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From joshelser <...@git.apache.org>
Subject [GitHub] accumulo pull request #244: Discuss ACCUMULO-3079: collapsing the iterator s...
Date Thu, 20 Apr 2017 16:18:46 GMT
Github user joshelser commented on a diff in the pull request:

    https://github.com/apache/accumulo/pull/244#discussion_r112494944
  
    --- Diff: core/src/main/java/org/apache/accumulo/core/iterators/ServerWrappingIterator.java
---
    @@ -0,0 +1,80 @@
    +/*
    + * 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;
    +
    +import java.io.IOException;
    +import java.util.Collection;
    +import java.util.Map;
    +
    +import org.apache.accumulo.core.data.ByteSequence;
    +import org.apache.accumulo.core.data.Key;
    +import org.apache.accumulo.core.data.Range;
    +import org.apache.accumulo.core.data.Value;
    +
    +/**
    + * A convenience class for implementing iterators that select, but do not modify, entries
read from a source iterator. Default implementations exist for all
    + * methods, but {@link #deepCopy} will throw an <code>UnsupportedOperationException</code>.
    + *
    + * This iterator has some checks in place to enforce the iterator contract. Specifically,
it verifies that it has a source iterator and that {@link #seek} has
    + * been called before any data is read. If either of these conditions does not hold true,
an <code>IllegalStateException</code> will be thrown. In particular,
    + * this means that <code>getSource().seek</code> and <code>super.seek</code>
no longer perform identical actions. Implementors should take note of this and if
    + * <code>seek</code> is overridden, ensure that <code>super.seek</code>
is called before data is read.
    + */
    +public abstract class ServerWrappingIterator implements SortedKeyValueIterator<Key,Value>
{
    +
    +  protected final SortedKeyValueIterator<Key,Value> source;
    +
    +  public ServerWrappingIterator(SortedKeyValueIterator<Key,Value> source) {
    +    this.source = source;
    +  }
    +
    +  @Override
    +  public SortedKeyValueIterator<Key,Value> deepCopy(IteratorEnvironment env) {
    +    throw new UnsupportedOperationException();
    --- End diff --
    
    Why the decision to throw this exception and not let the compiler tell the user (at compile
time, not run time) that they need to implement this method?


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