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HBase, mail # user - Re: Best technique for doing lookup with Secondary Index


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anil gupta 2012-10-26, 15:14
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anil gupta 2012-10-26, 16:43
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fding hbase 2012-10-26, 10:14
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Jerry Lam 2012-10-26, 14:29
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Ramkrishna.S.Vasudevan 2012-10-26, 14:33
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Re: Best technique for doing lookup with Secondary Index
anil gupta 2012-10-26, 06:46
>
> Now your main question is lookups right
> Now there are some more hooks in the scan flow called pre/postScannerOpen,
> pre/postScannerNext.
> May be you can try using them to do a look up on the secondary table and
> then use those values and pass it to the main table next().
>

In secondary index its hard to avoid at-least two RPC calls(1 from client
to table B and then from table B to Table A) whether you use coproc or not.
But, i believe using coproc is better than doing RPC calls from client
since it might be outside the subnet/network of cluster. In this case, the
RPC will be faster when we use coprocs. In my case the client is certainly
not in the same subnet or network zone. I need to provide results of query
in around 100 milliseconds or less so i need to be really frugal. Let me
know your views on this.

Have you implemented queries with Secondary indexes using coproc yet?
At present i have tried the client side query and i can get the results of
query in around 100 ms. I am enticed to try out the coproc implementation.

But this may involve more RPC calls as your regions of "A" and "B" may be in
> different RS.
>
AFAIK, RPC cannot be avoided even if Region A and Region B are on same RS
since these two regions are from different table. Am i right?
Thanks,
Anil Gupta

On Thu, Oct 25, 2012 at 9:20 PM, Ramkrishna.S.Vasudevan <
[EMAIL PROTECTED]> wrote:

> > Is it a
> > good idea to create Htable instance on "B" and do put in my mapper? I
> > might
> > try this idea.
> Yes you can do this..  May be the same mapper you can do a put for table
> "B".  This was how we have tried loading data to another table by using the
> main table "A"
> Puts.
>
> Now your main question is lookups right
> Now there are some more hooks in the scan flow called pre/postScannerOpen,
> pre/postScannerNext.
> May be you can try using them to do a look up on the secondary table and
> then use those values and pass it to the main table next().
> But this may involve more RPC calls as your regions of "A" and "B" may be
> in
> different RS.
>
> If something is wrong in my understanding of what you said, kindly spare
> me.
> :)
>
> Regards
> Ram
>
>
> > -----Original Message-----
> > From: anil gupta [mailto:[EMAIL PROTECTED]]
> > Sent: Friday, October 26, 2012 3:40 AM
> > To: [EMAIL PROTECTED]
> > Subject: Re: Best technique for doing lookup with Secondary Index
> >
> > Anoop:  In prePut hook u call HTable#put()?
> > Anil: Yes i call HTable#put() in prePut. Is there better way of doing
> > it?
> >
> > Anoop: Why use the network calls from server side here then?
> > Anil: I thought this is a cleaner approach since i am using BulkLoader.
> > I
> > decided not to run two jobs since i am generating a UniqueIdentifier at
> > runtime in bulkloader.
> >
> > Anoop: can not handle it from client alone?
> > Anil: I cannot handle it from client since i am using BulkLoader. Is it
> > a
> > good idea to create Htable instance on "B" and do put in my mapper? I
> > might
> > try this idea.
> >
> > Anoop: You can have a look at Lily project.
> > Anil: It's little late for us to evaluate Lily now and at present we
> > dont
> > need complex secondary index since our data is immutable.
> >
> > Ram: what is rowkey B here?
> > Anil: Suppose i am storing customer events in table A. I have two
> > requirement for data query:
> > 1. Query customer events on basis of customer_Id and event_ID.
> > 2. Query customer events on basis of event_timestamp and customer_ID.
> >
> > 70% of querying is done by query#1, so i will create
> > <customer_Id><event_ID> as row key of Table A.
> > Now, in order to support fast results for query#2, i need to create a
> > secondary index on A. I store that secondary index in B, rowkey of B is
> > <event_timestamp><customer_ID>  .Every row stores the corresponding
> > rowkey
> > of A.
> >
> > Ram:How is the startRow determined for every query?
> > Anil: Its determined by a very simple application logic.
> >
> > Thanks,
Thanks & Regards,
Anil Gupta
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Ramkrishna.S.Vasudevan 2012-10-26, 08:13
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anil gupta 2012-10-24, 21:40
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Anoop Sam John 2012-10-25, 04:44
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Ramkrishna.S.Vasudevan 2012-10-25, 05:16
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anil gupta 2012-10-25, 22:10
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Ramkrishna.S.Vasudevan 2012-10-26, 04:20
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Anoop Sam John 2012-10-26, 04:33
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Anoop Sam John 2012-10-26, 04:06
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anil gupta 2012-10-26, 04:44
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Doug Meil 2012-10-27, 00:35