chore: explain performance improvements.

[billy-the-fish]

Enable CAGGS to use MERGE for refresh operations rather than delete

[github-actions]

Allow 10 minutes from last push for the staging site to build. If the link doesn't work, try using incognito mode instead. For internal reviewers, check web-documentation repo actions for staging build status. Link to build for this PR: http://docs-dev.timescale.com/docs-3513-docs-rfc-add-documentation-about-using-merge-for-continuous-aggregate-refresh

[iroussos]

Looks good to me @billy-the-fish, thank you for adding this to the docs!

Two comments:

(1) This is a parameter that you set and forget when you create continuous aggregates, not something that you need to set when you manually refresh a specific continuous aggregate.

Feels to me that this should be part of the CREATE MATERIALIZED VIEW (Continuous Aggregate) page. What do you think?

(2) A small nitpick:
The "Configure database parameters" page only focuses on the Timescale Cloud UI, not mentioning how a self hosted user running TimescaleDB can enable those parameters. But this is a core feature of TimescaleDB available to all users.

Should we either add the command here or add a section on that page on how to enable parameters through psql?

[billy-the-fish]

Moved the config param to CREATE MATERIALIZED VIEW (Continuous Aggregate) and linked to it from the refresh page, added the config to the TimescaleDB ref.