Re: Fix error message for MERGE foreign tables

On Fri, Oct 14, 2022 at 7:19 PM Richard Guo <guofenglinux(at)gmail(dot)com> wrote:

>
> On Fri, Oct 14, 2022 at 5:24 PM Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>
> wrote:
>
>> Actually, I hadn't realized that the originally submitted patch had the
>> test in postgres_fdw only, but we really want it to catch any FDW, so it
>> needs to be somewhere more general. The best place I found to put this
>> test is in make_modifytable ... I searched for some earlier place in the
>> planner to do it, but couldn't find anything.
>>
>> So what do people think about this?
>
>
> Good point. I agree that the test should be in a more general place.
>
> I wonder if we can make it earlier in grouping_planner() just before we
> add ModifyTablePath.
>

Or maybe we can make it even earlier, when we expand an RTE for a
partitioned table and add result tables to leaf_result_relids.

--- a/src/backend/optimizer/util/inherit.c
+++ b/src/backend/optimizer/util/inherit.c
@@ -627,6 +627,16 @@ expand_single_inheritance_child(PlannerInfo *root,
RangeTblEntry *parentrte,
root->leaf_result_relids = bms_add_member(root->leaf_result_relids,
childRTindex);

+ if (parse->commandType == CMD_MERGE &&
+ childrte->relkind == RELKIND_FOREIGN_TABLE)
+ {
+ ereport(ERROR,
+ (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+ errmsg("cannot execute MERGE on relation \"%s\"",
+ RelationGetRelationName(childrel)),
+ errdetail_relkind_not_supported(childrte->relkind)));
+ }

Thanks
Richard