Some sites have a large number of categories and fetching the category
IDs or category topic IDs just to build another query can take a long
time or resources (i.e. memory).
In the past, CategoryFeaturedTopic.feature_topics raised an exception
sometimes because it tried to create multiple CategoryFeaturedTopic
records for the same topic.
This code should not raise any exceptions as long as the list of new
topic IDs is unique because all previous records are deleted first,
then recreated and everything happens inside a transaction. The previous
rescue block was dead code anyway because it tried to catch
PG::UniqueViolation instead of ActiveRecord::RecordNotUnique. This
commit includes a fix to ensure that the topic IDs are unique.
We have the `# frozen_string_literal: true` comment on all our
files. This means all string literals are frozen. There is no need
to call #freeze on any literals.
For files with `# frozen_string_literal: true`
```
puts %w{a b}[0].frozen?
=> true
puts "hi".frozen?
=> true
puts "a #{1} b".frozen?
=> true
puts ("a " + "b").frozen?
=> false
puts (-("a " + "b")).frozen?
=> true
```
For more details see: https://samsaffron.com/archive/2018/02/16/reducing-string-duplication-in-ruby
This reduces chances of errors where consumers of strings mutate inputs
and reduces memory usage of the app.
Test suite passes now, but there may be some stuff left, so we will run
a few sites on a branch prior to merging
Old query used to scan the full topics table, on home page
Instead we now perform 2 queries, one for pinned and one for unpinned and merge
results in a 10x improvement on a 1 million topic DB
- removes an (n+1) query for user data
- supports the preload store for the data to avoid a second request
- fix a bug where uncategorizes was reporting (0, 0, 0) for topics by week, month, year
