expression, planner: push cast down to control function with enum type. (#24542)

[ti-srebot]

cherry-pick #24542 to release-5.0
You can switch your code base to this Pull Request by using git-extras:

# In tidb repo:
git pr https://github.com/pingcap/tidb/pull/30857

After apply modifications, you can push your change to this PR via:

git push [email protected]:ti-srebot/tidb.git pr/30857:release-5.0-ac7e6a42c503

---

What problem does this PR solve?

Issue Number: close #23114

Problem Summary: Control function with enum type gets wrong result.

What is changed and how it works?

Proposal: xxx

What's Changed:

1. Try to push down cast funtion into control function(if/case..when/elt)
   (I have a test in mysql, ifnull(e,e) result is always string, and when compare with int, it will convert string to float)
2. Add cast to double for where condition if the eval type is ETString and the expression is control function with enum.

How it Works:

Related changes

Check List

Tests

• Unit test
• Integration test

Side effects

Release note

Fix wrong result for control function with enum type.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• XuHuaiyu
• guo-shaoge

To complete the pull request process, please ask the reviewers in the list to review by filling /cc @reviewer in the comment.
After your PR has acquired the required number of LGTMs, you can assign this pull request to the committer in the list by filling /assign @committer in the comment to help you merge this pull request.

The full list of commands accepted by this bot can be found here.

Reviewer can indicate their review by submitting an approval review.
Reviewer can cancel approval by submitting a request changes review.

[ti-srebot]

/run-all-tests

[ti-srebot]

@wshwsh12 you're already a collaborator in bot's repo.

[XuHuaiyu]

LGTM

[wshwsh12]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 5736a94

[zhouqiang-cl]

/merge

[wshwsh12]

/merge

[wshwsh12]

/merge

[ti-chi-bot]

@ti-srebot: Your PR was out of date, I have automatically updated it for you.

At the same time I will also trigger all tests for you:

/run-all-tests

If the CI test fails, you just re-trigger the test that failed and the bot will merge the PR for you after the CI passes.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the ti-community-infra/tichi repository.