damondouglas commented on a change in pull request #12448: URL: https://github.com/apache/beam/pull/12448#discussion_r464765533
########## File path: learning/katas/go/core_transforms/additional_parameters/additional_parameters/task.md ########## @@ -0,0 +1,84 @@ +<!-- + ~ 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. + --> + +# Additional Parameters - Window and Timestamp + +This lesson introduces the concept of windowing and timestamped PCollection elements. +Before discussing windowing, we need to distinguish bounded from unbounded data. +Bounded data is of a fixed size such as a file or database query. Unbounded data comes +from a continuously updated source such as a subscription or stream. + +A window is a view into a fixed beginning and fixed end to a set of data. In the beam model, windowing subdivides +a PCollection according to the timestamps of its individual elements. This is useful +for unbounded data because it allows the model to work with fixed element sizes. Note that windowing +is not unique to unbounded data. The beam model windows all data whether it is bounded or unbounded. +Yet, when you read from a fixed size source such as a file, beam applies the same timestamp to all the elements. Review comment: My gut was telling me "beam applies the timestamp" was not quite it but now the way you describe it makes sense. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to 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
