maximum number of rows in table - what about oid limits? 
Author Message
 maximum number of rows in table - what about oid limits?

Quote:

> well i wasn't interested in using oids in my application.
> i was curious about the relationship oids
> and the tuple/row limit.

> i guess if what you say is true, the oids are NOT used internally
> by postgres.  this seems odd.
> so, i guess my question still stands ... what happens when oids wrap?
> are oids nothing more than a sequence with an index,
> not used at all internally?

They are used for references between system tables.  That's why
you'll get intermittent failures on things like create statements after
rollover (system tables may have unique index on oid).
As far as I know the system doesn't do stuff with the oid on user rows.

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Mon, 24 Nov 2003 02:55:52 GMT
 maximum number of rows in table - what about oid limits?

<snip>
If it does happen, you can just retry the failed object-creation
command until you get a nonconflicting OID assignment.
<snip>

Tom, or anyone who'd know for that matter, what is the
exact error I would need to look for?

Tim

Quote:
----- Original Message -----




Sent: Wednesday, June 06, 2001 3:37 PM
Subject: [GENERAL] Re: [SQL] maximum number of rows in table - what about
oid limits?


> > my question is, since oid's are used by the
> > postgres kernel, what effect does oid wrapping have upon
> > the stability of the database.

> It doesn't affect stability, if by that you mean potential crashes.

> What can happen after a wrap is that the OID generated for a
> newly-created object might conflict with some already-existing object's
> OID.  If that happens, you get a duplicate-key-insertion error on the
> OID index of the relevant system catalog (pg_class, pg_type, etc).
> There is a unique index on OID for each system catalog wherein OID
> is used to identify objects.  It doesn't really matter whether the
> same OID is reused in different catalogs or in user tables.

> The odds of this happening seem pretty low, if you've got reasonable
> numbers of objects (eg, with a couple thousand tables in a database,
> you'd have a 2000/4G = 1 in 2 million chance of collision on pg_class
> OID).  If it does happen, you can just retry the failed object-creation
> command until you get a nonconflicting OID assignment.

> This is certainly not ideal, but it's not nearly as big a problem as
> transaction ID wraparound.  You can live with it, whereas right now
> xact ID wraparound is catastrophic.  That we gotta work on, soon.

> regards, tom lane

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Mon, 24 Nov 2003 23:49:39 GMT
 maximum number of rows in table - what about oid limits?

Quote:

> <snip>
> If it does happen, you can just retry the failed object-creation
> command until you get a nonconflicting OID assignment.
> <snip>
> Tom, or anyone who'd know for that matter, what is the
> exact error I would need to look for?

It'd be a complaint about attempt to insert a duplicate key into
the unique index on one of several system catalogs' OID columns.
There wouldn't be any earlier detection of the problem than that.

                        regards, tom lane

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Tue, 25 Nov 2003 22:57:07 GMT
 
 [ 3 post ] 

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