From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
cc: Arthur Zakirov <a.zakirov@postgrespro.ru>,
        Tomas Vondra <tomas.vondra@2ndquadrant.com>,
        Andres Freund <andres@anarazel.de>,
        Pavel Stehule <pavel.stehule@gmail.com>,
        pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: [PROPOSAL] Shared Ispell dictionaries
In-reply-to: 
 <CA+TgmoZfmJ1TJ3J3bDcfZA2ESSudK7RAaBpDG3Fp5naMzzyK6A@mail.gmail.com>
References: <27296.1522078068@sss.pgh.pa.us>
 <CA+TgmoaR_fVd_u60mA-PHO=J1u0PmdVGOt9WaxZ1UYuGq276oQ@mail.gmail.com>
 <20180516113631.GA29544@zakirov.localdomain>
 <20180614084015.GA12451@zakirov.localdomain>
 <20181001092204.GA5071@zakirov.localdomain>
 <68aaaff6-0efe-c14b-7aee-fb110bb97f69@2ndquadrant.com>
 <337f7a55-58b8-4fcc-a933-5e7799fa6882@postgrespro.ru>
 <e0a25563-cbb1-7089-8c25-44668cfb031b@postgrespro.ru>
 <42b1ded6-fd44-5975-77e4-72ada1f134a2@2ndquadrant.com>
 <20190120222121.ehistvcr4wsu2su5@alap3.anarazel.de>
 <95aea959-97a1-2ded-c881-eede4e5a1f0c@2ndquadrant.com>
 <cad38cdb-2bb1-da75-235f-2e6684826f10@postgrespro.ru>
 <b9e470f7-01b5-bf8c-78fc-5633ebc6fa2e@2ndquadrant.com>
 <5113daa6-b6e7-59f6-c4a8-96b5b81474fb@postgrespro.ru>
 <CAKNkYnyPxoByX0W7fUy=2NPvn880+DW3YZ5tBrFiV4cOaBX1xQ@mail.gmail.com>
 <1932084f-167a-8893-be24-c4c06afe113b@2ndquadrant.com>
 <26e59c3b-3598-cc2c-6b8d-81d24d6d0930@postgrespro.ru>
 <CA+TgmoYiWVvgUrDBJXVG9Crpg=s=Y1BLhMwVd1RZQOq5aF4Ctw@mail.gmail.com> <4c321!
 cb7-899f-0548-ecf4-5e965dd71335@postgrespro.ru>
 <CA+TgmoZfmJ1TJ3J3bDcfZA2ESSudK7RAaBpDG3Fp5naMzzyK6A@mail.gmail.com>
Comments: In-reply-to Robert Haas <robertmhaas@gmail.com>
	message dated "Thu, 21 Feb 2019 11:13:18 -0500"
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-ID: <27681.1550772480.1@sss.pgh.pa.us>
Date: Thu, 21 Feb 2019 13:08:00 -0500
Message-ID: <27682.1550772480@sss.pgh.pa.us>
Precedence: bulk

Robert Haas <robertmhaas@gmail.com> writes:
> Perhaps a better approach still would be to do what Andres proposed
> back in March:

> #> Is there any chance we can instead can convert dictionaries into a form
> #> we can just mmap() into memory?  That'd scale a lot higher and more
> #> dynamicallly?

That seems awfully attractive.  I was about to question whether we could
assume that mmap() works everywhere, but it's required by SUSv2 ... and
if anybody has anything sufficiently lame for it not to work, we could
fall back on malloc-a-hunk-of-memory-and-read-in-the-file.

We'd need a bunch of work to design a position-independent binary
representation for dictionaries, and then some tool to produce disk files
containing that, so this isn't exactly a quick route to a solution.
On the other hand, it isn't sounding like the current patch is getting
close to committable either.

(Actually, I guess you need a PI representation of a dictionary to
put it in a DSM either, so presumably that part of the work is
done already; although we might also wish for architecture independence
of the disk files, which we probably don't have right now.)

			regards, tom lane