Re: jsonb format is pessimal for toast compression

On 2014-08-26 15:17:13 -0400, Tom Lane wrote:
> Andres Freund <andres(at)2ndquadrant(dot)com> writes:
> > On 2014-08-26 15:01:27 -0400, Tom Lane wrote:
> >> Yeah, exactly. Given current hardware trends, data compression is
> >> becoming more of a win not less as time goes on: CPU cycles are cheap
> >> even compared to main memory access, let alone mass storage. So I'm
> >> thinking we want to adopt a compression-friendly data format even if
> >> it measures out as a small loss currently.
>
> > On the other hand the majority of databases these day fit into main
> > memory due to its increasing sizes and postgres is more often CPU than
> > IO bound.
>
> Well, better data compression helps make that true ;-).

People disable toast compression though because it results in better
performance :(. Part of that could be fixed by a faster compression
method, part of it by decompressing less often. But still.

> And don't forget cache effects; actual main memory is considered slow
> these days.

Right. But that plays the other way round too. Compressed datums need to
be copied to be accessed uncompressed. Whereas at least in comparison to
inline compressed datums that's not necessary.

Anyway, that's just to say that I don't really agree that CPU overhead
is a worthy price to pay for storage efficiency if the gains are small.

Greetings,

Andres Freund

--
Andres Freund http://www.2ndQuadrant.com/
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