Function ExecCrossPartitionUpdate

src/backend/executor/nodeModifyTable.c:1674–1817

* ExecCrossPartitionUpdate --- Move an updated tuple to another partition. * * This works by first deleting the old tuple from the current partition, * followed by inserting the new tuple into the root parent table, that is, * mtstate->rootResultRelInfo. It will be re-routed from there to the * correct partition. * * Returns true if the tuple has been successfully moved, or if it's found

 * and call this function again or perform a regular update accordingly.
 */
static bool
ExecCrossPartitionUpdate(ModifyTableState *mtstate,
						 ResultRelInfo *resultRelInfo,
						 ItemPointer tupleid, HeapTuple oldtuple,
						 TupleTableSlot *slot, TupleTableSlot *planSlot,
						 EPQState *epqstate, int32 segid, bool canSetTag,
						 TupleTableSlot **retry_slot,
						 TupleTableSlot **inserted_tuple)
{
	EState	   *estate = mtstate->ps.state;
	TupleConversionMap *tupconv_map;
	bool		tuple_deleted;
	TupleTableSlot *epqslot = NULL;

	*inserted_tuple = NULL;
	*retry_slot = NULL;

	/*
	 * Disallow an INSERT ON CONFLICT DO UPDATE that causes the original row
	 * to migrate to a different partition.  Maybe this can be implemented
	 * some day, but it seems a fringe feature with little redeeming value.
	 */
	if (((ModifyTable *) mtstate->ps.plan)->onConflictAction == ONCONFLICT_UPDATE)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("invalid ON UPDATE specification"),
				 errdetail("The result tuple would appear in a different partition than the original tuple.")));

	/*
	 * When an UPDATE is run directly on a leaf partition, simply fail with a
	 * partition constraint violation error.
	 */
	if (resultRelInfo == mtstate->rootResultRelInfo)
		ExecPartitionCheckEmitError(resultRelInfo, slot, estate);

	/* Initialize tuple routing info if not already done. */
	if (mtstate->mt_partition_tuple_routing == NULL)
	{
		Relation	rootRel = mtstate->rootResultRelInfo->ri_RelationDesc;
		MemoryContext oldcxt;

		/* Things built here have to last for the query duration. */
		oldcxt = MemoryContextSwitchTo(estate->es_query_cxt);

		mtstate->mt_partition_tuple_routing =
			ExecSetupPartitionTupleRouting(estate, rootRel);

		/*
		 * Before a partition's tuple can be re-routed, it must first be
		 * converted to the root's format, so we'll need a slot for storing
		 * such tuples.
		 */
		Assert(mtstate->mt_root_tuple_slot == NULL);
		mtstate->mt_root_tuple_slot = table_slot_create(rootRel, NULL);

		MemoryContextSwitchTo(oldcxt);
	}