Re: Internal error XX000 with enable_partition_pruning=on, pg 11 beta1 on Debian

David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> writes:
> So it looks like I've assumed that the Append path's partitioned_rels
> will only ever be set for partitioned tables, but it can, in fact, be
> set for UNION ALL parents too when the union children are partitioned
> tables.

> As a discussion topic, I've attached a patch which does resolve the
> error, but it also disables run-time pruning in this case.

> There might be some way we can treat UNION ALL parents differently
> when building the PartitionPruneInfos. I've just not thought of what
> this would be just yet. If I can't think of that, I wonder if this is
> a rare enough case not to bother with run-time partition pruning.

So, IIUC, the issue is that for partitioning cases Append expects *all*
its children to be partitions of the *same* partitioned table? That
is, you could also break it with

select * from partitioned_table_a
union all
select * from partitioned_table_b

?

If so, maybe the best solution is to not allow a partitioning appendrel
to be flattened into an appendrel generated in other ways (particularly,
via UNION ALL). I also wonder whether it was a bad idea to treat these
as the same kind of path/plan in the first place.

regards, tom lane