Directly modify foreign tables.

postgres_fdw can now sent an UPDATE or DELETE statement directly to
the foreign server in simple cases, rather than sending a SELECT FOR
UPDATE statement and then updating or deleting rows one-by-one.

Etsuro Fujita, reviewed by Rushabh Lathia, Shigeru Hanada, Kyotaro
Horiguchi, Albe Laurenz, Thom Brown, and me.

1 files changed, 50 insertions, 10 deletions

diff --git a/src/backend/executor/nodeModifyTable.c b/src/backend/executor/nodeModifyTable.c
index 27051e80b08..e62c8aad657 100644
--- a/src/backend/executor/nodeModifyTable.c
+++ b/src/backend/executor/nodeModifyTable.c
@@ -138,13 +138,17 @@ ExecCheckPlanOutput(Relation resultRel, List *targetList)
  * tupleSlot: slot holding tuple actually inserted/updated/deleted
  * planSlot: slot holding tuple returned by top subplan node
  *
+ * Note: If tupleSlot is NULL, the FDW should have already provided econtext's
+ * scan tuple.
+ *
  * Returns a slot holding the result tuple
  */
 static TupleTableSlot *
-ExecProcessReturning(ProjectionInfo *projectReturning,
+ExecProcessReturning(ResultRelInfo *resultRelInfo,
 					 TupleTableSlot *tupleSlot,
 					 TupleTableSlot *planSlot)
 {
+	ProjectionInfo *projectReturning = resultRelInfo->ri_projectReturning;
 	ExprContext *econtext = projectReturning->pi_exprContext;
 
 	/*
@@ -154,7 +158,20 @@ ExecProcessReturning(ProjectionInfo *projectReturning,
 	ResetExprContext(econtext);
 
 	/* Make tuple and any needed join variables available to ExecProject */
-	econtext->ecxt_scantuple = tupleSlot;
+	if (tupleSlot)
+		econtext->ecxt_scantuple = tupleSlot;
+	else
+	{
+		HeapTuple	tuple;
+
+		/*
+		 * RETURNING expressions might reference the tableoid column, so
+		 * initialize t_tableOid before evaluating them.
+		 */
+		Assert(!TupIsNull(econtext->ecxt_scantuple));
+		tuple = ExecMaterializeSlot(econtext->ecxt_scantuple);
+		tuple->t_tableOid = RelationGetRelid(resultRelInfo->ri_RelationDesc);
+	}
 	econtext->ecxt_outertuple = planSlot;
 
 	/* Compute the RETURNING expressions */
@@ -496,8 +513,7 @@ ExecInsert(ModifyTableState *mtstate,
 
 	/* Process RETURNING if present */
 	if (resultRelInfo->ri_projectReturning)
-		return ExecProcessReturning(resultRelInfo->ri_projectReturning,
-									slot, planSlot);
+		return ExecProcessReturning(resultRelInfo, slot, planSlot);
 
 	return NULL;
 }
@@ -738,8 +754,7 @@ ldelete:;
 			ExecStoreTuple(&deltuple, slot, InvalidBuffer, false);
 		}
 
-		rslot = ExecProcessReturning(resultRelInfo->ri_projectReturning,
-									 slot, planSlot);
+		rslot = ExecProcessReturning(resultRelInfo, slot, planSlot);
 
 		/*
 		 * Before releasing the target tuple again, make sure rslot has a
@@ -1024,8 +1039,7 @@ lreplace:;
 
 	/* Process RETURNING if present */
 	if (resultRelInfo->ri_projectReturning)
-		return ExecProcessReturning(resultRelInfo->ri_projectReturning,
-									slot, planSlot);
+		return ExecProcessReturning(resultRelInfo, slot, planSlot);
 
 	return NULL;
 }
@@ -1380,6 +1394,26 @@ ExecModifyTable(ModifyTableState *node)
 				break;
 		}
 
+		/*
+		 * If resultRelInfo->ri_usesFdwDirectModify is true, all we need to do
+		 * here is compute the RETURNING expressions.
+		 */
+		if (resultRelInfo->ri_usesFdwDirectModify)
+		{
+			Assert(resultRelInfo->ri_projectReturning);
+
+			/*
+			 * A scan slot containing the data that was actually inserted,
+			 * updated or deleted has already been made available to
+			 * ExecProcessReturning by IterateDirectModify, so no need to
+			 * provide it here.
+			 */
+			slot = ExecProcessReturning(resultRelInfo, NULL, planSlot);
+
+			estate->es_result_relation_info = saved_resultRelInfo;
+			return slot;
+		}
+
 		EvalPlanQualSetSlot(&node->mt_epqstate, planSlot);
 		slot = planSlot;
 
@@ -1559,6 +1593,10 @@ ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags)
 	{
 		subplan = (Plan *) lfirst(l);
 
+		/* Initialize the usesFdwDirectModify flag */
+		resultRelInfo->ri_usesFdwDirectModify = bms_is_member(i,
+												node->fdwDirectModifyPlans);
+
 		/*
 		 * Verify result relation is a valid target for the current operation
 		 */
@@ -1583,7 +1621,8 @@ ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags)
 		mtstate->mt_plans[i] = ExecInitNode(subplan, estate, eflags);
 
 		/* Also let FDWs init themselves for foreign-table result rels */
-		if (resultRelInfo->ri_FdwRoutine != NULL &&
+		if (!resultRelInfo->ri_usesFdwDirectModify &&
+			resultRelInfo->ri_FdwRoutine != NULL &&
 			resultRelInfo->ri_FdwRoutine->BeginForeignModify != NULL)
 		{
 			List	   *fdw_private = (List *) list_nth(node->fdwPrivLists, i);
@@ -1910,7 +1949,8 @@ ExecEndModifyTable(ModifyTableState *node)
 	{
 		ResultRelInfo *resultRelInfo = node->resultRelInfo + i;
 
-		if (resultRelInfo->ri_FdwRoutine != NULL &&
+		if (!resultRelInfo->ri_usesFdwDirectModify &&
+			resultRelInfo->ri_FdwRoutine != NULL &&
 			resultRelInfo->ri_FdwRoutine->EndForeignModify != NULL)
 			resultRelInfo->ri_FdwRoutine->EndForeignModify(node->ps.state,
 														   resultRelInfo);