Extend pgbench partitioning to pgbench_history

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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