Hello everyone,
Recently when I use Kylin to query like this:
select dt from table
where cast(dt as date) >= cast('2020-07-21' as date) and cast(dt as date) <=
cast('2020-07-22' as date)
group by dt;
The result is null, but when I use this query:
select dt from table
where dt >= '2020-07-21' and dt <= '2020-07-22'
group by dt;
The result is '2020-07-21'. By the way, 'dt' column type is string, and Kylin
version is 2.6.6.
When I read the source code, I found that when I use the first query, Kylin
server will transform constant in where condition to bigint: 1595289600000 and
1595376000000. When prune segments, these two values will compare to segment
range(20200721000000_20200722000000), which means compare bigint format
string(1595289600000) with date format string(2020-07-21).
I am not sure if my understanding is correct? Can we cast string type column to
date, and compare with constant in where clause?
