Re: Sustained inserts per sec ... ?

On Apr 4, 2005 3:46 PM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
> On Mon, 2005-04-04 at 09:48 -0400, Christopher Petrilli wrote:
> > The point, in the rough middle, is where the program begins inserting
> > into a new table (inherited). The X axis is the "total" number of rows
> > inserted.
>
> and you also mention the same data plotted with elapsed time:
> http://www.amber.org/~petrilli/diagrams/pgsql_copyperf_timeline.png
>
> Your graphs look identical to others I've seen, so I think we're
> touching on something wider than your specific situation. The big
> difference is that things seem to go back to high performance when you
> switch to a new inherited table.

This is correct.

> I'm very interested in the graphs of elapsed time for COPY 500 rows
> against rows inserted. The simplistic inference from those graphs are
> that if you only inserted 5 million rows into each table, rather than 10
> million rows then everything would be much quicker. I hope this doesn't
> work, but could you try that to see if it works? I'd like to rule out a
> function of "number of rows" as an issue, or focus in on it depending
> upon the results.
>
> Q: Please can you confirm that the discontinuity on the graph at around
> 5000 elapsed seconds matches EXACTLY with the switch from one table to
> another? That is an important point.

Well, the change over happens at 51593.395205 seconds :-) Here's two
lines from the results with row count and time added:

10000000 51584.9818912 8.41331386566
10000500 51593.395205 0.416964054108

Note that 10M is when it swaps. I see no reason to interpret it
differently, so it seems to be totally based around switching tables
(and thereby indices).

> Q: How many data files are there for these relations? Wouldn't be two,
> by any chance, when we have 10 million rows in them?

I allow PostgreSQL to manage all the data files itself, so here's the
default tablespace:

total 48
drwx------ 2 pgsql pgsql 4096 Jan 26 20:59 1
drwx------ 2 pgsql pgsql 4096 Dec 17 19:15 17229
drwx------ 2 pgsql pgsql 4096 Feb 16 17:55 26385357
drwx------ 2 pgsql pgsql 4096 Mar 24 23:56 26425059
drwx------ 2 pgsql pgsql 8192 Mar 28 11:31 26459063
drwx------ 2 pgsql pgsql 8192 Mar 31 23:54 26475755
drwx------ 2 pgsql pgsql 4096 Apr 4 15:07 26488263
[root(at)bigbird base]# du
16624 ./26425059
5028 ./26385357
5660 ./26459063
4636 ./17229
6796 ./26475755
4780 ./1
1862428 ./26488263
1905952 .

> Q: What is the average row length?
> About 150-160 bytes?

Raw data is around 150bytes, after insertion, I'd need to do some
other calculations.

Chris
--
| Christopher Petrilli
| petrilli(at)gmail(dot)com