Add simple_insert_returning_txn

synapse/storage/database.py

@@ -64,6 +64,7 @@ from synapse.metrics.background_process_metrics import run_as_background_process
 from synapse.storage.background_updates import BackgroundUpdater
 from synapse.storage.engines import BaseDatabaseEngine, PostgresEngine, Sqlite3Engine
 from synapse.storage.types import Connection, Cursor, SQLQueryParameters
+from synapse.types import StrCollection
 from synapse.util.async_helpers import delay_cancellation
 from synapse.util.iterutils import batch_iter
 
@@ -1095,6 +1096,50 @@ class DatabasePool:
 
         txn.execute(sql, vals)
 
+    @staticmethod
+    def simple_insert_returning_txn(
+        txn: LoggingTransaction,
+        table: str,
+        values: Dict[str, Any],
+        returning: StrCollection,
+    ) -> Tuple[Any, ...]:
+        """Executes a `INSERT INTO... RETURNING...` statement (or equivalent for
+        SQLite versions that don't support it).
+        """
+
+        if txn.database_engine.supports_returning:
+            keys, vals = zip(*values.items())
+
+            sql = "INSERT INTO %s (%s) VALUES(%s) RETURNING %s" % (
+                table,
+                ", ".join(k for k in keys),
+                ", ".join("?" for _ in keys),
+                ", ".join(k for k in returning),
+            )
+
+            txn.execute(sql, vals)
+            row = txn.fetchone()
+            assert row is not None
+            return row
+        else:
+            # For old versions of SQLite we do a standard insert and then can
+            # use `last_insert_rowid` to get at the row we just inserted
+            DatabasePool.simple_insert_txn(
+                txn,
+                table=table,
+                values=values,
+            )
+            txn.execute("SELECT last_insert_rowid()")
+            row = txn.fetchone()
+            assert row is not None
+            (rowid,) = row
+
+            row = DatabasePool.simple_select_one_txn(
+                txn, table=table, keyvalues={"rowid": rowid}, retcols=returning
+            )
+            assert row is not None
+            return row
+
     async def simple_insert_many(
         self,
         table: str,