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From rweeks <...@git.apache.org>
Subject [GitHub] accumulo pull request: Implementation of SeekingFilter, CfCqSliceF...
Date Sun, 16 Aug 2015 08:46:31 GMT
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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