2010/11/8 Tom Lane <tgl@sss.pgh.pa.us>:
> Marko Tiikkaja <marko.tiikkaja@cs.helsinki.fi> writes:
>> On 2010-11-07 6:23 PM +0200, Tom Lane wrote:
>>> Um ... why? I thought the whole point of breaking out ModifyTable
>>> as a separate node type was so that a query involving writeable CTEs
>>> would still be just one plan tree.
>
>> We tried that for 9.0 and it didn't work. Almost all work for 9.1 has
>> been spent on creating an infrastructure for running the executor
>> separately for every WITH list element when wCTEs are present.
>
> I guess I shoulda been paying closer attention :-(. That really, really
> seems like fundamentally the wrong direction. What was it that was
> unfixable about the other way? If it is unfixable, should we revert
> ModifyTable?
Especially snapshot should not be updated during execution so we
decided to separate plans and restart executor.
But reading closer your response, it occurred to me that ModifyTable
can be the storage to be shared among separated plans instead of newly
invented DtScan. Are you suggesting embed ModifyTable into the main
query, that is also on the top of child plans? In this way we can
still separate plans and scan the result of child plans without much
modification of portal/explain?
Regards,
--
Hitoshi Harada