Github user scubafuchs commented on a diff in the pull request:
https://github.com/apache/accumulo/pull/244#discussion_r112533329
--- 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 --
At least at the time, I believe that a bunch of the extending classes would
have implement this method the same way, so it reduces the amount of code to
have a common implementation here. I think this is more of a question about
whether deepCopy should really be common across all uses of the
SortedKeyValueIterator interface, or whether we should have organized it
differently. Interesting topic, but probably shouldn't hold up this project.
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