Re: EvalPlanQual behaves oddly for FDW queries involving system columns

Etsuro Fujita <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp> writes:
> Let me explain further. Here is the comment in ExecOpenScanRelation:

> * Determine the lock type we need. First, scan to see if target
> relation
> * is a result relation. If not, check if it's a FOR UPDATE/FOR SHARE
> * relation. In either of those cases, we got the lock already.

> I think this is not true for foreign tables selected FOR UPDATE/SHARE,
> which have markType = ROW_MARK_COPY, because such foreign tables don't
> get opened/locked by InitPlan. Then such foreign tables don't get
> locked by neither of InitPlan nor ExecOpenScanRelation. I think this is
> a bug.

You are right. I think it may not matter in practice, but if the executor
is taking its own locks here then it should not overlook ROW_MARK_COPY
cases.

> To fix it, I think we should open/lock such foreign tables at
> InitPlan as the original patch does.

I still don't like that; InitPlan is not doing something that would
require physical table access. The right thing is to fix
ExecOpenScanRelation's idea of whether InitPlan took a lock or not,
which I've now done.

regards, tom lane