[FLINK-24413] Casting to a CHAR() and VARCHAR() doesn't trim the stri…

[Jiabao-Sun]

Casting to a CHAR() and VARCHAR() doesn't trim the string to the specified precision

What is the purpose of the change

CAST('abcdfe' AS CHAR(3)) should trim the string to 3 chars but currently returns the whole string 'abcdfe'.

PostgreSQL and Oracle for example behave as such:

postgres=# select '123456afas'::char(4);
bpchar
--------
1234
(1 row)

postgres=# select '123456afas'::varchar(5);
varchar
---------
12345
(1 row)

Brief change log

Verifying this change

This change is already covered by existing tests CastFunctionITCase.

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): (no)
• The serializers: (no)
• The runtime per-record code paths (performance sensitive): (no)
• 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? (no)
• If yes, how is the feature documented? (docs)

[flinkbot]

CI report:

• 54a792b Azure: FAILURE

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Automated Checks

Last check on commit c27c0bb (Wed Oct 13 13:29:17 UTC 2021)

Warnings:

• No documentation files were touched! Remember to keep the Flink docs up to date!
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[matriv]

@Jiabao-Sun I think we should postpone a bit this change until the discussion on the jira issue concludes.

[Jiabao-Sun]

@magsol Got it.

[magsol]

@Jiabao-Sun I don't think you meant to tag me...

[Jiabao-Sun]

@Jiabao-Sun I don't think you meant to tag me...

Hah, Sorry for that.

[matriv]

Hi @Jiabao-Sun, With: #17658 the implementation of this change should be done with the new structure for casting rules. If you don't mind, I'd propose to close this PR as we are already working on this fix as a followup to #17658.

[Jiabao-Sun]

@matriv OK, that's fine.

[matriv]

Thx for understanding @Jiabao-Sun! Apologies for not accepting, but there was this rework in process, so it was preferable to not continue introducing new code in the code generator using the old style of structure there.