Re: Resetting a sequence's last value... - Mailing list pgsql-general

From Sean Chittenden
Subject Re: Resetting a sequence's last value...
Date
Msg-id 20030427193937.GN35599@perrin.int.nxad.com
Whole thread Raw
In response to Re: Resetting a sequence's last value...  (Tom Lane <tgl@sss.pgh.pa.us>)
Responses Re: Resetting a sequence's last value...
List pgsql-general
> > I'm looking to have things return an error if someone calls
> > currval() on the sequence.  -sc
>
> There isn't any mechanism for that, although I imagine it wouldn't
> be hard to add such a function to commands/sequence.c.  But the
> requirement seems a bit bizarre.  Maybe there's a better way to do
> whatever you're after?

Controlling/policing the source tree is the other option.  Here's a
quick description:

I have a transaction table that I use to record meta data about the
connection (current user, ip that they're connecting from, time,
etc.).  The transaction ID (txn_id) returned from the start_txn()
function calls nextval() on the txn_id_seq.  Every subsequent table
calls currval() on that particular sequence, however after certain
policy based places in the transaction, I need the caller to start a
new transaction.  If a programmer lapses to call start_txn() again,
then the audit trail gets really fuzzy and it becomes impossible to
differentiate a 1st transaction from a 2nd transaction.  As opposed to
policing the source tree for possible errors, I'd like a technological
solution that will allow me to call, "invalidate_currval('txn_id')" or
some such that way the next time someone tries to call
currval('txn_id'), they'll get a nice big fat juicy error that'll
abort the remainder of their transaction.

Thoughts?  I got a post offlist suggesting writing a C function, but
that's pretty dependent on the backend and would have to be recompiled
from version to version, something I'm not too wild about.  -sc

--
Sean Chittenden


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