Use native UPSERTs where possible (#4306)

1 files changed, 96 insertions, 0 deletions

diff --git a/synapse/storage/engines/sqlite.py b/synapse/storage/engines/sqlite.py
new file mode 100644
index 0000000000..c64d73ff21
--- /dev/null
+++ b/synapse/storage/engines/sqlite.py
@@ -0,0 +1,96 @@
+# -*- coding: utf-8 -*-
+# Copyright 2015, 2016 OpenMarket 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.
+
+import struct
+import threading
+from sqlite3 import sqlite_version_info
+
+from synapse.storage.prepare_database import prepare_database
+
+
+class Sqlite3Engine(object):
+    single_threaded = True
+
+    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()
+
+    @property
+    def can_native_upsert(self):
+        """
+        Do we support native UPSERTs? This requires SQLite3 3.24+, plus some
+        more work we haven't done yet to tell what was inserted vs updated.
+        """
+        return sqlite_version_info >= (3, 24, 0)
+
+    def check_database(self, txn):
+        pass
+
+    def convert_param_style(self, sql):
+        return sql
+
+    def on_new_connection(self, db_conn):
+        prepare_database(db_conn, self, config=None)
+        db_conn.create_function("rank", 1, _rank)
+
+    def is_deadlock(self, error):
+        return False
+
+    def is_connection_closed(self, conn):
+        return False
+
+    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
+
+def _parse_match_info(buf):
+    bufsize = len(buf)
+    return [struct.unpack('@I', buf[i:i + 4])[0] for i in range(0, bufsize, 4)]
+
+
+def _rank(raw_match_info):
+    """Handle match_info called w/default args 'pcx' - based on the example rank
+    function http://sqlite.org/fts3.html#appendix_a
+    """
+    match_info = _parse_match_info(raw_match_info)
+    score = 0.0
+    p, c = match_info[:2]
+    for phrase_num in range(p):
+        phrase_info_idx = 2 + (phrase_num * c * 3)
+        for col_num in range(c):
+            col_idx = phrase_info_idx + (col_num * 3)
+            x1, x2 = match_info[col_idx:col_idx + 2]
+            if x1 > 0:
+                score += float(x1) / x2
+    return score