cloud-fan commented on issue #26626: [SPARK-29986][SQL] Introduce java like string trim to UTF8String URL: https://github.com/apache/spark/pull/26626#issuecomment-557132578 From SQL standard ``` let SRC be <trim source>. TRIM ( SRC ) is equivalent to TRIM ( BOTH ' ' FROM SRC ). ``` ``` cast specification If SD is character string, then SV is replaced by SV with any leading or trailing <space>s removed. ``` some related information ``` L( <left bracket> <colon> SPACE <colon> <right bracket> ) is the set of all character strings of length 1 (one) that are the <space> character. r) L( <left bracket> <colon> WHITESPACE <colon> <right bracket> ) is the set of all character strings of length 1 (one) that are white space characters. ... white space consecutive sequences of one or more characters that have no glyphs ``` So space means `' '`, and white space means all chars whose ascii code <= 32. `trim` and `cast` should only remove spaces. However, seems most of the DBs don't follow the cast part, and we rely on `Double.valueOf` so hard to change this behavior. I think it's OK to trim white spaces in cast.
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