How do I initialize the size of a Hash in Ruby?

I would like to specify an initial size for my Hash in Ruby. I know I am going to be adding tens of millions of entries in the hash and a lot of time is wasting rehashing t开发者_运维问答he data every time Ruby decides it needs a larger hash.

Other languages support something like a "reserve" call to pre-size the hash. Can this be done in Ruby?

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Ruby's Hash doesn't have any way to do that. It should still be relatively performant either way, but you might want to consider other data storage methods, such as a database or key/value store like Memcached or Redis, for data sets of that magnitude.