yukkit commented on issue #7926:
URL: 
https://github.com/apache/arrow-datafusion/issues/7926#issuecomment-1813692801

   > However, I think it would be much harder to accept things like 
`Expr::Column` as it is not clear to me from where such input would come? Would 
it be other tables?
   
   Sorry for not being clear earlier, what I meant is exactly how you 
understood it.
   I saw some use cases for correlated subquery in the [PostgreSQL 
documentation](https://www.postgresql.org/docs/7.3/xfunc-tablefunctions.html)
   
   ```
   CREATE TABLE foo (fooid int, foosubid int, fooname text);
   
   CREATE FUNCTION getfoo(int) RETURNS setof foo AS '
       SELECT * FROM foo WHERE fooid = $1;
   ' LANGUAGE SQL;
   
   SELECT * FROM getfoo(1) AS t1;
   
   SELECT * FROM foo
   WHERE foosubid in (select foosubid from getfoo(foo.fooid) z
                      where z.fooid = foo.fooid);
   
   CREATE VIEW vw_getfoo AS SELECT * FROM getfoo(1);
   SELECT * FROM vw_getfoo;
   ```


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