Predicates pushdown to REAL type in MySQL and MemSQL return incorrect result

[ebyhr]

trino> create table tpch.test_real (c1 real);
trino> insert into tpch.test_real values (real '3.14');

trino> desc tpch.test_real;
 Column | Type | Extra | Comment 
--------+------+-------+---------
 c1     | real |       |      

trino> select * from tpch.test_real;
  c1  
------
 3.14 

trino> select * from tpch.test_real where c1 = real '3.14';
 c1 
----
(0 rows)

I haven't confirmed all connectors, but PostgreSQL works fine.

[findepi]

Any clue why this wasn't found by AbstractTestDistributedQueries#testDataMappingSmokeTest?

[ebyhr]

@findepi Because these connectors were overriding filterDataMappingSmokeTestData method even though the type is supported:

        if (typeName.equals("real")
                || typeName.equals("timestamp")) {
            // TODO this should either work or fail cleanly
            return Optional.empty();
        }

[ssheikin]

@ebyhr
Is the root cause known which causes the incorrect result?
Why it does not cause incorrect results for double type?

[ebyhr]

@ssheikin Sorry, I don't remember the details. I think the implementation in both JDBC drivers and servers has been changed. It worth checking the latest behavior.

[ssheikin]

For ClickHouse with 3.14 it's still reproducible for float, but not for double.