Function cdbpath_motion_for_join

src/backend/cdb/cdbpath.c:1361–2308

* cdbpath_motion_for_join * * Decides where a join should be done. Adds Motion operators atop * the subpaths if needed to deliver their results to the join locus. * Returns the join locus if ok, or a null locus otherwise. If * jointype is JOIN_SEMI_DEDUP or JOIN_SEMI_DEDUP_REVERSE, this also * tacks a RowIdExpr on one side of the join, and *p_rowidexpr_id is * set to the ID of that. The ca

 * It comes from select_mergejoin_clauses() in joinpath.c.
 */
CdbPathLocus
cdbpath_motion_for_join(PlannerInfo *root,
						JoinType jointype,	/* JOIN_INNER/FULL/LEFT/RIGHT/IN */
						Path **p_outer_path,	/* INOUT */
						Path **p_inner_path,	/* INOUT */
						int *p_rowidexpr_id,	/* OUT */
						List *redistribution_clauses, /* equijoin RestrictInfo list */
						List *restrict_clauses,
						List *outer_pathkeys,
						List *inner_pathkeys,
						bool outer_require_existing_order,
						bool inner_require_existing_order)
{
	CdbpathMfjRel 	outer;
	CdbpathMfjRel 	inner;
	int 			numsegments;
	bool 			join_quals_contain_outer_references;
	ListCell 		*lc;

	*p_rowidexpr_id = 0;

	outer.pathkeys = outer_pathkeys;
	inner.pathkeys = inner_pathkeys;
	outer.path = *p_outer_path;
	inner.path = *p_inner_path;
	outer.locus = outer.path->locus;
	inner.locus = inner.path->locus;
	CdbPathLocus_MakeNull(&outer.move_to);
	CdbPathLocus_MakeNull(&inner.move_to);

	Assert(cdbpathlocus_is_valid(outer.locus));
	Assert(cdbpathlocus_is_valid(inner.locus));

	/* No parallel paths should get here. */
	Assert(outer.locus.parallel_workers == 0);
	Assert(inner.locus.parallel_workers == 0);

	/*
	 * Does the join quals contain references to outer query? If so, we must
	 * evaluate them in the outer query's locus. That means pulling both
	 * inputs to outer locus, and performing the join there.
	 *
	 * XXX: If there are pseudoconstant quals, they will be executed by a
	 * gating Result with a One-Time Filter. In that case, the join's inputs
	 * wouldn't need to be brought to the outer locus. We could execute the
	 * join normally, and bring the result to the outer locus and put the
	 * gating Result above the Motion, instead. But for now, we're not smart
	 * like that.
	 */
	join_quals_contain_outer_references = false;
	foreach(lc, restrict_clauses)
	{
		RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);

		if (rinfo->contain_outer_query_references)
		{
			join_quals_contain_outer_references = true;
			break;