h2database源码浅析:TransactionMap、MVMap、MVStore

时间:2021-10-19 21:43:29
  • TransactionStore:A store that supports concurrent MVCC read-committed transactions.
  • TransactionStore.Transaction:A transaction.
  • TransactionStore.TransactionMap<K,V>:A map that supports transactions.

TransactionStore通过openMap获取到Map:

<K,V> TransactionStore.TransactionMap<K,V>
openMap(java.lang.String name, DataType keyType, DataType valueType) 
          Open the map to store the data.

TransactionStore通过open创建一个Transaction:
TransactionStore.Transaction begin() 
Begin a new transaction.

MVMap<K,V>

多版本Map
读操作:Read operations can happen concurrently with all other operations, without risk of corruption.
写操作:Write operations first read the relevant area from disk to memory concurrently, and only then modify the data. The in-memory part of write operations is synchronized. For scalable concurrent in-memory write operations, the map should be split into multiple smaller sub-maps that are then synchronized independently.

所有已实现的接口:
java.util.concurrent.ConcurrentMap<K,V>, java.util.Map<K,V>

直接已知子类:
MVMapConcurrent, MVRTreeMap

MVTableEngine.Store

public MVStore getStore() 获取MVStore

MVStore

A persistent storage for maps.
openMap()方法用以创建一个MVMap:

public <K,V> MVMap<K,V> openMap(java.lang.String name)