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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.quantiles;
import java.util.Comparator;
import java.util.List;
import org.apache.datasketches.ArrayOfStringsSerDe;
import org.apache.datasketches.hive.common.BytesWritableHelper;
import org.apache.datasketches.quantiles.ItemsSketch;
import org.apache.hadoop.hive.ql.exec.Description;
import org.apache.hadoop.hive.ql.exec.UDF;
import org.apache.hadoop.io.BytesWritable;
@Description(
name = "GetPMF",
value = "_FUNC_(sketch, split points...)",
extended = "Returns an approximation to the Probability Mass Function (PMF)"
+ " from a sketch given a set of split points (values)."
+ " Split points are an array of M unique, monotonically increasing values"
+ " that divide the domain into M+1 consecutive disjoint intervals."
+ " The function returns an array of M+1 doubles, each of which is an approximation"
+ " to the fraction of the values that fell into one of those intervals."
+ " The definition of an interval is inclusive of the left split point and exclusive"
+ " of the right split point")
@SuppressWarnings("deprecation")
public class GetPmfFromStringsSketchUDF extends UDF {
/**
* Returns a list of fractions (PMF) from a given sketch
* @param serializedSketch serialized sketch
* @param splitPoints list of unique and monotonically increasing values
* @return list of fractions from 0 to 1
*/
public List evaluate(final BytesWritable serializedSketch, final String... splitPoints) {
if (serializedSketch == null) { return null; }
final ItemsSketch sketch = ItemsSketch.getInstance(
BytesWritableHelper.wrapAsMemory(serializedSketch),
Comparator.naturalOrder(),
new ArrayOfStringsSerDe()
);
final double[] pmf = sketch.getPMF(splitPoints);
if (pmf == null) { return null; }
return Util.primitivesToList(pmf);
}
}
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