SearchArguments column names and nested columns

[Emilio Lahr-Vivaz]

Hello,

I have two questions related to SearchArguments and predicate push down 
that I couldn't find documented anywhere.

1. What is the 'columnNames' parameter used for in the searchArgument 
[1] method? In my testing, it doesn't seem to make a difference if I 
pass in the column I'm filtering, some other column, or even an empty array.

2. Is it possible to create a predicate on a nested column? From tracing 
through the code it doesn't appear to be possible, but wanted to 
confirm. For example, I'd like to filter on location.x given a type 
description like: struct<id:string,location:struct<x:double,y:double>>

Thanks,

Emilio

[1]: 
https://orc.apache.org/api/orc-core/org/apache/orc/Reader.Options.html#searchArgument-org.apache.hadoop.hive.ql.io.sarg.SearchArgument-java.lang.String:A-