Github user rweeks commented on a diff in the pull request:
https://github.com/apache/accumulo/pull/42#discussion_r37143631
--- Diff:
core/src/main/java/org/apache/accumulo/core/iterators/user/SeekingFilter.java
---
@@ -0,0 +1,206 @@
+/*
+ * 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.user;
+
+import org.apache.accumulo.core.data.ByteSequence;
+import org.apache.accumulo.core.data.Key;
+import org.apache.accumulo.core.data.PartialKey;
+import org.apache.accumulo.core.data.Range;
+import org.apache.accumulo.core.data.Value;
+import org.apache.accumulo.core.iterators.IteratorEnvironment;
+import org.apache.accumulo.core.iterators.SortedKeyValueIterator;
+import org.apache.accumulo.core.iterators.WrappingIterator;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.util.Collection;
+import java.util.Map;
+
+/**
+ * Base class for filters that can skip over key-value pairs which do not
match their filter predicate. In addition to returning true/false to accept or
reject
+ * a kv pair, subclasses can return an extra field which indicates how far
the source iterator should be advanced.
+ *
+ * Note that the behaviour of the negate option is different from the
Filter class. If a KV pair fails the subclass' filter predicate and negate is
true, then
+ * the KV pair will pass the filter. However if the subclass advances the
source past a bunch of KV pairs, all those pairs will be implicitly rejected and
+ * negate will have no effect.
+ *
+ * @see org.apache.accumulo.core.iterators.Filter
+ */
+public abstract class SeekingFilter extends WrappingIterator {
+ private static final Logger log =
LoggerFactory.getLogger(SeekingFilter.class);
+
+ protected static final String NEGATE = "negate";
+
+ public enum AdvanceResult {
+ NEXT, NEXT_CQ, NEXT_CF, NEXT_ROW, USE_HINT
+ }
+
+ public static class FilterResult {
+ final boolean accept;
+ final AdvanceResult advance;
+
+ public FilterResult(boolean accept, AdvanceResult advance) {
--- End diff --
I like the idea of limiting the number of FilterResult objects that need to
be created. I also like including the hint in the FilterResult object. I don't
see a simple way to achieve both goals - I think you'd wind up re-using mutable
objects. I've switched to a static factory method in d460ef1.
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