MartijnVisser commented on code in PR #26375: URL: https://github.com/apache/flink/pull/26375#discussion_r2021193523
########## docs/content/docs/dev/table/functions/ptfs.md: ########## @@ -0,0 +1,1349 @@ +--- +title: "Process Table Functions" +weight: 52 +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. +--> + +# Process Table Functions (PTFs) + +Process Table Functions (PTFs) are the most powerful function kind for Flink SQL and Table API. They enable implementing +user-defined operators that can be as feature-rich as built-in operations. PTFs can take (partitioned) tables to produce +a new table. They have access to Flink's managed state, event-time and timer services, and underlying table changelogs. + +Conceptually, a PTF is itself a [user-defined function]({{< ref "docs/dev/table/functions/udfs" >}}) that is a superset of all +other user-defined functions. It maps zero, one, or multiple tables to zero, one, or multiple rows (or structured types). +Scalar arguments are supported. Due to its stateful nature, implementing aggregating behavior is possible as well. + +A PTF enables the following tasks: +- Apply transformations on each row of a table. +- Logically partition the table into distinct sets and apply transformations per set. +- Store seen events for repeated access. +- Continue the processing at a later point in time enabling waiting, synchronization, or timeouts. +- Buffer and aggregate events using complex state machines or rule-based conditional logic. + +{{< top >}} + +Polymorphic Table Functions +--------------------------- + +PTFs are not exclusive to Flink; their query syntax and semantics are derived from SQL:2016's *Polymorphic Table Functions*. Review Comment: ```suggestion The PTF query syntax and semantics are derived from SQL:2016's *Polymorphic Table Functions*. ``` -- 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]
