What problem does this PR solve?

Issue Number: close #53103

Problem Summary:

After we introduced StaticExprContext, we can build and evaluate an expression more simply without relying on the session. So, we can make it simple to evalute a TTL expire time.

What changed and how does it work?

• introduce a new function EvalExpireTime to compute the TTL expire time. It only requires the current time and the expression info as the input argument. So it is more simple, the new function is:

func EvalExpireTime(now time.Time, interval string, unit ast.TimeUnitType) (time.Time, error) {
    // ...
}

• DDL use EvalExpireTime to check whether a expire expression is legal.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No need to test

  • I checked and no code files have been changed.

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

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None