jihoonson commented on a change in pull request #6430: Contributing Moving-Average Query to open source. URL: https://github.com/apache/incubator-druid/pull/6430#discussion_r259542057
########## File path: extensions-contrib/moving-average-query/src/main/java/org/apache/druid/query/movingaverage/averagers/BaseAverager.java ########## @@ -0,0 +1,198 @@ +/* + * 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.druid.query.movingaverage.averagers; + +import org.apache.druid.query.aggregation.AggregatorFactory; + +import java.lang.reflect.Array; +import java.util.Map; + +/** + * Common base class available for use by averagers. The base class implements methods that + * capture incoming and skipped rows and store them in an array, to be used later for + * calculating the actual value. + * + * @param <I> The type of intermediate value to be retrieved from the row and stored + * @param <R> The type of result the averager is expected to produce + */ +public abstract class BaseAverager<I, R extends Object> implements Averager<R> +{ + + private final int numBuckets; + private final int cycleSize; + private final String name; + private final String fieldName; + private final I[] buckets; + private int index; + + /* This flag checks if the intermediate sketches have to be finalized or not + for further computation involving sketches */ + private boolean shouldFinalize; + + /** + * @param storageType The class to use for storing intermediate values + * @param numBuckets The number of buckets to include in the window being aggregated + * @param name The name of the resulting metric + * @param fieldName The field to extra from incoming rows and stored in the window cache + * @param cycleSize Cycle group size. Used to calculate day-of-week option. Default=1 (single element in group). + * @param shouldFinalize Whether the intermediate values need to be finalized prior to averaging + */ + public BaseAverager(Class<I> storageType, int numBuckets, String name, String fieldName, int cycleSize, + boolean shouldFinalize) + { + this.numBuckets = numBuckets; + this.name = name; + this.fieldName = fieldName; + this.index = 0; + @SuppressWarnings("unchecked") + final I[] array = (I[]) Array.newInstance(storageType, numBuckets); + this.buckets = array; + this.shouldFinalize = shouldFinalize; + this.cycleSize = cycleSize; + } + + public BaseAverager(Class<I> storageType, int numBuckets, String name, String fieldName, int cycleSize) + { + this(storageType, numBuckets, name, fieldName, cycleSize, true); + } + + + /* (non-Javadoc) + * @see Averager#addElement(java.util.Map, java.util.Map) + */ + @SuppressWarnings("unchecked") + @Override + public void addElement(Map<String, Object> e, Map<String, AggregatorFactory> a) + { + Object metric = e.get(fieldName); + I finalMetric; + if (a.containsKey(fieldName) && shouldFinalize) { + AggregatorFactory af = a.get(fieldName); + finalMetric = metric != null ? (I) af.finalizeComputation(metric) : null; + } else { + finalMetric = (I) metric; + } + buckets[index++] = finalMetric; + index %= numBuckets; + } + + /* (non-Javadoc) + * @see Averager#skip() + */ + @Override + public void skip() + { + buckets[index++] = null; + index %= numBuckets; + } + + /* (non-Javadoc) + * @see Averager#getResult() + */ + @Override + public R getResult() + { + if (!hasData()) { + return null; + } + return computeResult(); + } + + /** + * Compute the result value to be returned by getResult. + * + * <p>This routine will only be called when there is valid data within the window + * and doesn't need to worry about detecting the case where no data should be returned. + * + * <p> + * The method typically should use {@link #getBuckets()} to retrieve the set of buckets + * within the window and then compute a value based on those. It should expect nulls within + * the array, indicating buckets where no row was found for the dimension combination. It is + * up to the actual implementation to determin how to evaluate those nulls. + * + * <p> + * The type returned is NOT required to be the same type as the intermediary value. For example, + * the intermediate value could be a Sketch, but the result a Long. + * + * @return the computed result + */ + protected abstract R computeResult(); + + /* (non-Javadoc) + * @see Averager#getName() + */ + @Override + public String getName() + { + return name; + } + + /** + * Returns the fieldname to be extracted from any event rows passed in and stored + * for use computing the windowed function. + * + * @return the fieldName + */ + public String getFieldName() + { + return fieldName; + } + + /** + * @return the numBuckets + */ + public int getNumBuckets() + { + return numBuckets; + } + + /** + * @return the cycleSize + */ + public int getCycleSize() + { + return cycleSize; + } + + /** + * @return the array of buckets + */ + protected I[] getBuckets() + { + return (I[]) buckets; Review comment: Unnecessary cast. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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