Function expandTupleDesc

src/backend/parser/parse_relation.c:3288–3359

* expandTupleDesc -- expandRTE subroutine * * Generate names and/or Vars for the first "count" attributes of the tupdesc, * and append them to colnames/colvars. "offset" is added to the varattno * that each Var would otherwise have, and we also skip the first "offset" * entries in eref->colnames. (These provisions allow use of this code for * an individual composite-returning function in a

 * an individual composite-returning function in an RTE_FUNCTION RTE.)
 */
static void
expandTupleDesc(TupleDesc tupdesc, Alias *eref, int count, int offset,
				int rtindex, int sublevels_up,
				int location, bool include_dropped,
				List **colnames, List **colvars, bool is_ivm)
{
	ListCell   *aliascell;
	int			varattno;

	aliascell = (offset < list_length(eref->colnames)) ?
		list_nth_cell(eref->colnames, offset) : NULL;

	Assert(count <= tupdesc->natts);
	for (varattno = 0; varattno < count; varattno++)
	{
		Form_pg_attribute attr = TupleDescAttr(tupdesc, varattno);

		if (is_ivm && isIvmName(NameStr(attr->attname)) && !MatViewIncrementalMaintenanceIsEnabled())
			continue;

		if (attr->attisdropped)
		{
			if (include_dropped)
			{
				if (colnames)
					*colnames = lappend(*colnames, makeString(pstrdup("")));
				if (colvars)
				{
					/*
					 * can't use atttypid here, but it doesn't really matter
					 * what type the Const claims to be.
					 */
					*colvars = lappend(*colvars,
									   makeNullConst(INT4OID, -1, InvalidOid));
				}
			}
			if (aliascell)
				aliascell = lnext(eref->colnames, aliascell);
			continue;
		}

		if (colnames)
		{
			char	   *label;

			if (aliascell)
			{
				label = strVal(lfirst(aliascell));
				aliascell = lnext(eref->colnames, aliascell);
			}
			else
			{
				/* If we run out of aliases, use the underlying name */
				label = NameStr(attr->attname);
			}
			*colnames = lappend(*colnames, makeString(pstrdup(label)));
		}