| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | Peter Geoghegan <pg(at)heroku(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Kevin Grittner <kgrittn(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: _mdfd_getseg can be expensive |
| Date: | 2016-08-31 21:37:20 |
| Message-ID: | 20160831213720.4axsjt25xaco5d4m@alap3.anarazel.de |
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| Lists: | pgsql-hackers |
On 2016-08-31 14:09:47 -0700, Peter Geoghegan wrote:
> On Thu, Aug 18, 2016 at 5:26 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
> > Rebased version attached. A review would be welcome. Plan to push this
> > forward otherwise in the not too far away future.
>
> This looks good.
Thanks for looking!
> The only thing that stuck out to any degree is that we don't grow the
> "reln->md_seg_fds[forknum]" array within the new _fdvec_resize()
> function geometrically. In other words, we don't separately keep track
> of the array size and allocated size, and grow the allocated size
> using the doubling strategy that you see in many places.
I can't really see that being worth the code here. The cost of
open()/lseek()'ing etc. is going to dwarf the cost of this.
Regards,
Andres
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