Function CachedPlanGetTargetList

src/backend/utils/cache/plancache.c:1719–1743

* CachedPlanGetTargetList: return tlist, if any, describing plan's output * * The result is guaranteed up-to-date. However, it is local storage * within the cached plan, and may disappear next time the plan is updated. */

 * within the cached plan, and may disappear next time the plan is updated.
 */
List *
CachedPlanGetTargetList(CachedPlanSource *plansource,
						QueryEnvironment *queryEnv)
{
	Query	   *pstmt;

	/* Assert caller is doing things in a sane order */
	Assert(plansource->magic == CACHEDPLANSOURCE_MAGIC);
	Assert(plansource->is_complete);

	/*
	 * No work needed if statement doesn't return tuples (we assume this
	 * feature cannot be changed by an invalidation)
	 */
	if (plansource->resultDesc == NULL)
		return NIL;

	/* Make sure the querytree list is valid and we have parse-time locks */
	RevalidateCachedQuery(plansource, queryEnv, NULL);

	/* Get the primary statement and find out what it returns */
	pstmt = QueryListGetPrimaryStmt(plansource->query_list);

	return FetchStatementTargetList((Node *) pstmt);
}

/*
 * GetCachedExpression: construct a CachedExpression for an expression.