DuckDB: a union branch selecting one column twice panics in prune or refuses #237

import duckdb, ddxdb.duckdb as dd
con = duckdb.connect()
con.execute("CREATE TABLE a AS SELECT * FROM (VALUES (0, 1, 0.5::DOUBLE), (1, 2, -1.0::DOUBLE)) t(r, i, x)")
con.execute("CREATE TABLE b AS SELECT * FROM (VALUES (0, 1, 2.0::DOUBLE), (1, 3, 1.5::DOUBLE)) t(r, i, x)")
con.execute("CREATE TABLE w AS SELECT * FROM (VALUES (1, 1.5::DOUBLE), (2, 0.5::DOUBLE)) t(i, val)")
g = " SELECT r, grad(loss, x) AS g FROM a"
# 1. panics: index out of bounds: the len is 2 but the index is 2 (crates/ddx-ad/src/opt/prune.rs:322)
dd.sql(con, """WITH u AS (SELECT i AS k, x AS v FROM a
                UNION ALL SELECT k, v FROM (SELECT i AS k, i AS v FROM b UNION ALL SELECT i AS k, i AS v FROM b) n),
     loss AS (SELECT SUM(u.v * w.val * u.v) AS l FROM u JOIN w ON u.k = w.i)""" + g)
# 2. invalid Substrait plan: field 1 is referenced, but the input has only 1 columns
dd.sql(con, """WITH u AS (SELECT k, v FROM (SELECT i AS k, i AS v FROM b UNION ALL SELECT i AS k, i AS v FROM a) n
                UNION ALL SELECT i AS k, x AS v FROM a),
     loss AS (SELECT SUM(t * t) AS l FROM (SELECT k, SUM(v) AS t FROM u GROUP BY k) g)""" + g)
# 3. invalid Substrait plan: a UNION ALL whose inputs have different numbers of columns
dd.sql(con, """WITH u AS (SELECT i AS k, x AS v, x AS v2 FROM a UNION ALL SELECT i AS k, x AS v, 1.0 AS v2 FROM b),
     loss AS (SELECT SUM(v * v2) AS l FROM u)""" + g)