Always use transactions for iteration

Author: lovelydinosaur

databases/backends/postgres.py

@@ -169,16 +169,9 @@ async def iterate(
         self, query: ClauseElement
     ) -> typing.AsyncGenerator[typing.Any, None]:
         assert self._connection is not None, "Connection is not acquired"
-        transaction = PostgresTransaction(self)
-        await transaction.start()
-        try:
-            query, args, result_columns = self._compile(query)
-            async for row in self._connection.cursor(query, *args):
-                yield Record(row, result_columns, self._dialect)
-        except:
-            transaction.rollback()
-        else:
-            transaction.commit()
+        query, args, result_columns = self._compile(query)
+        async for row in self._connection.cursor(query, *args):
+            yield Record(row, result_columns, self._dialect)
 
     def transaction(self) -> TransactionBackend:
         return PostgresTransaction(connection=self)

databases/core.py

@@ -219,11 +219,12 @@ async def execute_many(
     async def iterate(
         self, query: typing.Union[ClauseElement, str], values: dict = None
     ) -> typing.AsyncGenerator[typing.Any, None]:
-        async with self._query_lock:
-            async for record in self._connection.iterate(
-                self._build_query(query, values)
-            ):
-                yield record
+        async with self.transaction():
+            async with self._query_lock:
+                async for record in self._connection.iterate(
+                    self._build_query(query, values)
+                ):
+                    yield record
 
     def transaction(self, *, force_rollback: bool = False) -> "Transaction":
         return Transaction(self, force_rollback)