planner: Fix the problem that PlanBuilder.buildWindowFunctions may change sub operator's schema. (#27176)

[ti-srebot]

cherry-pick #27176 to release-5.2
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# In tidb repo:
git pr https://github.com/pingcap/tidb/pull/27203

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---

What problem does this PR solve?

Issue Number: close #27148

Problem Summary: buildWindowFunctions will use sub operator's schema as itself's, for example, here

		switch newArg.(type) {
		case *expression.Column, *expression.Constant:
			newArgList = append(newArgList, newArg)
			continue
		}

obtains the sub operator's schema, and then changed them here

		if col, ok := a.Args[i].(*expression.Column); ok {
			col.RetType = types.NewFieldType(col.RetType.Tp)
		}
		// originTp is used when the the `Tp` of column is TypeFloat32 while
		// the type of the aggregation function is TypeFloat64.
		originTp := a.Args[i].GetType().Tp
		*(a.Args[i].GetType()) = *(a.RetTp)
		a.Args[i].GetType().Tp = originTp

This may cause some unexpected behaviors, for example in mpp query, making the schema of exchangeReceiver and exchangeSender not equal and then throw errors as the issue said.

for example, it will build a plan like:

Proj <- Proj <- Window       <- Proj   <- Proj <- Agg  <- DataSource
47,1    47,1    47,1            47,1              47,1
        25,1    25,1            3,1              sum, arg=3,1, ret=25,1
                3,1
                sum
                retTp=47,1
                argTp=47,1

the (3,1), (25,1), (47,1) means output schema's attribute flen and decimal in typeDecimal, but the excepted is

Proj <- Proj <- Window       <- Proj   <- Proj <- Agg  <- DataSource
47,1    47,1    47,1            25,1              25,1
        25,1    25,1            3,1              sum, arg=3,1, ret=25,1
                3,1
                sum
                retTp=47,1
                argTp=25,1

What is changed and how it works?

Proposal: xxx

What's Changed: let it obtain a column's clone.

Are there any suggestions for fixing it better?

Check List

Tests

• Integration test
• Manual test (issue fixed.)

Release note

None

[ti-chi-bot]

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• LittleFall
• lzmhhh123

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[ti-srebot]

/run-all-tests

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[LittleFall]

/run-check_dev

[LittleFall]

/merge

[ti-chi-bot]

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

Commit hash: 047e1c5

[LittleFall]

/rebuild

[LittleFall]

/run-unit-test