optimize when we run the commit logic, no use starting, commit transa…

…ction that we do not use

CHANGELOG.rst

@@ -1,7 +1,8 @@
 2.5.7 (unreleased)
 ------------------
 
-- Nothing changed yet.
+- Only do commit and voting if we have objects to do it with
+  [vangheem]
 
 
 2.5.6 (2018-03-21)

guillotina/db/storages/pg.py

@@ -691,6 +691,8 @@ async def start_transaction(self, txn, retries=0):
 
     async def get_conflicts(self, txn):
         async with self._lock:
+            if len(txn.modified) == 0:
+                return []
             # use storage lock instead of transaction lock
             if len(txn.modified) < 1000:
                 # if it's too large, we're not going to check on object ids
@@ -704,7 +706,8 @@ async def commit(self, transaction):
         if transaction._db_txn is not None:
             async with transaction._lock:
                 await transaction._db_txn.commit()
-        elif self._transaction_strategy not in ('none', 'tidonly'):
+        elif (self._transaction_strategy not in ('none', 'tidonly') and
+                not transaction._skip_commit):
             log.warning('Do not have db transaction to commit')
         return transaction._tid
 

guillotina/db/transaction.py

@@ -74,6 +74,7 @@ async def _wrapper(self, *args, **kwargs):
 @implementer(ITransaction)
 class Transaction(object):
     _status = 'empty'
+    _skip_commit = False
 
     def __init__(self, manager, request=None, loop=None):
         self._txn_time = None
@@ -310,9 +311,14 @@ async def _commit(self):
         await self._call_before_commit_hooks()
         self.status = Status.COMMITTING
         try:
-            await self.tpc_commit()
-            # vote will do conflict resolution if there are conflicting writes
-            await self.tpc_vote()
+            if len(self.modified) > 0 or len(self.deleted) > 0 or len(self.added) > 0:
+                # only do the commit steps if we have objects to commit
+                await self.tpc_commit()
+                # vote will do conflict resolution if there are conflicting writes
+                await self.tpc_vote()
+            else:
+                # signal to not worry about not making a transaction here..
+                self._skip_commit = True
             await self.tpc_finish()
         except (ConflictError, TIDConflictError) as ex:
             # this exception should bubble up