Re: why partition pruning doesn't work?

On 2018/06/14 23:40, Tom Lane wrote:
> Robert Haas <robertmhaas@gmail.com> writes:
>> On Thu, Jun 14, 2018 at 7:23 AM, David Rowley
>> <david.rowley@2ndquadrant.com> wrote:
>>> However, I only spent about 10 mins looking into this, there may be
>>> some giant holes in the idea.  It would need much more research.
> 
>> It kind of flies in the face of the idea that a RangeTblEntry is just
>> a node that can be freely copied around, serialized and deserialized,
>> etc.
> 
> And also the idea that the Plan tree is read-only to the executor,
> which is not a good property to give up.
> 
>> I think it would be better to keep the pointer in the RelOptInfo in
>> the planner and in the EState or PlanState in the executor.  Those are
>> things we don't think can be copied, serialized, etc.
> 
> Yeah, RelOptInfo seems like the natural place in the planner; we might
> need index relcache links in IndexOptInfo, too.
> 
> I'm less sure what to do in the executor.  We already do keep open
> relation pointers in PlanStates; the problem is just that it's
> node-type-specific (ss_currentRelation, iss_RelationDesc, etc).  Perhaps
> that's unavoidable and we should just add more such fields as needed.

The patch I mentioned upthread maintains an array of Relation pointers in
AppendState with as many members as there are in the partitioned_rels list
that appears in the corresponding Append plan.

I revised that patch a bit to rename ExecLockNonLeafAppendTables to
ExecOpenAppendPartitionedTables to sound consistent with
ExecOpenScanRelation et al.

Thanks,
Amit