exec: CastExpr handling for relevant subset of TPCH

[jordanlewis]

sometimes CastExpr is planned, and we should handle that in vectorized execution.

[email protected]:63701/defaultdb> create table foo (a int8 primary key);
CREATE TABLE

[email protected]:63701/defaultdb> insert into foo values(10);
INSERT 1

[email protected]:63701/defaultdb> select (a/1) from foo;
  ?column?
+----------+
        10
(1 row)

[email protected]:63701/defaultdb> set experimental_vectorize=always;
SET

[email protected]:63701/?> select (a/1) from foo;


E190718 13:42:55.424737 697 sql/distsqlrun/server.go:464  [n1,client=127.0.0.1:63703,user=root] error setting up flow: unable to columnarize render expression "@1::DECIMAL": unhandled projection expression type: *tree.CastExpr

[rohany]

Going through the TPCH queries, it seems like none of them depend on having a cast operator. The blockers seem mainly to be mixed type comparisons.