
+                tryOpen();
+            }
+            return this.opened && this.conn != null;
+        }
+
         @Override
         public boolean closed() {
-            return !this.opened;
+            if (!this.opened || this.conn == null) {
+                return true;
+            }
+            try {
+                return this.conn.isClosed();
+            } catch (SQLException ignored) {
+                // Assume closed here
+                return true;
+            }
         }
 
         public void clear() {
@@ -398,6 +436,19 @@ public class MysqlSessions extends BackendSessionPool {
             }
         }
 
+        @Override
+        protected void reset() {
+            // NOTE: this method may be called by other threads
+            if (this.conn == null) {
+                return;
+            }
+            try {
+                this.doClose();
+            } catch (Exception e) {
+                LOG.warn("Failed to reset connection", e);
+            }
+        }
+
         public ResultSet select(String sql) throws SQLException {
             assert this.conn.getAutoCommit();
             return this.conn.createStatement().executeQuery(sql);

hugegraph-mysql/src/main/java/com/baidu/hugegraph/backend/store/mysql/MysqlStore.java

@@ -147,7 +147,7 @@ public abstract class MysqlStore extends AbstractBackendStore<Session> {
     @Override
     public boolean opened() {
         this.checkClusterConnected();
-        return !this.sessions.session().closed();
+        return this.sessions.session().opened();
     }
 
     @Override
@@ -157,7 +157,7 @@ public abstract class MysqlStore extends AbstractBackendStore<Session> {
         try {
             // Open a new session connected with specified database
             this.sessions.session().open();
-        } catch (SQLException e) {
+        } catch (Exception e) {
             throw new BackendException("Failed to connect database '%s'",
                                        this.database);
         }
@@ -168,14 +168,28 @@ public abstract class MysqlStore extends AbstractBackendStore<Session> {
     }
 
     @Override
-    public void clear() {
+    public void clear(boolean clearSpace) {
         // Check connected
         this.checkClusterConnected();
 
         if (this.sessions.existsDatabase()) {
-            this.checkOpened();
-            this.clearTables();
-            this.sessions.dropDatabase();
+            if (!clearSpace) {
+                this.checkOpened();
+                this.clearTables();
+                /*
+                 * Disconnect connections for following database drop.
+                 * Connections will be auto reconnected if not drop database
+                 * in next step, but never do this operation because database
+                 * might be blocked in mysql or throw 'terminating' exception.
+                 * we can't resetConnections() when dropDatabase(), because
+                 * there are 3 stores(schema,system,graph), which are shared
+                 * one database, other stores may keep connected with the
+                 * database when one store doing clear(clearSpace=false).
+                 */
+                this.sessions.resetConnections();
+            } else {
+                this.sessions.dropDatabase();
+            }
         }
 
         LOG.debug("Store cleared: {}", this.store);

hugegraph-mysql/src/main/java/com/baidu/hugegraph/backend/store/mysql/MysqlStoreProvider.java

@@ -19,14 +19,10 @@
 
 package com.baidu.hugegraph.backend.store.mysql;
 
-import java.util.Iterator;
-
-import com.baidu.hugegraph.backend.BackendException;
 import com.baidu.hugegraph.backend.store.AbstractBackendStoreProvider;
 import com.baidu.hugegraph.backend.store.BackendStore;
 import com.baidu.hugegraph.backend.store.mysql.MysqlStore.MysqlGraphStore;
 import com.baidu.hugegraph.backend.store.mysql.MysqlStore.MysqlSchemaStore;
-import com.baidu.hugegraph.util.Events;
 
 public class MysqlStoreProvider extends AbstractBackendStoreProvider {
 
@@ -44,20 +40,6 @@ public class MysqlStoreProvider extends AbstractBackendStoreProvider {
         return new MysqlGraphStore(this, this.database(), store);
     }
 
-    @Override
-    public void clear() throws BackendException {
-        this.checkOpened();
-        /*
-         * We should drop database once only with stores(schema/graph/system),
-         * otherwise it will easily lead to blocking when drop tables
-         */
-        Iterator<BackendStore> iter = this.stores.values().iterator();
-        if (iter.hasNext()) {
-            iter.next().clear();
-        }
-        this.notifyAndWaitEvent(Events.STORE_CLEAR);
-    }
-
     @Override
     public String type() {
         return "mysql";

hugegraph-mysql/src/main/java/com/baidu/hugegraph/backend/store/mysql/MysqlTable.java

@@ -296,7 +296,7 @@ public abstract class MysqlTable
     public Iterator<BackendEntry> query(Session session, Query query) {
         ExtendableIterator<BackendEntry> rs = new ExtendableIterator<>();
 
-        if (query.limit() == 0 && query.limit() != Query.NO_LIMIT) {
+        if (query.limit() == 0L && !query.nolimit()) {
             LOG.debug("Return empty result(limit=0) for query {}", query);
             return rs;
         }
@@ -344,7 +344,7 @@ public abstract class MysqlTable
             }
             if (query.paging()) {
                 this.wrapPage(selection, query);
-            } else if (query.limit() != Query.NO_LIMIT || query.offset() > 0) {
+            } else if (!query.nolimit() || query.offset() > 0) {
                 this.wrapOffset(selection, query);
             }
         }
@@ -512,7 +512,7 @@ public abstract class MysqlTable
 
         select.append(this.orderByKeys());
 
-        if (query.limit() != Query.NO_LIMIT) {
+        if (!query.nolimit()) {
             // Fetch `limit + 1` rows for judging whether reached the last page
             select.append(" limit ");
             select.append(query.limit() + 1);

hugegraph-rocksdb/src/main/java/com/baidu/hugegraph/backend/store/rocksdb/RocksDBStdSessions.java

@@ -536,14 +536,10 @@ public class RocksDBStdSessions extends RocksDBSessions {
      */
     private final class StdSession extends RocksDBSessions.Session {
 
-        private boolean closed;
-
         private WriteBatch batch;
         private WriteOptions writeOptions;
 
         public StdSession(HugeConfig conf) {
-            this.closed = false;
-
             boolean bulkload = conf.get(RocksDBOptions.BULKLOAD_MODE);
             this.batch = new WriteBatch();
             this.writeOptions = new WriteOptions();
@@ -551,15 +547,20 @@ public class RocksDBStdSessions extends RocksDBSessions {
             //this.writeOptions.setSync(false);
         }
 
+        @Override
+        public void open() {
+            this.opened = true;
+        }
+
         @Override
         public void close() {
             assert this.closeable();
-            this.closed = true;
+            this.opened = false;
         }
 
         @Override
         public boolean closed() {
-            return this.closed;
+            return !this.opened || !RocksDBStdSessions.this.opened();
         }
 
         /**

hugegraph-rocksdb/src/main/java/com/baidu/hugegraph/backend/store/rocksdb/RocksDBStore.java

@@ -333,7 +333,7 @@ public abstract class RocksDBStore extends AbstractBackendStore<Session> {
     @Override
     public boolean opened() {
         this.checkDbOpened();
-        return !this.sessions.session().closed();
+        return this.sessions.session().opened();
     }
 
     @Override
@@ -412,14 +412,15 @@ public abstract class RocksDBStore extends AbstractBackendStore<Session> {
     }
 
     @Override
-    public synchronized void clear() {
+    public synchronized void clear(boolean clearSpace) {
         this.checkDbOpened();
 
+        // Drop tables with main disk
         for (String table : this.tableNames()) {
             this.dropTable(this.sessions, table);
         }
 
-        // Drop table with optimized disk
+        // Drop tables with optimized disk
         Map<String, RocksDBSessions> tableDBMap = this.tableDBMapping();
         for (Map.Entry<String, RocksDBSessions> e : tableDBMap.entrySet()) {
             this.dropTable(e.getValue(), e.getKey());
@@ -461,7 +462,7 @@ public abstract class RocksDBStore extends AbstractBackendStore<Session> {
     public synchronized void truncate() {
         this.checkOpened();
 
-        this.clear();
+        this.clear(false);
         this.init();
 
         LOG.debug("Store truncated: {}", this.store);

hugegraph-rocksdb/src/main/java/com/baidu/hugegraph/backend/store/rocksdb/RocksDBTable.java

@@ -113,7 +113,7 @@ public class RocksDBTable extends BackendTable<Session, BackendEntry> {
 
     @Override
     public Iterator<BackendEntry> query(Session session, Query query) {
-        if (query.limit() == 0 && query.limit() != Query.NO_LIMIT) {
+        if (query.limit() == 0L && !query.nolimit()) {
             LOG.debug("Return empty result(limit=0) for query {}", query);
             return ImmutableList.<BackendEntry>of().iterator();
         }

hugegraph-rocksdb/src/main/java/com/baidu/hugegraph/backend/store/rocksdbsst/RocksDBSstSessions.java

@@ -172,23 +172,21 @@ public class RocksDBSstSessions extends RocksDBSessions {
      */
     private final class SstSession extends Session {
 
-        private boolean closed;
         private Map<String, Changes> batch;
 
         public SstSession() {
-            this.closed = false;
             this.batch = new HashMap<>();
         }
 
+        @Override
+        public void open() {
+            this.opened = true;
+        }
+
         @Override
         public void close() {
             assert this.closeable();
-            this.closed = true;
-        }
-
-        @Override
-        public boolean closed() {
-            return this.closed;
+            this.opened = false;
         }
 
         /**

hugegraph-test/src/main/java/com/baidu/hugegraph/api/GremlinApiTest.java

@@ -39,7 +39,7 @@ public class GremlinApiTest extends BaseApiTest {
                 + "\"bindings\":{},"
                 + "\"language\":\"gremlin-groovy\","
                 + "\"aliases\":{\"g\":\"__g_hugegraph\"}}";
-        Assert.assertEquals(200, client().post(path, body).getStatus());
+        assertResponseStatus(200, client().post(path, body));
     }
 
     @Test
@@ -49,4 +49,63 @@ public class GremlinApiTest extends BaseApiTest {
         Response r = client().get(path, params);
         Assert.assertEquals(r.readEntity(String.class), 200, r.getStatus());
     }
+
+    @Test
+    public void testScript() {
+        String bodyTemplate = "{"
+                + "\"gremlin\":\"%s\","
+                + "\"bindings\":{},"
+                + "\"language\":\"gremlin-groovy\","
+                + "\"aliases\":{\"g\":\"__g_hugegraph\"}}";
+
+        String script = "schema=hugegraph.schema();"
+                + "schema.propertyKey('name').asText().ifNotExist().create();"
+                + "schema.propertyKey('age').asInt().ifNotExist().create();"
+                + "schema.propertyKey('city').asUUID().ifNotExist().create();"
+                + "schema.propertyKey('lang').asText().ifNotExist().create();"
+                + "schema.propertyKey('date').asText().ifNotExist().create();"
+                + "schema.propertyKey('price').asInt().ifNotExist().create();"
+                + "person=schema.vertexLabel('person').properties('name','age','city').useCustomizeUuidId().ifNotExist().create();"
+                + "knows=schema.edgeLabel('knows').sourceLabel('person').targetLabel('person').properties('date').ifNotExist().create();"
+                + "marko=hugegraph.addVertex(T.id, '835e1153928149578691cf79258e90eb', T.label,'person','name','marko','age',29,'city','135e1153928149578691cf79258e90eb');"
+                + "vadas=hugegraph.addVertex(T.id, '935e1153928149578691cf79258e90eb', T.label,'person','name','vadas','age',27,'city','235e1153928149578691cf79258e90eb');"
+                + "marko.addEdge('knows',vadas,'date','20160110');";
+        String body = String.format(bodyTemplate, script);
+        assertResponseStatus(200, client().post(path, body));
+
+        String queryV = "g.V()";
+        body = String.format(bodyTemplate, queryV);
+        assertResponseStatus(200, client().post(path, body));
+
+        String queryE = "g.E()";
+        body = String.format(bodyTemplate, queryE);
+        assertResponseStatus(200, client().post(path, body));
+    }
+
+    @Test
+    public void testClearAndInit() {
+        String body = "{"
+                + "\"gremlin\":\"hugegraph.clearBackend()\","
+                + "\"bindings\":{},"
+                + "\"language\":\"gremlin-groovy\","
+                + "\"aliases\":{\"g\":\"__g_hugegraph\"}}";
+        assertResponseStatus(200, client().post(path, body));
+
+        body = "{"
+                + "\"gremlin\":\"hugegraph.initBackend()\","
+                + "\"bindings\":{},"
+                + "\"language\":\"gremlin-groovy\","
+                + "\"aliases\":{\"g\":\"__g_hugegraph\"}}";
+        assertResponseStatus(200, client().post(path, body));
+    }
+
+    @Test
+    public void testTruncate() {
+        String body = "{"
+                + "\"gremlin\":\"hugegraph.truncateBackend()\","
+                + "\"bindings\":{},"
+                + "\"language\":\"gremlin-groovy\","
+                + "\"aliases\":{\"g\":\"__g_hugegraph\"}}";
+        assertResponseStatus(200, client().post(path, body));
+    }
 }

hugegraph-test/src/main/java/com/baidu/hugegraph/core/VertexCoreTest.java

@@ -5768,14 +5768,14 @@ public class VertexCoreTest extends BaseCoreTest {
                                        .has("city", "Beijing").toList();
         Assert.assertEquals(3, vertices.size());
 
-        List<Vertex> vertices1 = graph().traversal().V()
-                                        .has("city", "Beijing")
-                                        .range(0, 2).toList();
+        Set<Vertex> vertices1 = graph().traversal().V()
+                                       .has("city", "Beijing")
+                                       .range(0, 2).toSet();
         Assert.assertEquals(2, vertices1.size());
 
-        List<Vertex> vertices2 = graph().traversal().V()
-                                        .has("city", "Beijing")
-                                        .range(2, 3).toList();
+        Set<Vertex> vertices2 = graph().traversal().V()
+                                       .has("city", "Beijing")
+                                       .range(2, 3).toSet();
         Assert.assertEquals(1, vertices2.size());
 
         vertices1.addAll(vertices2);
@@ -5791,13 +5791,13 @@ public class VertexCoreTest extends BaseCoreTest {
         List<Vertex> vertices = graph().traversal().V()
                                        .has("age", P.between(5, 22)).toList();
         Assert.assertEquals(4, vertices.size());
-        List<Vertex> vertices1 = graph().traversal().V()
-                                        .has("age", P.between(5, 22))
-                                        .range(0, 3).toList();
+        Set<Vertex> vertices1 = graph().traversal().V()
+                                       .has("age", P.between(5, 22))
+                                       .range(0, 3).toSet();
         Assert.assertEquals(3, vertices1.size());
-        List<Vertex> vertices2 = graph().traversal().V()
-                                        .has("age", P.between(5, 22))
-                                        .range(3, 4).toList();
+        Set<Vertex> vertices2 = graph().traversal().V()
+                                       .has("age", P.between(5, 22))
+                                       .range(3, 4).toSet();
         Assert.assertEquals(1, vertices2.size());
 
         vertices1.addAll(vertices2);
@@ -5813,19 +5813,19 @@ public class VertexCoreTest extends BaseCoreTest {
                                        .toList();
         Assert.assertEquals(5, vertices.size());
 
-        List<Vertex> vertices1 = graph().traversal().V()
-                                        .hasLabel("person")
-                                        .range(0, 3).toList();
+        Set<Vertex> vertices1 = graph().traversal().V()
+                                       .hasLabel("person")
+                                       .range(0, 3).toSet();
         Assert.assertEquals(3, vertices1.size());
 
-        List<Vertex> vertices2 = graph().traversal().V()
-                                        .hasLabel("person")
-                                        .range(3, 5).toList();
+        Set<Vertex> vertices2 = graph().traversal().V()
+                                       .hasLabel("person")
+                                       .range(3, 5).toSet();
         Assert.assertEquals(2, vertices2.size());
 
-        List<Vertex> vertices3 = graph().traversal().V()
-                                        .hasLabel("person")
-                                        .limit(4).toList();
+        Set<Vertex> vertices3 = graph().traversal().V()
+                                       .hasLabel("person")
+                                       .limit(4).toSet();
         Assert.assertEquals(4, vertices3.size());
 
         vertices1.addAll(vertices2);

hugegraph-test/src/main/java/com/baidu/hugegraph/unit/core/SecurityManagerTest.java

@@ -119,6 +119,14 @@ public class SecurityManagerTest {
         String result = runGremlinJob("new FileInputStream(new File(\"\"))");
         assertError(result, "Not allowed to read file via Gremlin");
 
+        // read file
+        String pom = System.getProperty("user.dir") + "/a.groovy";
+        try (FileInputStream fis = new FileInputStream(new File(pom))) {
+        } catch (IOException ignored) {}
+        result = runGremlinJob(String.format(
+                 "new FileInputStream(new File(\"%s\"))", pom));
+        assertError(result, "(No such file or directory)");
+
         // read file fd
         @SuppressWarnings({ "unused", "resource" })
         FileInputStream fis = new FileInputStream(FileDescriptor.in);
@@ -278,7 +286,8 @@ public class SecurityManagerTest {
     }
 
     private static void assertError(String result, String message) {
-        Assert.assertTrue(result, result.endsWith(message));
+        Assert.assertTrue(result, result.endsWith(message) ||
+                                  result.contains(message));
     }
 
     private static String runGremlinJob(String gremlin) {