Kagi:

First result is the official documentation with the page that contains information about the in operator

This was the result: https://www.postgresql.org/docs/9.0/functions.html

BUT it is the documentation for 9.0

Though if I would use postgresql documentation very often I could just use the Kagi feature that rewrites URLs with a regex, so I can replace it always with the latest version.

Kagi Documentation for that feature:

https://help.kagi.com/kagi/features/redirects.html#redirects-url-rewrites

Some use cases of redirects include:

• Change domains to a preferred domain (reddit.com to old.reddit.com)
• Fixing links to outdated documentation with bad SEO
• Rewriting proxied pages (like Google AMP) to their source URL
• Changing any http link to https