[GitHub] [spark] peter-toth commented on pull request #31940: [SPARK-34833][SQL] Apply right-padding correctly for correlated subqueries

[GitBox <gi...@apache.org>]

peter-toth commented on pull request #31940:
URL: https://github.com/apache/spark/pull/31940#issuecomment-805067105


   The PR LGTM.
   
   But I have a quick question, a bit unrelated to this PR but related to fixed-length string columns. Is this expected that we have in Spark:
   ```
   sql(s"CREATE TABLE t(c3 CHAR(3), c5 CHAR(5)) USING parquet")
   sql("INSERT INTO t VALUES ('a', 'a')")
   sql("SELECT c3, c5, c3 = c5, upper(c3) = upper(c5) FROM t").show()
   ```
   ```
   +---+-----+---------+-----------------------+
   | c3|   c5|(c3 = c5)|(upper(c3) = upper(c5))|
   +---+-----+---------+-----------------------+
   |a  |a    |     true|                  false|
   +---+-----+---------+-----------------------+
   ```
   But in PostgreSQL `upper(c3) = upper(c5)` is true:
   ```
   petertoth=# SELECT c3, c5, c3 = c5, upper(c3) = upper(c5) FROM t;
    c3  |  c5   | ?column? | ?column?
   -----+-------+----------+----------
    a   | a     | t        | t
   ```
   


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