Why is left join needed?

Support
#1

I have written a query

WHERE e.foo = 'example' OR e.f.bar = 'example'

Now I found that all entities with e.f == null aren’t found. Probably there is done a inner join.
After this I tried two alternatives

WHERE e.foo = 'example' 
OR e.f IN (SELECT f FROM ex_F f WHERE f.bar = 'example')

Although this works in plain SQL, it gives me the same entities as the first query. So only the next query with explicit LEFT JOIN gave me the expected results.

SELECT e FROM ex_E e 
LEFT JOIN e.f f 
WHERE e.foo = 'example' OR f.bar = 'example'

In my scenario many entities with e.foo == 'example' have no e.f so that we found this quite fast. But I am concerned that in other queries we miss this case.

Is there a way to achieve this with a better readable query? Do you have an idea why the second query doesn’t give entites with e.f == null?

#2

I found that the same behavior occurs at filters.
e.g.

<filter dataloder="eDl">
    <properties include=".*"/>
    <configurations>
        <configuration id="test" operation="OR">
            <propertyFilter property="foo" operation=EQUAL"/>
            <propertyFilter property="f.bar" operation=EQUAL"/>
        <configuration/>
    <configurations/>
<filter/>

As users with the according permissions can design their own filters this seems to be quite dangerous to me.