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Simple Apache Accumulo examples.
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/*
 * 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.examples.simple.shard;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Map.Entry;
import java.util.concurrent.TimeUnit;

import org.apache.accumulo.core.cli.BatchScannerOpts;
import org.apache.accumulo.core.cli.ClientOnRequiredTable;
import org.apache.accumulo.core.client.BatchScanner;
import org.apache.accumulo.core.client.Connector;
import org.apache.accumulo.core.client.IteratorSetting;
import org.apache.accumulo.core.client.sample.SamplerConfiguration;
import org.apache.accumulo.core.data.Key;
import org.apache.accumulo.core.data.Range;
import org.apache.accumulo.core.data.Value;
import org.apache.accumulo.core.iterators.user.IntersectingIterator;
import org.apache.hadoop.io.Text;

import com.beust.jcommander.Parameter;

/**
 * This program queries a set of terms in the shard table (populated by {@link Index}) using the
 * {@link IntersectingIterator}.
 *
 * See docs/examples/README.shard for instructions.
 */

public class Query {

  static class Opts extends ClientOnRequiredTable {
    @Parameter(description = " term {  ... }")
    List terms = new ArrayList<>();

    @Parameter(names = {"--sample"},
        description = "Do queries against sample, useful when sample is built"
            + " using column qualifier")
    private boolean useSample = false;

    @Parameter(names = {"--sampleCutoff"},
        description = "Use sample data to determine if a query might return a"
            + " number of documents over the cutoff. This check is per tablet.")
    private Integer sampleCutoff = null;
  }

  public static List query(BatchScanner bs, List terms, Integer cutoff) {

    Text columns[] = new Text[terms.size()];
    int i = 0;
    for (String term : terms) {
      columns[i++] = new Text(term);
    }

    IteratorSetting ii;

    if (cutoff != null) {
      ii = new IteratorSetting(20, "ii", CutoffIntersectingIterator.class);
      CutoffIntersectingIterator.setCutoff(ii, cutoff);
    } else {
      ii = new IteratorSetting(20, "ii", IntersectingIterator.class);
    }

    IntersectingIterator.setColumnFamilies(ii, columns);
    bs.addScanIterator(ii);
    bs.setRanges(Collections.singleton(new Range()));
    List result = new ArrayList<>();
    for (Entry entry : bs) {
      result.add(entry.getKey().getColumnQualifier().toString());
    }
    return result;
  }

  public static void main(String[] args) throws Exception {
    Opts opts = new Opts();
    BatchScannerOpts bsOpts = new BatchScannerOpts();
    opts.parseArgs(Query.class.getName(), args, bsOpts);
    Connector conn = opts.getConnector();
    BatchScanner bs = conn.createBatchScanner(opts.getTableName(), opts.auths, bsOpts.scanThreads);
    bs.setTimeout(bsOpts.scanTimeout, TimeUnit.MILLISECONDS);
    if (opts.useSample) {
      SamplerConfiguration samplerConfig = conn.tableOperations()
          .getSamplerConfiguration(opts.getTableName());
      CutoffIntersectingIterator.validateSamplerConfig(
          conn.tableOperations().getSamplerConfiguration(opts.getTableName()));
      bs.setSamplerConfiguration(samplerConfig);
    }
    for (String entry : query(bs, opts.terms, opts.sampleCutoff))
      System.out.println("  " + entry);

    bs.close();
  }

}