Function cdbpathlocus_parallel_join

src/backend/cdb/cdbpathlocus.c:1226–1476

* cdbpathlocus_parallel_join * This is parallel version of cdbpathlocus_join. * We only handle parallel join here(either path's parallel_works > 1, or both). */

 * We only handle parallel join here(either path's parallel_works > 1, or both).
 */
CdbPathLocus
cdbpathlocus_parallel_join(JoinType jointype, CdbPathLocus a, CdbPathLocus b, bool parallel_aware)
{
	ListCell   *acell;
	ListCell   *bcell;
	CdbPathLocus resultlocus = {0};
	int			numsegments;
	int outerParallel PG_USED_FOR_ASSERTS_ONLY = CdbPathLocus_NumParallelWorkers(a);
	int innerParallel PG_USED_FOR_ASSERTS_ONLY = CdbPathLocus_NumParallelWorkers(b);

	Assert(cdbpathlocus_is_valid(a));
	Assert(cdbpathlocus_is_valid(b));

	/* Do both input rels have same locus? */
	if (cdbpathlocus_equal(a, b))
		return a;

	/*
	 * SingleQE may have different segment counts.
	 */
	if (CdbPathLocus_IsSingleQE(a) &&
		CdbPathLocus_IsSingleQE(b))
	{
		CdbPathLocus_MakeSingleQE(&resultlocus,
								  CdbPathLocus_CommonSegments(a, b));
		return resultlocus;
	}

	if (CdbPathLocus_IsGeneral(a))
		return b;

	if (CdbPathLocus_IsGeneral(b))
		return a;

	/*
	 * If one rel is replicated, result stays with the other rel,
	 * but need to ensure the result is on the common segments.
	 */
	if (CdbPathLocus_IsReplicated(a))
	{
		b.numsegments = CdbPathLocus_CommonSegments(a, b);
		return b;
	}
	if (CdbPathLocus_IsReplicatedWorkers(a))
	{
		b.numsegments = CdbPathLocus_CommonSegments(a, b);
		if (CdbPathLocus_IsHashed(b))
		{
			b.locustype = CdbLocusType_HashedWorkers;
		}
		return b;
	}
	if (CdbPathLocus_IsReplicated(b) || CdbPathLocus_IsReplicatedWorkers(b))
	{
		a.numsegments = CdbPathLocus_CommonSegments(a, b);
		return a;
	}