question for put(K key,V value) in DefaultStoreClient.java

[Evan Zeng]

recently I am having being studying voldemort's source code for detail implementation,and today  disturbed by a question that implementing put operator in DefaultStoreClient.java. My question is that what's the difference between getVersion(key) and get(key,null) except that "get" can return useless value.In my opinion, if getVersion can get more than one versions,get(key,null)  also throw an "InconsistentDataException" Exception.  So it seems no  meaning to do so

 

    public Version put(K key, V value) {

        List<Version> versions = getVersions(key);

        Versioned<V> versioned;

        if(versions.isEmpty())

            versioned = Versioned.value(value, new VectorClock());

        else if(versions.size() == 1)

            versioned = Versioned.value(value, versions.get(0));

        else {

            versioned = get(key, null);

            if(versioned == null)

                versioned = Versioned.value(value, new VectorClock());

            else

                versioned.setObject(value);

        }

        return put(key, versioned);

    }

[Vinoth Chandar]

Hi,

I don't think getVersion(k) is used anymore.

If you are asking about the difference between get and getVersions, its pretty much self explanatory. getVersion fetches the version of the value alone (It can fetch multiple versions for the same key, if they exist and can't be auto merged). get does the same thing, except, it will return the actual value too.

Hope that helps.

-Vinoth