left outer join

Author: brunovcosta

abstra_json_sql/apply.py

@@ -539,7 +539,6 @@ def apply_from(
     table = tables.get_table(from_part.table)
     if not table:
         raise ValueError(f"Table {from_part.table} not found")
-    data = table.data
     if from_part.join:
         for join in from_part.join:
             join_table = tables.get_table(join.table)
@@ -550,7 +549,7 @@ def apply_from(
                     **add_scope_to_keys(table.name, row),
                     **add_scope_to_keys(join_table.name, join_row),
                 }
-                for row in data
+                for row in table.data
                 for join_row in join_table.data
                 if apply_expression(
                     join.on,
@@ -561,8 +560,31 @@ def apply_from(
                     },
                 )
             ]
+
+            if join.join_type == "LEFT":
+                data += [
+                    {
+                        **add_scope_to_keys(table.name, row),
+                        **add_scope_to_keys(
+                            join_table.name,
+                            {join_col.name: None for join_col in join_table.columns},
+                        ),
+                    }
+                    for row in table.data
+                    if not any(
+                        apply_expression(
+                            join.on,
+                            {
+                                **ctx,
+                                **add_scope_to_keys(table.name, row),
+                                **add_scope_to_keys(join_table.name, join_row),
+                            },
+                        )
+                        for join_row in join_table.data
+                    )
+                ]
     else:
-        data = [{**add_scope_to_keys(table.name, row)} for row in data]
+        data = [{**add_scope_to_keys(table.name, row)} for row in table.data]
     return data
 
 

abstra_json_sql/eval_test.py

@@ -508,6 +508,7 @@ def test_join(self):
                     data=[
                         {"id": 1, "foo": "a1"},
                         {"id": 2, "foo": "a2"},
+                        {"id": 3, "foo": "a3"},
                     ],
                 ),
                 Table(
@@ -519,6 +520,7 @@ def test_join(self):
                     data=[
                         {"a_id": 1, "bar": "b1"},
                         {"a_id": 2, "bar": "b2"},
+                        {"a_id": 2, "bar": "b3"},
                     ],
                 ),
             ],
@@ -530,6 +532,49 @@ def test_join(self):
             [
                 {"foo": "a1", "bar": "b1"},
                 {"foo": "a2", "bar": "b2"},
+                {"foo": "a2", "bar": "b3"},
+            ],
+        )
+
+    def test_left_outer_join(self):
+        code = "select a.foo, b.bar from a left outer join b on a.id = b.a_id"
+        tables = InMemoryTables(
+            tables=[
+                Table(
+                    name="a",
+                    columns=[
+                        Column(name="id", type="int"),
+                        Column(name="foo", type="text"),
+                    ],
+                    data=[
+                        {"id": 1, "foo": "a1"},
+                        {"id": 2, "foo": "a2"},
+                        {"id": 3, "foo": "a3"},
+                    ],
+                ),
+                Table(
+                    name="b",
+                    columns=[
+                        Column(name="a_id", type="int"),
+                        Column(name="bar", type="text"),
+                    ],
+                    data=[
+                        {"a_id": 1, "bar": "b1"},
+                        {"a_id": 2, "bar": "b2"},
+                        {"a_id": 2, "bar": "b3"},
+                    ],
+                ),
+            ],
+        )
+        ctx = {}
+        result = eval_sql(code=code, tables=tables, ctx=ctx)
+        self.assertEqual(
+            result,
+            [
+                {"foo": "a1", "bar": "b1"},
+                {"foo": "a2", "bar": "b2"},
+                {"foo": "a2", "bar": "b3"},
+                {"foo": "a3", "bar": None},
             ],
         )