Fix query rewriting unproperly with multibyte characters

[markrui3]

Description

Babelfish doesn't rewrite query with multibyte characters properly.

Analysis

Babelfish preprocess the query string and remove unsupported syntax before sending the query to PG backend. The implementation didn’t consider multibyte unicode characters, so when unicode characters are used ahead of the unsupported syntax, Babelfish will emit a broken query. In specific, character offset is used instead of byte offset during the character replacement. For example:
Input T-SQL : select "你好世界" from tbl with(nolock);
Executed SQL: select "你好世界" f (nolock);

Solution

Consolidate all rewriting behaviors to PLtsql_expr_query_mutator. It’s more maintainable because there will only be one interface for query rewriting. We support Chinese unicode charset as identifier in this patch.

Description

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Issues Resolved

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Test Scenarios Covered

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• Boundary conditions -

• Arbitrary inputs -

• Negative test cases -

• Minor version upgrade tests -

• Major version upgrade tests -

• Performance tests -

• Tooling impact -

• Client tests -

Check List

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