Extend pgbench partitioning to pgbench_history

Hi there,

While benchmarking a new feature involving tablespace support in
CloudNativePG (Kubernetes operator), I wanted to try out the partitioning
feature of pgbench. I saw it supporting both range and hash partitioning,
but limited to pgbench_accounts.

With the attached patch, I extend the partitioning capability to the
pgbench_history table too.

I have been thinking of adding an option to control this, but I preferred
to ask in this list whether it really makes sense or not (I struggle indeed
to see use cases where accounts is partitioned and history is not).

Please let me know what you think.

Thanks,
Gabriele
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Gabriele Bartolini
Vice President, Cloud Native at EDB
enterprisedb.com