Function transformTargetList

src/backend/parser/parse_target.c:122–205

* transformTargetList() * Turns a list of ResTarget's into a list of TargetEntry's. * * This code acts mostly the same for SELECT, UPDATE, or RETURNING lists; * the main thing is to transform the given expressions (the "val" fields). * The exprKind parameter distinguishes these cases when necessary. */

 * The exprKind parameter distinguishes these cases when necessary.
 */
List *
transformTargetList(ParseState *pstate, List *targetlist,
					ParseExprKind exprKind)
{
	List	   *p_target = NIL;
	bool		expand_star;
	ListCell   *o_target;

	/* Shouldn't have any leftover multiassign items at start */
	Assert(pstate->p_multiassign_exprs == NIL);

	/* Expand "something.*" in SELECT and RETURNING, but not UPDATE */
	expand_star = (exprKind != EXPR_KIND_UPDATE_SOURCE);

	foreach(o_target, targetlist)
	{
		ResTarget  *res = (ResTarget *) lfirst(o_target);

		/*
		 * Check for "something.*".  Depending on the complexity of the
		 * "something", the star could appear as the last field in ColumnRef,
		 * or as the last indirection item in A_Indirection.
		 */
		if (expand_star)
		{
			if (IsA(res->val, ColumnRef))
			{
				ColumnRef  *cref = (ColumnRef *) res->val;

				if (IsA(llast(cref->fields), A_Star))
				{
					/* It is something.*, expand into multiple items */
					p_target = list_concat(p_target,
										   ExpandColumnRefStar(pstate,
															   cref,
															   true));
					continue;
				}
			}
			else if (IsA(res->val, A_Indirection))
			{
				A_Indirection *ind = (A_Indirection *) res->val;

				if (IsA(llast(ind->indirection), A_Star))
				{
					/* It is something.*, expand into multiple items */
					p_target = list_concat(p_target,
										   ExpandIndirectionStar(pstate,
																 ind,
																 true,
																 exprKind));
					continue;
				}
			}
		}

		/*
		 * Not "something.*", or we want to treat that as a plain whole-row