Re: Creating Lucene index in Hadoop

[ctam <ct...@gmail.com>]

hi Ning , I am also looking at different approaches on indexing with hadoop ,
I could index using contrib package for hadoop into HDFS but since its not
designed for random access  what would be the other recommended ways to move
them to Local file system

Also what would be the best approach to begin with ? should we look into
katta or solr integrations ?

thanks in advance.


Ning Li-5 wrote:
> 
>> I'm missing why you would ever want the Lucene index in HDFS for
>> reading.
> 
> The Lucene indexes are written to HDFS, but that does not mean you
> conduct search on the indexes stored in HDFS directly. HDFS is not
> designed for random access. Usually the indexes are copied to the
> nodes where search will be served. With
> http://issues.apache.org/jira/browse/HADOOP-4801, however, it may
> become feasible to search on HDFS directly.
> 
> Cheers,
> Ning
> 
> 
> On Mon, Mar 16, 2009 at 4:52 PM, Ian Soboroff <ia...@nist.gov>
> wrote:
>>
>> Does anyone have stats on how multiple readers on an optimized Lucene
>> index in HDFS compares with a ParallelMultiReader (or whatever its
>> called) over RPC on a local filesystem?
>>
>> I'm missing why you would ever want the Lucene index in HDFS for
>> reading.
>>
>> Ian
>>
>> Ning Li <ni...@gmail.com> writes:
>>
>>> I should have pointed out that Nutch index build and contrib/index
>>> targets different applications. The latter is for applications who
>>> simply want to build Lucene index from a set of documents - e.g. no
>>> link analysis.
>>>
>>> As to writing Lucene indexes, both work the same way - write the final
>>> results to local file system and then copy to HDFS. In contrib/index,
>>> the intermediate results are in memory and not written to HDFS.
>>>
>>> Hope it clarifies things.
>>>
>>> Cheers,
>>> Ning
>>>
>>>
>>> On Mon, Mar 16, 2009 at 2:57 PM, Ian Soboroff <ia...@nist.gov>
>>> wrote:
>>>>
>>>> I understand why you would index in the reduce phase, because the
>>>> anchor
>>>> text gets shuffled to be next to the document.  However, when you index
>>>> in the map phase, don't you just have to reindex later?
>>>>
>>>> The main point to the OP is that HDFS is a bad FS for writing Lucene
>>>> indexes because of how Lucene works.  The simple approach is to write
>>>> your index outside of HDFS in the reduce phase, and then merge the
>>>> indexes from each reducer manually.
>>>>
>>>> Ian
>>>>
>>>> Ning Li <ni...@gmail.com> writes:
>>>>
>>>>> Or you can check out the index contrib. The difference of the two is
>>>>> that:
>>>>>   - In Nutch's indexing map/reduce job, indexes are built in the
>>>>> reduce phase. Afterwards, they are merged into smaller number of
>>>>> shards if necessary. The last time I checked, the merge process does
>>>>> not use map/reduce.
>>>>>   - In contrib/index, small indexes are built in the map phase. They
>>>>> are merged into the desired number of shards in the reduce phase. In
>>>>> addition, they can be merged into existing shards.
>>>>>
>>>>> Cheers,
>>>>> Ning
>>>>>
>>>>>
>>>>> On Fri, Mar 13, 2009 at 1:34 AM, 王红宝 <im...@126.com> wrote:
>>>>>> you can see the nutch code.
>>>>>>
>>>>>> 2009/3/13 Mark Kerzner <ma...@gmail.com>
>>>>>>
>>>>>>> Hi,
>>>>>>>
>>>>>>> How do I allow multiple nodes to write to the same index file in
>>>>>>> HDFS?
>>>>>>>
>>>>>>> Thank you,
>>>>>>> Mark
>>>>>>>
>>>>>>
>>>>
>>>>
>>
>>
> 
> 

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Re: Creating Lucene index in Hadoop

[Jason Venner <ja...@gmail.com>]

Check out katta, as it can pull indexes from hdfs and deploy them into your
search cluster.
Katta also handles index directories that have been packed into a zip file.
Katta can pull indexes from any file system that hadoop supports, hdfs, s3,
hftp, file etc.

We have been doing this with our solr (solr-1301) indexes and getting an 80%
reduction in size, which is a big gain for us.

I need to feed a 2 line change back into solr-1301 as the close method can
fail to heart beat while the optimize is happening, in some situations right
now.


On Tue, Oct 6, 2009 at 9:30 PM, ctam <ct...@gmail.com> wrote:

>
> hi Ning , I am also looking at different approaches on indexing with hadoop
> ,
> I could index using contrib package for hadoop into HDFS but since its not
> designed for random access  what would be the other recommended ways to
> move
> them to Local file system
>
> Also what would be the best approach to begin with ? should we look into
> katta or solr integrations ?
>
> thanks in advance.
>
>
> Ning Li-5 wrote:
> >
> >> I'm missing why you would ever want the Lucene index in HDFS for
> >> reading.
> >
> > The Lucene indexes are written to HDFS, but that does not mean you
> > conduct search on the indexes stored in HDFS directly. HDFS is not
> > designed for random access. Usually the indexes are copied to the
> > nodes where search will be served. With
> > http://issues.apache.org/jira/browse/HADOOP-4801, however, it may
> > become feasible to search on HDFS directly.
> >
> > Cheers,
> > Ning
> >
> >
> > On Mon, Mar 16, 2009 at 4:52 PM, Ian Soboroff <ia...@nist.gov>
> > wrote:
> >>
> >> Does anyone have stats on how multiple readers on an optimized Lucene
> >> index in HDFS compares with a ParallelMultiReader (or whatever its
> >> called) over RPC on a local filesystem?
> >>
> >> I'm missing why you would ever want the Lucene index in HDFS for
> >> reading.
> >>
> >> Ian
> >>
> >> Ning Li <ni...@gmail.com> writes:
> >>
> >>> I should have pointed out that Nutch index build and contrib/index
> >>> targets different applications. The latter is for applications who
> >>> simply want to build Lucene index from a set of documents - e.g. no
> >>> link analysis.
> >>>
> >>> As to writing Lucene indexes, both work the same way - write the final
> >>> results to local file system and then copy to HDFS. In contrib/index,
> >>> the intermediate results are in memory and not written to HDFS.
> >>>
> >>> Hope it clarifies things.
> >>>
> >>> Cheers,
> >>> Ning
> >>>
> >>>
> >>> On Mon, Mar 16, 2009 at 2:57 PM, Ian Soboroff <ia...@nist.gov>
> >>> wrote:
> >>>>
> >>>> I understand why you would index in the reduce phase, because the
> >>>> anchor
> >>>> text gets shuffled to be next to the document.  However, when you
> index
> >>>> in the map phase, don't you just have to reindex later?
> >>>>
> >>>> The main point to the OP is that HDFS is a bad FS for writing Lucene
> >>>> indexes because of how Lucene works.  The simple approach is to write
> >>>> your index outside of HDFS in the reduce phase, and then merge the
> >>>> indexes from each reducer manually.
> >>>>
> >>>> Ian
> >>>>
> >>>> Ning Li <ni...@gmail.com> writes:
> >>>>
> >>>>> Or you can check out the index contrib. The difference of the two is
> >>>>> that:
> >>>>>   - In Nutch's indexing map/reduce job, indexes are built in the
> >>>>> reduce phase. Afterwards, they are merged into smaller number of
> >>>>> shards if necessary. The last time I checked, the merge process does
> >>>>> not use map/reduce.
> >>>>>   - In contrib/index, small indexes are built in the map phase. They
> >>>>> are merged into the desired number of shards in the reduce phase. In
> >>>>> addition, they can be merged into existing shards.
> >>>>>
> >>>>> Cheers,
> >>>>> Ning
> >>>>>
> >>>>>
> >>>>> On Fri, Mar 13, 2009 at 1:34 AM, 王红宝 <im...@126.com> wrote:
> >>>>>> you can see the nutch code.
> >>>>>>
> >>>>>> 2009/3/13 Mark Kerzner <ma...@gmail.com>
> >>>>>>
> >>>>>>> Hi,
> >>>>>>>
> >>>>>>> How do I allow multiple nodes to write to the same index file in
> >>>>>>> HDFS?
> >>>>>>>
> >>>>>>> Thank you,
> >>>>>>> Mark
> >>>>>>>
> >>>>>>
> >>>>
> >>>>
> >>
> >>
> >
> >
>
> --
> View this message in context:
> http://www.nabble.com/Creating-Lucene-index-in-Hadoop-tp22490120p25780366.html
> Sent from the Hadoop core-user mailing list archive at Nabble.com.
>
>


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