On Mon, 26 May 2025 at 12:50, Tender Wang <tndrw...@gmail.com> wrote: > >> > "it is possible for the parent to be excluded from the >> > plan and so all of the entries in the resultRelInfo array may be for >> > different relations than rootResultRelInfo." >> > >> > I didn't fully understand the above sentence. Can you give me more >> > information or an example? >> > If the parent is excluded from the plan, the first entry in the >> > resultRelInfo array will not be the parent but some surviving child. >> >> There's an example in the updated regression tests. A non-inherited >> CHECK constraint on the parent causes the planner to exclude the >> parent from the relations being scanned and from the resultRelInfo >> array, so the first resultRelInfo entry is for a child relation. > > Yes, it is. I debugged the updated regression tests. It would crash if > resultRelInfo were used instead of rootResultInfo. > Is that the reason that we must use rootResultInfo? >
Yes. To work correctly for an inherited table, ExecInsert() must be passed a pointer to a ResultRelInfo structure that points to the parent table. As I mentioned before, this goes back to commit 387f9ed0a08, so it's worth reading that in more detail. Prior to commit 387f9ed0a08, rootResultInfo was equal to resultRelInfo for an inherited table, which was wrong because that could point to a child table, if the parent table was excluded from the plan. Commit 387f9ed0a08 fixed that by changing the planner so that it set ModifyTable.rootRelation to the index of the parent table, if it was an inherited table. As a result, starting from that commit, for an inherited table, rootResultInfo is a different ResultRelInfo structure which always points to the parent table, making it the correct thing to pass to ExecInsert() under all circumstances. The thing that was overlooked was that the separate ResultRelInfo structure in rootResultInfo, and the insert projection, weren't being correctly initialised for MERGE, which is what this patch aims to fix. Unless there are any further comments, I plan to commit it in a day or so. Regards, Dean
