Fix: Resolve breakage where the BigQuery Dialect unnest clobbers unnest definitions in other dialects

sqlalchemy_bigquery/base.py

@@ -1377,7 +1377,12 @@ def get_view_definition(self, connection, view_name, schema=None, **kw):
         return view.view_query
 
 
-class unnest(sqlalchemy.sql.functions.GenericFunction):
+# unnest is a reserved keyword in some dialects.
+# It is defined here to avoid conflicts.
+# https://github.com/googleapis/python-bigquery-sqlalchemy/issues/882
+class _unnest(sqlalchemy.sql.expression.FunctionElement):
+    inherit_cache = True
+
     def __init__(self, *args, **kwargs):
         expr = kwargs.pop("expr", None)
         if expr is not None:
@@ -1395,9 +1400,18 @@ def __init__(self, *args, **kwargs):
             ):
                 raise TypeError("The argument to unnest must have an ARRAY type.")
             self.type = arg.type.item_type
+
         super().__init__(*args, **kwargs)
 
 
+@compiles(_unnest, "bigquery")
+def bigquery_unnest(element, compiler, **kw):
+    return "UNNEST({})".format(compiler.process(element.clauses, **kw))
+
+
+sqlalchemy.sql.functions._FunctionGenerator.unnest = _unnest
+
+
 dialect = BigQueryDialect
 
 try:

tests/unit/test_compiler.py

@@ -93,7 +93,7 @@ def test_no_alias_for_known_tables(faux_conn, metadata):
 
     expected_sql = (
         "SELECT `table1`.`foo` \n"
-        "FROM `table1`, unnest(`table1`.`bar`) AS `anon_1` \n"
+        "FROM `table1`, UNNEST(`table1`.`bar`) AS `anon_1` \n"
         "WHERE `anon_1` = %(param_1:INT64)s"
     )
     found_sql = q.compile(faux_conn).string
@@ -116,7 +116,7 @@ def test_no_alias_for_known_tables_cte(faux_conn, metadata):
 
     expected_initial_sql = (
         "SELECT `table1`.`foo`, `bar` \n"
-        "FROM `table1`, unnest(`table1`.`bars`) AS `bar`"
+        "FROM `table1`, UNNEST(`table1`.`bars`) AS `bar`"
     )
     found_initial_sql = q.compile(faux_conn).string
     assert found_initial_sql == expected_initial_sql
@@ -127,7 +127,7 @@ def test_no_alias_for_known_tables_cte(faux_conn, metadata):
     expected_cte_sql = (
         "WITH `cte` AS \n"
         "(SELECT `table1`.`foo` AS `foo`, `bar` \n"
-        "FROM `table1`, unnest(`table1`.`bars`) AS `bar`)\n"
+        "FROM `table1`, UNNEST(`table1`.`bars`) AS `bar`)\n"
         " SELECT `cte`.`foo`, `cte`.`bar` \n"
         "FROM `cte`"
     )
@@ -196,7 +196,7 @@ def test_no_implicit_join_asterix_for_inner_unnest_before_2_0(faux_conn, metadat
     q = prepare_implicit_join_base_query(faux_conn, metadata, True, False)
     expected_initial_sql = (
         "SELECT `table1`.`foo`, `table2`.`bar` \n"
-        "FROM `table2`, unnest(`table2`.`foos`) AS `unnested_foos` JOIN `table1` ON `table1`.`foo` = `unnested_foos`"
+        "FROM `table2`, UNNEST(`table2`.`foos`) AS `unnested_foos` JOIN `table1` ON `table1`.`foo` = `unnested_foos`"
     )
     found_initial_sql = q.compile(faux_conn).string
     assert found_initial_sql == expected_initial_sql
@@ -207,7 +207,7 @@ def test_no_implicit_join_asterix_for_inner_unnest_before_2_0(faux_conn, metadat
     expected_outer_sql = (
         "SELECT * \n"
         "FROM (SELECT `table1`.`foo` AS `foo`, `table2`.`bar` AS `bar` \n"
-        "FROM `table2`, unnest(`table2`.`foos`) AS `unnested_foos` JOIN `table1` ON `table1`.`foo` = `unnested_foos`) AS `anon_1`"
+        "FROM `table2`, UNNEST(`table2`.`foos`) AS `unnested_foos` JOIN `table1` ON `table1`.`foo` = `unnested_foos`) AS `anon_1`"
     )
     found_outer_sql = q.compile(faux_conn).string
     assert found_outer_sql == expected_outer_sql
@@ -219,7 +219,7 @@ def test_no_implicit_join_asterix_for_inner_unnest(faux_conn, metadata):
     q = prepare_implicit_join_base_query(faux_conn, metadata, True, False)
     expected_initial_sql = (
         "SELECT `table1`.`foo`, `table2`.`bar` \n"
-        "FROM unnest(`table2`.`foos`) AS `unnested_foos` JOIN `table1` ON `table1`.`foo` = `unnested_foos`, `table2`"
+        "FROM UNNEST(`table2`.`foos`) AS `unnested_foos` JOIN `table1` ON `table1`.`foo` = `unnested_foos`, `table2`"
     )
     found_initial_sql = q.compile(faux_conn).string
     assert found_initial_sql == expected_initial_sql
@@ -230,7 +230,7 @@ def test_no_implicit_join_asterix_for_inner_unnest(faux_conn, metadata):
     expected_outer_sql = (
         "SELECT * \n"
         "FROM (SELECT `table1`.`foo` AS `foo`, `table2`.`bar` AS `bar` \n"
-        "FROM unnest(`table2`.`foos`) AS `unnested_foos` JOIN `table1` ON `table1`.`foo` = `unnested_foos`, `table2`) AS `anon_1`"
+        "FROM UNNEST(`table2`.`foos`) AS `unnested_foos` JOIN `table1` ON `table1`.`foo` = `unnested_foos`, `table2`) AS `anon_1`"
     )
     found_outer_sql = q.compile(faux_conn).string
     assert found_outer_sql == expected_outer_sql
@@ -242,7 +242,7 @@ def test_no_implicit_join_for_inner_unnest_before_2_0(faux_conn, metadata):
     q = prepare_implicit_join_base_query(faux_conn, metadata, True, False)
     expected_initial_sql = (
         "SELECT `table1`.`foo`, `table2`.`bar` \n"
-        "FROM `table2`, unnest(`table2`.`foos`) AS `unnested_foos` JOIN `table1` ON `table1`.`foo` = `unnested_foos`"
+        "FROM `table2`, UNNEST(`table2`.`foos`) AS `unnested_foos` JOIN `table1` ON `table1`.`foo` = `unnested_foos`"
     )
     found_initial_sql = q.compile(faux_conn).string
     assert found_initial_sql == expected_initial_sql
@@ -253,7 +253,7 @@ def test_no_implicit_join_for_inner_unnest_before_2_0(faux_conn, metadata):
     expected_outer_sql = (
         "SELECT `anon_1`.`foo` \n"
         "FROM (SELECT `table1`.`foo` AS `foo`, `table2`.`bar` AS `bar` \n"
-        "FROM `table2`, unnest(`table2`.`foos`) AS `unnested_foos` JOIN `table1` ON `table1`.`foo` = `unnested_foos`) AS `anon_1`"
+        "FROM `table2`, UNNEST(`table2`.`foos`) AS `unnested_foos` JOIN `table1` ON `table1`.`foo` = `unnested_foos`) AS `anon_1`"
     )
     found_outer_sql = q.compile(faux_conn).string
     assert found_outer_sql == expected_outer_sql
@@ -265,7 +265,7 @@ def test_no_implicit_join_for_inner_unnest(faux_conn, metadata):
     q = prepare_implicit_join_base_query(faux_conn, metadata, True, False)
     expected_initial_sql = (
         "SELECT `table1`.`foo`, `table2`.`bar` \n"
-        "FROM unnest(`table2`.`foos`) AS `unnested_foos` JOIN `table1` ON `table1`.`foo` = `unnested_foos`, `table2`"
+        "FROM UNNEST(`table2`.`foos`) AS `unnested_foos` JOIN `table1` ON `table1`.`foo` = `unnested_foos`, `table2`"
     )
     found_initial_sql = q.compile(faux_conn).string
     assert found_initial_sql == expected_initial_sql
@@ -276,7 +276,7 @@ def test_no_implicit_join_for_inner_unnest(faux_conn, metadata):
     expected_outer_sql = (
         "SELECT `anon_1`.`foo` \n"
         "FROM (SELECT `table1`.`foo` AS `foo`, `table2`.`bar` AS `bar` \n"
-        "FROM unnest(`table2`.`foos`) AS `unnested_foos` JOIN `table1` ON `table1`.`foo` = `unnested_foos`, `table2`) AS `anon_1`"
+        "FROM UNNEST(`table2`.`foos`) AS `unnested_foos` JOIN `table1` ON `table1`.`foo` = `unnested_foos`, `table2`) AS `anon_1`"
     )
     found_outer_sql = q.compile(faux_conn).string
     assert found_outer_sql == expected_outer_sql
@@ -289,7 +289,7 @@ def test_no_implicit_join_asterix_for_inner_unnest_no_table2_column(
     q = prepare_implicit_join_base_query(faux_conn, metadata, False, False)
     expected_initial_sql = (
         "SELECT `table1`.`foo` \n"
-        "FROM `table2` `table2_1`, unnest(`table2_1`.`foos`) AS `unnested_foos` JOIN `table1` ON `table1`.`foo` = `unnested_foos`"
+        "FROM `table2` `table2_1`, UNNEST(`table2_1`.`foos`) AS `unnested_foos` JOIN `table1` ON `table1`.`foo` = `unnested_foos`"
     )
     found_initial_sql = q.compile(faux_conn).string
     assert found_initial_sql == expected_initial_sql
@@ -300,7 +300,7 @@ def test_no_implicit_join_asterix_for_inner_unnest_no_table2_column(
     expected_outer_sql = (
         "SELECT * \n"
         "FROM (SELECT `table1`.`foo` AS `foo` \n"
-        "FROM `table2` `table2_1`, unnest(`table2_1`.`foos`) AS `unnested_foos` JOIN `table1` ON `table1`.`foo` = `unnested_foos`) AS `anon_1`"
+        "FROM `table2` `table2_1`, UNNEST(`table2_1`.`foos`) AS `unnested_foos` JOIN `table1` ON `table1`.`foo` = `unnested_foos`) AS `anon_1`"
     )
     found_outer_sql = q.compile(faux_conn).string
     assert found_outer_sql == expected_outer_sql
@@ -311,7 +311,7 @@ def test_no_implicit_join_for_inner_unnest_no_table2_column(faux_conn, metadata)
     q = prepare_implicit_join_base_query(faux_conn, metadata, False, False)
     expected_initial_sql = (
         "SELECT `table1`.`foo` \n"
-        "FROM `table2` `table2_1`, unnest(`table2_1`.`foos`) AS `unnested_foos` JOIN `table1` ON `table1`.`foo` = `unnested_foos`"
+        "FROM `table2` `table2_1`, UNNEST(`table2_1`.`foos`) AS `unnested_foos` JOIN `table1` ON `table1`.`foo` = `unnested_foos`"
     )
     found_initial_sql = q.compile(faux_conn).string
     assert found_initial_sql == expected_initial_sql
@@ -322,7 +322,7 @@ def test_no_implicit_join_for_inner_unnest_no_table2_column(faux_conn, metadata)
     expected_outer_sql = (
         "SELECT `anon_1`.`foo` \n"
         "FROM (SELECT `table1`.`foo` AS `foo` \n"
-        "FROM `table2` `table2_1`, unnest(`table2_1`.`foos`) AS `unnested_foos` JOIN `table1` ON `table1`.`foo` = `unnested_foos`) AS `anon_1`"
+        "FROM `table2` `table2_1`, UNNEST(`table2_1`.`foos`) AS `unnested_foos` JOIN `table1` ON `table1`.`foo` = `unnested_foos`) AS `anon_1`"
     )
     found_outer_sql = q.compile(faux_conn).string
     assert found_outer_sql == expected_outer_sql

tests/unit/test_select.py

@@ -419,7 +419,7 @@ def test_unnest(faux_conn, alias):
         query = fcall.column_valued("foo_objects")
     compiled = str(sqlalchemy.select(query).compile(faux_conn.engine))
     assert " ".join(compiled.strip().split()) == (
-        "SELECT `foo_objects` FROM `t` `t_1`, unnest(`t_1`.`objects`) AS `foo_objects`"
+        "SELECT `foo_objects` FROM `t` `t_1`, UNNEST(`t_1`.`objects`) AS `foo_objects`"
     )
 
 
@@ -450,7 +450,7 @@ def test_unnest_w_no_table_references(faux_conn, alias):
         query = fcall.column_valued()
     compiled = str(sqlalchemy.select(query).compile(faux_conn.engine))
     assert " ".join(compiled.strip().split()) == (
-        "SELECT `anon_1` FROM unnest(%(unnest_1)s) AS `anon_1`"
+        "SELECT `anon_1` FROM UNNEST(%(param_1)s) AS `anon_1`"
     )
 
 

tests/unit/test_sqlalchemy_bigquery.py

@@ -226,7 +226,10 @@ def test_unnest_function(args, kw):
 
     f = sqlalchemy.func.unnest(*args, **kw)
     assert isinstance(f.type, sqlalchemy.String)
-    assert isinstance(sqlalchemy.select(f).subquery().c.unnest.type, sqlalchemy.String)
+    assert isinstance(
+        sqlalchemy.select(f.label("unnested_value")).subquery().c.unnested_value.type,
+        sqlalchemy.String,
+    )
 
 
 @mock.patch("sqlalchemy_bigquery._helpers.create_bigquery_client")