But if DB Browser for SQLite is really built in a way to forcibly load the entire database
Not intentionally it doesn't - there is a lot of work to make it as smooth as possible (the reason for the 'prefetch block size') but the first thing it has to do is work out how many rows the table has, so it does a 'select count(*) from table', and it's this that can hammer large databases. Even with an index, a 100 GB database is going to take time to get this figure.
How do you manage to count the number of rows so quickly ?
I knoweth not. I tend to steer clear of the DB4S code ... here be dragons. I know a lot has gone into making it optimised though... tweaks here and there, etc.
The application log in DB4S might assist in working out where the freeze is occurring.
If you don't need to edit records, the 'execute SQL' tab is useful to grab records, and that should be speedy. The grid is 'read only' which isn't always great.
But I thought it was impossible to have an accurate count of the number of rows quickly (i.e. faster than "select count(*)" which is taking ages
Depends on the version of SQLite. I know SQLite itself (so not DB4S) has sexy internal methods to make this query fast. Depending on the table contents, it can be quicker doing a 'select (1)' rather than a 'select (*)' which would pull in a load of data, only to discard it.
So there is something wrong around this last query but no means for me to debug this further
That's useful to know - thanks for digging that out.
I would have suggested raising an official issue for it, as it's something we'd like to get fixed, but development has ... er, kinda stalled at the moment and the issue count is >470, so it's going to get lost in the noise for a while, so won't get solved in the short-term.
I have a sqlite database with many tables, is there any way to set certain tables to be read-only?
Unfortunately not - a database is a collection of tables, and each table is a collection of rows. That data is either all readable, or if the database is in a read-only file structure, all the data is read-only. If you wanted certain tables to be read-only, you'd have to separate them out into their own database, and make that database read-only. You could then attach the two databases together. This isn't a great solution though, and if someone moved the database to a non-read-only location, could manipulate the database again.
You could encrypt the database, but again, that's an all-or-nothing - you can't just encrypt individual tables. Unless, you wrote the data yourself, of course - if your own application read/wrote to the database, you could write data in an encrypted format so 'joe public' couldn't edit it.
where can I set the command for "Open in external application"?
I believe this saves a .txt file and tries to open that using whatever application normally opens a .txt file. In Firefox, what file is it showing? I assume you're editing text, and not an image or binary data. What operating system are you using?