Ramin Gharib created FLINK-41414:
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Summary: Add AGENTS.md guidance for adding a built-in function
Key: FLINK-41414
URL: https://issues.apache.org/jira/browse/FLINK-41414
Project: Flink
Issue Type: Sub-task
Components: Table SQL / API
Reporter: Ramin Gharib
Assignee: Ramin Gharib
The root {{AGENTS.md}} lists six steps for a new built-in function, and the
planner and runtime {{AGENTS.md}} files add a few lines on base classes and
tests. Several steps that every function PR needs are not named anywhere, so an
agent or a new contributor has to find them by reading earlier PRs.
||Step||Named in an AGENTS.md today||
|Register the definition in {{BuiltInFunctionDefinitions}}|Yes|
|Input and output type strategies, such as {{SpecificInputTypeStrategies}}|No|
|Runtime class that extends {{BuiltInScalarFunction}} or another base class|Yes|
|Table API method in {{BaseExpressions}}|No, only "Extend Table API support"|
|PyFlink expression in {{expressions.py}}, checked by
{{test_expression_completeness.py}}|No|
|ITCase with {{TestSetSpec}}|Yes|
|Docs in {{docs/data/sql_functions.yml}} and {{sql_functions_zh.yml}}|No, only
"Document in docs/"|
Scope:
* Expand the "Adding a new SQL built-in function" section of the root
{{AGENTS.md}} into a checklist that names the file for each step, for scalar,
aggregate and table functions.
* Cover the parts that are easy to miss: validating literal arguments at
planning time, TRY_ forms, SQL NULL handling, the visibility annotation that
ArchUnit requires on new public classes, and registering a definition only
once, since a duplicate registration makes compiled plans that use it fail to
restore.
* Keep module details in {{flink-table-runtime/AGENTS.md}} and
{{flink-table-planner/AGENTS.md}}, and link them from the checklist.
* Point at one merged function PR as a worked example, such as VARIANT_GET from
FLINK-39049.
The FLIP-618 function subtasks follow this guide, so it lands before them.
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