From 4b7eeaa4ed0ea19642a24bf8c7f0b3b252228620 Mon Sep 17 00:00:00 2001
From: Fabio Manganiello <info@fabiomanganiello.com>
Date: Tue, 5 Apr 2022 21:17:58 +0200
Subject: [PATCH] Smarter merging of entities with the same key before they are
 committed

---
 platypush/entities/_engine.py | 71 ++++++++++++++++++++++-------------
 1 file changed, 45 insertions(+), 26 deletions(-)

diff --git a/platypush/entities/_engine.py b/platypush/entities/_engine.py
index f99a4725c..f747027ee 100644
--- a/platypush/entities/_engine.py
+++ b/platypush/entities/_engine.py
@@ -6,14 +6,13 @@ from typing import Iterable, List
 
 from sqlalchemy import and_, or_, inspect as schema_inspect
 from sqlalchemy.orm import Session
-from sqlalchemy.sql.elements import Null
 
 from ._base import Entity
 
 
 class EntitiesEngine(Thread):
     # Processing queue timeout in seconds
-    _queue_timeout = 5.
+    _queue_timeout = 5.0
 
     def __init__(self):
         obj_name = self.__class__.__name__
@@ -42,7 +41,8 @@ class EntitiesEngine(Thread):
             last_poll_time = time()
 
             while not self.should_stop and (
-                    time() - last_poll_time < self._queue_timeout):
+                time() - last_poll_time < self._queue_timeout
+            ):
                 try:
                     msg = self._queue.get(block=True, timeout=0.5)
                 except Empty:
@@ -58,44 +58,64 @@ class EntitiesEngine(Thread):
 
         self.logger.info('Stopped entities engine')
 
-    def _get_if_exist(self, session: Session, entities: Iterable[Entity]) -> Iterable[Entity]:
+    def _get_if_exist(
+        self, session: Session, entities: Iterable[Entity]
+    ) -> Iterable[Entity]:
         existing_entities = {
             (entity.external_id or entity.name, entity.plugin): entity
-            for entity in session.query(Entity).filter(
-                or_(*[
-                    and_(Entity.external_id == entity.external_id, Entity.plugin == entity.plugin)
-                    if entity.external_id is not None else
-                    and_(Entity.name == entity.name, Entity.plugin == entity.plugin)
-                    for entity in entities
-                ])
-            ).all()
+            for entity in session.query(Entity)
+            .filter(
+                or_(
+                    *[
+                        and_(
+                            Entity.external_id == entity.external_id,
+                            Entity.plugin == entity.plugin,
+                        )
+                        if entity.external_id is not None
+                        else and_(
+                            Entity.name == entity.name, Entity.plugin == entity.plugin
+                        )
+                        for entity in entities
+                    ]
+                )
+            )
+            .all()
         }
 
         return [
             existing_entities.get(
                 (entity.external_id or entity.name, entity.plugin), None
-            ) for entity in entities
+            )
+            for entity in entities
         ]
 
     def _merge_entities(
-        self, entities: List[Entity],
-        existing_entities: List[Entity]
+        self, entities: List[Entity], existing_entities: List[Entity]
     ) -> List[Entity]:
-        new_entities = []
+        def merge(entity: Entity, existing_entity: Entity) -> Entity:
+            inspector = schema_inspect(entity.__class__)
+            columns = [col.key for col in inspector.mapper.column_attrs]
+            for col in columns:
+                if col not in ('id', 'created_at'):
+                    setattr(existing_entity, col, getattr(entity, col))
 
+            return existing_entity
+
+        new_entities = []
+        entities_map = {}
+
+        # Get the latest update for each ((id|name), plugin) record
+        for e in entities:
+            key = ((e.external_id or e.name), e.plugin)
+            entities_map[key] = e
+
+        # Retrieve existing records and merge them
         for i, entity in enumerate(entities):
             existing_entity = existing_entities[i]
             if existing_entity:
-                inspector = schema_inspect(entity.__class__)
-                columns = [col.key for col in inspector.mapper.column_attrs]
-                for col in columns:
-                    new_value = getattr(entity, col)
-                    if new_value is not None and new_value.__class__ != Null:
-                        setattr(existing_entity, col, getattr(entity, col))
+                entity = merge(entity, existing_entity)
 
-                new_entities.append(existing_entity)
-            else:
-                new_entities.append(entity)
+            new_entities.append(entity)
 
         return new_entities
 
@@ -107,4 +127,3 @@ class EntitiesEngine(Thread):
             entities = self._merge_entities(entities, existing_entities)  # type: ignore
             session.add_all(entities)
             session.commit()
-