Use comments counter cache instead of additional query

[ahukkanen]

🎩 What? Why?

When browsing e.g. the blogs index, you can see from the benchmarks that there are bunch of COUNT queries done against the comments table.

The counter caches were already added at #6438 but they are not properly used.

It also does not work if we would add counter_cache: :comments_count to the commentable concern:

decidim/decidim-comments/lib/decidim/comments/commentable.rb

Line 13 in 96c78cb

has_many :comments, as: :commentable, foreign_key: "decidim_root_commentable_id", foreign_type: "decidim_root_commentable_type", class_name: "Decidim::Comments::Comment"

Even after it is added there and the Comment model (as with other counter caches), the queries won't disappear.

The only way how I could figure out to get rid of the extra queries was by accessing the cache column directly.

📌 Related Issues

• Related to Debates filtering #6438, Improving caching #7574

Testing

• Create an instance with the test seeds
• Go to one of the blogs components
• Check the benchmark section at the top right
• See a bunch of COUNT queries against the comments table (see screenshot)

📋 Checklist

• ❓ CONSIDER adding a unit test if your PR resolves an issue.
• ✔️ DO check open PR's to avoid duplicates.
• ✔️ DO keep pull requests small so they can be easily reviewed.
• ✔️ DO build locally before pushing.
• ✔️ DO make sure tests pass.
• ✔️ DO make sure any new changes are documented in docs/.
• ✔️ DO add and modify seeds if necessary.
• ✔️ DO add CHANGELOG upgrade notes if required.
• ✔️ DO add to GraphQL API if there are new public fields.
• ✔️ DO add link to MetaDecidim if it's a new feature.
• ❌AVOID breaking the continuous integration build.
• ❌AVOID making significant changes to the overall architecture.

📷 Screenshots