The official Postgres manual instantly comes to mind whenever I think about great documentation. There's just something about the way it's split up, and especially the typical length of a leaf page, that makes it absurdly helpful.
And the fact that you can usually find the exact page you want from Google is nice. As a bonus, if google gives you the wrong version, that page links to the same page for every other version too.
The official Postgres manual instantly comes to mind whenever I think about great documentation. There's just something about the way it's split up, and especially the typical length of a leaf page, that makes it absurdly helpful.
https://www.postgresql.org/docs/10/static/index.html
https://www.postgresql.org/docs/10/static/reference.html