Hi,

I have a table with details:
hbase(main):024:0> scan 'test'
ROW                                                                  COLUMN+CELL                                                                                                                                                                                              
 row1                                                                column=cf:a, timestamp=1339581548508, value=value1                                                                                                                                                      
 row2                                                                column=cf:b, timestamp=1339581557585, value=value2                                                                                                                                                      
 row3                                                                column=cf:c, timestamp=1339581566227, value=value3                                                                                                                                                      
3 row(s) in 0.0200 seconds

When my MR job tries to access TableRecordReader
org.apache.hadoop.hbase.client.HTable.ClientScanner.nextScanner set the "value" to null for every call which gives a sense to my MR application that there are no records in the table.

I am using: 0.92.1 HBase and 0.23.1 Hadoop…..

What can be the possible reason(s) behind it??

Cheers,
Subroto Sanyal

Hi Subroto,

How are you configuring your job? Are you providing any Scan options? Check
Chapter 7 of the ref guide at

http://hbase.apache.org/book/mapreduce.example.html

Best Regards,
Sonal
Crux: Reporting for HBase <https://github.com/sonalgoyal/crux>
Nube Technologies <http://www.nubetech.co>

<http://in.linkedin.com/in/sonalgoyal>

On Wed, Jun 13, 2012 at 4:47 PM, Subroto <[EMAIL PROTECTED]> wrote:

> Hi,
>
> I have a table with details:
> hbase(main):024:0> scan 'test'
> ROW
>  COLUMN+CELL
>  row1
>  column=cf:a, timestamp=1339581548508, value=value1
>  row2
>  column=cf:b, timestamp=1339581557585, value=value2
>  row3
>  column=cf:c, timestamp=1339581566227, value=value3
> 3 row(s) in 0.0200 seconds
>
> When my MR job tries to access TableRecordReader
> org.apache.hadoop.hbase.client.HTable.ClientScanner.nextScanner set the
> "value" to null for every call which gives a sense to my MR application
> that there are no records in the table.
>
> I am using: 0.92.1 HBase and 0.23.1 Hadoop…..
>
> What can be the possible reason(s) behind it??
>
> Cheers,
> Subroto Sanyal

Hi Sonal,

The Scan is being created by:
void org.apache.hadoop.hbase.mapreduce.TableInputFormat.setConf(Configuration configuration)
I am not providing any other scan options…. :-(

Cheers,
Subroto Sanyal

On Jun 13, 2012, at 1:30 PM, Sonal Goyal wrote:

> Hi Subroto,
>
> How are you configuring your job? Are you providing any Scan options? Check
> Chapter 7 of the ref guide at
>
> http://hbase.apache.org/book/mapreduce.example.html
>
> Best Regards,
> Sonal
> Crux: Reporting for HBase <https://github.com/sonalgoyal/crux>
> Nube Technologies <http://www.nubetech.co>
>
> <http://in.linkedin.com/in/sonalgoyal>
>
>
>
>
>
> On Wed, Jun 13, 2012 at 4:47 PM, Subroto <[EMAIL PROTECTED]> wrote:
>
>> Hi,
>>
>> I have a table with details:
>> hbase(main):024:0> scan 'test'
>> ROW
>> COLUMN+CELL
>> row1
>> column=cf:a, timestamp=1339581548508, value=value1
>> row2
>> column=cf:b, timestamp=1339581557585, value=value2
>> row3
>> column=cf:c, timestamp=1339581566227, value=value3
>> 3 row(s) in 0.0200 seconds
>>
>> When my MR job tries to access TableRecordReader
>> org.apache.hadoop.hbase.client.HTable.ClientScanner.nextScanner set the
>> "value" to null for every call which gives a sense to my MR application
>> that there are no records in the table.
>>
>> I am using: 0.92.1 HBase and 0.23.1 Hadoop…..
>>
>> What can be the possible reason(s) behind it??
>>
>> Cheers,
>> Subroto Sanyal

Are you doing something specific with the RecordReader? Maybe you can post
more of your code as it is difficult to tell anything right now.

Best Regards,
Sonal
Crux: Reporting for HBase <https://github.com/sonalgoyal/crux>
Nube Technologies <http://www.nubetech.co>

<http://in.linkedin.com/in/sonalgoyal>

On Wed, Jun 13, 2012 at 7:28 PM, Subroto <[EMAIL PROTECTED]> wrote:

> Hi Sonal,
>
> The Scan is being created by:
> void
> org.apache.hadoop.hbase.mapreduce.TableInputFormat.setConf(Configuration
> configuration)
> I am not providing any other scan options…. :-(
>
> Cheers,
> Subroto Sanyal
>
> On Jun 13, 2012, at 1:30 PM, Sonal Goyal wrote:
>
> > Hi Subroto,
> >
> > How are you configuring your job? Are you providing any Scan options?
> Check
> > Chapter 7 of the ref guide at
> >
> > http://hbase.apache.org/book/mapreduce.example.html
> >
> > Best Regards,
> > Sonal
> > Crux: Reporting for HBase <https://github.com/sonalgoyal/crux>
> > Nube Technologies <http://www.nubetech.co>
> >
> > <http://in.linkedin.com/in/sonalgoyal>
> >
> >
> >
> >
> >
> > On Wed, Jun 13, 2012 at 4:47 PM, Subroto <[EMAIL PROTECTED]> wrote:
> >
> >> Hi,
> >>
> >> I have a table with details:
> >> hbase(main):024:0> scan 'test'
> >> ROW
> >> COLUMN+CELL
> >> row1
> >> column=cf:a, timestamp=1339581548508, value=value1
> >> row2
> >> column=cf:b, timestamp=1339581557585, value=value2
> >> row3
> >> column=cf:c, timestamp=1339581566227, value=value3
> >> 3 row(s) in 0.0200 seconds
> >>
> >> When my MR job tries to access TableRecordReader
> >> org.apache.hadoop.hbase.client.HTable.ClientScanner.nextScanner set the
> >> "value" to null for every call which gives a sense to my MR application
> >> that there are no records in the table.
> >>
> >> I am using: 0.92.1 HBase and 0.23.1 Hadoop…..
> >>
> >> What can be the possible reason(s) behind it??
> >>
> >> Cheers,
> >> Subroto Sanyal
>
>

Hi Sonal,

Thanks for your suggestion… I checked my code and found out that I was doing something like this:
for (String column : columns) {
scan.addColumn(Bytes.toBytes(column), Bytes.toBytes(""))
}

The same scan object was being set in the configuration. After removing this piece of code, the MR Job worked fine.

One more doubt:
Scan.addColumn takes two argument:
public Scan addColumn(byte[] family,
                      byte[] qualifier)
The first one is the column name in bytes. What should be passed as second argument if I want the qualifier to be ignored(I mean to include any qualifier)???
My HBase table looks like this:
ROW                                                                  COLUMN+CELL                                                                                                                                                                                              
 row1                                                                column=cf:a, timestamp=1339581548508, value=value1                                                                                                                                                      
 row2                                                                column=cf:b, timestamp=1339581557585, value=value2                                                                                                                                                      
 row3                                                                column=cf:c, timestamp=1339581566227, value=value3  

Thanks again for the correct pointers…. :-)

Cheers,
Subroto Sanyal
On Jun 14, 2012, at 9:07 AM, Sonal Goyal wrote:

> Are you doing something specific with the RecordReader? Maybe you can post
> more of your code as it is difficult to tell anything right now.
>
> Best Regards,
> Sonal
> Crux: Reporting for HBase <https://github.com/sonalgoyal/crux>
> Nube Technologies <http://www.nubetech.co>
>
> <http://in.linkedin.com/in/sonalgoyal>
>
>
>
>
>
> On Wed, Jun 13, 2012 at 7:28 PM, Subroto <[EMAIL PROTECTED]> wrote:
>
>> Hi Sonal,
>>
>> The Scan is being created by:
>> void
>> org.apache.hadoop.hbase.mapreduce.TableInputFormat.setConf(Configuration
>> configuration)
>> I am not providing any other scan options…. :-(
>>
>> Cheers,
>> Subroto Sanyal
>>
>> On Jun 13, 2012, at 1:30 PM, Sonal Goyal wrote:
>>
>>> Hi Subroto,
>>>
>>> How are you configuring your job? Are you providing any Scan options?
>> Check
>>> Chapter 7 of the ref guide at
>>>
>>> http://hbase.apache.org/book/mapreduce.example.html
>>>
>>> Best Regards,
>>> Sonal
>>> Crux: Reporting for HBase <https://github.com/sonalgoyal/crux>
>>> Nube Technologies <http://www.nubetech.co>
>>>
>>> <http://in.linkedin.com/in/sonalgoyal>
>>>
>>>
>>>
>>>
>>>
>>> On Wed, Jun 13, 2012 at 4:47 PM, Subroto <[EMAIL PROTECTED]> wrote:
>>>
>>>> Hi,
>>>>
>>>> I have a table with details:
>>>> hbase(main):024:0> scan 'test'
>>>> ROW
>>>> COLUMN+CELL
>>>> row1
>>>> column=cf:a, timestamp=1339581548508, value=value1
>>>> row2
>>>> column=cf:b, timestamp=1339581557585, value=value2
>>>> row3
>>>> column=cf:c, timestamp=1339581566227, value=value3
>>>> 3 row(s) in 0.0200 seconds
>>>>
>>>> When my MR job tries to access TableRecordReader
>>>> org.apache.hadoop.hbase.client.HTable.ClientScanner.nextScanner set the
>>>> "value" to null for every call which gives a sense to my MR application
>>>> that there are no records in the table.
>>>>
>>>> I am using: 0.92.1 HBase and 0.23.1 Hadoop…..
>>>>
>>>> What can be the possible reason(s) behind it??
>>>>
>>>> Cheers,
>>>> Subroto Sanyal
>>
>>

Hi Subroto
          Scan.addColumn you can use when u want only specific columns to be retrieved in the sacn . U can read the javadoc in addColumn() and addFamily() methods and then it will be clear.
scan.addColumn(Bytes.toBytes(column), Bytes.toBytes(""))
As you do this empty qualifier name is getting added in the family list which needs to be retrieved.

So if you want to retrieve whole data avoid addColumn and addFamily.
If want want specific CFs to be retrieved go with addFamily
Within a CF u want specific qualifier only then only go for addColumn

-Anoop-
________________________________________
From: Subroto [[EMAIL PROTECTED]]
Sent: Thursday, June 14, 2012 1:35 PM
To: [EMAIL PROTECTED]
Subject: Re: TableRecordReaderImpl is not able to get the rows

Hi Sonal,

Thanks for your suggestion… I checked my code and found out that I was doing something like this:
for (String column : columns) {
        scan.addColumn(Bytes.toBytes(column), Bytes.toBytes(""))
}

The same scan object was being set in the configuration. After removing this piece of code, the MR Job worked fine.

One more doubt:
Scan.addColumn takes two argument:
public Scan addColumn(byte[] family,
                      byte[] qualifier)
The first one is the column name in bytes. What should be passed as second argument if I want the qualifier to be ignored(I mean to include any qualifier)???
My HBase table looks like this:
ROW                                                                  COLUMN+CELL
 row1                                                                column=cf:a, timestamp=1339581548508, value=value1
 row2                                                                column=cf:b, timestamp=1339581557585, value=value2
 row3                                                                column=cf:c, timestamp=1339581566227, value=value3

Thanks again for the correct pointers…. :-)

Cheers,
Subroto Sanyal
On Jun 14, 2012, at 9:07 AM, Sonal Goyal wrote:

> Are you doing something specific with the RecordReader? Maybe you can post
> more of your code as it is difficult to tell anything right now.
>
> Best Regards,
> Sonal
> Crux: Reporting for HBase <https://github.com/sonalgoyal/crux>
> Nube Technologies <http://www.nubetech.co>
>
> <http://in.linkedin.com/in/sonalgoyal>
>
>
>
>
>
> On Wed, Jun 13, 2012 at 7:28 PM, Subroto <[EMAIL PROTECTED]> wrote:
>
>> Hi Sonal,
>>
>> The Scan is being created by:
>> void
>> org.apache.hadoop.hbase.mapreduce.TableInputFormat.setConf(Configuration
>> configuration)
>> I am not providing any other scan options…. :-(
>>
>> Cheers,
>> Subroto Sanyal
>>
>> On Jun 13, 2012, at 1:30 PM, Sonal Goyal wrote:
>>
>>> Hi Subroto,
>>>
>>> How are you configuring your job? Are you providing any Scan options?
>> Check
>>> Chapter 7 of the ref guide at
>>>
>>> http://hbase.apache.org/book/mapreduce.example.html
>>>
>>> Best Regards,
>>> Sonal
>>> Crux: Reporting for HBase <https://github.com/sonalgoyal/crux>
>>> Nube Technologies <http://www.nubetech.co>
>>>
>>> <http://in.linkedin.com/in/sonalgoyal>
>>>
>>>
>>>
>>>
>>>
>>> On Wed, Jun 13, 2012 at 4:47 PM, Subroto <[EMAIL PROTECTED]> wrote:
>>>
>>>> Hi,
>>>>
>>>> I have a table with details:
>>>> hbase(main):024:0> scan 'test'
>>>> ROW
>>>> COLUMN+CELL
>>>> row1
>>>> column=cf:a, timestamp=1339581548508, value=value1
>>>> row2
>>>> column=cf:b, timestamp=1339581557585, value=value2
>>>> row3
>>>> column=cf:c, timestamp=1339581566227, value=value3
>>>> 3 row(s) in 0.0200 seconds
>>>>
>>>> When my MR job tries to access TableRecordReader
>>>> org.apache.hadoop.hbase.client.HTable.ClientScanner.nextScanner set the
>>>> "value" to null for every call which gives a sense to my MR application
>>>> that there are no records in the table.
>>>>
>>>> I am using: 0.92.1 HBase and 0.23.1 Hadoop…..
>>>>
>>>> What can be the possible reason(s) behind it??
>>>>
>>>> Cheers,
>>>> Subroto Sanyal
>>
>>

Hi Anoop,

Thanks a lot for the explanation.
Need to go through the documentation properly…. ;-)

Cheers,
Subroto Sanyal

On Jun 14, 2012, at 10:15 AM, Anoop Sam John wrote:

> Hi Subroto
>          Scan.addColumn you can use when u want only specific columns to be retrieved in the sacn . U can read the javadoc in addColumn() and addFamily() methods and then it will be clear.
> scan.addColumn(Bytes.toBytes(column), Bytes.toBytes(""))
> As you do this empty qualifier name is getting added in the family list which needs to be retrieved.
>
> So if you want to retrieve whole data avoid addColumn and addFamily.
> If want want specific CFs to be retrieved go with addFamily
> Within a CF u want specific qualifier only then only go for addColumn
>
> -Anoop-
> ________________________________________
> From: Subroto [[EMAIL PROTECTED]]
> Sent: Thursday, June 14, 2012 1:35 PM
> To: [EMAIL PROTECTED]
> Subject: Re: TableRecordReaderImpl is not able to get the rows
>
> Hi Sonal,
>
> Thanks for your suggestion… I checked my code and found out that I was doing something like this:
> for (String column : columns) {
>        scan.addColumn(Bytes.toBytes(column), Bytes.toBytes(""))
> }
>
> The same scan object was being set in the configuration. After removing this piece of code, the MR Job worked fine.
>
> One more doubt:
> Scan.addColumn takes two argument:
> public Scan addColumn(byte[] family,
>                      byte[] qualifier)
> The first one is the column name in bytes. What should be passed as second argument if I want the qualifier to be ignored(I mean to include any qualifier)???
> My HBase table looks like this:
> ROW                                                                  COLUMN+CELL
> row1                                                                column=cf:a, timestamp=1339581548508, value=value1
> row2                                                                column=cf:b, timestamp=1339581557585, value=value2
> row3                                                                column=cf:c, timestamp=1339581566227, value=value3
>
> Thanks again for the correct pointers…. :-)
>
> Cheers,
> Subroto Sanyal
> On Jun 14, 2012, at 9:07 AM, Sonal Goyal wrote:
>
>> Are you doing something specific with the RecordReader? Maybe you can post
>> more of your code as it is difficult to tell anything right now.
>>
>> Best Regards,
>> Sonal
>> Crux: Reporting for HBase <https://github.com/sonalgoyal/crux>
>> Nube Technologies <http://www.nubetech.co>
>>
>> <http://in.linkedin.com/in/sonalgoyal>
>>
>>
>>
>>
>>
>> On Wed, Jun 13, 2012 at 7:28 PM, Subroto <[EMAIL PROTECTED]> wrote:
>>
>>> Hi Sonal,
>>>
>>> The Scan is being created by:
>>> void
>>> org.apache.hadoop.hbase.mapreduce.TableInputFormat.setConf(Configuration
>>> configuration)
>>> I am not providing any other scan options…. :-(
>>>
>>> Cheers,
>>> Subroto Sanyal
>>>
>>> On Jun 13, 2012, at 1:30 PM, Sonal Goyal wrote:
>>>
>>>> Hi Subroto,
>>>>
>>>> How are you configuring your job? Are you providing any Scan options?
>>> Check
>>>> Chapter 7 of the ref guide at
>>>>
>>>> http://hbase.apache.org/book/mapreduce.example.html
>>>>
>>>> Best Regards,
>>>> Sonal
>>>> Crux: Reporting for HBase <https://github.com/sonalgoyal/crux>
>>>> Nube Technologies <http://www.nubetech.co>
>>>>
>>>> <http://in.linkedin.com/in/sonalgoyal>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> On Wed, Jun 13, 2012 at 4:47 PM, Subroto <[EMAIL PROTECTED]> wrote:
>>>>
>>>>> Hi,
>>>>>
>>>>> I have a table with details:
>>>>> hbase(main):024:0> scan 'test'
>>>>> ROW
>>>>> COLUMN+CELL
>>>>> row1
>>>>> column=cf:a, timestamp=1339581548508, value=value1
>>>>> row2
>>>>> column=cf:b, timestamp=1339581557585, value=value2
>>>>> row3
>>>>> column=cf:c, timestamp=1339581566227, value=value3
>>>>> 3 row(s) in 0.0200 seconds
>>>>>
>>>>> When my MR job tries to access TableRecordReader
>>>>> org.apache.hadoop.hbase.client.HTable.ClientScanner.nextScanner set the
>>>>> "value" to null for every call which gives a sense to my MR application