/*
 * Check if changes on one relation can be applied by an apply background
 * worker and assign the 'parallel_apply' flag.
 *
 * There are two requirements for applying changes in an apply background
 * worker: 1) The unique column in the relation on the subscriber-side should
 * also be the unique column on the publisher-side; 2) There cannot be any
 * non-immutable functions used by the subscriber-side.
 *
 * We just mark the relation entry as 'PARALLEL_APPLY_UNSAFE' here if changes
 * on one relation can not be applied by an apply background worker and leave
 * it to apply_bgworker_relation_check() to throw the actual error if needed.
 */
static void
logicalrep_rel_mark_parallel_apply(LogicalRepRelMapEntry *entry)
{
	Bitmapset   *ukey;
	int			i;
	TupleDesc	tupdesc;
	int			attnum;
	List	   *fkeys = NIL;

	/* Fast path if 'parallel_apply' flag is already known. */
	if (entry->parallel_apply != PARALLEL_APPLY_UNKNOWN)
		return;

	/*
	 * First, check if the unique column in the relation on the subscriber-side
	 * is also the unique column on the publisher-side.
	 */
	ukey = RelationGetIndexAttrBitmap(entry->localrel,
									  INDEX_ATTR_BITMAP_KEY);

	if (ukey)
	{
		i = -1;
		while ((i = bms_next_member(ukey, i)) >= 0)
		{
			attnum = AttrNumberGetAttrOffset(i + FirstLowInvalidHeapAttributeNumber);

			if (entry->attrmap->attnums[attnum] < 0 ||
				!bms_is_member(entry->attrmap->attnums[attnum], entry->remoterel.attunique))
				goto parallel_apply_unsafe;
		}

		bms_free(ukey);
	}

	/*
	 * Then, check if there is any non-immutable function used by the local
	 * table. Look for functions in the following places:
	 * a. trigger functions;
	 * b. Column default value expressions and domain constraints;
	 * c. Constraint expressions;
	 * d. Foreign keys.
	 */
	/* Check the trigger functions. */
	if (entry->localrel->trigdesc != NULL)
	{
		for (i = 0; i < entry->localrel->trigdesc->numtriggers; i++)
		{
			Trigger    *trig = entry->localrel->trigdesc->triggers + i;

			if (trig->tgenabled != TRIGGER_FIRES_ALWAYS &&
				trig->tgenabled != TRIGGER_FIRES_ON_REPLICA)
				continue;

			if (func_volatile(trig->tgfoid) != PROVOLATILE_IMMUTABLE)
				goto parallel_apply_unsafe;
		}
	}

	/* Check the columns. */
	tupdesc = RelationGetDescr(entry->localrel);
	for (attnum = 0; attnum < tupdesc->natts; attnum++)
	{
		Form_pg_attribute att = TupleDescAttr(tupdesc, attnum);

		/* We don't need info for dropped or generated attributes */
		if (att->attisdropped || att->attgenerated)
			continue;

		/*
		 * We don't need to check columns that only exist on the
		 * subscriber
		 */
		if (entry->attrmap->attnums[attnum] < 0)
			continue;

		if (att->atthasdef)
		{
			Node	   *defaultexpr;

			defaultexpr = build_column_default(entry->localrel, attnum + 1);
			if (contain_mutable_functions(defaultexpr))
				goto parallel_apply_unsafe;
		}

		/*
		 * If the column is of a DOMAIN type, determine whether
		 * that domain has any CHECK expressions that are not
		 * immutable.
		 */
		if (get_typtype(att->atttypid) == TYPTYPE_DOMAIN)
		{
			List	   *domain_constraints;
			ListCell   *lc;

			domain_constraints = GetDomainConstraints(att->atttypid);

			foreach(lc, domain_constraints)
			{
				DomainConstraintState *con = (DomainConstraintState *) lfirst(lc);

				if (con->check_expr && contain_mutable_functions((Node *) con->check_expr))
					goto parallel_apply_unsafe;
			}
		}
	}

	/* Check the constraints. */
	if (tupdesc->constr)
	{
		ConstrCheck *check = tupdesc->constr->check;

		/*
		 * Determine if there are any CHECK constraints which
		 * contains non-immutable function.
		 */
		for (i = 0; i < tupdesc->constr->num_check; i++)
		{
			Expr	   *check_expr = stringToNode(check[i].ccbin);

			if (contain_mutable_functions((Node *) check_expr))
				goto parallel_apply_unsafe;
		}
	}

	/* Check the foreign keys. */
	fkeys = RelationGetFKeyList(entry->localrel);
	if (fkeys)
		goto parallel_apply_unsafe;

parallel_apply_safe:		
	entry->parallel_apply = PARALLEL_APPLY_SAFE;
	return;	
	
parallel_apply_unsafe:
	entry->parallel_apply = PARALLEL_APPLY_UNSAFE;
	return;
}