Fix empty map read #433

mymarilyn · Apr 23, 2024 · c123f2c · c123f2c
1 parent 2b35f97
commit c123f2c
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Showing 2 changed files with 16 additions and 0 deletions.
diff --git a/clickhouse_driver/columns/mapcolumn.py b/clickhouse_driver/columns/mapcolumn.py
@@ -31,6 +31,9 @@ def write_state_prefix(self, buf):
         self.value_column.write_state_prefix(buf)
 
     def read_items(self, n_items, buf):
+        if not n_items:
+            return [{}]
+
         offsets = list(self.offset_column.read_items(n_items, buf))
         last_offset = offsets[-1]
         keys = self.key_column.read_data(last_offset, buf)

diff --git a/tests/columns/test_map.py b/tests/columns/test_map.py
@@ -120,3 +120,16 @@ def test_decimal(self):
             )
             inserted = self.client.execute(query)
             self.assertEqual(inserted, data)
+
+    def test_only_empty_map(self):
+        columns = 'a Map(String, Map(String, Int32))'
+        with self.create_table(columns):
+            data = [
+                ({}, ),
+            ]
+            self.client.execute('INSERT INTO test (a) VALUES', data)
+            query = 'SELECT * FROM test'
+            inserted = self.emit_cli(query)
+            self.assertEqual(inserted, '{}\n')
+            inserted = self.client.execute(query)
+            self.assertEqual(inserted, data)