Function transformRangeFunction

src/backend/parser/parse_clause.c:611–894

* transformRangeFunction --- transform a function call appearing in FROM */

 * transformRangeFunction --- transform a function call appearing in FROM
 */
static ParseNamespaceItem *
transformRangeFunction(ParseState *pstate, RangeFunction *r)
{
	List	   *funcexprs = NIL;
	List	   *funcnames = NIL;
	List	   *coldeflists = NIL;
	bool		is_lateral;
	ListCell   *lc;

	if (!r->is_rowsfrom && list_length(r->functions) == 1)
	{
		List	   *pair = (List *) linitial(r->functions);
		Node	   *fexpr;
		List	   *coldeflist;
		
		/* Disassemble the function-call/column-def-list pairs */
		Assert(list_length(pair) == 2);
		fexpr = (Node *) linitial(pair);
		coldeflist = (List *) lsecond(pair);

		/* If we see a gp_dist_random('name') call with no special decoration, it actually
		 * refers to a table.
		 */
		if (IsA(fexpr, FuncCall))
		{
			FuncCall   *fc = (FuncCall *) fexpr;

			if (list_length(fc->funcname) == 1 &&
				pg_strcasecmp(strVal(linitial(fc->funcname)), GP_DIST_RANDOM_NAME) == 0 &&
				fc->agg_order == NIL &&
				fc->agg_filter == NULL &&
				!fc->agg_star &&
				!fc->agg_distinct &&
				!fc->func_variadic &&
				fc->over == NULL &&
				coldeflist == NIL)
			{
				/* OK, now we need to check the arguments and generate a RTE */

				if (list_length(fc->args) != 1)
					elog(ERROR, "Invalid %s syntax.", GP_DIST_RANDOM_NAME);

				if (IsA(linitial(fc->args), A_Const))
				{
					A_Const *arg_val;
					List *qualified_name_list;
					RangeVar *rel;
					ParseNamespaceItem *rte;

					arg_val = linitial(fc->args);
					if (!IsA(&arg_val->val, String))
					{
						elog(ERROR, "%s: invalid argument type, non-string in value", GP_DIST_RANDOM_NAME);
					}

					/* Build the RTE for the table. */
					qualified_name_list = stringToQualifiedNameList(strVal(&arg_val->val));
					rel = makeRangeVarFromNameList(qualified_name_list);