[Answer Query Using Materialized Views] Consider mutable functions and bypass expressions have no Vars for view query target.

[avamingli]

Fix misc of AQUMV, please review by commits:

Bypass expression has no Vars for view query target.

For expressions have no Vars, we don't need to sort and take
them into account.

Origin query has mutable functions can not use AQUMV.

We have disabled view query has mutable functions, but forget the
origin query.
Mutable functions should be kept in the origin relation.

Example:

  SELECT random() from t1;

Function random() should be projected on t1 itself.

Add case HAVING clause doesn't have column reference.

HAVING quals like: having 2 > 1, the clause without column reference
should be ok in AQUMV.

-- having quals without column reference.
explain(costs off, verbose)
select c1, c3, avg(c2) from aqumv_t4 where c1 > 90 group by (c1, c3) having 2 > 1;
                                    QUERY PLAN                                    
----------------------------------------------------------------------------------
 Gather Motion 3:1  (slice1; segments: 3)
   Output: mc1, mc3, (avg(mc2))
   ->  HashAggregate
         Output: mc1, mc3, avg(mc2)
         Group Key: aqumv_mvt4_0.mc1, aqumv_mvt4_0.mc3
         ->  Seq Scan on public.aqumv_mvt4_0
               Output: mc1, mc2, mc3
 Settings: enable_answer_query_using_materialized_views = 'on', optimizer = 'off'
 Optimizer: Postgres query optimizer
(9 rows)

Expression 2 > 1 is always true if there were tuples form the underlying relations, same for materialized views we use.
So we could just drop things like that.

Use shcema aqumv for tests