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From keith-turner <...@git.apache.org>
Subject [GitHub] accumulo pull request #260: ACCUMULO-4643 initial implementation
Date Mon, 05 Jun 2017 17:27:31 GMT
Github user keith-turner commented on a diff in the pull request:

    https://github.com/apache/accumulo/pull/260#discussion_r120162160
  
    --- Diff: core/src/main/java/org/apache/accumulo/core/iterators/YieldCallback.java ---
    @@ -0,0 +1,57 @@
    +/*
    + * Licensed to the Apache Software Foundation (ASF) under one or more
    + * contributor license agreements.  See the NOTICE file distributed with
    + * this work for additional information regarding copyright ownership.
    + * The ASF licenses this file to You under the Apache License, Version 2.0
    + * (the "License"); you may not use this file except in compliance with
    + * the License.  You may obtain a copy of the License at
    + *
    + *     http://www.apache.org/licenses/LICENSE-2.0
    + *
    + * Unless required by applicable law or agreed to in writing, software
    + * distributed under the License is distributed on an "AS IS" BASIS,
    + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    + * See the License for the specific language governing permissions and
    + * limitations under the License.
    + */
    +package org.apache.accumulo.core.iterators;
    +
    +/**
    + * This callback handles the state of yielding within an iterator
    + */
    +public class YieldCallback<K> {
    --- End diff --
    
    Transform could possibly be handled in a push down manner also.  This could be made easier
with a utility method.  Just sharing thoughts I had on this for discussion, not saying this
is something we should do.
    
    ```java
    class YieldCallback {
      /**
       * Returns a new YieldCallback that wraps the passed in a transforms the key when yeild
is called.
       */
      YieldCallback transform(YieldCallback yc, Function<Key, Key> keyTransform);
    }
    ```
    
    ```java
    class MyIter implements SKVI {
      @Override
      void enableYielding(YieldCallback yc) {
        source.enableYielding(YieldCallback.transform(yc, k -> transform(k));
      }
    }
    
    ``` 


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