acelyc111 opened a new issue #4928:
URL: https://github.com/apache/incubator-doris/issues/4928
**Is your feature request related to a problem? Please describe.**
Suppose there is a table:
```
CREATE TABLE `test_table3` (
`key_int` int(11) NULL COMMENT "",
`key_varchar` varchar(16) NULL COMMENT "",
`val_int` int(11) NULL COMMENT ""
) ENGINE=OLAP
DUPLICATE KEY(`key_int`, `key_varchar`)
COMMENT "OLAP"
DISTRIBUTED BY HASH(`key_int`) BUCKETS 1
PROPERTIES (
"replication_num" = "1",
"in_memory" = "false",
"storage_format" = "V2"
);
```
And a query like:
```
select count(1) from test_table3 where key_int = 1 and key_varchar in
('1','2','3','4','5','6','7','8','9');
```
The scanner on BE may do the IN predicate at first, it's more costly than EQ
predicate.
**Describe the solution you'd like**
We can sort conditions based on cost, roughly:
- unary operators (IS) is cheaper than binary operators(EQ,NE,LT,LE,GT,GE)
- binary operators are cheaper than IN/NOT IN
And also different column types have different cost:
- INT is cheaper than CHAR or VARCHAR basically
- shorter INT or VARCHAR is cheaper than longer one
We can sort conditions base on cost before do actual scan.
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