Function create_plain_partial_paths

src/backend/optimizer/path/allpaths.c:1082–1099

* create_plain_partial_paths * Build partial access paths for parallel scan of a plain relation */

 *	  Build partial access paths for parallel scan of a plain relation
 */
void
create_plain_partial_paths(PlannerInfo *root, RelOptInfo *rel)
{
	int			parallel_workers;

	parallel_workers = compute_parallel_worker(root, rel, rel->pages, -1,
											   max_parallel_workers_per_gather);

	/* If any limit was set to zero, the user doesn't want a parallel scan. */
	/* GPDB parallel, parallel_workers <= 1 is bogus */
	if (parallel_workers <= 1)
		return;

	/* CBDB_PARALLEL_FIXME: update locus.parallel_workers? */

	/* Add an unordered partial path based on a parallel sequential scan. */
	add_partial_path(rel, create_seqscan_path(root, rel, NULL, parallel_workers));
}

/*
 * set_tablesample_rel_size