hequn8128 commented on issue #6519: [FLINK-9559] [table] The type of a union of CHAR columns of different lengths should be VARCHAR URL: https://github.com/apache/flink/pull/6519#issuecomment-416603955 @pnowojski Thanks for providing amazing ways to prove `case when` return types. Simply change type to VARCHAR can not solve the comparison problem. For sql, `SELECT * FROM country WHERE country_name = 'GERMANY '`, VARCHAR still can't handle blanks correctly. The main reason I hesitate to change literal to VARCHAR is Calcite treat it as CHAR. In Calcite, character constant, for example 'Hello, world!', '', _N'Bonjour', _ISO-8859-1'It''s superman!' COLLATE SHIFT_JIS$ja_JP$2. These are always CHAR, never VARCHAR. I am not sure we can do it. And Calcite provides a simple way to override shouldConvertRaggedUnionTypesToVarying to solve the problem.
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