Filter pushdown not working for struct fields

Working with a dataset containing struct fields, and enabling debug logging in the ES connector, I'm seeing the following behavior. The dataframe is created over the ES connector and then the schema is extended with a couple column aliases, such as.

df.withColumn("f2", df("foo"))

Queries vs those alias columns work as expected for fields that are non-struct members.

scala> df.withColumn("f2", df("foo")).where("f2 == '1'").limit(0).show
17/02/16 15:06:49 DEBUG DataSource: Pushing down filters [IsNotNull(foo),EqualTo(foo,1)]
17/02/16 15:06:49 TRACE DataSource: Transformed filters into DSL [{"exists":{"field":"foo"}},{"match":{"foo":"1"}}]

However, try the same with an alias over a struct field, and no filters are pushed down.

scala> df.withColumn("bar_baz", df("bar.baz")).where("bar_baz == '1'").limit(1).show

In fact, this is the case even when no alias is used at all.

scala> df.where("bar.baz == '1'").limit(1).show

Basically, pushdown for structs doesn't work at all.

Maybe this is specific to the ES connector?