function result name should contain collator info (#2808)

[ti-chi-bot]

This is an automated cherry-pick of #2808

What problem does this PR solve?

Issue Number: close #2793

Problem Summary:
As the issue described.

What is changed and how it works?

Proposal: xxx

What's Changed:

The root cause is, the join other condition of query is
eq(test.t1.col_varchar_20_key_signed, test.t2.col_char_20_key_signed) with ci collator
and
not(in(test.t1.col_varchar_20_key_signed, test.t1.col_varbinary_20_key_signed, test.t1.col_varbinary_20_undef_signed, test.t2.col_varchar_20_undef_signed, test.t2.col_char_20_key_signed)) with bin collator

And for patterns like col in (col_1, col_2), since TiFlash does not support this directly, it will be rewritten to col = col_1 or col = col_2, so in TiFlash, the join other condition is actually:
eq(test.t1.col_varchar_20_key_signed, test.t2.col_char_20_key_signed) with ci collator
and
not (eq(test.t1.col_varchar_20_key_signed, test.t1.col_varbinary_20_key_signed) with bin collator or eq(test.t1.col_varchar_20_key_signed, test.t1.col_varbinary_20_undef_signed) with bin collator or eq(test.t1.col_varchar_20_key_signed, test.t2.col_varchar_20_undef_signed) with bin collator or eq(test.t1.col_varchar_20_key_signed, test.t2.col_char_20_key_signed) with bin collator))

And in TiFlash, if a function is already calucated, it will try to reuse the result to avoid redundancy calculation, and the result name for a function is generated by genFuncString, it just concat the function name and all its arguments' name, for eq(test.t1.col_varchar_20_key_signed, test.t2.col_char_20_key_signed) with ci collator and eq(test.t1.col_varchar_20_key_signed, test.t2.col_char_20_key_signed) with bin collator, they will have the same result name, so only one of them will be executed, and the other will result the result, this will clearly cause a collation related bug.

This pr add collation related info in genFuncString

Related changes

• PR to update pingcap/docs/pingcap/docs-cn:
• Need to cherry-pick to the release branch:

Check List

Tests

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

Side effects

Release note

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[ti-chi-bot]

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• windtalker

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[windtalker]

LGTM

[windtalker]

/merge

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

Commit hash: 8de13a3