| From: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
|---|---|
| To: | Heikki Linnakangas <hlinnaka(at)iki(dot)fi> |
| Cc: | Simon Riggs <simon(at)2ndquadrant(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, Peter Geoghegan <pg(at)heroku(dot)com>, Claudio Freire <klaussfreire(at)gmail(dot)com> |
| Subject: | Re: Logical tape pause/resume |
| Date: | 2016-10-04 14:58:37 |
| Message-ID: | CANP8+j+APb7pC96UN-46N0DxjKGFEEp6TS1nGNW8Ti54-Byncg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On 4 October 2016 at 12:47, Heikki Linnakangas <hlinnaka(at)iki(dot)fi> wrote:
>> Why not just make each new run start at a block boundary?
>> That way we waste on average BLCKSZ/2 disk space per run, which is
>> negligible but we avoid any need to have code to read back in the last
>> block.
>
>
> Hmm. You'd still have to read back the last block, so that you can update
> its next-pointer.
If each run is in its own file, then you can skip that bit.
And we do want the sort to disk to use multiple files so we can
parallelize I/O as well as CPU.
So since we know we'll want multiple files, we should be thinking
about how to split things up between files.
--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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