Re: FOR PORTION OF does not recompute GENERATED STORED columns that depend on the range column

> On May 8, 2026, at 07:47, Paul A Jungwirth <pj(at)illuminatedcomputing(dot)com> wrote:
>
> On Thu, May 7, 2026 at 12:06 AM Chao Li <li(dot)evan(dot)chao(at)gmail(dot)com> wrote:
>>> <v10-0001-Fix-some-problems-with-UPDATE-FOR-PORTION-OF.patch><v10-0002-Fix-FOR-PORTION-OF-on-inherited-children-with-di.patch>
>>
>> A few comments for 0001:
>>
>> 1 - execUtils.c
>> The comment explicitly says that it is unsafe to mutate perminfo, but bms_add_member() does not always allocate a new bitmapset. So if updatedCols still points to perminfo->updatedCols, then bms_add_member() may mutate perminfo->updatedCols.
>>
>> To verify that, I added Assert(updatedCols != perminfo->updatedCols); right after the bms_add_member(), then ran "make check". A lot of tests failed, which seems to confirm that perminfo->updatedCols was being mutated.
>>
>> So, I think we should make a copy the bitmapset before bms_add_member when needed, to make sure perminfo is not mutated, something like:
>> ```
>> if (updatedCols == perminfo->updatedCols)
>> updatedCols = bms_copy(updatedCols);
>>
>> updatedCols =
>> bms_add_member(updatedCols,
>> rangeAttno - FirstLowInvalidHeapAttributeNumber);
>> ```
>
> Ah, thanks for catching this! Fixed.
>
>> 2 - execUtils.c
>> ```
>> + * because the user does not need UPDATE permission on it. Now manualy
>> ```
>>
>> Typo: manualy -> manually
>
> Fixed.
>
>> 3 - nodeModifyTable.c
>> ```
>> + /*
>> + * If we don't have a ForPortionOfState yet, we must be a partition
>> + * child being hit for the first time. Make a copy from the root, with
>> + * our own TupleTableSlot. We do this lazily so that we don't pay the
>> + * price of unused partitions.
>> + */
>> + if ((((ModifyTable *) context.mtstate->ps.plan)->forPortionOf) &&
>> + !resultRelInfo->ri_forPortionOf)
>> + {
>> + ExecInitForPortionOf(context.mtstate, estate, resultRelInfo);
>> + }
>> ```
>>
>> I think this comment is stale. It could be a partition child or an inheritance child.
>
> Okay.
>
>> 4 - nodeModifyTable.c
>> ```
>> + /* Each partition needs a slot matching its tuple descriptor */
>> + leafState->fp_Existing =
>> + table_slot_create(resultRelInfo->ri_RelationDesc,
>> + &mtstate->ps.state->es_tupleTable);
>> ```
>>
>> I think the comment should say "each child relation" rather than "each partition".
>
> Okay.
>
> In these v11 patches I've tried to separate (1) the fix for GENERATED
> STORED columns and UPDATE OF triggers (2) fixing inheritance and (and
> partitions too, for the bugs in #1). I understand why jian he combined
> these into one patch: there is some overlap. If you don't like my
> separation, let me know.
>
> Yours,
>
> --
> Paul ~{:-)
> pj(at)illuminatedcomputing(dot)com
> <v11-0001-Fix-FOR-PORTION-OF-column-dependency-tracking.patch><v11-0002-Fix-FOR-PORTION-OF-with-partitions-and-inheritan.patch>

Thanks for updating the patch and making the separation. After reading v11, I still have a few comments for 0001.

```
+ if (relinfo->ri_forPortionOf)
+ {
+ AttrNumber rangeAttno = relinfo->ri_forPortionOf->fp_rangeAttno;
+
+ if (!bms_is_member(rangeAttno - FirstLowInvalidHeapAttributeNumber,
+ updatedCols))
+ {
+ MemoryContext oldContext;
+
+ oldContext = MemoryContextSwitchTo(estate->es_query_cxt);
+
+ updatedCols = bms_copy(updatedCols);
+ updatedCols =
+ bms_add_member(updatedCols,
+ rangeAttno - FirstLowInvalidHeapAttributeNumber);
+
+ MemoryContextSwitchTo(oldContext);
+ }
}
```

1. I don’t think we should unconditionally do bms_copy, only if (updatedCols == perminfo->updatedCols), we need to make the copy.

2. I doubt if we need to switch to estate->es_query_cxt. Because ExecGetUpdatedCols() is called by ExecGetAllUpdatedCols(), and its header comment says the function runs in per-tuple memory context:
```
/*
* Return columns being updated, including generated columns
*
* The bitmap is allocated in per-tuple memory context. It's up to the caller to
* copy it into a different context with the appropriate lifespan, if needed.
*/
Bitmapset *
ExecGetAllUpdatedCols(ResultRelInfo *relinfo, EState *estate)
```

So I think bms_copy and bms_add_member should be just done in the current memory context.

3. "rangeAttno - FirstLowInvalidHeapAttributeNumber” appears twice, maybe add a local variable to avoid the duplication.

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/