prepare for mapdb backend

Change-Id: I046bde4a32b3fd6693f788d27a9165e2646bc5cb

hugegraph-api/src/main/java/com/baidu/hugegraph/core/GraphManager.java

@@ -42,7 +42,6 @@
 import com.baidu.hugegraph.backend.cache.Cache;
 import com.baidu.hugegraph.backend.cache.CacheManager;
 import com.baidu.hugegraph.backend.store.BackendStoreSystemInfo;
-import com.baidu.hugegraph.backend.store.memory.InMemoryDBStoreProvider;
 import com.baidu.hugegraph.config.HugeConfig;
 import com.baidu.hugegraph.config.ServerOptions;
 import com.baidu.hugegraph.exception.NotSupportException;
@@ -189,7 +188,9 @@ private void loadGraph(String name, String path) {
     private void checkBackendVersionOrExit() {
         for (String graph : this.graphs()) {
             HugeGraph hugegraph = this.graph(graph);
-            if (InMemoryDBStoreProvider.matchType(hugegraph.backend())) {
+            boolean persistence = hugegraph.graphTransaction().store()
+                                           .features().supportsPersistence();
+            if (!persistence) {
                 hugegraph.initBackend();
             }
             BackendStoreSystemInfo info = new BackendStoreSystemInfo(hugegraph);

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

@@ -104,12 +104,12 @@ public final synchronized Cluster cluster() {
     }
 
     @Override
-    public final synchronized Session session() {
+    public final Session session() {
         return (Session) super.getOrNewSession();
     }
 
     @Override
-    protected final synchronized Session newSession() {
+    protected Session newSession() {
         E.checkState(this.cluster != null,
                      "Cassandra cluster has not been initialized");
         return new Session();
@@ -157,7 +157,7 @@ public BatchStatement add(Statement statement) {
         }
 
         @Override
-        public void clear() {
+        public void rollback() {
             this.batch.clear();
         }
 

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

@@ -356,7 +356,7 @@ public void rollbackTx() {
 
         session.txState(TxState.ROLLBACKING);
         try {
-            session.clear();
+            session.rollback();
         } finally {
             // Assume batch commit would auto rollback
             session.txState(TxState.CLEAN);

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

@@ -40,7 +40,7 @@
 import com.baidu.hugegraph.type.HugeType;
 import com.google.common.collect.ImmutableList;
 
-public class CachedGraphTransaction extends GraphTransaction {
+public final class CachedGraphTransaction extends GraphTransaction {
 
     private final static int MAX_CACHE_EDGES_PER_QUERY = 100;
 

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

@@ -24,7 +24,6 @@
 import java.util.Map;
 import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
-import java.util.function.Function;
 
 import com.baidu.hugegraph.HugeGraph;
 import com.baidu.hugegraph.backend.id.Id;
@@ -40,7 +39,7 @@
 import com.baidu.hugegraph.util.Events;
 import com.google.common.collect.ImmutableSet;
 
-public class CachedSchemaTransaction extends SchemaTransaction {
+public final class CachedSchemaTransaction extends SchemaTransaction {
 
     private final Cache idCache;
     private final Cache nameCache;
@@ -153,12 +152,26 @@ private static Id generateId(HugeType type, String name) {
         return IdGenerator.of(type.string() + "-" + name);
     }
 
-    private Object getOrFetch(HugeType type, Id id,
-                              Function<Id, Object> fetcher) {
+    @Override
+    protected void addSchema(SchemaElement schema) {
+        super.addSchema(schema);
+
+        this.resetCachedAllIfReachedCapacity();
+
+        Id prefixedId = generateId(schema.type(), schema.id());
+        this.idCache.update(prefixedId, schema);
+
+        Id prefixedName = generateId(schema.type(), schema.name());
+        this.nameCache.update(prefixedName, schema);
+    }
+
+    @Override
+    @SuppressWarnings("unchecked")
+    protected <T extends SchemaElement> T getSchema(HugeType type, Id id) {
         Id prefixedId = generateId(type, id);
         Object value = this.idCache.get(prefixedId);
         if (value == null) {
-            value = fetcher.apply(id);
+            value = super.getSchema(type, id);
             if (value != null) {
                 this.resetCachedAllIfReachedCapacity();
 
@@ -169,15 +182,17 @@ private Object getOrFetch(HugeType type, Id id,
                 this.nameCache.update(prefixedName, schema);
             }
         }
-        return value;
+        return (T) value;
     }
 
-    private Object getOrFetch(HugeType type, String name,
-                              Function<String, Object> fetcher) {
+    @Override
+    @SuppressWarnings("unchecked")
+    protected <T extends SchemaElement> T getSchema(HugeType type,
+                                                    String name) {
         Id prefixedName = generateId(type, name);
         Object value = this.nameCache.get(prefixedName);
         if (value == null) {
-            value = fetcher.apply(name);
+            value = super.getSchema(type, name);
             if (value != null) {
                 this.resetCachedAllIfReachedCapacity();
 
@@ -188,36 +203,6 @@ private Object getOrFetch(HugeType type, String name,
                 this.idCache.update(prefixedId, schema);
             }
         }
-        return value;
-    }
-
-    @Override
-    protected void addSchema(SchemaElement schema) {
-        super.addSchema(schema);
-
-        this.resetCachedAllIfReachedCapacity();
-
-        Id prefixedId = generateId(schema.type(), schema.id());
-        this.idCache.update(prefixedId, schema);
-
-        Id prefixedName = generateId(schema.type(), schema.name());
-        this.nameCache.update(prefixedName, schema);
-    }
-
-    @Override
-    @SuppressWarnings("unchecked")
-    protected <T extends SchemaElement> T getSchema(HugeType type, Id id) {
-        Object value = this.getOrFetch(type, id,
-                                       k -> super.getSchema(type, id));
-        return (T) value;
-    }
-
-    @Override
-    @SuppressWarnings("unchecked")
-    protected <T extends SchemaElement> T getSchema(HugeType type,
-                                                    String name) {
-        Object value = this.getOrFetch(type, name,
-                                       k -> super.getSchema(type, name));
         return (T) value;
     }
 

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

@@ -51,6 +51,7 @@ public class RamCache implements Cache {
 
     // NOTE: the count in number of items, not in bytes
     private final int capacity;
+    private final int halfCapacity;
 
     // Implement LRU cache
     private final ConcurrentMap<Id, LinkNode<Id, Object>> map;
@@ -63,14 +64,14 @@ public RamCache() {
     }
 
     public RamCache(int capacity) {
-        this.keyLock = new KeyLock();
-
-        if (capacity < 1) {
-            capacity = 1;
+        if (capacity < 0) {
+            capacity = 0;
         }
+        this.keyLock = new KeyLock();
         this.capacity = capacity;
+        this.halfCapacity = this.capacity >> 1;
 
-        int initialCapacity = capacity >> 3;
+        int initialCapacity = capacity >= MB ? capacity >> 10 : 256;
         if (initialCapacity > MAX_INIT_CAP) {
             initialCapacity = MAX_INIT_CAP;
         }
@@ -80,9 +81,18 @@ public RamCache(int capacity) {
     }
 
     @Watched(prefix = "ramcache")
-    private Object access(Id id) {
+    private final Object access(Id id) {
         assert id != null;
 
+        if (this.map.size() <= this.halfCapacity) {
+            LinkNode<Id, Object> node = this.map.get(id);
+            if (node == null) {
+                return null;
+            }
+            assert id.equals(node.key());
+            return node.value();
+        }
+
         final Lock lock = this.keyLock.lock(id);
         try {
             LinkNode<Id, Object> node = this.map.get(id);
@@ -91,7 +101,7 @@ private Object access(Id id) {
             }
 
             // NOTE: update the queue only if the size > capacity/2
-            if (this.map.size() > this.capacity >> 1) {
+            if (this.map.size() > this.halfCapacity) {
                 // Move the node from mid to tail
                 if (this.queue.remove(node) == null) {
                     // The node may be removed by others through dequeue()
@@ -100,13 +110,6 @@ private Object access(Id id) {
                 this.queue.enqueue(node);
             }
 
-            // Ignore concurrent write for hits
-            ++this.hits;
-            if (LOG.isDebugEnabled()) {
-                LOG.debug("RamCache cached '{}' (hits={}, miss={})",
-                          id, this.hits, this.miss);
-            }
-
             assert id.equals(node.key());
             return node.value();
         } finally {
@@ -115,7 +118,7 @@ private Object access(Id id) {
     }
 
     @Watched(prefix = "ramcache")
-    private void write(Id id, Object value) {
+    private final void write(Id id, Object value) {
         assert id != null;
         assert this.capacity > 0;
 
@@ -163,14 +166,13 @@ private void write(Id id, Object value) {
 
             // Add the new item to tail of the queue, then map it
             this.map.put(id, this.queue.enqueue(id, value));
-
         } finally {
             lock.unlock();
         }
     }
 
     @Watched(prefix = "ramcache")
-    private void remove(Id id) {
+    private final void remove(Id id) {
         assert id != null;
 
         final Lock lock = this.keyLock.lock(id);
@@ -192,16 +194,23 @@ private void remove(Id id) {
     @Override
     public Object get(Id id) {
         Object value = null;
-        if (this.map.containsKey(id)) {
+        if (this.map.size() <= this.halfCapacity || this.map.containsKey(id)) {
             // Maybe the id removed by other threads and returned null value
             value = this.access(id);
         }
+
         if (value == null) {
             ++this.miss;
             if (LOG.isDebugEnabled()) {
                 LOG.debug("RamCache missed '{}' (miss={}, hits={})",
                           id, this.miss, this.hits);
             }
+        } else {
+            ++this.hits;
+            if (LOG.isDebugEnabled()) {
+                LOG.debug("RamCache cached '{}' (hits={}, miss={})",
+                          id, this.hits, this.miss);
+            }
         }
         return value;
     }
@@ -210,10 +219,11 @@ public Object get(Id id) {
     @Override
     public Object getOrFetch(Id id, Function<Id, Object> fetcher) {
         Object value = null;
-        if (this.map.containsKey(id)) {
+        if (this.map.size() <= this.halfCapacity || this.map.containsKey(id)) {
             // Maybe the id removed by other threads and returned null value
             value = this.access(id);
         }
+
         if (value == null) {
             ++this.miss;
             if (LOG.isDebugEnabled()) {
@@ -223,6 +233,12 @@ public Object getOrFetch(Id id, Function<Id, Object> fetcher) {
             // Do fetch and update the cache
             value = fetcher.apply(id);
             this.update(id, value);
+        } else {
+            ++this.hits;
+            if (LOG.isDebugEnabled()) {
+                LOG.debug("RamCache cached '{}' (hits={}, miss={})",
+                          id, this.hits, this.miss);
+            }
         }
         return value;
     }

hugegraph-core/src/main/java/com/baidu/hugegraph/backend/id/IdGenerator.java

@@ -28,15 +28,15 @@ public abstract class IdGenerator {
 
     public abstract Id generate(HugeVertex vertex);
 
-    public static Id of(String id) {
+    public final static Id of(String id) {
         return new StringId(id);
     }
 
-    public static Id of(long id) {
+    public final static Id of(long id) {
         return new LongId(id);
     }
 
-    public static Id of(byte[] bytes, boolean number) {
+    public final static Id of(byte[] bytes, boolean number) {
         return number ? new LongId(bytes) : new StringId(bytes);
     }
 
@@ -45,7 +45,7 @@ public static Id of(byte[] bytes, boolean number) {
      * @param id original string id value
      * @return   wrapped id object
      */
-    public Id generate(String id) {
+    public final Id generate(String id) {
         return of(id);
     }
 
@@ -54,7 +54,7 @@ public Id generate(String id) {
      * @param id original long id value
      * @return   wrapped id object
      */
-    public Id generate(long id) {
+    public final Id generate(long id) {
         return of(id);
     }
 

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

@@ -397,12 +397,6 @@ public boolean test(HugeElement element) {
         public Condition copy() {
             return new And(this.left().copy(), this.right().copy());
         }
-
-        @Override
-        public boolean isFlattened() {
-            // If this is flattened, its sub-condition should not be nested
-            return this.left().isRelation() && this.right().isRelation();
-        }
     }
 
     public static class Or extends BinCondition {
@@ -442,6 +436,10 @@ public abstract static class Relation extends Condition {
         // The value serialized(code/string) by backend store.
         protected Object serialValue;
 
+        protected Set<RelationType> UNFLATTEN_RELATION_TYPES = ImmutableSet.of(
+                                    RelationType.IN, RelationType.NOT_IN,
+                                    RelationType.TEXT_CONTAINS_ANY);
+
         @Override
         public ConditionType type() {
             return ConditionType.RELATION;
@@ -476,6 +474,11 @@ public boolean test(Object value) {
             return this.relation.test(value, this.value);
         }
 
+        @Override
+        public boolean isFlattened() {
+            return !this.UNFLATTEN_RELATION_TYPES.contains(this.relation);
+        }
+
         @Override
         public List<? extends Relation> relations() {
             return ImmutableList.of(this);