Graph database_neo4j 底层存储结构分析(2)

3       neo4j存储结构

neo4j 中,主要有4类节点，属性，关系等文件是以数组作为核心存储结构；同时对节点，属性，关系等类型的每个数据项都会分配一个唯一的ID，在存储时以该ID 为数组的下标。这样，在访问时通过其ID作为下标，实现快速定位。所以在图遍历等操作时，可以实现 free-index。

3.1  neo4j 的 store 部分类图

3.1.1   CommonAbstractStore.java

CommonAbstractStore 是所有 Store 类的基类，下面的代码片段是 CommonAbstractStore 的成员变量，比较重要的是飘红的几个，特别是IdGenerator，每种Store 的实例都有自己的 id 分配管理器; StoreChannel 是负责Store文件的读写和定位；WindowsPool 是与Store Record相关的缓存，用来提升性能的。

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</pre> <div>public abstract class CommonAbstractStore implements IdSequence   {   public static abstract class Configuration   {   public static final Setting store_dir = InternalAbstractGraphDatabase.Configuration.store_dir;   public static final Setting neo_store = InternalAbstractGraphDatabase.Configuration.neo_store;   public static final Setting read_only = GraphDatabaseSettings.read_only;   public static final Setting backup_slave = GraphDatabaseSettings.backup_slave;   public static final Setting use_memory_mapped_buffers = GraphDatabaseSettings.use_memory_mapped_buffers;   }   public static final String ALL_STORES_VERSION = "v0.A.2";   public static final String UNKNOWN_VERSION = "Uknown";   protected Config configuration;   private final IdGeneratorFactory idGeneratorFactory;   private final WindowPoolFactory windowPoolFactory;   protected FileSystemAbstraction fileSystemAbstraction;   protected final File storageFileName;   protected final IdType idType;   protected StringLogger stringLogger;   private IdGenerator idGenerator = null;   private StoreChannel fileChannel = null;   private WindowPool windowPool;   private boolean storeOk = true;   private Throwable causeOfStoreNotOk;   private FileLock fileLock;   private boolean readOnly = false;   private boolean backupSlave = false;   private long highestUpdateRecordId = -1;

1.2  neo4j 的db文件及对应的存储格式类型

文件名	文件存储格式
neostore.labeltokenstore.db	LabelTokenStore（TokenStore）
neostore.labeltokenstore.db.id	ID 类型
neostore.labeltokenstore.db.names	StringPropertyStore (AbstractDynamicStore, NAME_STORE_BLOCK_SIZE = 30)
neostore.labeltokenstore.db.names.id	ID 类型
neostore.nodestore.db	NodeStore
neostore.nodestore.db.id	ID 类型
neostore.nodestore.db.labels	ArrayPropertyStore (AbstractDynamicStorelabel_block_size=60)
neostore.nodestore.db.labels.id	ID 类型
neostore.propertystore.db	PropertyStore
neostore.propertystore.db.arrays	ArrayPropertyStore (AbstractDynamicStorearray_block_size=120)
neostore.propertystore.db.arrays.id	ID 类型
neostore.propertystore.db.id	ID 类型
neostore.propertystore.db.index	PropertyIndexStore
neostore.propertystore.db.index.id	ID 类型
neostore.propertystore.db.index.keys	StringPropertyStore (AbstractDynamicStore, NAME_STORE_BLOCK_SIZE = 30)
neostore.propertystore.db.index.keys.id	ID 类型
neostore.propertystore.db.strings	StringPropertyStore (AbstractDynamicStorestring_block_size=120)
neostore.propertystore.db.strings.id	ID 类型
neostore.relationshipgroupstore.db	RelationshipGroupStore
neostore.relationshipgroupstore.db.id	ID 类型
neostore.relationshipstore.db	RelationshipStore
neostore.relationshipstore.db.id	ID 类型
neostore.relationshiptypestore.db	RelationshipTypeTokenStore（TokenStore）
neostore.relationshiptypestore.db.id	ID 类型
neostore.relationshiptypestore.db.names	StringPropertyStore (AbstractDynamicStore, NAME_STORE_BLOCK_SIZE = 30)
neostore.relationshiptypestore.db.names.id	ID 类型
neostore.schemastore.db	SchemaStore(AbstractDynamicStore, BLOCK_SIZE = 56)
neostore.schemastore.db.id	ID 类型