Re: sqlite3

[Alexandre Garreau]

Le mardo, 14-a de decembro 2021, 9-a horo kaj 57:51 CET Lars Ingebrigtsen 
a écrit :
> Lars Ingebrigtsen <larsi@gnus.org> writes:
> 
> 
> > I think it'd be good to bring that into core, and then write a small
> > wrapper library (well, a trivial ORM) for the rest of Emacs to use, so
> > that we don't have to write SQL all over the place.  That is:
> > 
> > (setf (persistent-data :namespace "emoji" :key "favorites")
> > emoji--favorites)
> > 
> > I.e., what Emacs needs is a persistent key/value store, and this would
> > give us that.
> 
> This is now implemented under the name of `multisession-value' (but not
> merged to the trunk yet; I'll probably do that later today, unless
> somebody comes up with a better name).
> 
> As for the sqlite part of this: My initial benchmarking of this was
> wrong.  I thought sqlite3 was going to be a real advantage for this
> thing, since I'd benchmarked excellent performance (more than 50K
> updates per second, for instance).  But that's only when not committing
> after every transaction, which we want to do here, really.
> 
> But it turns out that sqlite3 is actually slower for this particular use
> case than just writing the data to a file (i.e., using the file system
> as the database; one file per value).  So multisession.el now offers
> two backends (`files' and `sqlite'), and defaults to `files'.

What about having an intermediary abstraction for persistent stores in 
general, and on top of that multisession variables?

What about a all-variables-in-one-file very trivial backend? a gdbm 
backend? would that be possible/allowable if gdbm is only integrated as a 
module?

What fs did you benchmark with? did you try with an old-linked-list-like 
ext4, or a modern btree btrfs?  I think the later might (unportably, 
though) display some advantages that sqlite (portably) provides.

gdbm might provide some others.  I would find benchmarking of all these 
relevant and interesting (and why not of qiantan’s incremental’s store as 
well, if he integrates it)