berkeley db je 的几个问题

1. cache 容量的规划
$ ./calBdb.sh 2000000 64 256 128
Inputs: records=2000000 keySize=64 dataSize=256 nodeMax=128 density=80% overhead=10%

    Cache Size      Btree Size  Description
--------------  --------------  -----------
   219,994,975     197,995,478  Minimum, internal nodes only 
   259,343,313     233,408,982  Maximum, internal nodes only 
   877,772,753     789,995,478  Minimum, internal nodes and leaf nodes 
   917,121,091     825,408,982  Maximum, internal nodes and leaf nodes 

Btree levels: 4
./calBdb.sh 10000000 64 256 128
Inputs: records=10000000 keySize=64 dataSize=256 nodeMax=128 density=80% overhead=10%

    Cache Size      Btree Size  Description
--------------  --------------  -----------
1,099,974,877     989,977,390  Minimum, internal nodes only 
1,296,716,566   1,167,044,910  Maximum, internal nodes only 
4,388,863,766   3,949,977,390  Minimum, internal nodes and leaf nodes 
4,585,605,455   4,127,044,910  Maximum, internal nodes and leaf nodes 

对内存的需求还是不小的。10m ,1G.

2.transaction 太慢，难以忍受
3.防止， "phantoms" when not using transactions?
这个我遇到了，不过，我没有按照bdb 的提示解决。

boolean exists = false;
boolean done = false;

while (!done) {
  OperationStatus status = cursor.putNoOverwrite(key, insertData);
  if (status == OperationStatus.SUCCESS) {
    /* A new record is inserted */
    exists = false;
    done = true;
  } else {
    status = cursor.getSearchKey(key, foundData, LockMode.RMW);
    if (status == OperationStatus.SUCCESS) {
      /* An existing record is found */
      exists = true;
      done = true;
    }
    /* else continue loop */
  }
}

4.cache percetage 一定要设，否则， outofmemory .

5.bdb ,nio 的时候，不能用thread.currentthread.interupt() 停止thread .