Add per database engine code for state group id gen

5 files changed, 51 insertions, 3 deletions

diff --git a/synapse/storage/engines/postgres.py b/synapse/storage/engines/postgres.py
index a6ae79dfad..8a0386c1a4 100644
--- a/synapse/storage/engines/postgres.py
+++ b/synapse/storage/engines/postgres.py
@@ -62,3 +62,9 @@ class PostgresEngine(object):
 
     def lock_table(self, txn, table):
         txn.execute("LOCK TABLE %s in EXCLUSIVE MODE" % (table,))
+
+    def get_next_state_group_id(self, txn):
+        """Returns an int that can be used as a new state_group ID
+        """
+        txn.execute("SELECT nextval('state_group_id_seq')")
+        return txn.fetchone()[0]
diff --git a/synapse/storage/engines/sqlite3.py b/synapse/storage/engines/sqlite3.py
index 755c9a1f07..60f0fa7fb3 100644
--- a/synapse/storage/engines/sqlite3.py
+++ b/synapse/storage/engines/sqlite3.py
@@ -16,6 +16,7 @@
 from synapse.storage.prepare_database import prepare_database
 
 import struct
+import threading
 
 
 class Sqlite3Engine(object):
@@ -24,6 +25,11 @@ class Sqlite3Engine(object):
     def __init__(self, database_module, database_config):
         self.module = database_module
 
+        # The current max state_group, or None if we haven't looked
+        # in the DB yet.
+        self._current_state_group_id = None
+        self._current_state_group_id_lock = threading.Lock()
+
     def check_database(self, txn):
         pass
 
@@ -43,6 +49,19 @@ class Sqlite3Engine(object):
     def lock_table(self, txn, table):
         return
 
+    def get_next_state_group_id(self, txn):
+        """Returns an int that can be used as a new state_group ID
+        """
+        # We do application locking here since if we're using sqlite then
+        # we are a single process synapse.
+        with self._current_state_group_id_lock:
+            if self._current_state_group_id is None:
+                txn.execute("SELECT COALESCE(max(id), 0) FROM state_groups")
+                self._current_state_group_id = txn.fetchone()[0]
+
+            self._current_state_group_id += 1
+            return self._current_state_group_id
+
 
 # Following functions taken from: https://github.com/coleifer/peewee
 
diff --git a/synapse/storage/prepare_database.py b/synapse/storage/prepare_database.py
index d1691bbac2..c845a0cec5 100644
--- a/synapse/storage/prepare_database.py
+++ b/synapse/storage/prepare_database.py
@@ -25,7 +25,7 @@ logger = logging.getLogger(__name__)
 
 # Remember to update this number every time a change is made to database
 # schema files, so the users will be informed on server restarts.
-SCHEMA_VERSION = 46
+SCHEMA_VERSION = 47
 
 dir_path = os.path.abspath(os.path.dirname(__file__))
 
diff --git a/synapse/storage/schema/delta/47/state_group_seq.py b/synapse/storage/schema/delta/47/state_group_seq.py
new file mode 100644
index 0000000000..006a94bd60
--- /dev/null
+++ b/synapse/storage/schema/delta/47/state_group_seq.py
@@ -0,0 +1,24 @@
+# Copyright 2018 New Vector Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from synapse.storage.engines import PostgresEngine
+
+
+def run_create(cur, database_engine, *args, **kwargs):
+    if isinstance(database_engine, PostgresEngine):
+        cur.execute("CREATE SEQUENCE state_group_id_seq")
+
+
+def run_upgrade(*args, **kwargs):
+    pass
diff --git a/synapse/storage/state.py b/synapse/storage/state.py
index 044d30e97b..a942f59adc 100644
--- a/synapse/storage/state.py
+++ b/synapse/storage/state.py
@@ -641,8 +641,7 @@ class StateStore(StateGroupReadStore, BackgroundUpdateStore):
                 )
                 return
 
-            # FIXME Replace this with Postgres/SQLITE specific ID generation
-            state_group = 456
+            state_group = self.database_engine.get_next_state_group_id(txn)
 
             self._simple_insert_txn(
                 txn,