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From "Nicolas Liochon (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-9963) Remove the ReentrantReadWriteLock in the MemStore
Date Wed, 13 Nov 2013 12:01:26 GMT
Nicolas Liochon created HBASE-9963:
--------------------------------------

             Summary: Remove the ReentrantReadWriteLock in the MemStore
                 Key: HBASE-9963
                 URL: https://issues.apache.org/jira/browse/HBASE-9963
             Project: HBase
          Issue Type: Improvement
          Components: regionserver
    Affects Versions: 0.96.0, 0.98.0
            Reporter: Nicolas Liochon
            Assignee: Nicolas Liochon
            Priority: Minor
             Fix For: 0.98.0, 0.96.1


If I'm not wrong, the MemStore is always used from the HStore. The code in HStore puts a lock
before calling MemStore. So the lock in Memstore is useless. 

For example, in HStore
{code}
  @Override
  public long upsert(Iterable<Cell> cells, long readpoint) throws IOException {
    this.lock.readLock().lock();
    try {
      return this.memstore.upsert(cells, readpoint);
    } finally {
      this.lock.readLock().unlock();
    }
  }
{code}

With this in MemStore

{code}
  public long upsert(Iterable<Cell> cells, long readpoint) {
   this.lock.readLock().lock(); // <==========Am I useful?
    try {
      long size = 0;
      for (Cell cell : cells) {
        size += upsert(cell, readpoint);
      }
      return size;
    } finally {
      this.lock.readLock().unlock();
    }
  }
{code}

I've checked, all the locks in MemStore are backed by a lock in HStore, the only exception
beeing
{code}
  void snapshot() {
    this.memstore.snapshot();
  }
{code}
And I would say it's a bug. If it's confirm ([~lhofhansl], what do you think?), I will add
a lock there and remove all of them in MemStore. They do appear in the profiling.



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