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Subject [GitHub] hequn8128 commented on issue #6519: [FLINK-9559] [table] The type of a union of CHAR columns of different lengths should be VARCHAR
Date Sat, 25 Aug 2018 09:58:21 GMT
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-415957994
 
 
   @pnowojski Hi,I'm wrong at the root cause of the two examples I listed above. Thanks
for pointing it out and giving a detailed explanation. It should be a comparison problem for
CHAR/VARCHAR. We probably should implement support for `CHAR` as you said,  making trailing
spaces insignificant in comparisons. 
   I think this pr tries to solve the output problem. Once we solve the comparison problem,
we still have to solve the output problem. Output `case when` results to a nonbinary strings
field in storages. Some storages treat CHAR/VARCHAR with trailing spaces equally('a' equals
to 'a '), like mysql, so no problems here. Others don't, for example, kafka or elasticsearch.
So, I think we should not add trailing spaces in result of `case when`, just like most DBMSs
do.
   What do you think?
   Thanks again. Hequn

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