optimizer & runner should consider NULL special rules

[aceforeverd]

For a index optimizer, the most common pattern is, for example, SQL SELECT * FROM t1 WHERE gp = {const_val}, is optimized based on FILTER expression gp = {const_val}:

So if index key=gp exists for table t1, that index is utilized, as ** SEEK BY KEY {const_val} >> OUTPUT ALL ROWS`**.

However, if {const_val} is NULL, this optimize rule should not go that approach, since <ANY_VAL> = NULL is NULL.

This also happens for SQL like LAST JOIN t1 LAST JOIN t2 on t1.key = t2.key, where there is row exists in t1 that t1.key = NULL. It never joins.

Optimizer should consider const NULL values, and Runner should consider NULL values as index_key

[aceforeverd]

relate issue #3685

[aceforeverd]

some of the yaml testing cases are wrong:

• OpenMLDB/cases/function/join/test_lastjoin_complex.yaml

  Lines 560 to 655 in d9bb344

  	- id: 10
  	desc: t1 join t2 join t3,t2的key产出为null
  	mode: offline-unsupport
  	tags: ["@chendihao", "这个场景离线的预期不正确，需要迪豪看看"]
  	inputs:
  	-
  	columns : ["id int","c1 string","c3 int","c4 bigint","c5 float","c6 double","c7 timestamp","c8 date"]
  	indexs: ["index1:c1:c7"]
  	rows:
  	- [1,"aa",20,30,1.1,2.1,1590738990000,"2020-05-01"]
  	- [2,"bb",21,31,1.2,2.2,1590738991000,"2020-05-02"]
  	- [3,"cc",22,32,1.3,2.3,1590738992000,"2020-05-03"]
  	- [4,"dd",23,33,1.4,2.4,1590738993000,"2020-05-04"]
  	- [5,"ee",24,34,1.5,2.5,1590738994000,"2020-05-05"]
  	-
  	columns: ["id int","c1 string","c3 int","c4 bigint","c5 float","c6 double","c7 timestamp","c8 date"]
  	indexs: ["index1:c1:c7","index2:c3:c7"]
  	rows:
  	- [1,"aa",20,30,1.1,2.1,1606755660000,"2020-05-01"]
  	- [2,"aa",21,31,1.1,2.1,1606755720000,"2020-05-01"]
  	- [3,"cc",21,32,1.1,2.1,1606755780000,"2020-05-01"]
  	- [4,"dd",21,33,1.1,2.1,1606755840000,"2020-05-01"]
  	- [5,"ee",24,34,1.2,2.2,1606755660000,"2020-05-02"]
  	-
  	columns : ["id int","c1 string","c3 int","c4 bigint","c5 float","c6 double","c7 timestamp","c8 date"]
  	indexs: ["index1:c1:c7","index2:c3:c7"]
  	rows:
  	- [1,"aa",20,30,1.1,2.1,1606755600000,"2020-05-01"]
  	- [2,"bb",20,31,1.2,2.1,1606759200000,"2020-05-01"]
  	- [3,"bb",null,32,1.3,2.1,1606762800000,"2020-05-01"]
  	- [4,"bb",21,33,1.4,2.1,1606766400000,"2020-05-01"]
  	- [5,"ee",21,34,1.5,2.2,1606766401000,"2020-05-02"]
  	sql: |
  	select {0}.id,{0}.c1,{0}.c3,{1}.c3,{2}.c4
  	from {0}
  	last join {1} ORDER BY {1}.c7 on {0}.c1={1}.c1
  	last join {2} ORDER BY {2}.c7 on {1}.c3={2}.c3
  	;
  	expect:
  	order: id
  	columns: ["id int","c1 string","c3 int","c3 int","c4 bigint"]
  	rows:
  	- [1,"aa",20,21,34]
  	- [2,"bb",21,null,32]
  	- [3,"cc",22,21,34]
  	- [4,"dd",23,21,34]
  	- [5,"ee",24,24,null]
  	- id: 11
  	desc: (t1 join t2) join t3
  	mode: offline-unsupport
  	inputs:
  	-
  	columns : ["id int","c1 string","c3 int","c4 bigint","c5 float","c6 double","c7 timestamp","c8 date"]
  	indexs: ["index1:c1:c7"]
  	rows:
  	- [1,"aa",20,30,1.1,2.1,1590738990000,"2020-05-01"]
  	- [2,"bb",21,31,1.2,2.2,1590738991000,"2020-05-02"]
  	- [3,"cc",22,32,1.3,2.3,1590738992000,"2020-05-03"]
  	- [4,"dd",23,33,1.4,2.4,1590738993000,"2020-05-04"]
  	- [5,"ee",24,34,1.5,2.5,1590738994000,"2020-05-05"]
  	-
  	columns: ["id int","c1 string","c3 int","c4 bigint","c5 float","c6 double","c7 timestamp","c8 date"]
  	indexs: ["index1:c1:c7","index2:c3:c7"]
  	rows:
  	- [1,"aa",20,30,1.1,2.1,1606755660000,"2020-05-01"]
  	- [2,"aa",21,31,1.1,2.1,1606755720000,"2020-05-01"]
  	- [3,"cc",21,32,1.1,2.1,1606755780000,"2020-05-01"]
  	- [4,"dd",21,33,1.1,2.1,1606755840000,"2020-05-01"]
  	- [5,"ee",24,34,1.2,2.2,1606755660000,"2020-05-02"]
  	-
  	columns : ["id int","c1 string","c3 int","c4 bigint","c5 float","c6 double","c7 timestamp","c8 date"]
  	indexs: ["index1:c1:c7","index2:c3:c7"]
  	rows:
  	- [1,"aa",20,30,1.1,2.1,1606755600000,"2020-05-01"]
  	- [2,"bb",20,31,1.2,2.1,1606759200000,"2020-05-01"]
  	- [3,"bb",null,32,1.3,2.1,1606762800000,"2020-05-01"]
  	- [4,"bb",21,33,1.4,2.1,1606766400000,"2020-05-01"]
  	- [5,"ee",21,34,1.5,2.2,1606766401000,"2020-05-02"]
  	sql: |
  	select
  	t1.id,t1.c1,t1.c3,{2}.c4
  	from (
  	select {0}.id,{0}.c1,{1}.c3
  	from {0}
  	last join {1} ORDER BY {1}.c7 on {0}.c1={1}.c1
  	) as t1 last join {2} ORDER BY {2}.c7 on t1.c3={2}.c3
  	;
  	expect:
  	order: id
  	columns: ["id int","c1 string","c3 int","c4 bigint"]
  	rows:
  	- [1,"aa",21,34]
  	- [2,"bb",null,32]
  	- [3,"cc",21,34]
  	- [4,"dd",21,34]
  	- [5,"ee",24,null]