Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/1255#discussion_r43951220
--- Diff:
flink-java/src/main/java/org/apache/flink/api/java/functions/RangeBoundaryBuilder.java
---
@@ -0,0 +1,71 @@
+/*
+ * 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.flink.api.java.functions;
+
+import org.apache.flink.api.common.distributions.CommonRangeBoundaries;
+import org.apache.flink.api.common.distributions.RangeBoundaries;
+import org.apache.flink.api.common.functions.RichMapPartitionFunction;
+import org.apache.flink.api.common.typeutils.TypeComparator;
+import org.apache.flink.api.common.typeutils.TypeComparatorFactory;
+import org.apache.flink.util.Collector;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
+
+/**
+ * Build RangeBoundaries with input records. First, sort the input
records, and then select
+ * the boundaries with same interval.
+ *
+ * @param <T>
+ */
+public class RangeBoundaryBuilder<T> extends RichMapPartitionFunction<T,
RangeBoundaries<T>> {
+
+ private int parallelism;
+ private final TypeComparatorFactory<T> comparatorFactory;
+
+ public RangeBoundaryBuilder(TypeComparatorFactory<T> comparator, int
parallelism) {
+ this.comparatorFactory = comparator;
+ this.parallelism = parallelism;
+ }
+
+ @Override
+ public void mapPartition(Iterable<T> values,
Collector<RangeBoundaries<T>> out) throws Exception {
+ final TypeComparator<T> comparator =
this.comparatorFactory.createComparator();
+ List<T> sampledData = new ArrayList<>();
+ for (T value : values) {
--- End diff --
We can use `TypeComparator.extractKeys()` to extract only the key fields as
`Object[]` from the records. `TypeComparator[]
TypeComparator.getFlatComparators()` returns comparators for all fields
returned by `extractKeys()`. That way we can reduce the size of the
distribution, because only keys are stored.
---
If your project is set up for it, you can reply to this email and have your
reply appear on GitHub as well. If your project does not have this feature
enabled and wishes so, or if the feature is enabled but not working, please
contact infrastructure at infrastruct...@apache.org or file a JIRA ticket
with INFRA.
---
