twalthr commented on code in PR #29834: URL: https://github.com/apache/flink/pull/29834#discussion_r4526489436
########## docs/content/docs/sql/built-in-functions/_index.md: ########## @@ -0,0 +1,62 @@ +--- +title: "Built-in Functions" +weight: 4 +type: docs +bookCollapseSection: true +aliases: + - /dev/table/functions/systemFunctions.html + - /docs/sql/functions/ + - /docs/sql/functions/built-in-functions/ + - /dev/python/table-api-users-guide/built_in_functions.html +--- +<!-- +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. +--> + +# System (Built-in) Functions + +Flink Table API & SQL provides users with a set of built-in functions for data transformations. This page gives a brief overview of them. +If a function that you need is not supported yet, you can implement a [user-defined function]({{< ref "docs/dev/table/functions/udfs" >}}). +If you think that the function is general enough, please <a href="https://issues.apache.org/jira/secure/CreateIssue!default.jspa";>open a Jira issue</a> for it with a detailed description. + +[All Functions]({{< ref "docs/sql/built-in-functions/all-functions" >}}) lists every built-in function from A to Z. + +## Kinds of Functions + +### Scalar + +A scalar function returns one value per call, usually one value per row, such as `UPPER` or `DATE_FORMAT`. Most categories hold scalar functions, such as [String and Binary]({{< ref "docs/sql/built-in-functions/string-and-binary" >}}) and [Date and Time]({{< ref "docs/sql/built-in-functions/date-and-time" >}}). + +### Aggregate + +An aggregate function returns one value for a group of rows, such as `SUM` or `COUNT`. See [Aggregate]({{< ref "docs/sql/built-in-functions/aggregate" >}}) and the [bitmap aggregate functions]({{< ref "docs/sql/built-in-functions/bitmap" >}}#bitmap-aggregate-functions). Aggregate functions also work over an [OVER window]({{< ref "docs/sql/reference/queries/over-agg" >}}). + +### Window + +A window function returns one value per row, computed from the window of rows that an `OVER` clause defines, such as `ROW_NUMBER` or `LAG`. See [Window]({{< ref "docs/sql/built-in-functions/window" >}}). + +### Table + +A table function returns a table. The built-in ones are [process table functions]({{< ref "docs/sql/built-in-functions/process-table-functions" >}}), such as `FROM_CHANGELOG`, and [window table functions]({{< ref "docs/sql/built-in-functions/window" >}}#window-table-functions), such as `TUMBLE`. + +### User-Defined + +Besides the built-in functions, you can write your own. See [User-Defined Functions]({{< ref "docs/sql/user-defined-functions" >}}) and [Named Arguments]({{< ref "docs/sql/named-arguments" >}}). Built-in functions are system functions without a namespace. For catalog and temporary functions and how Flink resolves a function name, see [Functions]({{< ref "docs/dev/table/functions/overview" >}}) in the Table API docs. Review Comment: the named argument section should go here or to a dedicated Function Basics page. ########## docs/content/docs/sql/built-in-functions/_index.md: ########## @@ -0,0 +1,62 @@ +--- +title: "Built-in Functions" +weight: 4 +type: docs +bookCollapseSection: true +aliases: + - /dev/table/functions/systemFunctions.html + - /docs/sql/functions/ + - /docs/sql/functions/built-in-functions/ + - /dev/python/table-api-users-guide/built_in_functions.html +--- +<!-- +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. +--> + +# System (Built-in) Functions + +Flink Table API & SQL provides users with a set of built-in functions for data transformations. This page gives a brief overview of them. +If a function that you need is not supported yet, you can implement a [user-defined function]({{< ref "docs/dev/table/functions/udfs" >}}). +If you think that the function is general enough, please <a href="https://issues.apache.org/jira/secure/CreateIssue!default.jspa";>open a Jira issue</a> for it with a detailed description. + +[All Functions]({{< ref "docs/sql/built-in-functions/all-functions" >}}) lists every built-in function from A to Z. + +## Kinds of Functions + +### Scalar + +A scalar function returns one value per call, usually one value per row, such as `UPPER` or `DATE_FORMAT`. Most categories hold scalar functions, such as [String and Binary]({{< ref "docs/sql/built-in-functions/string-and-binary" >}}) and [Date and Time]({{< ref "docs/sql/built-in-functions/date-and-time" >}}). + +### Aggregate + +An aggregate function returns one value for a group of rows, such as `SUM` or `COUNT`. See [Aggregate]({{< ref "docs/sql/built-in-functions/aggregate" >}}) and the [bitmap aggregate functions]({{< ref "docs/sql/built-in-functions/bitmap" >}}#bitmap-aggregate-functions). Aggregate functions also work over an [OVER window]({{< ref "docs/sql/reference/queries/over-agg" >}}). + +### Window + +A window function returns one value per row, computed from the window of rows that an `OVER` clause defines, such as `ROW_NUMBER` or `LAG`. See [Window]({{< ref "docs/sql/built-in-functions/window" >}}). + +### Table Review Comment: We should split by table function such as UNNEST, and process table functions. PTFs are able to take one or more tables as arguments. Table functions take scalar input and return a table. Take the JavaDoc of PTFs and TableFunction as reference. -- 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]
