> would be "database system identification" - the rather unique ID of a
> database installation. Third line in pg_controldata output:Ah, good point. I don't see any SQL API for access to that value. The
> ----------------------------------------------------------------------------------------------
> Datenbanksystemidentifikation: 5293702538224708457
> ----------------------------------------------------------------------------------------------
value is used to make sure the xlogs match the server, and pg_resetxlog
will change that identifier. The value is generated from the
time-of-day that xlog is initialized at bootstrap time:
gettimeofday(&tv, NULL);
sysidentifier = ((uint64) tv.tv_sec) << 32;
sysidentifier |= (uint32) (tv.tv_sec | tv.tv_usec);
I am afraid the setting isn't as unique as you probably want.
Why do you want the value and can we provide a better value for you?
The databases on those laptops are (to some extend) replications of the central PostgreSQL database.
Now I have to keep track of information like "Laptop xxx allready got the changes xxx"; esp. with DML-changes which get replicated.
Challenge is to identify the entity "Laptop"... actually I have one table named "dbidentity", which gets populated with a GUID, and use this to mark the databases. Which has some potential for misstakes... so I am looking for something "hard-coded" into PostgreSQL to really identify two different databases (with rather the same content) via a single marker.
So probably this identifier also gets resetted on pg_resetlxlog, and is not really what I would need :( (on the other hand: that system is running since 5 years on different machines an pg_resetxlog was not used one time :) )
Thanks for caring,
Harald
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GHUM Harald Massa
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Harald Armin Massa
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