Evaluate Case When Expr in Fe when possible

[wangbo]

In the query case partition column compare with a case when Expr, evaluate Case when Expr in Fe can void unnecessary partition scan.

See a example as below

SQL

select event_day,sum(pv) from table2  where 
event_day= case when date_format(now(),'%H%i') = 0 then 1 else 2 end group by event_day

BEFORE

 0:OlapScanNode                                                 |
|      TABLE: table2                                               |
|      PREAGGREGATION: ON                                          |
|      PREDICATES: `event_day` = CASE WHEN FALSE THEN 1 ELSE 2 END |
|      partitions=1/3                                              |
|      rollup: table2                                              |
|      buckets=10/10                                               |
|      cardinality=14                                              |
|      avgRowSize=723.5714                                         |
|      numNodes=1                                                  |
|      tuple ids: 0      

AFTER

   0:OlapScanNode                        |
|      TABLE: table2                      |
|      PREAGGREGATION: ON                 |
|      PREDICATES: `event_day` = 2.0      |
|      partitions=1/3                     |
|      rollup: table2                     |
|      buckets=10/10                      |
|      cardinality=14                     |
|      avgRowSize=723.5714                |
|      numNodes=1                         |
|      tuple ids: 0