Re: persistent data feature

[Tassilo Horn]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

>> There will, of course, be large amounts of data, and that will be
>> slow.  (People already do this with a number things, and the results
>> are predictably sluggish.)
>
> To help me understand this discussion, I think it would help me to
> have examples of such large databases currently implemented as text
> files, along with an idea of what "large" means in this context (how
> many MBs) and where the "slow"ness manifests itself.

I think the Gnus registry (info "(gnus) The Gnus Registry") is a good
example.  Mine is 3.6 MB but only because I've set
`gnus-registry-max-entries' to 10000 and `gnus-registry-track-extra' to
nil because I've basically only ever used it to be able to refer to an
article's parent.

There should be no reason to cap its number of entries or the number of
things it tracks.  By default it would also track sender, subject, and
recipients of messages.  I guess that would easily quadruple its size
for me.

I also think the Gnus registry is an example of where a DB with a
specific schema and queries would make sense instead of some persistent
variable.  There's no value in having that huge pile of hash-maps in
memory if I just want to, e.g., move the current mail into the folder
where its parent already resides.

Bye,
Tassilo