Re: PartitionDispatch's partdesc field

On 2018/07/26 5:23, Robert Haas wrote:
> I noticed today that in the PartitionDispatch structure, the partdesc
> field is set but not used.  So we could remove it.  See attached
> pd-partdesc-remove.patch.  If we want to go this route, I suggest
> doing a slightly more thorough removal and getting rid of the key
> field as well.  See attached pd-partdesc-and-key-remove.patch.
> 
> Another alternative, which I think might make more sense, is to make
> use pd->key and pd->partdesc in preference to pd->reldesc->rd_partkey
> and pd->reldesc->rd_partdesc.  It seems to me that the idea of the
> PartitionDispatch structure is that it gathers together all of the
> information that we need for tuple routing, so it might make sense for
> the tuple routing code ought to get the information from there rather
> than referring back to the RelationDesc.  See attached
> pd-partdesc-use.patch.

+1 to pd-partdesc-use.patch.

> Basically, the decision here is whether we want to avoid invoking
> RelationGetPartitionKey and RelationGetPartitionDesc over and over
> again, either for reasons of notational cleanliness (macro names are
> long) or safety (absolutely no chance that the answer will change) or
> efficiency (maybe those macros will someday do more than just a
> pointer dereference?).  If so, we should cache the data in the
> PartitionDispatch object and then use it.

I agree.

Thanks,
Amit