Re: postgres_fdw : altering foreign table not invalidating prepare statement execution plan.

On 2016/10/07 10:26, Amit Langote wrote:
> On 2016/10/06 21:55, Etsuro Fujita wrote:
>> On 2016/10/06 20:17, Amit Langote wrote:
>>> On 2016/10/05 20:45, Etsuro Fujita wrote:

>> I noticed that we were wrong.  Your patch was modified so that
>> dependencies on FDW-related objects would be extracted from a given plan
>> in create_foreignscan_plan (by Ashutosh) and then in
>> set_foreignscan_references by me, but that wouldn't work well for INSERT
>> cases.  To fix that, I'd like to propose that we collect the dependencies
>> from the given rte in add_rte_to_flat_rtable, instead.

> I see.  So, doing it from set_foreignscan_references() fails to capture
> plan dependencies in case of INSERT because it won't be invoked at all
> unlike the UPDATE/DELETE case.

Right.

>>>> If some writable FDW consulted foreign table/server/FDW options in
>>>> AddForeignUpdateTarget, which adds the extra junk columns for
>>>> UPDATE/DELETE to the targetList of the given query tree, the rewritten
>>>> query tree would also need to be invalidated.  But I don't think such an
>>>> FDW really exists because that routine in a practical FDW wouldn't change
>>>> such columns depending on those options.

>> I had second thoughts about that; since the possibility wouldn't be zero,
>> I added to extract_query_dependencies_walker the same code I added to
>> add_rte_to_flat_rtable.

> And here, since AddForeignUpdateTargets() could possibly utilize foreign
> options which would cause *query tree* dependencies.  It's possible that
> add_rte_to_flat_rtable may not be called before an option change, causing
> invalidation of any cached objects created based on the changed options.
> So, must record dependencies from extract_query_dependencies as well.

Right.

> I think this (v4) patch is in the best shape so far.

Thanks for the review!

Best regards,
Etsuro Fujita