Function build_aggregate_combinefn_expr

src/backend/parser/parse_agg.c:2111–2134

* Like build_aggregate_transfn_expr, but creates an expression tree for the * combine function of an aggregate, rather than the transition function. */

 * combine function of an aggregate, rather than the transition function.
 */
void
build_aggregate_combinefn_expr(Oid agg_state_type,
							   Oid agg_input_collation,
							   Oid combinefn_oid,
							   Expr **combinefnexpr)
{
	Node	   *argp;
	List	   *args;
	FuncExpr   *fexpr;

	/* combinefn takes two arguments of the aggregate state type */
	argp = make_agg_arg(agg_state_type, agg_input_collation);

	args = list_make2(argp, argp);

	fexpr = makeFuncExpr(combinefn_oid,
						 agg_state_type,
						 args,
						 InvalidOid,
						 agg_input_collation,
						 COERCE_EXPLICIT_CALL);
	/* combinefn is currently never treated as variadic */
	*combinefnexpr = (Expr *) fexpr;
}

/*
 * Like build_aggregate_transfn_expr, but creates an expression tree for the