Re: POC: postgres_fdw insert batching

On 1/21/21 2:24 AM, Amit Langote wrote:
> On Thu, Jan 21, 2021 at 9:56 AM Tomas Vondra
> <tomas(dot)vondra(at)enterprisedb(dot)com> wrote:
>> On 1/21/21 1:17 AM, Zhihong Yu wrote:
>>> Hi,
>>> The assignment to resultRelInfo is done when junk_filter_needed is true:
>>>
>>> if (junk_filter_needed)
>>> {
>>> resultRelInfo = mtstate->resultRelInfo;
>>>
>>> Should the code for determining batch size access mtstate->resultRelInfo
>>> directly ?
>>>
>>
>> IMO the issue is that code iterates over all plans and moves to the next
>> for each one:
>>
>> resultRelInfo++;
>>
>> so it ends up pointing past the last element, hence the failures. So
>> yeah, either the code needs to move before the loop (per my patch), or
>> we need to access mtstate->resultRelInfo directly.
>
> Accessing mtstate->resultRelInfo directly would do. The only
> constraint on where this block should be placed is that
> ri_projectReturning must be valid as of calling
> GetForeignModifyBatchSize(), as Tsunakawa-san pointed out upthread.
> So, after this block in ExecInitModifyTable:
>
> /*
> * Initialize RETURNING projections if needed.
> */
> if (node->returningLists)
> {
> ....
> /*
> * Build a projection for each result rel.
> */
> resultRelInfo = mtstate->resultRelInfo;
> foreach(l, node->returningLists)
> {
> List *rlist = (List *) lfirst(l);
>
> resultRelInfo->ri_returningList = rlist;
> resultRelInfo->ri_projectReturning =
> ExecBuildProjectionInfo(rlist, econtext, slot, &mtstate->ps,
> resultRelInfo->ri_RelationDesc->rd_att);
> resultRelInfo++;
> }
> }
>

Right. But I think Tom is right this should initialize ri_BatchSize for
all the resultRelInfo elements, not just the first one. Per the attached
patch, which resolves the issue both on x86_64 and armv7l for me.

regards

--
Tomas Vondra
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