Function bring_to_singleQE

src/backend/optimizer/path/allpaths.c:596–667

* The following function "steals" ideas and most of the code from the * function bring_to_outer_query. * * Decorate the Paths of 'rel' with Motions to bring the relation's * result to SingleQE locus. The final plan will look something like * this: * * Result (with quals from 'outer_quals') * \ * \_Material * \ * \_ Gather *

 *                            \_SeqScan (with quals from 'baserestrictinfo')
 */
static void
bring_to_singleQE(PlannerInfo *root, RelOptInfo *rel)
{
	List	   *origpathlist;
	ListCell   *lc;

	origpathlist = rel->pathlist;
	rel->cheapest_startup_path = NULL;
	rel->cheapest_total_path = NULL;
	rel->cheapest_unique_path = NULL;
	rel->cheapest_parameterized_paths = NIL;
	rel->pathlist = NIL;

	foreach(lc, origpathlist)
	{
		Path	     *origpath = (Path *) lfirst(lc);
		Path	     *path;
		CdbPathLocus  target_locus;

		if (CdbPathLocus_IsGeneral(origpath->locus) ||
			CdbPathLocus_IsEntry(origpath->locus) ||
			CdbPathLocus_IsSingleQE(origpath->locus) ||
			CdbPathLocus_IsOuterQuery(origpath->locus))
			path = origpath;
		else
		{
			/*
			 * Cannot pass a param through motion, so if this is a parameterized
			 * path, we can't use it.
			 */
			if (origpath->param_info)
				continue;

			/*
			 * param_info cannot cover the case that an index path's orderbyclauses
			 * See github issue: https://github.com/greenplum-db/gpdb/issues/9733
			 */
			if (IsA(origpath, IndexPath))
			{
				IndexPath *ipath = (IndexPath *) origpath;
				if (contains_outer_params((Node *) ipath->indexorderbys,
										  (void *) root))
					continue;
			}

			CdbPathLocus_MakeSingleQE(&target_locus,
									  origpath->locus.numsegments);

			path = cdbpath_create_motion_path(root,
											  origpath,
											  NIL, // DESTROY pathkeys
											  false,
											  target_locus);

			path = (Path *) create_material_path(rel, path);
		}

		add_path(rel, path, root);