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Apache Hive adaptors for the DataSketches library.
/*
* 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.datasketches.hive.kll;
import org.apache.datasketches.hive.common.BytesWritableHelper;
import org.apache.datasketches.kll.KllFloatsSketch;
import org.apache.hadoop.hive.ql.exec.Description;
import org.apache.hadoop.hive.ql.exec.UDF;
import org.apache.hadoop.io.BytesWritable;
@Description(name = "GetQuantile", value = "_FUNC_(sketch, fraction)",
extended = " Returns a quantile value from a given KllFloatsSketch."
+ " A single value for a given fraction is returned."
+ " The fraction represents a normalized rank, and must be from 0 to 1 inclusive."
+ " For example, a fraction of 0.5 corresponds to 50th percentile, which is"
+ " the median value of the distribution (the number separating the higher half"
+ " of the probability distribution from the lower half).")
@SuppressWarnings("deprecation")
public class GetQuantileUDF extends UDF {
/**
* Returns a quantile value from a given sketch
* @param serializedSketch serialized sketch
* @param fraction value from 0 to 1 inclusive
* @return quantile value
*/
public Float evaluate(final BytesWritable serializedSketch, final double fraction) {
if (serializedSketch == null) { return null; }
final KllFloatsSketch sketch =
KllFloatsSketch.heapify(BytesWritableHelper.wrapAsMemory(serializedSketch));
return sketch.getQuantile(fraction);
}
}
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