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https://issues.apache.org/jira/browse/BEAM-5922?focusedWorklogId=160857&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-160857
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ASF GitHub Bot logged work on BEAM-5922:
----------------------------------------
Author: ASF GitHub Bot
Created on: 30/Oct/18 20:58
Start Date: 30/Oct/18 20:58
Worklog Time Spent: 10m
Work Description: jklukas commented on a change in pull request #6892:
[BEAM-5922] Refactor Map, FlatMap, and Filter on MapperBase
URL: https://github.com/apache/beam/pull/6892#discussion_r229483690
##########
File path:
sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/MapperBase.java
##########
@@ -0,0 +1,111 @@
+/*
+ * 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.beam.sdk.transforms;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+import static com.google.common.base.Preconditions.checkState;
+
+import javax.annotation.Nullable;
+import org.apache.beam.sdk.transforms.Contextful.Fn;
+import org.apache.beam.sdk.transforms.display.DisplayData;
+import org.apache.beam.sdk.transforms.display.HasDisplayData;
+import org.apache.beam.sdk.values.PCollection;
+import org.apache.beam.sdk.values.TypeDescriptor;
+
+/**
+ * Abstract class providing a base for {@link PTransform}s that map a simple
function over elements.
+ *
+ * <p>The passed {@code fn} returns an {@link Iterable}, each element of which
will be sent to
+ * output. That interface naturally expresses a FlatMap, but both Map (always
one output element)
+ * and Filter (either the input element is passed through or an empty
collection) can both be
+ * expressed as special cases.
+ */
+abstract class MapperBase<InputT, OutputT>
+ extends PTransform<PCollection<? extends InputT>, PCollection<OutputT>> {
+ @Nullable private final transient TypeDescriptor<InputT> inputType;
+ @Nullable final transient TypeDescriptor<OutputT> outputType;
+ @Nullable private final transient Object originalFnForDisplayData;
+ @Nullable private final Contextful<Fn<InputT, Iterable<OutputT>>> fn;
+
+ MapperBase(
+ @Nullable String name,
+ @Nullable Contextful<Fn<InputT, Iterable<OutputT>>> fn,
+ @Nullable Object originalFnForDisplayData,
+ @Nullable TypeDescriptor<InputT> inputType,
+ TypeDescriptor<OutputT> outputType) {
+ super(name);
Review comment:
Previously, MapElements and FlatMapElements called `apply(name, transform)`
but Filter omitted the name. Browsing through the DisplayData code, it looks
that passing `name` to the `PTransform` constructor here has the same effect as
passing a name to `apply`.
If the naming here ends up being different from previous versions, will that
cause issues with state if a pipeline is redeployed with an updated version of
the Beam API? If this is critical, I can do more investigation into how to test
this. Currently, it looks like a tricky thing to test since the DoFn is created
internally and isn't available to the class.
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Issue Time Tracking
-------------------
Worklog Id: (was: 160857)
Time Spent: 50m (was: 40m)
> Common base class for FlatMapElements, MapElements, and Filter
> --------------------------------------------------------------
>
> Key: BEAM-5922
> URL: https://issues.apache.org/jira/browse/BEAM-5922
> Project: Beam
> Issue Type: Improvement
> Components: sdk-java-core
> Reporter: Jeff Klukas
> Assignee: Jeff Klukas
> Priority: Minor
> Labels: pull-request-available
> Time Spent: 50m
> Remaining Estimate: 0h
>
> By having FlatMapElements, MapElements, and Filter all inherit from a common
> MapperBase, we can reduce code duplication between these three classes for
> better consistency in future changes. There should be no change in
> functionality or public interface with this change.
> In particular, this change will simplify the implementation of failure
> handling
> across these transforms in https://issues.apache.org/jira/browse/BEAM-5638
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