Function addRangeTableEntryForSubquery

src/backend/parser/parse_relation.c:1654–1736

* Add an entry for a subquery to the pstate's range table (p_rtable). * Then, construct and return a ParseNamespaceItem for the new RTE. * * This is much like addRangeTableEntry() except that it makes a subquery RTE. * Note that an alias clause *must* be supplied. */

 * Note that an alias clause *must* be supplied.
 */
ParseNamespaceItem *
addRangeTableEntryForSubquery(ParseState *pstate,
							  Query *subquery,
							  Alias *alias,
							  bool lateral,
							  bool inFromCl)
{
	RangeTblEntry *rte = makeNode(RangeTblEntry);
	char	   *refname = alias->aliasname;
	Alias	   *eref;
	int			numaliases;
	List	   *coltypes,
			   *coltypmods,
			   *colcollations;
	int			varattno;
	ListCell   *tlistitem;

	rte->rtekind = RTE_SUBQUERY;
	rte->subquery = subquery;
	rte->alias = alias;

	eref = copyObject(alias);
	numaliases = list_length(eref->colnames);

	/* fill in any unspecified alias columns, and extract column type info */
	coltypes = coltypmods = colcollations = NIL;
	varattno = 0;
	foreach(tlistitem, subquery->targetList)
	{
		TargetEntry *te = (TargetEntry *) lfirst(tlistitem);

		if (te->resjunk)
			continue;
		varattno++;
		Assert(varattno == te->resno);
		if (varattno > numaliases)
		{
			char	   *attrname;

			attrname = pstrdup(te->resname);
			eref->colnames = lappend(eref->colnames, makeString(attrname));
		}
		coltypes = lappend_oid(coltypes,
							   exprType((Node *) te->expr));
		coltypmods = lappend_int(coltypmods,
								 exprTypmod((Node *) te->expr));
		colcollations = lappend_oid(colcollations,
									exprCollation((Node *) te->expr));
	}
	if (varattno < numaliases)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_COLUMN_REFERENCE),
				 errmsg("table \"%s\" has %d columns available but %d columns specified",
						refname, varattno, numaliases)));

	rte->eref = eref;

	/*