On 1/21/21 2:24 AM, Amit Langote wrote:
On Thu, Jan 21, 2021 at 9:56 AM Tomas Vondra
<tomas.von...@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++;
         }
     }


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
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
diff --git a/src/backend/executor/nodeModifyTable.c b/src/backend/executor/nodeModifyTable.c
index 9c36860704..10febcae8a 100644
--- a/src/backend/executor/nodeModifyTable.c
+++ b/src/backend/executor/nodeModifyTable.c
@@ -2798,17 +2798,23 @@ ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags)
 	 * size (a FDW may support batching, but it may be disabled for the
 	 * server/table).
 	 */
-	if (!resultRelInfo->ri_usesFdwDirectModify &&
-		operation == CMD_INSERT &&
-		resultRelInfo->ri_FdwRoutine != NULL &&
-		resultRelInfo->ri_FdwRoutine->GetForeignModifyBatchSize &&
-		resultRelInfo->ri_FdwRoutine->ExecForeignBatchInsert)
-		resultRelInfo->ri_BatchSize =
-			resultRelInfo->ri_FdwRoutine->GetForeignModifyBatchSize(resultRelInfo);
-	else
-		resultRelInfo->ri_BatchSize = 1;
+	resultRelInfo = mtstate->resultRelInfo;
+	for (i = 0; i < nplans; i++)
+	{
+		if (!resultRelInfo->ri_usesFdwDirectModify &&
+			operation == CMD_INSERT &&
+			resultRelInfo->ri_FdwRoutine != NULL &&
+			resultRelInfo->ri_FdwRoutine->GetForeignModifyBatchSize &&
+			resultRelInfo->ri_FdwRoutine->ExecForeignBatchInsert)
+			resultRelInfo->ri_BatchSize =
+				resultRelInfo->ri_FdwRoutine->GetForeignModifyBatchSize(resultRelInfo);
+		else
+			resultRelInfo->ri_BatchSize = 1;
+
+		Assert(resultRelInfo->ri_BatchSize >= 1);
 
-	Assert(resultRelInfo->ri_BatchSize >= 1);
+		resultRelInfo++;
+	}
 
 	/*
 	 * Lastly, if this is not the primary (canSetTag) ModifyTable node, add it

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