> -----Original Message-----
> From: Bruce Momjian [mailto:pgman@candle.pha.pa.us]
>
> I am not sure if there is a TODO item here, but if there is, please let
> me know. Thanks.
There seems to be no consensus on this item currently.
IMHO both the command counters and the snapshots
in a function should advance except the leading SELECT
statements.
Note that SELECT .. FOR UPDATE statements aren't
SELECT statements.
regards,
Hiroshi Inoue
>
>
> > > -----Original Message-----
> > > From: Tom Lane
> > >
> > > I believe the reason for this is that in Read Committed mode,
> > > each separate query from the client computes a new snapshot (see
> > > SetQuerySnapshot calls in postgres.c). So, when your
> > > "select ctid, i from t1" query executes, it computes a snapshot
> > > that says T1 is committed, and then it doesn't see the row left
> > > over from T1. On the other hand, your plpgsql function operates
> > > inside a single client query and so it's using just one QuerySnaphot.
> > >
> > > One way to make the results equivalent is to compute a new
> QuerySnapshot
> > > for each SPI query. Quite aside from the cost of doing so, I do not
> > > think it makes sense, considering that the previous QuerySnapshot must
> > > be restored when we return from the function. Do we really want
> > > functions to see transaction status different from what's seen outside
> > > the function call?
> >
> > Yes I do.
> >
> > > I doubt it.
> > >
> > > The other way to make the results the same is to omit the
> > > SetQuerySnapshot calls for successive client-issued queries in one
> > > transaction.
> >
> > What's different from SERIALIZABLE mode ?
> >
> > regards,
> > Hiroshi Inoue
> >
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> >
>
> --
> Bruce Momjian | http://candle.pha.pa.us
> pgman@candle.pha.pa.us | (610) 853-3000
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