Under the hood, the selectable::add_and_get_index() function
deliberately filters out duplicate columns. This causes
simple_selector::get_output_row() to return a row with all duplicate
columns filtered out, which triggers and assertion because of row
mismatch with metadata (which contains the duplicate columns).
The fix is rather simple: just make selection::from_selectors() use
selection_with_processing if the number of selectors and column
definitions doesn't match -- like Apache Cassandra does.
Fixes#1367
Message-Id: <1477989740-6485-1-git-send-email-penberg@scylladb.com>
e1e8ca2788