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--- code:django [2017/08/15 10:05]
hansek
+++ code:django [2020/01/09 10:00] (current)
hansek
@@ Line 35: / Line 35: @@
 sudo nginx -s reload
 </code>
+===== ORM =====
+==== Subqueries ====
+=== Count ===
+<code python>
+# database optimization
+subquery = Subquery(
+    Job.objects.published().filter(school=OuterRef('pk'))
+        .values('school').annotate(count=Count('pk'))
+        .values('count'), output_field=IntegerField()
+    )
+    qs = qs.annotate(jobs_count=Coalesce(subquery, 0))
+</code>

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