"Jan Wieck" <[EMAIL PROTECTED]> writes:

>     backend1: select publish_snapshot(); -- will block
>     backend2: start transaction;
>     backend2: set transaction isolation level serializable;
>     backend2: select clone_snapshot(<pid>); -- will unblock backend1

It seems simpler to have a current_snapshot() function that returns an bytea
or a new snapshot data type which set_current_snapshot(bytea) took to change
your snapshot. Then you could use tables or out-of-band communication to pass
around your snapshots however you please. 

set_current_snapshot() would have to sanity check that the xmin of the new
snapshot isn't older than the current globaloldestxmin. 

That could be handy for debugging purposes too. 

  Gregory Stark
  EnterpriseDB          http://www.enterprisedb.com

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