Support NULL literals in where clause

[xinlifoobar]

Which issue does this PR close?

Closes #11248

Rationale for this change

What changes are included in this PR?

Are these changes tested?

Are there any user-facing changes?

[xinlifoobar]

In the previous it will throw a downcast_error, which mess up the debugging logs.

[xinlifoobar]

From postgres,

postgres=# select 1 where null and 1=1;
 ?column? 
----------
(0 rows)

postgres=# select 1 where null and 1=1;
 ?column? 
----------
(0 rows)

postgres=# select 1 where null or 1=1;
 ?column? 
----------
        1
(1 row)

[alamb]

Thanks @xinlifoobar -- this makes sense to me

Another potential way to fix this issue would be to cast / coerce NULL literals in the WHERE clause to boolean

Basically we could add the equivalent of NULL::boolean

For example, given the input

SELECT ... FROM foo WHERE NULL and x = 5;

We could transform it to

SELECT ... FROM foo WHERE NULL::boolean and x = 5;

That might result in simpler code as FilterExec would not have to be aware of DataType::null

Perhaps it would fit in https://github.com/apache/datafusion/blob/main/datafusion/optimizer/src/analyzer/type_coercion.rs

However, I think this PR is better than main and we could try to see if the alternate approach loked better as a future work (or never)

[alamb]

Thanks again @xinlifoobar

[xinlifoobar]

Thanks @xinlifoobar -- this makes sense to me

Another potential way to fix this issue would be to cast / coerce NULL literals in the WHERE clause to boolean

Basically we could add the equivalent of NULL::boolean

For example, given the input

SELECT ... FROM foo WHERE NULL and x = 5;

We could transform it to

SELECT ... FROM foo WHERE NULL::boolean and x = 5;

That might result in simpler code as FilterExec would not have to be aware of DataType::null

Perhaps it would fit in https://github.com/apache/datafusion/blob/main/datafusion/optimizer/src/analyzer/type_coercion.rs

However, I think this PR is better than main and we could try to see if the alternate approach loked better as a future work (or never)

This is a lot... Let me looking into this.