Function adjust_modifytable_subpath

src/backend/optimizer/util/pathnode.c:5945–6044

* Add Motions to the subpath of a ModifyTable path, so that data * is modified on the correct segments. * * The input to a ModifyTable node must be distributed according to the * DISTRIBUTED BY of the target table. Add Motion paths to the child * plans for that. Returns a locus to represent the distribution of the * ModifyTable node itself. */

 * ModifyTable node itself.
 */
static CdbPathLocus
adjust_modifytable_subpath(PlannerInfo *root, CmdType operation,
							int resultRelationRTI, Path **pSubpath,
							bool splitUpdate)
{
	/*
	 * The input plans must be distributed correctly.
	 */
	bool		all_subplans_entry = true,
				all_subplans_replicated = true;
	int			numsegments = -1;


	{
		int			rti = resultRelationRTI;
		Path *subpath = *pSubpath;
		RangeTblEntry *rte = rt_fetch(rti, root->parse->rtable);
		GpPolicy   *targetPolicy;
		GpPolicyType targetPolicyType;

		Assert(rte->rtekind == RTE_RELATION);

		targetPolicy = GpPolicyFetch(rte->relid);
		targetPolicyType = targetPolicy->ptype;

		numsegments = Max(targetPolicy->numsegments, numsegments);

		if (targetPolicyType == POLICYTYPE_PARTITIONED)
		{
			all_subplans_entry = false;
			all_subplans_replicated = false;
		}
		else if (targetPolicyType == POLICYTYPE_ENTRY)
		{
			/* Master-only table */
			all_subplans_replicated = false;
		}
		else if (targetPolicyType == POLICYTYPE_REPLICATED)
		{
			all_subplans_entry = false;
		}
		else
			elog(ERROR, "unrecognized policy type %u", targetPolicyType);

		if (operation == CMD_INSERT)
		{
			subpath = create_motion_path_for_insert(root, targetPolicy, subpath);
		}
		else if (operation == CMD_DELETE)
		{
			subpath = create_motion_path_for_upddel(root, rti, targetPolicy, subpath);
		}
		else if (operation == CMD_UPDATE)
		{
			if (splitUpdate)
				subpath = create_split_update_path(root, rti, targetPolicy, subpath);
			else
				subpath = create_motion_path_for_upddel(root, rti, targetPolicy, subpath);