Re: jsonb format is pessimal for toast compression

On 16/09/14 21:20, Robert Haas wrote:
> In practice, I'm not very surprised that the impact doesn't seem too
> bad when you're running SQL queries from the client. There's so much
> other overhead, for de-TOASTing and client communication and even just
> planner and executor costs, that this gets lost in the noise. But
> think about a PL/pgsql procedure, say, where somebody might loop over
> all of the elements in array. If those operations go from O(1) to
> O(n), then the loop goes from O(n) to O(n^2). I will bet you a
> beverage of your choice that somebody will find that behavior within a
> year of release and be dismayed by it.
>

As somebody who did see server melt (quite literally that time
unfortunately) thanks to the CPU overhead of operations on varlena
arrays +1 (in fact +many).

Especially if we are trying to promote the json improvements in 9.4 as
"best of both worlds" kind of thing.

--
Petr Jelinek http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services