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From Flavio Pompermaier <pomperma...@okkam.it>
Subject Re: Help in designing row key
Date Wed, 03 Jul 2013 11:25:32 GMT
No, I've never seen Phoenix, but it looks like a very useful project!
However I don't have such strict performance issues in my use case, I just
want to have balanced regions as much as possible.
So I think that in this case I will still use Bytes concatenation if
someone confirm I'm doing it in the right way.


On Wed, Jul 3, 2013 at 12:33 PM, James Taylor <jtaylor@salesforce.com>wrote:

> Hi Flavio,
> Have you had a look at Phoenix (https://github.com/**forcedotcom/phoenix<https://github.com/forcedotcom/phoenix>)?
> It will allow you to model your multi-part row key like this:
>
> CREATE TABLE flavio.analytics (
>     source INTEGER,
>     type INTEGER,
>     qual VARCHAR,
>     hash VARCHAR,
>     ts DATE
>     CONSTRAINT pk PRIMARY KEY (source, type, qual, hash, ts) // Defines
> columns that make up the row key
> )
>
> Then you can issue SQL queries like this (to query for the last 7 days
> worth of data):
> SELECT * FROM flavio.analytics WHERE source IN (1,2,5) AND type IN (55,66)
> AND ts > CURRENT_DATE() - 7
>
> This will internally take advantage of our SkipScan (http://phoenix-hbase.
> **blogspot.com/2013/05/**demystifying-skip-scan-in-**phoenix.html<http://phoenix-hbase.blogspot.com/2013/05/demystifying-skip-scan-in-phoenix.html>)
> to jump through your key space similar to FuzzyRowFilter, but in parallel
> from the client taking into account your region boundaries.
>
> Or do more complex GROUP BY queries like this (to aggregate over the last
> 30 days worth of data, bucketized by day):
> SELECT type,COUNT(*) FROM flavio.analytics WHERE ts > CURRENT_DATE() - 30
> GROUP BY type,TRUNCATE(ts,'DAY')
>
> No need to worry about lexicographical sort order, flipping sign bits,
> normalizing/padding integer values, and all the other nuances of working
> with an API that works at the level of bytes. No need to write and manage
> installation of your own coprocessors to make aggregation efficient,
> perform topN queries, etc.
>
> HTH.
>
> Regards,
> James
> @JamesPlusPlus
>
>
> On 07/03/2013 02:58 AM, Anoop John wrote:
>
>> When you make the RK and convert the int parts into byte[] ( Use
>> org.apache.hadoop.hbase.util.**Bytes#toBytes(*int) *)  it will give 4
>> bytes
>> for every byte..  Be careful about the ordering...   When u convert a +ve
>> and -ve integer into byte[] and u do Lexiographical compare (as done in
>> HBase) u will see -ve number being greater than +ve..  If you dont have to
>> do deal with -ve numbers no issues  :)
>>
>> Well when all the parts of the RK is of fixed width u will need any
>> seperator??
>>
>> -Anoop-
>>
>> On Wed, Jul 3, 2013 at 2:44 PM, Flavio Pompermaier <pompermaier@okkam.it
>> >wrote:
>>
>>  Yeah, I was thinking to use a normalization step in order to allow the
>>> use
>>> of FuzzyRowFilter but what is not clear to me is if integers must also be
>>> normalized or not.
>>> I will explain myself better. Suppose that i follow your advice and I
>>> produce keys like:
>>>   - 1|1|somehash|sometimestamp
>>>   - 55|555|somehash|sometimestamp
>>>
>>> Whould they match the same pattern or do I have to normalize them to the
>>> following?
>>>   - 001|001|somehash|sometimestamp
>>>   - 055|555|somehash|sometimestamp
>>>
>>> Moreover, I noticed that you used dots ('.') to separate things instead
>>> of
>>> pipe ('|')..is there a reason for that (maybe performance or whatever) or
>>> is just your favourite separator?
>>>
>>> Best,
>>> Flavio
>>>
>>>
>>> On Wed, Jul 3, 2013 at 10:12 AM, Mike Axiak <mike@axiak.net> wrote:
>>>
>>>  I'm not sure if you're eliding this fact or not, but you'd be much
>>>> better off if you used a fixed-width format for your keys. So in your
>>>> example, you'd have:
>>>>
>>>> PATTERN: source(4-byte-int).type(4-**byte-int or smaller).fixed 128-bit
>>>> hash.8-byte timestamp
>>>>
>>>> Example: \x00\x00\x00\x01\x00\x00\x02\**x03....
>>>>
>>>> The advantage of this is not only that it's significantly less data
>>>> (remember your key is stored on each KeyValue), but also you can now
>>>> use FuzzyRowFilter and other techniques to quickly perform scans. The
>>>> disadvantage is that you have to normalize the source-> integer but I
>>>> find I can either store that in an enum or cache it for a long time so
>>>> it's not a big issue.
>>>>
>>>> -Mike
>>>>
>>>> On Wed, Jul 3, 2013 at 4:05 AM, Flavio Pompermaier <
>>>> pompermaier@okkam.it
>>>>
>>>> wrote:
>>>>
>>>>> Thank you very much for the great support!
>>>>> This is how I thought to design my key:
>>>>>
>>>>> PATTERN: source|type|qualifier|hash(**name)|timestamp
>>>>> EXAMPLE:
>>>>> google|appliance|oven|**be9173589a7471a7179e928adc1a86**
>>>>> f7|1372837702753
>>>>>
>>>>> Do you think my key could be good for my scope (my search will be
>>>>> essentially by source or source|type)?
>>>>> Another point is that initially I will not have so many sources, so I
>>>>>
>>>> will
>>>>
>>>>> probably have only google|* but in the next phases there could be more
>>>>> sources..
>>>>>
>>>>> Best,
>>>>> Flavio
>>>>>
>>>>> On Tue, Jul 2, 2013 at 7:53 PM, Ted Yu <yuzhihong@gmail.com> wrote:
>>>>>
>>>>>  For #1, yes - the client receives less data after filtering.
>>>>>>
>>>>>> For #2, please take a look at TestMultiVersions
>>>>>> (./src/test/java/org/apache/**hadoop/hbase/**TestMultiVersions.java
>>>>>> in
>>>>>>
>>>>> 0.94)
>>>
>>>> for time range:
>>>>>>
>>>>>>      scan = new Scan();
>>>>>>
>>>>>>      scan.setTimeRange(1000L, Long.MAX_VALUE);
>>>>>> For row key selection, you need a filter. Take a look at
>>>>>> FuzzyRowFilter.java
>>>>>>
>>>>>> Cheers
>>>>>>
>>>>>> On Tue, Jul 2, 2013 at 10:35 AM, Flavio Pompermaier <
>>>>>>
>>>>> pompermaier@okkam.it
>>>>
>>>>> wrote:
>>>>>>>   Thanks for the reply! I thus have two questions more:
>>>>>>>
>>>>>>> 1) is it true that filtering on timestamps doesn't affect
>>>>>>>
>>>>>> performance..?
>>>>
>>>>> 2) could you send me a little snippet of how you would do such a
>>>>>>>
>>>>>> filter
>>>>
>>>>> (by
>>>>>>
>>>>>>> row key + timestamps)? For example get all rows whose key starts
>>>>>>>
>>>>>> with
>>>
>>>>  'someid-' and whose timestamps is greater than some timestamp?
>>>>>>>
>>>>>>> Best,
>>>>>>> Flavio
>>>>>>>
>>>>>>>
>>>>>>> On Tue, Jul 2, 2013 at 6:25 PM, Ted Yu <yuzhihong@gmail.com>
wrote:
>>>>>>>
>>>>>>>  bq. Using timestamp in row-keys is discouraged
>>>>>>>>
>>>>>>>> The above is true.
>>>>>>>> Prefixing row key with timestamp would create hot region.
>>>>>>>>
>>>>>>>> bq. should I filter by a simpler row-key plus a filter on
>>>>>>>>
>>>>>>> timestamp?
>>>
>>>>  You can do the above.
>>>>>>>>
>>>>>>>> On Tue, Jul 2, 2013 at 9:13 AM, Flavio Pompermaier <
>>>>>>>>
>>>>>>> pompermaier@okkam.it
>>>>>>
>>>>>>> wrote:
>>>>>>>>> Hi to everybody,
>>>>>>>>>
>>>>>>>>> in my use case I have to perform batch analysis skipping
old
>>>>>>>>>
>>>>>>>> data.
>>>
>>>>  For example, I want to process all rows created after a certain
>>>>>>>>>
>>>>>>>> timestamp,
>>>>>>>>
>>>>>>>>> passed as parameter.
>>>>>>>>>
>>>>>>>>> What is the most effective way to do this?
>>>>>>>>> Should I design my row-key to embed timestamp?
>>>>>>>>> Or just filtering by timestamp of the row is fast as
well? Or
>>>>>>>>>
>>>>>>>> what
>>>
>>>>  else?
>>>>>>>
>>>>>>>> Initially I was thinking to compose my key as:
>>>>>>>>> timestamp|source|title|type
>>>>>>>>>
>>>>>>>>> but:
>>>>>>>>>
>>>>>>>>> 1) Using timestamp in row-keys is discouraged
>>>>>>>>> 2) If this design is ok, using this approach I still
have
>>>>>>>>>
>>>>>>>> problems
>>>
>>>>  filtering by timestamp because I cannot found a way to
>>>>>>>>>
>>>>>>>> numerically
>>>
>>>>  filer
>>>>>>>
>>>>>>>> (instead of alphanumerically/by string). Example:
>>>>>>>>> 1372776400441|something has timestamp lesser
>>>>>>>>> than 1372778470913|somethingelse but I cannot filter
all row
>>>>>>>>>
>>>>>>>> whose
>>>
>>>> key
>>>>>>
>>>>>>> is
>>>>>>>
>>>>>>>> "numerically" greater than 1372776400441. Is it possible
to
>>>>>>>>>
>>>>>>>> overcome
>>>>
>>>>> this
>>>>>>>
>>>>>>>> issue?
>>>>>>>>> 3) If this design is not ok, should I filter by a simpler
>>>>>>>>>
>>>>>>>> row-key
>>>
>>>> plus
>>>>>>
>>>>>>> a
>>>>>>>
>>>>>>>> filter on timestamp? Or what else?
>>>>>>>>>
>>>>>>>>> Best,
>>>>>>>>> Flavio
>>>>>>>>>
>>>>>>>>>
>


-- 

Flavio Pompermaier
*Development Department
*_______________________________________________
*OKKAM**Srl **- www.okkam.it*

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