fix: add workaround for NULL map bugs

partially addresses ibis-project#8632

postgres started failing these new test too,
so had to adjust that visit_Map()

ibis/backends/duckdb/compiler.py

@@ -199,6 +199,12 @@ def visit_ArrayZip(self, op, *, arg):
         any_arg_null = sg.or_(*(arr.is_(NULL) for arr in arg))
         return self.if_(any_arg_null, NULL, zipped_arrays)
 
+    def visit_Map(self, op, *, keys, values):
+        # workaround for https://github.com/ibis-project/ibis/issues/8632
+        regular = self.f.map(keys, values)
+        either_null = sg.or_(keys.is_(NULL), values.is_(NULL))
+        return self.if_(either_null, NULL, regular)
+
     def visit_MapGet(self, op, *, arg, key, default):
         return self.f.ifnull(
             self.f.list_extract(self.f.element_at(arg, key), 1), default

ibis/backends/duckdb/tests/test_client.py

@@ -276,3 +276,12 @@ def test_invalid_connect(tmp_path):
     url = f"duckdb://{tmp_path}?read_only=invalid_value"
     with pytest.raises(ValueError):
         ibis.connect(url)
+
+
+@pytest.mark.xfail(
+    raises=duckdb.BinderException,
+    reason="https://github.com/ibis-project/ibis/issues/8632",
+)
+def test_map_null_workaround_xfail():
+    conn = duckdb.connect()
+    conn.sql("SELECT MAP([0, 1, 2], NULL::INT[]);").fetchone()

ibis/backends/postgres/compiler.py

@@ -330,7 +330,10 @@ def visit_ToJSONArray(self, op, *, arg):
         )
 
     def visit_Map(self, op, *, keys, values):
-        return self.f.map(self.f.array(*keys), self.f.array(*values))
+        # map(["a", "b"], NULL) results in {"a": NULL, "b": NULL} in regular postgres,
+        # so we need to modify it to return NULL instead
+        regular = self.f.map(keys, values)
+        return self.if_(values.is_(NULL), NULL, regular)
 
     def visit_MapLength(self, op, *, arg):
         return self.f.cardinality(self.f.akeys(arg))

ibis/backends/tests/test_map.py

@@ -26,6 +26,24 @@
 ]
 
 
+@pytest.mark.notyet("clickhouse", reason="nested types can't be NULL")
+@pytest.mark.broken(["pandas", "dask"], reason="TypeError: iteration over a 0-d array")
+@pytest.mark.parametrize(
+    "kv",
+    [
+        param((["a", "b"], None), id="null_values"),
+        param((None, ["c", "d"]), id="null_keys"),
+        param((None, None), id="null_both"),
+    ],
+)
+def test_map_nulls(con, kv):
+    k, v = kv
+    k = ibis.literal(k, type="array<string>")
+    v = ibis.literal(v, type="array<string>")
+    m = ibis.map(k, v)
+    assert con.execute(m) is None
+
+
 @pytest.mark.notimpl(["pandas", "dask"])
 def test_map_table(backend):
     table = backend.map