Could there be a significant performance improvement by maintaining a second hash of just 'attr1' to pre-determine if any keys start with attr1?

No!

The time saved hashing a slightly shorter key for the first lookup will be completely negated by the need to do a second lookup if the first hits.

And using 3 keys will be significantly slower.

Moreover, multilevel hashes require considerably more memory (and memory management).

With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
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In reply to Re: Hash space/ time tradeoff by BrowserUk
in thread Hash space/ time tradeoff by Wiggins

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