Most of the time it's persisted into the MemoryStore or MemCachedStore, when
that's the case there is no real need to go through the Batch mechanism as it
incurs multiple copies of the data.
Importing 1.5M mainnet blocks with verification turned off, before:
real 12m39,484s
user 20m48,300s
sys 2m25,022s
After:
real 11m15,053s
user 18m2,755s
sys 2m4,162s
So it's around 10% improvement which looks good enough.
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