Re: POC: postgres_fdw insert batching

On Thu, Jan 21, 2021 at 9:56 AM Tomas Vondra
<tomas.vondra@enterprisedb.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