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From: Bruce Momjian <[email protected]>
To: Simon Riggs <[email protected]>
Cc: pgsql-docs <[email protected]>
Cc: Jan Wieck <[email protected]>
Subject: Re: Incorrect description of xmax and xip in functions docs
Date: Wed, 7 Jan 2009 20:30:18 -0500 (EST)
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

Simon Riggs wrote:
> 
> On Sun, 2008-09-07 at 08:31 -0400, Bruce Momjian wrote:
> > Simon Riggs wrote:
> > > 
> > > On Sat, 2008-09-06 at 21:31 -0400, Bruce Momjian wrote:
> > > > Applied, and attached.
> > > 
> > > Thanks.
> > > 
> > > > > And for txid_visible_in_snapshot() comment added:
> > > > > "Function should not be used with subtransaction xids. It is possible
> > > > > that this function will return a true result for a subtransaction xid
> > > > > that was actually still in progress at the time of the snapshot".
> > > > 
> > > > I think the cleaner solution is to throw an appropriate error if a
> > > > subtransaction xid is used, rather than adding documentation.
> > > 
> > > Or maybe check subtrans for it, as it really should be doing.
> > 
> > Yea, that's what I meant.  You can't be sure everyone is going to read
> > the documentation but they are sure to see the function results or error
> > message.
> 
> In fact, neither is possible. We cannot assume subtrans is available on
> the system on which the check is made, neither can we identify which
> xids are subtransactions and which are not.
> 
> The only way is to document it.

Sorry, I am just getting back to this.  Why would we not know if
something is a subtransaction or if subtransactions are supported?  Are
you assuming txid_visible_in_snapshot() will be used on different
servers?  What are these txid_* functions for anyway?

-- 
  Bruce Momjian  <[email protected]>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + If your life is a hard drive, Christ can be your backup. +

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