And even if it always creates this range - can I somehow magically (maybe
through iterators etc) interpret it in a different way?
-----Original Message-----
From: Drapeko, Roman (UK Guildford)
Sent: 14 September 2015 21:39
To: Josh Elser; user@accumulo.apache.org
Cc: Drapeko, Roman (UK Guildford)
Subject: RE: RowID design and Hive push down
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.el...@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.drap...@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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