Date: Tue, 20 Nov 2018 12:28:30 -0500
From: Stephen Frost <sfrost@snowman.net>
To: Merlin Moncure <mmoncure@gmail.com>
Cc: f.pardi@portavita.eu,
	postgres performance list <pgsql-performance@postgresql.org>
Subject: Re: PostgreSQL VS MongoDB: a use case comparison
Message-ID: <20181120172829.GF3415@tamriel.snowman.net>
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Greetings,

* Merlin Moncure (mmoncure@gmail.com) wrote:
> On Tue, Nov 20, 2018 at 10:43 AM Stephen Frost <sfrost@snowman.net> wrote:
> > * Merlin Moncure (mmoncure@gmail.com) wrote:
> > > On Mon, Nov 19, 2018 at 11:26 AM Stephen Frost <sfrost@snowman.net> w=
rote:
> > > > Looks like a lot of the difference being seen and the comments made
> > > > about one being faster than the other are because one system is
> > > > compressing *everything*, while PG (quite intentionally...) only
> > > > compresses the data sometimes- once it hits the TOAST limit.  That
> > > > likely also contributes to why you're seeing the on-disk size
> > > > differences that you are.
> > >
> > > Hm.  It may be intentional, but is it ideal?  Employing datum
> > > compression in the 1kb-8kb range with a faster but less compressing
> > > algorithm could give benefits.
> >
> > Well, pglz is actually pretty fast and not as good at compression as
> > other things.  I could certainly see an argument for allowing a column
> > to always be (or at least attempted to be) compressed.
> >
> > There's been a lot of discussion around supporting alternative
> > compression algorithms but making that happen is a pretty big task.
>=20
> Yeah; pglz is closer to zlib.  There's much faster stuff out
> there...Andres summed it up pretty well;
> https://www.postgresql.org/message-id/20130605150144.GD28067%40alap2.anar=
azel.de
>=20
> There are also some interesting discussions on jsonb specific
> discussion approaches.

Oh yes, having a dictionary would be a great start to reducing the size
of the jsonb data, though it could then become a contention point if
there's a lot of new values being inserted and such.  Naturally there
would also be a cost to pulling that data back out as well but likely it
would be well worth the benefit of not having to store the field names
repeatedly.

Then again, taken far enough, what you end up with are tables... :)

Thanks!

Stephen

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