Overly slow loading times for article lists on home page

[eplebel]

It takes about 3 seconds to load the lists of "Recently Added" and "Recently Updated" articles on the homepage and about 2 seconds to display lists of articles on search results page. This didn't used to be the case; it started happening sometime in late November 2014 (in case this helps identify the problem).

This is perhaps related to open issue #94 (HTTP keep-alive doesn't seem to be working ), given that load times do seem quicker if you keep repeating the action.

[alexkyllo]

I believe the slow loading times are due to table scans on the Article table. The landing page shows the 5 recently created and 5 most recently updated articles, and it has to query all 288,330 articles and sort them in order to do this. Adding indexes on created_at and updated_at columns should fix this.

[alexkyllo]

Great success! These queries that took 20 seconds on my laptop previously, are now instantaneous. Pushed the migration to master and will run it on the production db shortly.

[alexkyllo]

Deployed to production. I'm seeing faster loading times at https://www.curatescience.org/beta#/ . Reopening this issue though, because I only addressed the home page. The search results page is hitting elasticsearch, so different steps would need to be taken to speed up the search results.

[eplebel]

Great, that definitely fixed the problem for the homepage! I created a separate issues for the slow loading times for search results, see #160