[jira] [Created] (ARROW-17301) implement compute function "utf8_slice_charunits"

["ChenTsing (Jira)" <ji...@apache.org>]

ChenTsing created ARROW-17301:
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             Summary: implement compute function "utf8_slice_charunits"
                 Key: ARROW-17301
                 URL: https://issues.apache.org/jira/browse/ARROW-17301
             Project: Apache Arrow
          Issue Type: Improvement
          Components: C++
    Affects Versions: 8.0.1
            Reporter: ChenTsing
             Fix For: 10.0.0


In some situations, may  request an access method to get binary or sting likes array one or some continuous bytes , for example start 1 end 3 step 1,  the two bytes, it seems like "{{{}binary_replace_slice{}}} " function, provide byte and code two measurement unit

 

 
h1. *application case:*

 
here, I can give one example to descirbe why need a function to extract binary in byte unit:
 
          In distribute database, data has distribute policy and relatived hash algorithm for different data type, here we just discuss string-like and binary type, the hash algorithm need detach string-like or binary in bytes to calculating, for example , take 1-4 byte cast to integer and shift-left 16 bits, then take 5-6byte cast to integer and the result from last step, and so on, the  'utf8_slice_codeunits' function can partly meet the require if all are ascii,  but if the string-like contain chinese, one chinese may occupied three bytes,  start 1 to end 3, three utf8 character
  may take nine bytes, but it not meet the hash algorithm, it only need 3 bytes, so if provide a function but not cast, the same function arguments like 'utf8_slice_codeunits', it may called 'binary_slice_byteunit'



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