I am writing two background workers - autoreindex and scheduler. In Both I need to execute queries from top level. I had to wrote redundant code https://github.com/okbob/autoreindex/blob/master/utils.c autoreindex_execute_sql_command .Same code is in pglogical. Some statements - like VACUUM or REINDEX CONCURRENTLY is not possible call from SPI.
Can be nice to have this function in core.
pg_background handles this. Somebody might want to resurrect that patch.
Here is the link for that patch, which works with 9.5
