Re: POC: postgres_fdw insert batching

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++;
}
}

--
Amit Langote
EDB: http://www.enterprisedb.com