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Accumulo >> mail # user >> Re: Reverse Index Timestamp


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Roshan Punnoose 2012-11-27, 18:22
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Re: Reverse Index Timestamp
On Tue, Nov 27, 2012 at 1:22 PM, Roshan Punnoose <[EMAIL PROTECTED]> wrote:

> Thanks!
>
> The fact that you are using a binary tree behind the scenes makes perfect
> sense. Btw, what do you use in the standalone (non native) implementation?
> Does it use a TreeMap?
>

When not using native code, ConcurrentSkipListMap is used.
>
>
> On Tue, Nov 27, 2012 at 12:57 PM, Keith Turner <[EMAIL PROTECTED]> wrote:
>
>>
>>
>> On Tue, Nov 27, 2012 at 12:21 PM, Roshan Punnoose <[EMAIL PROTECTED]>wrote:
>>
>>> The <string> would most likely be a fixed set of strings that do not
>>> change over time.
>>>
>>> My question is if it is bad to use a reverse index timestamp in the row
>>> id? Will it cause problems with the tablet splitting, compaction, and
>>> performance if the data is always being sent to the top of the tablet? If I
>>> define a split as everything prefixed with <string>, then the ingest will
>>> go to one tablet, but then I add a reverse timestamp in the row, and that
>>> would mean I am always copying data to the top of the tablet. Will this
>>> cause performance issues? Or is it better to append to a tablet?
>>>
>>
>> I do not think it should matter. Inserts go into a C++ STL map on the
>> tablet server if using the nativemap.   I think the implementation of that
>> is a balanced binary tree.  So I do not think inserting at the beginning vs
>> the end would make difference.  That being said, I do not think I have
>> tried this so I do not know if there would be any suprises.  I would be
>> interested in hearing about your experiences.
>>
>>
>>>
>>>
>>> On Tue, Nov 27, 2012 at 11:51 AM, Keith Turner <[EMAIL PROTECTED]> wrote:
>>>
>>>>
>>>>
>>>> Keith
>>>>
>>>> On Tue, Nov 27, 2012 at 10:41 AM, Roshan Punnoose <[EMAIL PROTECTED]>wrote:
>>>>
>>>>> I want to have a table where the row will consist of
>>>>> "<string>-<reverse index timestamp>". But this means that the data is
>>>>> always being prefixed to the beginning of the row (or tablet if the row is
>>>>> large). Will this be a problem for compaction or performance?
>>>>
>>>>
>>>> Can you tell me more about what <string> is?  For example is it a hash
>>>> or does it come from the set "foo1","foo2","foo3".   How does it change
>>>> over time?  I think the answer to your question depends on what <string> is.
>>>>
>>>>
>>>>>
>>>>> I don't know if I heard this correctly, but someone once mentioned
>>>>> that making the row id the direct timestamp could cause performance issues
>>>>> because data is always going to one tablet, but also because there is
>>>>> trouble splitting since it always appends to the tablet. Is this true, is
>>>>> it similar to what could happen if I am always prefixing to a tablet?
>>>>>
>>>>
>>>> Yes using a timestamp for a row could cause data from many clients to
>>>> always go to the same tablet, which would be bad for performance on a
>>>> cluster.
>>>>
>>>>
>>>>>
>>>>> Thanks!
>>>>> Roshan
>>>>>
>>>>
>>>>
>>>
>>
>
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Jim Klucar 2012-11-27, 21:45
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Roshan Punnoose 2012-11-27, 22:53
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Jim Klucar 2012-12-03, 14:02