From: Amit Langote <amitlangot...@gmail.com> > Andrey's original patch had the flag to, as I understand it, make the > partitioning case work correctly. When inserting into a > non-partitioned table, there's only one relation to care about. In > that case, CopyFrom() can use either the new COPY interface or the > INSERT interface for the entire operation when talking to a foreign > target relation's FDW driver. With partitions, that has to be > considered separately for each partition. What complicates the matter > further is that while the original target relation (the root > partitioned table in the partitioning case) is fully initialized in > CopyFrom(), partitions are lazily initialized by ExecFindPartition().
Yeah, I felt it a bit confusing to see the calls to Begin/EndForeignInsert() in both CopyFrom() and ExecInitRoutingInfo(). > Note that the initialization of a given target relation can also > optionally involve calling the FDW to perform any pre-COPY > initializations. So if a given partition is a foreign table, whether > the copy operation was initialized using the COPY interface or the > INSERT interface is determined away from CopyFrom(). Andrey created > ri_usesMultiInsert to remember which was used so that CopyFrom() can > use the correct interface during the subsequent interactions with the > partition's driver. > > Now, it does not seem outright impossible to do this without the flag, > but maybe Andrey thinks it is good for readability? If it is > confusing from a modularity standpoint, maybe we should rethink that. > That said, I still think that there should be a way for CopyFrom() to > tell ExecFindPartition() which FDW interface to initialize a given > foreign table partition's copy operation with -- COPY if the copy > allows multi-insert, INSERT if not. Maybe the multi_insert parameter > I mentioned earlier would serve that purpose. I agree with your idea of adding multi_insert argument to ExecFindPartition() to request a multi-insert-capable partition. At first, I thought ExecFindPartition() is used for all operations, insert/delete/update/select, so I found it odd to add multi_insert argument. But ExecFindPartion() is used only for insert, so multi_insert argument seems okay. Regards Takayuki Tsunakawa
