davidradl commented on code in PR #29090: URL: https://github.com/apache/flink/pull/29090#discussion_r3979776889
########## docs/content/docs/concepts/sql-table-concepts/interpreting_changelog.md: ########## @@ -0,0 +1,326 @@ +--- +title: "Interpreting Flink's Changelog" +weight: 3 +type: docs +--- +<!-- +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. +--> + +# Interpreting Flink's Changelog + +A Flink table can change over time: rows get inserted, updated, or deleted. This is internally encoded internally as changelogs inside the Flink SQL engine. When you consume that table as a stream — after writing the table to another system, through `toChangelogStream`, a table connector, or your own service reading the output — each row carries a change flag telling you what kind of change it represents. This page describes how to read that stream correctly so you're able to built a table representation out of it. + +## The four row kinds + +Every row in a changelog stream has a `RowKind`: Review Comment: maybe define where the symbol is used. -- 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. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
