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ASF GitHub Bot logged work on BEAM-4461: ---------------------------------------- Author: ASF GitHub Bot Created on: 05/Oct/18 16:59 Start Date: 05/Oct/18 16:59 Worklog Time Spent: 10m Work Description: akedin commented on a change in pull request #6298: [BEAM-4461] Introduce Group transform. URL: https://github.com/apache/beam/pull/6298#discussion_r223073239 ########## File path: sdks/java/core/src/main/java/org/apache/beam/sdk/schemas/transforms/Group.java ########## @@ -0,0 +1,684 @@ +/* + * 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 java.util.List; +import javax.annotation.Nullable; +import org.apache.beam.sdk.annotations.Experimental; +import org.apache.beam.sdk.annotations.Experimental.Kind; +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.Field; +import org.apache.beam.sdk.schemas.SchemaCoder; +import org.apache.beam.sdk.transforms.Combine; +import org.apache.beam.sdk.transforms.Combine.CombineFn; +import org.apache.beam.sdk.transforms.DoFn; +import org.apache.beam.sdk.transforms.GroupByKey; +import org.apache.beam.sdk.transforms.PTransform; +import org.apache.beam.sdk.transforms.ParDo; +import org.apache.beam.sdk.transforms.Values; +import org.apache.beam.sdk.transforms.WithKeys; +import org.apache.beam.sdk.values.KV; +import org.apache.beam.sdk.values.PCollection; +import org.apache.beam.sdk.values.Row; + +/** + * A generic grouping transform for schema {@link PCollection}s. + * + * <p>When used without a combiner, this transforms simply acts as a {@link GroupByKey} but without + * the need for the user to explicitly extract the keys. For example, consider the following input + * type: + * + * <pre>{@code + * {@literal @DefaultSchema(JavaFieldSchema.class)} + * public class UserPurchase { + * public String userId; + * public String country; + * public long cost; + * public double transactionDuration; + * } + * + * {@literal PCollection<UserPurchase>} purchases = readUserPurchases(); + * }</pre> + * + * <p>You can group all purchases by user and country as follows: + * + * <pre>{@code + * {@literal @DefaultSchema(JavaFieldSchema.class)} + * {@literal PCollection<KV<Row, Iterable<UserPurchase>>} byUser = + * purchases.apply(Group.byFieldNames("userId', "country")); + * }</pre> + * + * <p>However often an aggregation of some form is desired. The builder methods inside the Group + * class allows building up separate aggregations for every field (or set of fields) on the input + * schema, and generating an output schema based on these aggregations. For example: + * + * <pre>{@code + * {@literal PCollection<KV<Row, Row>>} aggregated = purchases + * .apply(Group.byFieldNames("userId', "country") + * .aggregateField("cost", Sum.ofLongs(), "total_cost") Review comment: I think that we definitely should have support for DataFrames model, but am not sure whether we should adjust internal Beam functionality to partially match it to get a similar feel in some places (but not the others). I'd rather keep everything Beam-specific here, and implement a more robust DataFrames model in a separate layer, and then maybe adjust Beam model if there are common things ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org Issue Time Tracking ------------------- Worklog Id: (was: 151691) Time Spent: 12h 20m (was: 12h 10m) > 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: 12h 20m > Remaining Estimate: 0h > > e.g. JoinBy(fields). Project, Filter, etc. -- This message was sent by Atlassian JIRA (v7.6.3#76005)