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https://issues.apache.org/jira/browse/BEAM-4461?focusedWorklogId=162835&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-162835
]
ASF GitHub Bot logged work on BEAM-4461:
----------------------------------------
Author: ASF GitHub Bot
Created on: 06/Nov/18 01:26
Start Date: 06/Nov/18 01:26
Worklog Time Spent: 10m
Work Description: reuvenlax commented on a change in pull request #6832:
[BEAM-4461] CoGroup transforms for schemas.
URL: https://github.com/apache/beam/pull/6832#discussion_r230973954
##########
File path:
sdks/java/core/src/main/java/org/apache/beam/sdk/schemas/transforms/CoGroup.java
##########
@@ -0,0 +1,326 @@
+/*
+ * 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.schemas.transforms;
+
+import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.Lists;
+import com.google.common.collect.Maps;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
+import java.util.Map;
+import java.util.TreeMap;
+import java.util.stream.Collectors;
+import javax.annotation.Nullable;
+import org.apache.beam.sdk.coders.KvCoder;
+import org.apache.beam.sdk.schemas.FieldAccessDescriptor;
+import org.apache.beam.sdk.schemas.Schema;
+import org.apache.beam.sdk.schemas.Schema.FieldType;
+import org.apache.beam.sdk.schemas.SchemaCoder;
+import org.apache.beam.sdk.transforms.DoFn;
+import org.apache.beam.sdk.transforms.PTransform;
+import org.apache.beam.sdk.transforms.ParDo;
+import org.apache.beam.sdk.transforms.SerializableFunction;
+import org.apache.beam.sdk.transforms.join.CoGbkResult;
+import org.apache.beam.sdk.transforms.join.CoGroupByKey;
+import org.apache.beam.sdk.transforms.join.KeyedPCollectionTuple;
+import org.apache.beam.sdk.values.KV;
+import org.apache.beam.sdk.values.PCollection;
+import org.apache.beam.sdk.values.PCollectionTuple;
+import org.apache.beam.sdk.values.Row;
+import org.apache.beam.sdk.values.TupleTag;
+
+/**
+ * A transform that performs equijoins across multiple schema {@link
PCollection}s.
+ *
+ * <p>This transform has similarites to {@link CoGroupByKey}, however works on
PCollections that
+ * have schemas. This allows users of the transform to simply specify schema
fields to join on. The
+ * output type of the transform is a {@literal KV<Row, Row>} where the value
contains one field for
+ * every input PCollection and the key represents the fields that were joined
on. By default the
+ * cross product is not expanded, so all fields in the output row are array
fields.
+ *
+ * <p>For example, the following demonstrates joining three PCollections on
the "user" and "country"
+ * fields.
+ *
+ * <pre>{@code
+ * TupleTag<Input1Type> input1Tag = new TupleTag<>("input1");
+ * TupleTag<Input2Type> input2Tag = new TupleTag<>("input2");
+ * TupleTag<Input3Type> input3Tag = new TupleTag<>("input3");
+ * PCollection<KV<Row, Row>> joined = PCollectionTuple
+ * .of(input1Tag, input1)
+ * .and(input2Tag, input2)
+ * .and(input3Tag, input3)
+ * .apply(CoGroup.byFieldNames("user", "country"));
+ * }</pre>
+ *
+ * <p>In the above case, the key schema will contain the two string fields
"user" and "country"; in
+ * this case, the schemas for Input1, Input2, Input3 must all have fields
named "user" and
+ * "country". The value schema will contain three array of Row fields named
"input1" "input2" and
Review comment:
Also part of the advantage of this API is not needing CoGbkResult.
CoGbkResult is sort of a poor-persons schema via use of java generics. Since we
know the actual types here, we can do better by just returning a row. Also we
want to remove the necessity to use TupleTags (allowing the user to just use
strings is nicer, and since we know the types of everything via schemas there's
no need for typed TupleTags), and without TupleTags CoGbkResult makes even less
sense.
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Issue Time Tracking
-------------------
Worklog Id: (was: 162835)
Time Spent: 17h 10m (was: 17h)
> Create a library of useful transforms that use schemas
> ------------------------------------------------------
>
> Key: BEAM-4461
> URL: https://issues.apache.org/jira/browse/BEAM-4461
> Project: Beam
> Issue Type: Sub-task
> Components: sdk-java-core
> Reporter: Reuven Lax
> Assignee: Reuven Lax
> Priority: Major
> Time Spent: 17h 10m
> Remaining Estimate: 0h
>
> e.g. JoinBy(fields). Project, Filter, etc.
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