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From rweeks <...@git.apache.org>
Subject [GitHub] accumulo pull request: Implementation of SeekingFilter, CfCqSliceF...
Date Mon, 17 Aug 2015 22:34:41 GMT
Github user rweeks commented on a diff in the pull request:

    https://github.com/apache/accumulo/pull/42#discussion_r37245182
  
    --- Diff: core/src/main/java/org/apache/accumulo/core/iterators/user/SeekingFilter.java
---
    @@ -0,0 +1,221 @@
    +/*
    + * 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.EnumMap;
    +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 {
    +    private static final EnumMap<AdvanceResult,FilterResult> PASSES = new EnumMap<>(AdvanceResult.class);
    +    private static final EnumMap<AdvanceResult,FilterResult> FAILS = new EnumMap<>(AdvanceResult.class);
    +    static {
    +      for (AdvanceResult ar : AdvanceResult.values()) {
    +        PASSES.put(ar, new FilterResult(true, ar));
    +        FAILS.put(ar, new FilterResult(false, ar));
    +      }
    +    }
    +
    +    final boolean accept;
    +    final AdvanceResult advance;
    +
    +    public FilterResult(boolean accept, AdvanceResult advance) {
    +      this.accept = accept;
    +      this.advance = advance;
    +    }
    +
    +    public static FilterResult of(boolean accept, AdvanceResult advance) {
    +      return accept ? PASSES.get(advance) : FAILS.get(advance);
    +    }
    +
    +    public String toString() {
    +      return "Acc: " + accept + " Adv: " + advance;
    +    }
    +  }
    +
    +  /**
    +   * Subclasses must provide an implementation which examines the given key and value
and determines (1) whether to accept the KV pair and (2) how far to
    +   * advance the source iterator past the key.
    +   *
    +   * @param k
    +   *          a key
    +   * @param v
    +   *          a value
    +   * @return indicating whether to pass or block the key, and how far the source iterator
should be advanced.
    +   */
    +  public abstract FilterResult filter(Key k, Value v);
    +
    +  /**
    +   * Whenever the subclass returns AdvanceResult.USE_HINT from its filter predicate,
this method will be called to see how far to advance the source iterator.
    +   * The return value must be a key which is greater than (sorts after) the input key.
If the subclass never returns USE_HINT, this method will never be called
    +   * and may safely return null.
    +   *
    +   * @param k
    +   *          a key
    +   * @param v
    +   *          a value
    +   * @return as above
    +   */
    +  public abstract Key getNextKeyHint(Key k, Value v);
    +
    +  private Collection<ByteSequence> columnFamilies;
    +  private boolean inclusive;
    +  private Range seekRange;
    +  private boolean negate;
    +
    +  private AdvanceResult advance;
    +
    +  private boolean advancedPastSeek = false;
    +
    +  @Override
    +  public void next() throws IOException {
    +    findTop();
    +  }
    +
    +  @Override
    +  public boolean hasTop() {
    +    return !advancedPastSeek && super.hasTop();
    +  }
    +
    +  @Override
    +  public void seek(Range range, Collection<ByteSequence> columnFamilies, boolean
inclusive) throws IOException {
    +    super.seek(range, columnFamilies, inclusive);
    +    advance = null;
    +    this.columnFamilies = columnFamilies;
    +    this.inclusive = inclusive;
    +    seekRange = range;
    +    advancedPastSeek = false;
    +    findTop();
    +  }
    +
    +  @Override
    +  public void init(SortedKeyValueIterator<Key,Value> source, Map<String,String>
options, IteratorEnvironment env) throws IOException {
    +    super.init(source, options, env);
    +    negate = Boolean.parseBoolean(options.get(NEGATE));
    +  }
    +
    +  @Override
    +  public SortedKeyValueIterator<Key,Value> deepCopy(IteratorEnvironment env) {
    +    SeekingFilter newInstance;
    +    try {
    +      newInstance = this.getClass().newInstance();
    +    } catch (Exception e) {
    +      throw new RuntimeException(e);
    +    }
    +    newInstance.setSource(getSource().deepCopy(env));
    +    newInstance.negate = negate;
    +    return newInstance;
    +  }
    +
    +  protected void findTop() throws IOException {
    +    SortedKeyValueIterator<Key,Value> src = getSource();
    +    // advance could be null if we've just been seeked
    +    if (src.hasTop() && advance != null) {
    --- End diff --
    
    Good point. Fixed in 71b1b20. In `next()`, `advance` should never be null and no need
to check `src.hasTop()` because `hasTop` already checks that, and calling `next` when `hasTop`
is false is a violation of the iterator contract.


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