Re: file cloning in pg_upgrade and CREATE DATABASE

On 02/21/2018 04:00 AM, Peter Eisentraut wrote:
> ...
> 
> Some example measurements:
> 
> 6 GB database, pg_upgrade unpatched 30 seconds, patched 3 seconds (XFS
> and APFS)
> 
> similar for a CREATE DATABASE from a large template
> 

Nice improvement, of course. How does that affect performance on the
cloned database? If I understand this correctly, it essentially enables
CoW on the files, so what's the overhead on that? It'd be unfortunate to
speed up CREATE DATABASE only to get degraded performance later.

In any case, I find this interesting mainly for pg_upgrade use case. On
running systems I think the main issue with CREATE DATABASE is that it
forces a checkpoint.

regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
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