Re: [PROPOSAL] Shared Ispell dictionaries

Hello Tomas,

Arthur, what are your plans with this patch in the current CF?

I think dsm-based approach is in good shape already and works nice.
I've planned only to improve the documentation a little. Also it seems I
should change 0004 part, I found that extension upgrade scripts may be made
in wrong way.
In my opinion RELOAD and UNLOAD commands can be made in next commitfest
(2018-09).
Did you look it? Have you arguments about how shared memory allocation and
releasing functions are made?

>
> It does not seem to be moving towards RFC very much, and reworking the
> patch to use mmap() seems like a quite significant change late in the
> CF. Which means it's likely to cause the patch get get bumped to the
> next CF (2018-09).

Agree. I have a draft version for mmap-based approach which works in
platforms with mmap. In Windows it is necessary to use another API
(CreateFileMapping, etc). But this approach requires more work on handling
processed dictionary files (how name them, when remove).

>
> FWIW I am not quite sure if the mmap() approach is better than what was
> implemented by the patch. I'm not sure how exactly will it behave under
> memory pressure (AFAIK it goes through page cache, which means random
> parts of dictionaries might get evicted) or how well is it supported on
> various platforms (say, Windows).
>

Yes, as I wrote mmap-based approach requires more work. The only benefit I
see is that you don't need to process a dictionary after server restart.
I'd vote for dsm-based approach.

--
Arthur Zakirov
Postgres Professional: http://www.postgrespro.com
Russian Postgres Company