atomic operations

[Casey Bodley]

I was looking at atomic_add() with the following use case in mind: generating unique, auto-incrementing keys.

space autoincrement
dimensions key (int64), next_value (int64)
key key auto 1 3

results = hyperclient.atomic_add('autoincrement', 0, {'next_value': 1})
unique_key = results['next_value']

However, none of the atomic functions appear to return the resulting values. This really seems to limit their usefulness, if you can't also retrieve the result atomically. Would this be a reasonable feature request?

[Emin Gün Sirer]

Absolutely! This is on our short-term todo list.

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[Robert Escriva]

To follow up, I've created a public issue[1] on GitHub.

-Robert

1. https://github.com/rescrv/HyperDex/issues/72

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[Holger Winkelmann]

HI,

We are just evaluation hyperdex, there was the expectation for this behavior for atomic operations. Do you have some news here?

BTW: I have asked the same question in the github issue.

[Robert Escriva]

Hi Holger,

We chatted on IRC, but I'm following up here with the same discussion
for the wider audience on the mailing list.

You can get much the same behavior as an atomic_add that returns the
value as a pair of get/cond_put operations. Imagine that we had a space
like this:

space kv key k attribute int count

we could do an atomic increment from Python like this:

>>> c = hyperdex.client.Client('localhost', 1982)
>>> v = c.get('kv', 'some key')
>>> c.cond_put('kv', 'some key', {'v': v['count']}, {'v': v['count'] + 1})
True
>>> old_value = v['count']
>>> new_value = v['count'] + 1

Best,
Robert

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