oen advice about snapshot

[cmumford]

Original issue 170 created by wangtengchao on 2013-05-15T11:37:30.000Z:

What steps will reproduce the problem?
1.all code adn information showed in the additional information
2.
3.

What is the expected output? What do you see instead?

What version of the product are you using? On what operating system?
leveldb 1.9 fedora17

Please provide any additional information below.

    const leveldb::Snapshot* snap_shot = db->GetSnapshot();
    leveldb::ReadOptions read_options;
    // change "key0"'s value from "value0" to "new"
    db->Put(leveldb::WriteOptions(),"key0","new");
    string val;
    db->Get(read_options,"key0",&val);
    cout<<"no snapshot value: "<<val<<endl;//output " new" . 
    read_options.snapshot = snap_shot;
    db->Get(read_options,"key0",&val);
    cout<<"snapshot value: "<<val<<endl;//output "value0" . 

    // release snapshot
    db->ReleaseSnapshot(read_options.snapshot);

    db->Get(read_options,"key0",&val);
    cout<<"after release snapshot: "<<val<<endl;
    //output "value0" !!! It's wrong

Advice:
If i release the snapshot ,i should get the newest infomation.
But only i add the "read_options.snapshot = NULL; " after db->ReleaseSnapshot(...) anually,can i get the right result---output "new".

I deep into the code in db_imp.cc and know it will judge "options.snapshot!=NULL" when call NewIterator(...) and Get(...) .
SO I think set the read_options.snapshot=NULL in DB::ReleaseSnapshot() is a good idea. Or you should modify the document clearly and add "read_options.snapshot = NULL;" to the example in the Snapshots part of http://leveldb.googlecode.com/svn/trunk/doc/index.html

[cmumford]

Several year old question. I'm assuming either answered or no longer needed.