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Message from discussion Lua script execution time
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Marc Gravell  
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 More options Nov 5 2012, 7:36 am
From: Marc Gravell <marc.grav...@gmail.com>
Date: Mon, 5 Nov 2012 12:35:49 +0000
Local: Mon, Nov 5 2012 7:35 am
Subject: Re: Lua script execution time
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Hmmm.... maybe calling it a bug is a bit strong - it is really a special
case of violating the "scripts as pure functions" guidance - however, since
every key could in theory have an expiration, I'm not quite sure how we can
guarantee a pure function unless we never use lua to talk to a key that has
an expiry.

Intriguing.

Marc

On 5 November 2012 12:28, Marc Gravell <marc.grav...@gmail.com> wrote:

> OK, this is ***really*** nasty: I **strongly** suggest you don't use this,
> because it suggests that PTTL is incorrectly not being flagged as
> non-deterministic (unless I'm missing something - Salvatore might be able
> to advise more):

> redis.call('setex', KEYS[1], 60, 'timing')
> for i = 1,100000 do
>     redis.call('set', 'ignore','abc')
> end
> local timeTaken = 60000 - redis.call('pttl', KEYS[1])
> redis.call('del', KEYS[1])
> return timeTaken

> this is **really** ugly; note here that KEYS[1] is just a nasty guid I
> used for a scratch key, and `ignore` is just something to make the time
> detectable (that isn't meant to be illustrative).

> Seriously, don't do this!

> I would probably just time it at the client (which includes bandwidth
> costs), or issue a TIME before and after the EVAL/EVALSHA (which may
> include timings from other connections), and call it "close enough".

> But I would consider the fact that the above *works* to be a bug...

> Marc

> On 5 November 2012 12:17, Yiftach Shoolman <yiftach.shool...@gmail.com>wrote:

>> redis-cli --latency -h `host` -p `port`

>> More info here <http://redis.io/topics/latency>

>> On Mon, Nov 5, 2012 at 2:04 PM, Peter Choo <peterc...@gmail.com> wrote:

>>> Due to Redis not allowing write commands after TIME has been called,
>>>  How can I benchmark the execution time of a small lua script?

>>> Is there a function I can call to ask how long it took to run the last
>>> script?  I am not interested in the data transfer time, just how long it
>>> took to run in Redis.

>>> --
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>> --

>> Yiftach Shoolman
>> +972-54-7634621

>>  --
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> --
> Regards,

> Marc

--
Regards,

Marc


 
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