Function coerceSetOpTypes

src/backend/parser/analyze.c:2477–2718

* Label every SetOperationStmt in the tree with the given datatypes. */

 * Label every SetOperationStmt in the tree with the given datatypes.
 */
static void
coerceSetOpTypes(ParseState *pstate, Node *sop,
				 List *preselected_coltypes, List *preselected_coltypmods,
				 List **targetlist)
{
	if (IsA(sop, RangeTblRef))
	{
		RangeTblEntry *rte = rt_fetch((((RangeTblRef *) sop)->rtindex), pstate->p_rtable);
		Query	   *selectQuery = rte->subquery;
		ListCell   *tl;

		/*
		 * Extract a list of the non-junk TLEs for upper-level processing.
		 * This is the same we did in the first pass, in
		 * transformSetOperationTree_internal().
		 */
		if (targetlist)
		{
			*targetlist = NIL;
			foreach(tl, selectQuery->targetList)
			{
				TargetEntry *tle = (TargetEntry *) lfirst(tl);

				if (!tle->resjunk)
					*targetlist = lappend(*targetlist, tle);
			}
		}
		return;
	}
	else
	{
		SetOperationStmt *op = (SetOperationStmt *) sop;
		List	   *ltargetlist;
		List	   *rtargetlist;
		ListCell   *ltl;
		ListCell   *rtl;
		ListCell   *pct;
		ListCell   *pcm;
		const char *context;
		bool recursive = (pstate->p_parent_cte &&
						  pstate->p_parent_cte->cterecursive);

		Assert(IsA(op, SetOperationStmt));

		context = (op->op == SETOP_UNION ? "UNION" :
				   op->op == SETOP_INTERSECT ? "INTERSECT" :
				   "EXCEPT");

		/* Recurse to determine the children's types first */
		coerceSetOpTypes(pstate, op->larg,
						 preselected_coltypes, preselected_coltypmods,
						 &ltargetlist);

		coerceSetOpTypes(pstate, op->rarg,
						 preselected_coltypes, preselected_coltypmods,
						 &rtargetlist);

		/*