== Public Projects
This finder class now _only_ returns public projects. Previously this
finder would also return private and internal projects. Including these
projects makes caching data much harder and less efficient. Meanwhile
including this data isn't very useful as very few users would be
interested in seeing projects they have access to as trending. That is,
the feature is more useful when you want to see what _other_ popular
projects there are.
== Caching
The data returned by TrendingProjectsFinder is now cached for a day
based on the number of months the data should be restricted to. The
cache is not flushed explicitly, instead it's rebuilt whenever it
expires.
== Timings
To measure the impact I changed the finder code to use the last 24
months instead of the last month. I then executed and measured 10
requests to the explore page. On the current "master" branch (commit
88fa5916ff) this would take an average of
2.43 seconds. Using the changes of this commit this was reduced to
around 1.7 seconds.
Fixesgitlab-org/gitlab-ce#22164
This changes the query to use a COUNT nested in an INNER JOIN, instead
of a COUNT plus a GROUP BY. There are two reasons for this:
1. Using a COUNT in an INNER JOIN can be quite a bit faster.
2. The use of a GROUP BY means that method calls such as "any?"
(and everything else that calls "count") operate on a Hash that
counts the amount of notes on a per project basis, instead of just
counting the total amount of projects.
The query has been moved into Project.trending as its logic is simple
enough. As a result of this testing the TrendingProjectsFinder class
simply involves testing if the right methods are called, removing the
need for setting up database records.
Yorick Peterse