[GitHub] [spark] beliefer edited a comment on pull request #31128: [SPARK-28123][SQL] String Functions: support btrim

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beliefer edited a comment on pull request #31128:
URL: https://github.com/apache/spark/pull/31128#issuecomment-759156667


   > There are a number of PRs floating around about this. For the record, I don't strongly oppose it, but, does not seem like a semantically useful function, even if some legacy DBs support it.
   
   This PR is different from the others, this is also because my previous misunderstanding of `btrim`. At the first, I Investigated the `PostgreSql`, the implement of `btrim` in `PostgreSql` accepts byte array and return byte array as result.
   So I mistakenly thought that `btrim`'s behavior is like this.
   
   Then I created two PR as you know. But the two PR try to let `btrim` or `trim` accepts byte array and return byte array as result.
   
   After that, I Investigated other database and found `btrim` means trim from both ends of source string and it is just an alternate form of `TRIM(BOTH <chars> FROM <expr>)`.
   `btrim` is a little similar to `ltrim` or `rtrim`. 
   
   This PR only need minor changes (such as giving `trim` an alias) can support it.


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