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From keith-turner <...@git.apache.org>
Subject [GitHub] accumulo pull request: ACCUMULO-3913 Added per table sampling
Date Tue, 15 Sep 2015 14:42:13 GMT
Github user keith-turner commented on a diff in the pull request:

    https://github.com/apache/accumulo/pull/46#discussion_r39518313
  
    --- Diff: core/src/main/java/org/apache/accumulo/core/sample/Sampler.java ---
    @@ -0,0 +1,45 @@
    +/*
    + * 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.sample;
    +
    +import org.apache.accumulo.core.client.admin.SamplerConfiguration;
    +import org.apache.accumulo.core.data.Key;
    +
    +/**
    + * A function that decides which key values are stored in a tables sample. As Accumuo
compacts data and creates rfiles it uses a Sampler to decided what to
    + * store in the rfiles sample section. The class name of the Sampler and the Samplers
configuration are stored in each rfile. A scan of a tables sample will
    + * only succeed if all rfiles were created with the same sampler and sampler configuration.
    + *
    + * <p>
    + * Since the decisions that Sampler makes are persisted, the behavior of a Sampler for
a given configuration should always be the same. One way to offer a new
    + * behavior is to offer new options, while still supporting old behavior with a Samplers
existing options.
    + *
    + * <p>
    + * Ideally a sampler that selects a Key k1 would also select updates for k1. For example
if a Sampler selects :
    + * {@code row='000989' family='name' qualifier='last' visibility='ADMIN' time=9 value='Doe'},
it would be nice if it also selected :
    + * {@code row='000989' family='name' qualifier='last' visibility='ADMIN' time=20 value='Dough'}.
Using hash and modulo on the key fields is a good way to
    + * accomplish this and {@link AbstractHashSampler} provides a good basis for implementation.
    + *
    + * @since 1.8.0
    + */
    +
    +public interface Sampler {
    +  void init(SamplerConfiguration config);
    +
    +  boolean accept(Key k);
    --- End diff --
    
    Added javadoc in 3d0be31


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