Re: Further pg_upgrade analysis for many tables - Mailing list pgsql-hackers

On 11/7/12 9:17 PM, Bruce Momjian wrote:
> As a followup to Magnus's report that pg_upgrade was slow for many
> tables, I did some more testing with many tables, e.g.:
> 
>     CREATE TABLE test991 (x SERIAL);
> 
> I ran it for 0, 1k, 2k, ... 16k tables, and got these results:
> 
>     tables    pg_dump     restore     pg_upgrade(increase)
>         0       0.30        0.24       11.73(-)
>      1000       6.46        6.55       28.79(2.45x)
>      2000      29.82       20.96       69.75(2.42x)
>      4000      95.70      115.88      289.82(4.16x)
>      8000     405.38      505.93     1168.60(4.03x)
>     16000    1702.23     2197.56     5022.82(4.30x)

I can reproduce these numbers, more or less.  (Additionally, it ran out
of shared memory with the default setting when dumping the 8000 tables.)

But this issue seems to be entirely the fault of sequences being
present.  When I replace the serial column with an int, everything
finishes within seconds and scales seemingly linearly.