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https://issues.apache.org/jira/browse/PHOENIX-3070?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15376937#comment-15376937
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Lars Hofhansl commented on PHOENIX-3070:
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Oops... I was wrong by a factor of 1000 :( (my mirco benchmark was 1m loops,
not 1000 loops as I had throught).
So a call to {{randomUUID}} takes 3us (not 3ms). It still shows up in a
profiler session (sampling, so it's real).
Note that I tested with a single Thread only and that both {{SecureRandom}} and
{{Random}} are very multithreading unfriendly, whereas {{ThreadLocalRandom}} is
not.
> Unnecessary use of UUID.randomUUID()
> ------------------------------------
>
> Key: PHOENIX-3070
> URL: https://issues.apache.org/jira/browse/PHOENIX-3070
> Project: Phoenix
> Issue Type: Bug
> Reporter: Lars Hofhansl
>
> I see {{UUID.randomUUID()}} used all over Phoenix a lot.
> {{randomUUID}} uses {{SecureRandom}} internally, which - on my machine -
> takes almost 3ms, and that is _per UUID_!
> I don't think we need a UUIDs from a cryptographically sound random number
> generator.
> We could do {{new UUID(random.nextLong(), random.nextLong())}}, which takes
> 0.06ms (60us), or even better: {{new
> UUID(ThreadLocalRandom.current().nextLong(),
> ThreadLocalRandom.current().nextLong())}}, which takes less than 0.004ms
> (4us) on my box.
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