Merge pull request #214 from OpenDataPolicingNC/TRH-2688-improve-sear…

…ch-query-time

[TRH-2688] Improve Search Query Time

nc/data/copy.sql

@@ -96,6 +96,7 @@ CREATE INDEX nc_searchbasis_5fad4402 ON nc_searchbasis USING btree (search_id);
 CREATE INDEX nc_searchbasis_91455da7 ON nc_searchbasis USING btree (stop_id);
 CREATE INDEX nc_searchbasis_a8452ca7 ON nc_searchbasis USING btree (person_id);
 CREATE INDEX nc_stop_169fc544 ON nc_stop USING btree (agency_id);
+CREATE INDEX nc_stop_date_7d643c8a9c590bf7_uniq ON nc_stop USING btree (date);
 
 ANALYZE;
 COMMIT;

nc/migrations/0003_auto_20180115_1141.py

@@ -0,0 +1,19 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('nc', '0002_agency_census_profile_id'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='stop',
+            name='date',
+            field=models.DateTimeField(db_index=True),
+        ),
+    ]

nc/models.py

@@ -60,7 +60,7 @@ class Stop(CachingMixin, models.Model):
     stop_id = models.PositiveIntegerField(primary_key=True)
     agency_description = models.CharField(max_length=100)
     agency = models.ForeignKey('Agency', null=True, related_name='stops')
-    date = models.DateTimeField()
+    date = models.DateTimeField(db_index=True)
     purpose = models.PositiveSmallIntegerField(choices=PURPOSE_CHOICES)
     action = models.PositiveSmallIntegerField(choices=ACTION_CHOICES)
     driver_arrest = models.BooleanField(default=False)

nc/views.py

@@ -1,3 +1,4 @@
+from django.db import connections
 from django.shortcuts import render
 from .models import Stop, Agency, Person
 from . import forms
@@ -31,6 +32,16 @@ def search(request):
     else:
         people = Person.objects.none()
     people = people.select_related('stop').order_by('stop__date')
+    connection = connections[people.db]
+    with connection.cursor() as cursor:
+        # Disable seq scanning when generating this count
+        # Override the count to produce this result for the pagination
+        # Might not be necessary if we adjusted the random_page_cost
+        # See https://stackoverflow.com/questions/10643215/
+        cursor.execute('SET enable_seqscan = OFF;')
+        total = people.count()
+        people.count = lambda: total
+        cursor.execute('SET enable_seqscan = ON;')
     context = {
         'form': form,
         'people': people,