What is the proper way to merge small ORC files?

[Ben Johnson]

Hi, I'm new to this group, thank you for the help in advance. I had a question
about merging ORC files via a CONCATENATE query like so:
ALTER TABLE my_table [PARTITION partition_spec] CONCATENATE;
We have thousands of small ORC files whose data is ordered by a date attribute.
My questions are:
 1. If we merge these files using the above query, will the ordering be
    preserved?
 2. And will the file be structured in a way that it will take full advantage of
    the indexes?
 3. Or are we better served transitioning the data through a traditional INSERT
    query from a second table?




Thanks!
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