Re: PATCH: Extending the HyperLogLog API a bit

On 01/01/2016 12:08 AM, Peter Geoghegan wrote:
> On Thu, Dec 31, 2015 at 12:48 PM, Tomas Vondra
> <tomas.vondra@2ndquadrant.com> wrote:
>> 1) initHyperLogLogError(hyperLogLogState *cState, double error)
>>
>>     Instead of specifying bwidth (essentially the number of bits used
>>     for addressing in the counter), this allows specifying the expected
>>     error rate for the counter, which is
>>
>>        error_rate = 1.04 / sqrt(2^bwidth)
>>
>>     So for 5% we get bwidth=5, and so on. This makes the API a bit easier
>>     the use, because there are pretty much no comments about the meaning
>>     of bwidth, and the existing callers simply use 10 without details.
>
> Fair, but you didn't add any better comments!
>
>> 2) freeHyperLogLog(hyperLogLogState *cState)
>>
>>     I think it's a good idea to provide function "undoing" what init
>>     does, i.e. freeing the internal memory etc. Currently that's trivial
>>     to do, but perhaps we'll make the structure more complicated in the
>>     future (albeit that might be unlikely).
>
> Seems reasonable.

Attached is v2 of the patch, adding the comments.

regards

--
Tomas Vondra                  http://www.2ndQuadrant.com
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