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From Josh Elser <josh.el...@gmail.com>
Subject Re: RowID design and Hive push down
Date Mon, 14 Sep 2015 21:36:31 GMT
Yes, the reason the simple approach below would work is before you'd 
just operate on the day boundary (as specified by the yyyyMMdd) and the 
suffix would just naturally fall into the prefix range.

Some code might help draw it together. The comments should bridge the gap

https://github.com/apache/hive/blob/release-1.2.1/accumulo-handler/src/java/org/apache/hadoop/hive/accumulo/predicate/AccumuloRangeGenerator.java#L277

roman.drapeko@baesystems.com wrote:
> Hi Josh,
>
> Thanks for response.
>
> Well, I am not an expert in Accumulo (so looking for a clue how to implement so we avoid
as much as possible custom code) - I will try to extend my answer a little bit and explain
what I don't understand.
>
> For example, if my rowID looks like this: 20060101_blabla
>
> I can query Hive something like that: select * from tbl where rowid>  '20060101' and
rowid<  '20060102', to my understanding what's happening under the hood is AccumuloPredicateHandler
 creates a Range('20060101', '20060102') that used for scanning (?)
>
> Am I correct in saying that AccumuloPredicateHandler always creates a range that works
with strings only and it's not possible to amend this logic?
>
> Regarding java primitives - it always can be represented as byte[4]
>
> Roman
>
>
>
> -----Original Message-----
> From: Josh Elser [mailto:josh.elser@gmail.com]
> Sent: 14 September 2015 21:10
> To: user@accumulo.apache.org
> Cc: Drapeko, Roman (UK Guildford)
> Subject: Re: RowID design and Hive push down
>
> I'm not positive what you mean by the "in-built RowID push down mechanism won't work
with unsigned bytes". Are you saying that you're trying to change your current rowID structure
to
> unixTime+logicalSplit+hash structure? And you're trying to evaluate the
> 3 listed requirements against the new form?
>
> First off, the Java primitives are signed, so you're going to be limited
> by that. Don't forget that.
>
> Have you seen accumulo.composite.rowid from
> https://cwiki.apache.org/confluence/display/Hive/AccumuloIntegration.
> Hypothetically, you can provide some logic which will do custom parsing
> on your row and generate a struct from the components in your row ID.
>
> Of interest might be:
>
> https://github.com/apache/hive/blob/release-1.2.1/accumulo-handler/src/java/org/apache/hadoop/hive/accumulo/serde/AccumuloRowSerializer.java
>
> https://github.com/apache/hive/blob/release-1.2.1/accumulo-handler/src/test/org/apache/hadoop/hive/accumulo/serde/TestAccumuloRowSerializer.java
>
> You could extend the AccumuloRowSerializer to parse the bytes of the
> rowId according to your own spec. I haven't explicitly tried this
> myself, but in theory, I think your problems are meant to be solved by
> this support. It will take a little bit of effort. Hive's LazyObject
> type system is not my favorite framework to work with. Referencing some
> of the HBaseStorageHandler code might also be worthwhile (as the two are
> very similar).
>
> - Josh
>
> roman.drapeko@baesystems.com wrote:
>> Hi there,
>>
>> Our current rowid format is yyyyMMdd_payload_sha256(raw data). It works
>> nicely as we have a date and uniqueness guaranteed by hash, however
>> unfortunately, rowid is around 50-60 bytes per record.
>>
>> Requirements are the following:
>>
>> 1)Support Hive on top of Accumulo for ad-hoc queries
>>
>> 2)Query original table by date range (e.g rowID<  '20060101' AND rowID
>>   >= '20060103') both in code and hive
>>
>> 3)Additional queries by ~20 different fields
>>
>> Requirement 3) requires secondary indexes and of course because each
>> RowID is 50-60 bytes, they become super massive (99% of overall space)
>> and really expensive to store.
>>
>> What we are looking to do is to reduce index size to a fixed size:
>> {unixTime}{logicalSplit}{hash}, where unixTime is 4 bytes unsigned
>> integer, logicalSplit - 2 bytes unsigned integer, and hash is 4 bytes -
>> overall 10 bytes.
>>
>> What is unclear to me is how second requirement can be met in Hive as to
>> my understanding an in-built RowID push down mechanism won't work with
>> unsigned bytes?
>>
>> Regards,
>>
>> Roman
>>
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under the control of BAE Systems Applied Intelligence Limited, details of which can be found
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