refactor: Optimise landing page performance (#461)

* refactor: Mark all datasets as browsable

* refactor: Optimise count by using estimate

* chore: Move estimate_count function to query.py

* revert: "chore: Move estimate_count function to query.py"

ref: cc28c65

* revert: "refactor: Optimise count by using estimate"

ref: 46b5d1d

* refactor: Remove query for getting row count of api_ref_data

main/templates/browse/home.html

@@ -40,8 +40,8 @@
   <div class="{% include "_side_block_classes.html" %} md:row-span-3">
     <p class="text-xs m-4">
       {% if browsable_datasets %}
-        {{ total_indexed_human }} bibliographic&nbsp;items
-        now indexed among&nbsp;sources:
+        Bibliographic&nbsp;items
+        are indexed among&nbsp;sources:
         {% for ds_id in browsable_datasets %}
           <a class="{% if dataset_id == ds_id %}font-bold{% endif %}" href="{% url "browse_dataset" ds_id %}"
             >{{ ds_id }}</a>{% if not forloop.last %}, {% endif %}

main/views.py

@@ -56,28 +56,9 @@ def home(request):
 
     metrics.gui_home_page_hits.inc()
 
-    non_empty_datasets = (
-        RefData.objects.values_list('dataset', flat=True).
-        distinct())
-
-    total_indexed_citations = RefData.objects.count()
-    units = ('', 'k', 'M', 'G', 'T', 'P')
-    factor = 1000.0
-    magnitude = int(floor(log_(max(abs(total_indexed_citations), 1), factor)))
-    total_indexed_human = '%.2f%s' % (
-        total_indexed_citations / factor**magnitude,
-        units[magnitude],
-    )
-
-    browsable_datasets = [
-        ds_id
-        for ds_id in settings.RELATON_DATASETS
-        if ds_id in non_empty_datasets]
-
     return render(request, 'browse/home.html', dict(
         **shared_context,
-        total_indexed_human=total_indexed_human,
-        browsable_datasets=browsable_datasets,
+        browsable_datasets=settings.RELATON_DATASETS,
     ))