Re: BUG #18830: ExecInitMerge Segfault on MERGE

On Tue, Mar 4, 2025 at 5:36 PM Tender Wang <tndrwang@gmail.com> wrote:
> Amit Langote <amitlangote09@gmail.com> 于2025年3月4日周二 19:51写道：
>> On Mon, Mar 3, 2025 at 9:16 PM Tender Wang <tndrwang@gmail.com> wrote:
>> > nrels = list_length(resultRelations);
>> > ...
>> > mtstate->resultRelInfo = (ResultRelInfo *)
>> >               palloc(nrels * sizeof(ResultRelInfo));
>> >
>> > The memory of mtstate->resultRelInfo point to is undefined. When we access its memory in ExecInitMerge(),
>>
>> This needs to be fixed saparately.
>>
>> > relationDesc = RelationGetDescr(resultRelInfo->ri_RelationDesc);
>> >
>> > crash happened.
>>
>> Do you have a case where this access to undefined
>> ModifyTableState.resultRelInfo occurs? I would have thought that it
>> should not happen.
>
>
> "undefined" may not be accurate, "invalid" seems more correct.
> I still use  the case:
> merge into part_abc_view pt
> using (select stable_one() + 2 as pid) as q join part_abc_1 pt1 on (true)
> on pt.a = stable_one() +2
> when not matched then insert values(1, 'd', false);
>
> (gdb) p *resultRelInfo
> $5 = {type = 2139062142, ri_RangeTableIndex = 2139062143, ri_RelationDesc = 0x180, ri_NumIndices = 195, ri_IndexRelationDescs = 0x500000182, ri_IndexRelationInfo = 0x7f8773b2aa38, ri_RowIdAttNo = 0, ri_extraUpdatedCols = 0x0, ri_projectNew = 0x0,
>   ri_newTupleSlot = 0x0, ri_oldTupleSlot = 0x0, ri_projectNewInfoValid = false, ri_needLockTagTuple = false, ri_TrigDesc = 0x0, ri_TrigFunctions = 0x0, ri_TrigWhenExprs = 0x0, ri_TrigInstrument = 0x0, ri_ReturningSlot = 0x0, ri_TrigOldSlot = 0x0,
>   ri_TrigNewSlot = 0x0, ri_AllNullSlot = 0x0, ri_FdwRoutine = 0x0, ri_FdwState = 0x0, ri_usesFdwDirectModify = false, ri_NumSlots = 0, ri_NumSlotsInitialized = 0, ri_BatchSize = 0, ri_Slots = 0x0, ri_PlanSlots = 0x0, ri_WithCheckOptions = 0x0,
>   ri_WithCheckOptionExprs = 0x0, ri_ConstraintExprs = 0x0, ri_GeneratedExprsI = 0x0, ri_GeneratedExprsU = 0x0, ri_NumGeneratedNeededI = 0, ri_NumGeneratedNeededU = 0, ri_returningList = 0x0, ri_projectReturning = 0x0,
>   ri_onConflictArbiterIndexes = 0x0, ri_onConflict = 0x0, ri_MergeActions = {0x0, 0x0, 0x0}, ri_MergeJoinCondition = 0x0, ri_PartitionCheckExpr = 0x0, ri_ChildToRootMap = 0x0, ri_ChildToRootMapValid = false, ri_RootToChildMap = 0x0,
>   ri_RootToChildMapValid = false, ri_RootResultRelInfo = 0x0, ri_PartitionTupleSlot = 0x0, ri_CopyMultiInsertBuffer = 0x0, ri_ancestorResultRels = 0x0}
>
>  ri_RelationDesc = 0x180,  this address is not invalid.

Does the query crash or are you just able to see invalid memory
address using gdb?

-- 
Thanks, Amit Langote