Function try_hashjoin_path

src/backend/optimizer/path/joinpath.c:1102–1161

* try_hashjoin_path * Consider a hash join path; if it appears useful, push it into * the joinrel's pathlist via add_path(). */

 *	  the joinrel's pathlist via add_path().
 */
static void
try_hashjoin_path(PlannerInfo *root,
				  RelOptInfo *joinrel,
				  Path *outer_path,
				  Path *inner_path,
				  List *hashclauses,
				  JoinType jointype,
				  JoinType orig_jointype,
				  JoinPathExtraData *extra)
{
	Relids		required_outer;
	JoinCostWorkspace workspace;

	/*
	 * Check to see if proposed path is still parameterized, and reject if the
	 * parameterization wouldn't be sensible.
	 */
	required_outer = calc_non_nestloop_required_outer(outer_path,
													  inner_path);
	if (required_outer &&
		!bms_overlap(required_outer, extra->param_source_rels))
	{
		/* Waste no memory when we reject a path here */
		bms_free(required_outer);
		return;
	}

	/*
	 * See comments in try_nestloop_path().  Also note that hashjoin paths
	 * never have any output pathkeys, per comments in create_hashjoin_path.
	 */
	initial_cost_hashjoin(root, &workspace, jointype, hashclauses,
						  outer_path, inner_path, extra, false);

	if (add_path_precheck(joinrel,
						  workspace.startup_cost, workspace.total_cost,
						  NIL, required_outer))
	{
		add_path(joinrel, (Path *)
				 create_hashjoin_path(root,
									  joinrel,
									  jointype,
									  orig_jointype,
									  &workspace,
									  extra,
									  outer_path,
									  inner_path,
									  false,	/* parallel_hash */
									  extra->restrictlist,
									  required_outer,
									  extra->redistribution_clauses,
									  hashclauses),
				 root);
	}
	else
	{
		/* Waste no memory when we reject a path here */
		bms_free(required_outer);