Window functions panic due to interface conversion error

[angelamayxie]

New window function tests were added in dolthub/go-mysql-server#3666 but fail in Doltgres, panicking due to an interface conversion error.

ERROR: DoltgresHandler caught panic: interface conversion: interface {} is float64, not int32

These queries work in Postgres, but some of them do return slightly different results than MySQL, likely due to floating point or rounding errors.

postgres=# CREATE TABLE t2 (id BIGINT PRIMARY KEY, grp VARCHAR(10), val INT);
CREATE TABLE
postgres=# INSERT INTO t2 VALUES (1,'a',10), (2,'a',20), (3,'b',30), (4,'b',5), (5,'c',15), (6,'c',25);
INSERT 0 6
postgres=# SELECT id, STDDEV_POP(val) OVER (ORDER BY grp) FROM t2 ORDER BY id;
 id |     stddev_pop     
----+--------------------
  1 | 5.0000000000000000
  2 | 5.0000000000000000
  3 | 9.6014321848357602
  4 | 9.6014321848357602
  5 | 8.5391256382996653
  6 | 8.5391256382996653
(6 rows)

postgres=# SELECT id, STDDEV_SAMP(val) OVER (ORDER BY grp) FROM t2 ORDER BY id;
 id |     stddev_samp     
----+---------------------
  1 |  7.0710678118654752
  2 |  7.0710678118654752
  3 | 11.0867789130417256
  4 | 11.0867789130417256
  5 |  9.3541434669348535
  6 |  9.3541434669348535
(6 rows)

postgres=# SELECT id, VAR_POP(val) OVER (ORDER BY grp) FROM t2 ORDER BY id;
 id |       var_pop       
----+---------------------
  1 | 25.0000000000000000
  2 | 25.0000000000000000
  3 | 92.1875000000000000
  4 | 92.1875000000000000
  5 | 72.9166666666666667
  6 | 72.9166666666666667
(6 rows)

postgres=# SELECT id, VAR_SAMP(val) OVER (ORDER BY grp) FROM t2 ORDER BY id;
 id |       var_samp       
----+----------------------
  1 |  50.0000000000000000
  2 |  50.0000000000000000
  3 | 122.9166666666666667
  4 | 122.9166666666666667
  5 |  87.5000000000000000
  6 |  87.5000000000000000
(6 rows)

Failing test cases are skipped in Doltgres for now but please unskip them once they've been fixed.