[FLINK-37914][table] Add built-in OBJECT_UPDATE function

[raminqaf]

What is the purpose of the change

This pull request implements the OBJECT_UPDATE built-in function as part of FLIP-520: Simplify StructuredType handling. The function allows users to update existing fields in structured objects by providing key-value pairs, enabling mutation operations on structured types in both SQL and Table API without requiring custom UDFs.

Brief change log

• Added ObjectUpdateInputTypeStrategy for validating input arguments (structured object + key-value pairs)
• Added ObjectUpdateTypeStrategy for inferring return types (same as input structured type)
• Implemented ObjectUpdateFunction runtime function for performing field updates
• Added OBJECT_UPDATE to BuiltInFunctionDefinitions with proper type inference strategies
• Added Table API expression support via objectUpdate() method on expressions
• Updated SQL and Table API documentation with examples and usage patterns
• Added comprehensive validation for field names, types, and compatibility checking
• Implemented proper error handling for non-existent fields and type mismatches

Verifying this change

This change added tests and can be verified as follows:

• Added unit tests in ObjectUpdateInputTypeStrategyTest for input validation scenarios
• Added integration tests in StructuredFunctionsITCase for end-to-end SQL functionality

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no
• The public API, i.e., is any changed class annotated with @Public(Evolving): yes (new built-in function)
• The serializers: no
• The runtime per-record code paths (performance sensitive): yes (new scalar function execution)
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? yes
• If yes, how is the feature documented? docs / JavaDocs (updated SQL functions documentation and comprehensive JavaDoc comments)

[flinkbot]

CI report:

• 336f2b3 Azure: FAILURE

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[davidradl]

I am curious:

• I assume that arrays are not included in this
• are there restrictions on the values, i.e. can they be maps, lists, objects or arrays. If there are restrictions , we should document them. If there are no restrictions we should include examples of more complex objects.
• in the example I assume "com.example.User" is a "path".
  • could dots in the field name clash with the path?
  • could you give an example or pointer to documentaiton around how to construct these paths in the documentation - examples around nested objects would be useful - including an array of objects where you want to update the value of the 3rd object.
• can we set null values.
• if the field is defined as not nullable - do we error if an attempt to put a null there occurs.

[raminqaf]

• Arrays should be supported. In the background, the OBJECT_UPDATE uses a structured type, and this test evaluates its functionality.
• There should be no restrictions on the values. We only check if the type of the updated value matches the one in the structured type.
• For now, we decided to skip any validation on the field name format. The user is allowed to write OBJECT_UPDATE(obj, "my.field.name", 14). This should be up to the user to pass valid field names. For the first iteration, this validation was not necessary.
• If I understand you correctly, you cannot update an ARRAY type with OBJECT_UPDATE. The OBJECT_UPDATE applies to STRUCTURED_TYPE.
• Yes, values can be null
• Yes, validation errors will be thrown if the field name is null:
  • Here is the validation check, where we see if the field is a non-null String literal.
  • Tests backing this logic.

[twalthr]

These examples are a bit misleading. They read as if User userObject = objectOf is Java code and the function returns a class instance User. The explanation in docs is better.