[GitHub] [arrow-datafusion] alamb commented on issue #6508: octet_length(char) doesn't behave as expected.

["alamb (via GitHub)" <gi...@apache.org>]

alamb commented on issue #6508:
URL: https://github.com/apache/arrow-datafusion/issues/6508#issuecomment-1572597041

   Thanks for the report @osawyerr 
   
   TLDR is that DataFusion treats `VARCHAR` and `CHAR` the same (because they use the same underlying Arrow type)
   
   🤔  I am not quite sure what to do here. Postgres has the notion of a max width character column `CHAR` but arrow does not . DataFusion maps the SQL type `CHAR` --> arrow type `Utf8` 
   
   Thus I am no sure we were be able to replicate the behavior of postgres in this instance. 
   
   For anyone following along, here is what postgres does
   
   ```sql
   postgres=# create table example(name varchar(20));
   CREATE TABLE
   postgres=# insert into example values ('foo'), ('barrr');
   INSERT 0 2
   postgres=# select octet_length(name) from example;
    octet_length
   --------------
               3
               5
   (2 rows)
   postgres=# select octet_length(name::char(25)) from example;
    octet_length
   --------------
              25
              25
   (2 rows)
   postgres=# select octet_length(name::varchar(25)) from example;
    octet_length
   --------------
               3
               5
   (2 rows)
   
   postgres=#
   ```


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