Function check_srf_call_placement

src/backend/parser/parse_func.c:2565–2737

* check_srf_call_placement * Verify that a set-returning function is called in a valid place, * and throw a nice error if not. * * A side-effect is to set pstate->p_hasTargetSRFs true if appropriate. * * last_srf should be a copy of pstate->p_last_srf from just before we * started transforming the function's arguments. This allows detection * of whether the SRF's arguments contain any S

 * of whether the SRF's arguments contain any SRFs.
 */
void
check_srf_call_placement(ParseState *pstate, Node *last_srf, int location)
{
	const char *err;
	bool		errkind;

	/*
	 * Check to see if the set-returning function is in an invalid place
	 * within the query.  Basically, we don't allow SRFs anywhere except in
	 * the targetlist (which includes GROUP BY/ORDER BY expressions), VALUES,
	 * and functions in FROM.
	 *
	 * For brevity we support two schemes for reporting an error here: set
	 * "err" to a custom message, or set "errkind" true if the error context
	 * is sufficiently identified by what ParseExprKindName will return, *and*
	 * what it will return is just a SQL keyword.  (Otherwise, use a custom
	 * message to avoid creating translation problems.)
	 */
	err = NULL;
	errkind = false;
	switch (pstate->p_expr_kind)
	{
		case EXPR_KIND_NONE:
			Assert(false);		/* can't happen */
			break;
		case EXPR_KIND_OTHER:
			/* Accept SRF here; caller must throw error if wanted */
			break;
		case EXPR_KIND_JOIN_ON:
		case EXPR_KIND_JOIN_USING:
			err = _("set-returning functions are not allowed in JOIN conditions");
			break;
		case EXPR_KIND_FROM_SUBSELECT:
			/* can't get here, but just in case, throw an error */
			errkind = true;
			break;
		case EXPR_KIND_FROM_FUNCTION:
			/* okay, but we don't allow nested SRFs here */
			/* errmsg is chosen to match transformRangeFunction() */
			/* errposition should point to the inner SRF */
			if (pstate->p_last_srf != last_srf)
				ereport(ERROR,
						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
						 errmsg("set-returning functions must appear at top level of FROM"),
						 parser_errposition(pstate,
											exprLocation(pstate->p_last_srf))));
			break;
		case EXPR_KIND_WHERE:
			errkind = true;
			break;
		case EXPR_KIND_POLICY:
			err = _("set-returning functions are not allowed in policy expressions");
			break;
		case EXPR_KIND_HAVING:
			errkind = true;
			break;
		case EXPR_KIND_FILTER:
			errkind = true;