fix(mssql): ensure that dot-sql can be executed when column names are…

… not provided (ibis-project#10028)

Closes ibis-project#10025.

ibis/backends/mssql/__init__.py

@@ -307,6 +307,9 @@ def _get_schema_using_query(self, query: str) -> sch.Schema:
             elif newtyp.is_timestamp():
                 newtyp = newtyp.copy(scale=scale)
 
+            if name is None:
+                name = util.gen_name("col")
+
             schema[name] = newtyp
 
         return sch.Schema(schema)

ibis/backends/mssql/tests/test_client.py

@@ -241,3 +241,27 @@ def test_from_url():
     )
     result = new_con.sql("SELECT 1 AS [a]").to_pandas().a.iat[0]
     assert result == 1
+
+
+def test_dot_sql_with_unnamed_columns(con):
+    expr = con.sql(
+        "SELECT CAST('2024-01-01 00:00:00' AS DATETIMEOFFSET), 'a' + 'b', 1 AS [col42]"
+    )
+
+    schema = expr.schema()
+    names = schema.names
+
+    assert len(names) == 3
+
+    assert names[0].startswith("ibis_col")
+    assert names[1].startswith("ibis_col")
+    assert names[2] == "col42"
+
+    assert schema.types == (
+        dt.Timestamp(timezone="UTC", scale=7),
+        dt.String(nullable=False),
+        dt.Int32(nullable=False),
+    )
+
+    df = expr.execute()
+    assert len(df) == 1

ibis/backends/tests/test_dot_sql.py

@@ -13,7 +13,11 @@
 from ibis import _
 from ibis.backends import _get_backend_names
 from ibis.backends.tests.base import PYTHON_SHORT_VERSION
-from ibis.backends.tests.errors import GoogleBadRequest, OracleDatabaseError
+from ibis.backends.tests.errors import (
+    ExaQueryError,
+    GoogleBadRequest,
+    OracleDatabaseError,
+)
 
 pd = pytest.importorskip("pandas")
 tm = pytest.importorskip("pandas.testing")
@@ -330,3 +334,26 @@ def test_embedded_cte(alltypes, ftname_raw):
     expr = alltypes.sql(sql, dialect="duckdb")
     result = expr.head(1).execute()
     assert len(result) == 1
+
+
+@dot_sql_never
+@pytest.mark.never(["exasol"], raises=ExaQueryError, reason="backend requires aliasing")
+@pytest.mark.never(
+    ["oracle"], raises=OracleDatabaseError, reason="backend requires aliasing"
+)
+def test_unnamed_columns(con):
+    sql = "SELECT 'a', 1 AS col42"
+    sgexpr = sg.parse_one(sql, read="duckdb")
+    expr = con.sql(sgexpr.sql(con.dialect))
+
+    schema = expr.schema()
+    names = schema.names
+    types = schema.types
+
+    assert len(names) == 2
+
+    assert names[0]
+    assert names[1] == "col42"
+
+    assert types[0].is_string()
+    assert types[1].is_integer()