Revert: Allow table AM tuple_insert() method to return the different slot

This commit reverts c35a3fb5e0 per review by Andres Freund.

Discussion: https://postgr.es/m/20240410165236.rwyrny7ihi4ddxw4%40awork3.anarazel.de

src/backend/access/heap/heapam_handler.c

@@ -238,7 +238,7 @@ heapam_tuple_satisfies_snapshot(Relation rel, TupleTableSlot *slot,
  * ----------------------------------------------------------------------------
  */
 
-static TupleTableSlot *
+static void
 heapam_tuple_insert(Relation relation, TupleTableSlot *slot, CommandId cid,
 					int options, BulkInsertState bistate)
 {
@@ -255,8 +255,6 @@ heapam_tuple_insert(Relation relation, TupleTableSlot *slot, CommandId cid,
 
 	if (shouldFree)
 		pfree(tuple);
-
-	return slot;
 }
 
 static void

src/backend/commands/tablecmds.c

@@ -21086,8 +21086,8 @@ moveSplitTableRows(Relation rel, Relation splitRel, List *partlist, List *newPar
 		}
 
 		/* Write the tuple out to the new relation. */
-		(void) table_tuple_insert(pc->partRel, insertslot, mycid,
-								  ti_options, pc->bistate);
+		table_tuple_insert(pc->partRel, insertslot, mycid,
+						   ti_options, pc->bistate);
 
 		ResetExprContext(econtext);
 
@@ -21381,8 +21381,8 @@ moveMergedTablesRows(Relation rel, List *mergingPartitionsList,
 			}
 
 			/* Write the tuple out to the new relation. */
-			(void) table_tuple_insert(newPartRel, insertslot, mycid,
-									  ti_options, bistate);
+			table_tuple_insert(newPartRel, insertslot, mycid,
+							   ti_options, bistate);
 
 			CHECK_FOR_INTERRUPTS();
 		}

src/backend/executor/nodeModifyTable.c

@@ -1127,9 +1127,9 @@ ExecInsert(ModifyTableContext *context,
 		else
 		{
 			/* insert the tuple normally */
-			slot = table_tuple_insert(resultRelationDesc, slot,
-									  estate->es_output_cid,
-									  0, NULL);
+			table_tuple_insert(resultRelationDesc, slot,
+							   estate->es_output_cid,
+							   0, NULL);
 
 			/* insert index entries for tuple */
 			if (resultRelInfo->ri_NumIndices > 0)

src/include/access/tableam.h

@@ -508,9 +508,9 @@ typedef struct TableAmRoutine
 	 */
 
 	/* see table_tuple_insert() for reference about parameters */
-	TupleTableSlot *(*tuple_insert) (Relation rel, TupleTableSlot *slot,
-									 CommandId cid, int options,
-									 struct BulkInsertStateData *bistate);
+	void		(*tuple_insert) (Relation rel, TupleTableSlot *slot,
+								 CommandId cid, int options,
+								 struct BulkInsertStateData *bistate);
 
 	/* see table_tuple_insert_speculative() for reference about parameters */
 	void		(*tuple_insert_speculative) (Relation rel,
@@ -1374,19 +1374,16 @@ table_index_delete_tuples(Relation rel, TM_IndexDeleteOp *delstate)
  * behavior) is also just passed through to RelationGetBufferForTuple. If
  * `bistate` is provided, table_finish_bulk_insert() needs to be called.
  *
- * Returns the slot containing the inserted tuple, which may differ from the
- * given slot. For instance, the source slot may be VirtualTupleTableSlot, but
- * the result slot may correspond to the table AM. On return the slot's
- * tts_tid and tts_tableOid are updated to reflect the insertion. But note
- * that any toasting of fields within the slot is NOT reflected in the slots
- * contents.
+ * On return the slot's tts_tid and tts_tableOid are updated to reflect the
+ * insertion. But note that any toasting of fields within the slot is NOT
+ * reflected in the slots contents.
  */
-static inline TupleTableSlot *
+static inline void
 table_tuple_insert(Relation rel, TupleTableSlot *slot, CommandId cid,
 				   int options, struct BulkInsertStateData *bistate)
 {
-	return rel->rd_tableam->tuple_insert(rel, slot, cid, options,
-										 bistate);
+	rel->rd_tableam->tuple_insert(rel, slot, cid, options,
+								  bistate);
 }
 
 /*