On 2010-11-14 5:28 PM +0200, Hitoshi Harada wrote:
2010/11/14 Marko Tiikkaja<marko.tiikk...@cs.helsinki.fi>:
.. and a wild patch appears.
Could you update wiki on this feature if you think we've reached the consensus?
You're probably referring to
http://archives.postgresql.org/pgsql-hackers/2010-11/msg00660.php
which was unfortunately just me talking too soon. There still doesn't
appear to be a consensus on the difference (if any) between these queries:
WITH t AS (DELETE FROM foo RETURNING *)
SELECT 1 LIMIT 0; -- unreferenced CTE
WITH t AS (DELETE FROM foo RETURNING *)
SELECT 1 FROM t LIMIT 0; -- referenced, but not read
WITH t AS (DELETE FROM foo RETURNING *)
SELECT 1 FROM t LIMIT 1; -- referenced, but only partly read
WITH t AS (DELETE FROM foo RETURNING *)
SELECT 1 FROM t t1, t t2; -- referenced, read multiple times
In my opinion, all of these should have the same effect: DELETE all rows
from "foo". Any other option means we're going to have trouble
predicting how a query is going to behave.
As far as I know, we do have a consensus that the order of execution
should be an implementation detail, and that the statements should
always be executed in the exact same snapshot (i.e. no CID bump between).
Also, wrapping up the discussion like pros& cons on the different
execution models helps not only the advance discussions but also
reviews of this patch.
Do you mean between the "execute in order, bump CID" and "execute in
whatever order but to completion" behaviours?
Regards,
Marko Tiikkaja
--
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers
