On Fri, Sep 11, 2015 at 10:31 AM, Amit Kapila <amit.kapil...@gmail.com> wrote:
> > Could you perhaps try to create a testcase where xids are accessed that
> > are so far apart on average that they're unlikely to be in memory? And
> > then test that across a number of client counts?
> >
> Now about the test, create a table with large number of rows (say 11617457,
> I have tried to create larger, but it was taking too much time (more than a 
> day))
> and have each row with different transaction id.  Now each transaction should
> update rows that are at least 1048576 (number of transactions whose status can
> be held in 32 CLog buffers) distance apart, that way ideally for each update 
> it will
> try to access Clog page that is not in-memory, however as the value to update
> is getting selected randomly and that leads to every 100th access as disk 
> access.

What about just running a regular pgbench test, but hacking the
XID-assignment code so that we increment the XID counter by 100 each
time instead of 1?

Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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