org.apache.hadoop.hive.ql.parse.SamplePruner.java Source code

Introduction

Here is the source code for org.apache.hadoop.hive.ql.parse.SamplePruner.java

Source

/**
 * 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.hadoop.hive.ql.parse;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.hive.ql.metadata.Partition;
import org.apache.hadoop.fs.Path;
import java.util.*;

public class SamplePruner {
    private String tabAlias;
    private TableSample tableSample;
    // The log
    @SuppressWarnings("nls")
    private static final Log LOG = LogFactory.getLog("hive.ql.parse.SamplePruner");

    public SamplePruner(String alias, TableSample tableSample) {
        this.tabAlias = alias;
        this.tableSample = tableSample;
    }

    public String getTabAlias() {
        return this.tabAlias;
    }

    public void setTabAlias(String tabAlias) {
        this.tabAlias = tabAlias;
    }

    public TableSample getTableSample() {
        return this.tableSample;
    }

    public void setTableSample(TableSample tableSample) {
        this.tableSample = tableSample;
    }

    @SuppressWarnings("nls")
    public Path[] prune(Partition part) throws SemanticException {
        int num = this.tableSample.getNumerator();
        int den = this.tableSample.getDenominator();
        int bucketCount = part.getBucketCount();
        List<String> tabBucketCols = part.getBucketCols();
        ArrayList<String> sampleCols = this.tableSample.getCols();
        String fullScanMsg = "";
        // check if input pruning is possible
        if (sampleCols == null || sampleCols.size() == 0 || tabBucketCols.equals(sampleCols)) {
            LOG.trace("numerator = " + num);
            LOG.trace("denominator = " + den);
            LOG.trace("bucket count = " + bucketCount);
            if (bucketCount == den) {
                Path[] ret = new Path[1];
                ret[0] = part.getBucketPath(num - 1);
                return (ret);
            } else if (bucketCount > den && bucketCount % den == 0) {
                int numPathsInSample = bucketCount / den;
                Path[] ret = new Path[numPathsInSample];
                for (int i = 0; i < numPathsInSample; i++) {
                    ret[i] = part.getBucketPath(i * den + num - 1);
                }
                return ret;
            } else if (bucketCount < den && den % bucketCount == 0) {
                Path[] ret = new Path[1];
                ret[0] = part.getBucketPath((num - 1) % bucketCount);
                return ret;
            } else {
                // need to do full scan
                fullScanMsg = "Tablesample denominator " + den + " is not multiple/divisor of bucket count "
                        + bucketCount + " of table " + this.tabAlias;
            }
        } else {
            // need to do full scan
            fullScanMsg = "Tablesample not on clustered columns";
        }
        LOG.warn(fullScanMsg + ", using full table scan");
        Path[] ret = part.getPath();
        return ret;
    }
}