Re: Splitting up an HBase Table into partitions
On Mar 18, 2015, at 1:52 AM, Gokul Balakrishnan royal...@gmail.com wrote:
@Sean this was exactly what I was looking for. Based on the region
boundaries, I should be able to create virtual groups of rows which can
then be retrieved from the table (e.g. through a scan) on demand.
Huh?
You don’t need to do this.
Its already done for you by the existing APIs.
A scan will allow you to do either a full table scan (no range limits provided)
or a range scan where you provide the boundaries.
So if you’re using a client connection to HBase, its done for you.
If you’re writing a M/R job, you are already getting one mapper task assigned
per region. So your parallelism is already done for you.
Its possible that the Input Format is smart enough to pre-check the regions to
see if they are within the boundaries or not and if not, no mapper task is
generated.
HTH
-Mike
Thanks everyone for your help.
On 18 March 2015 at 00:57, Sean Busbey bus...@cloudera.com wrote:
You should ask for a RegionLocator if you want to know the boundaries of
all the regions in a table
final Connection connection = ConnectionFactory.createConnection(config);
try {
final RegionLocator locator =
connection.getRegionLocator(TableName.valueOf(myTable));
final Pairbyte[][], byte[][] startEndKeys = locator.getStartEndKeys();
final byte[][] startKeys = startEndKeys.getFirst();
final byte[][] endKeys = startEndKeys.getSecond();
for (int i=0; i startKeys.length i endKeys.length; i++) {
System.out.println(Region + i + starts at ' +
Bytes.toStringBinary(startKeys[i]) +
' and ends at ' + Bytes.toStringBinary(endKeys[i]));
}
} finally {
connection.close();
}
There are other methods in RegionLocator if you need other details.
On Tue, Mar 17, 2015 at 2:09 PM, Gokul Balakrishnan royal...@gmail.com
wrote:
Hi Michael,
Thanks for the reply. Yes, I do realise that HBase has regions, perhaps
my
usage of the term partitions was misleading. What I'm looking for is
exactly what you've mentioned - a means of creating splits based on
regions, without having to iterate over all rows in the table through the
client API. Do you have any idea how I might achieve this?
Thanks,
On Tuesday, March 17, 2015, Michael Segel michael_se...@hotmail.com
wrote:
Hbase doesn't have partitions. It has regions.
The split occurs against the regions so that if you have n regions, you
have n splits.
Please don't confuse partitions and regions because they are not the
same
or synonymous.
On Mar 17, 2015, at 7:30 AM, Gokul Balakrishnan royal...@gmail.com
javascript:; wrote:
Hi,
My requirement is to partition an HBase Table and return a group of
records
(i.e. rows having a specific format) without having to iterate over
all
of
its rows. These partitions (which should ideally be along regions)
will
eventually be sent to Spark but rather than use the HBase or Hadoop
RDDs
directly, I'll be using a custom RDD which recognizes partitions as
the
aforementioned group of records.
I was looking at achieving this through creating InputSplits through
TableInputFormat.getSplits(), as being done in the HBase RDD [1] but
I
can't figure out a way to do this without having access to the mapred
context etc.
Would greatly appreciate if someone could point me in the right
direction.
[1]
https://github.com/tmalaska/SparkOnHBase/blob/master/src/main/scala/com/cloudera/spark/hbase/HBaseScanRDD.scala
Thanks,
Gokul
The opinions expressed here are mine, while they may reflect a
cognitive
thought, that is purely accidental.
Use at your own risk.
Michael Segel
michael_segel (AT) hotmail.com
--
Sean
The opinions expressed here are mine, while they may reflect a cognitive
thought, that is purely accidental.
Use at your own risk.
Michael Segel
michael_segel (AT) hotmail.com
Re: Splitting up an HBase Table into partitions
@Mikhail I wanted to split the table into groups of rows, but did not want
to initialize a scan and go over all rows and group them into batches in
the client code. In other words, I'm looking for a way to divide the rows
in the table and merely maintain the boundary information of each division
rather than actually populate them at the time of creation.
@Shahab yes, the row key ranges for the splits are not known in advance,
which was why I was looking at retrieving the region information of the
table and create the groupings that way.
@Sean this was exactly what I was looking for. Based on the region
boundaries, I should be able to create virtual groups of rows which can
then be retrieved from the table (e.g. through a scan) on demand.
Thanks everyone for your help.
On 18 March 2015 at 00:57, Sean Busbey bus...@cloudera.com wrote:
You should ask for a RegionLocator if you want to know the boundaries of
all the regions in a table
final Connection connection = ConnectionFactory.createConnection(config);
try {
final RegionLocator locator =
connection.getRegionLocator(TableName.valueOf(myTable));
final Pairbyte[][], byte[][] startEndKeys = locator.getStartEndKeys();
final byte[][] startKeys = startEndKeys.getFirst();
final byte[][] endKeys = startEndKeys.getSecond();
for (int i=0; i startKeys.length i endKeys.length; i++) {
System.out.println(Region + i + starts at ' +
Bytes.toStringBinary(startKeys[i]) +
' and ends at ' + Bytes.toStringBinary(endKeys[i]));
}
} finally {
connection.close();
}
There are other methods in RegionLocator if you need other details.
On Tue, Mar 17, 2015 at 2:09 PM, Gokul Balakrishnan royal...@gmail.com
wrote:
Hi Michael,
Thanks for the reply. Yes, I do realise that HBase has regions, perhaps
my
usage of the term partitions was misleading. What I'm looking for is
exactly what you've mentioned - a means of creating splits based on
regions, without having to iterate over all rows in the table through the
client API. Do you have any idea how I might achieve this?
Thanks,
On Tuesday, March 17, 2015, Michael Segel michael_se...@hotmail.com
wrote:
Hbase doesn't have partitions. It has regions.
The split occurs against the regions so that if you have n regions, you
have n splits.
Please don't confuse partitions and regions because they are not the
same
or synonymous.
On Mar 17, 2015, at 7:30 AM, Gokul Balakrishnan royal...@gmail.com
javascript:; wrote:
Hi,
My requirement is to partition an HBase Table and return a group of
records
(i.e. rows having a specific format) without having to iterate over
all
of
its rows. These partitions (which should ideally be along regions)
will
eventually be sent to Spark but rather than use the HBase or Hadoop
RDDs
directly, I'll be using a custom RDD which recognizes partitions as
the
aforementioned group of records.
I was looking at achieving this through creating InputSplits through
TableInputFormat.getSplits(), as being done in the HBase RDD [1] but
I
can't figure out a way to do this without having access to the mapred
context etc.
Would greatly appreciate if someone could point me in the right
direction.
[1]
https://github.com/tmalaska/SparkOnHBase/blob/master/src/main/scala/com/cloudera/spark/hbase/HBaseScanRDD.scala
Thanks,
Gokul
The opinions expressed here are mine, while they may reflect a
cognitive
thought, that is purely accidental.
Use at your own risk.
Michael Segel
michael_segel (AT) hotmail.com
--
Sean
Re: Splitting up an HBase Table into partitions
If you know the row key range of your data, then you can create splits points yourself and then use HBase api to actually make the splits. E.g. If you know that your row key (and it is a very contrived example) has a range of A - Z then you can decide on split points as every 5 th letter as your split points and then use HBaseAdmin.split method to do the split for you. This way you don't have to iterate of your data. Or are you saying that you don't have the row key range? Regards, Shahab On Tue, Mar 17, 2015 at 3:12 PM, Mikhail Antonov olorinb...@gmail.com wrote: Not sure what do you mean by a means of creating splits based on regions, without having to iterate over all rows in the table through the client API.. Could you elaborate? -Mikhail On Tue, Mar 17, 2015 at 12:09 PM, Gokul Balakrishnan royal...@gmail.com wrote: Hi Michael, Thanks for the reply. Yes, I do realise that HBase has regions, perhaps my usage of the term partitions was misleading. What I'm looking for is exactly what you've mentioned - a means of creating splits based on regions, without having to iterate over all rows in the table through the client API. Do you have any idea how I might achieve this? Thanks, On Tuesday, March 17, 2015, Michael Segel michael_se...@hotmail.com wrote: Hbase doesn't have partitions. It has regions. The split occurs against the regions so that if you have n regions, you have n splits. Please don't confuse partitions and regions because they are not the same or synonymous. On Mar 17, 2015, at 7:30 AM, Gokul Balakrishnan royal...@gmail.com javascript:; wrote: Hi, My requirement is to partition an HBase Table and return a group of records (i.e. rows having a specific format) without having to iterate over all of its rows. These partitions (which should ideally be along regions) will eventually be sent to Spark but rather than use the HBase or Hadoop RDDs directly, I'll be using a custom RDD which recognizes partitions as the aforementioned group of records. I was looking at achieving this through creating InputSplits through TableInputFormat.getSplits(), as being done in the HBase RDD [1] but I can't figure out a way to do this without having access to the mapred context etc. Would greatly appreciate if someone could point me in the right direction. [1] https://github.com/tmalaska/SparkOnHBase/blob/master/src/main/scala/com/cloudera/spark/hbase/HBaseScanRDD.scala Thanks, Gokul The opinions expressed here are mine, while they may reflect a cognitive thought, that is purely accidental. Use at your own risk. Michael Segel michael_segel (AT) hotmail.com -- Thanks, Michael Antonov
Re: Splitting up an HBase Table into partitions
If you don't want to use the getSplits method, you're welcome to pull the relevant code out into your own RDD. The RegionLocator object is public API, and the code is trivial if you're not interested in normalizing the split points as the MR job does. On Tue, Mar 17, 2015 at 12:12 PM, Mikhail Antonov olorinb...@gmail.com wrote: Not sure what do you mean by a means of creating splits based on regions, without having to iterate over all rows in the table through the client API.. Could you elaborate? -Mikhail On Tue, Mar 17, 2015 at 12:09 PM, Gokul Balakrishnan royal...@gmail.com wrote: Hi Michael, Thanks for the reply. Yes, I do realise that HBase has regions, perhaps my usage of the term partitions was misleading. What I'm looking for is exactly what you've mentioned - a means of creating splits based on regions, without having to iterate over all rows in the table through the client API. Do you have any idea how I might achieve this? Thanks, On Tuesday, March 17, 2015, Michael Segel michael_se...@hotmail.com wrote: Hbase doesn't have partitions. It has regions. The split occurs against the regions so that if you have n regions, you have n splits. Please don't confuse partitions and regions because they are not the same or synonymous. On Mar 17, 2015, at 7:30 AM, Gokul Balakrishnan royal...@gmail.com javascript:; wrote: Hi, My requirement is to partition an HBase Table and return a group of records (i.e. rows having a specific format) without having to iterate over all of its rows. These partitions (which should ideally be along regions) will eventually be sent to Spark but rather than use the HBase or Hadoop RDDs directly, I'll be using a custom RDD which recognizes partitions as the aforementioned group of records. I was looking at achieving this through creating InputSplits through TableInputFormat.getSplits(), as being done in the HBase RDD [1] but I can't figure out a way to do this without having access to the mapred context etc. Would greatly appreciate if someone could point me in the right direction. [1] https://github.com/tmalaska/SparkOnHBase/blob/master/src/main/scala/com/cloudera/spark/hbase/HBaseScanRDD.scala Thanks, Gokul The opinions expressed here are mine, while they may reflect a cognitive thought, that is purely accidental. Use at your own risk. Michael Segel michael_segel (AT) hotmail.com -- Thanks, Michael Antonov
Splitting up an HBase Table into partitions
Hi, My requirement is to partition an HBase Table and return a group of records (i.e. rows having a specific format) without having to iterate over all of its rows. These partitions (which should ideally be along regions) will eventually be sent to Spark but rather than use the HBase or Hadoop RDDs directly, I'll be using a custom RDD which recognizes partitions as the aforementioned group of records. I was looking at achieving this through creating InputSplits through TableInputFormat.getSplits(), as being done in the HBase RDD [1] but I can't figure out a way to do this without having access to the mapred context etc. Would greatly appreciate if someone could point me in the right direction. [1] https://github.com/tmalaska/SparkOnHBase/blob/master/src/main/scala/com/cloudera/spark/hbase/HBaseScanRDD.scala Thanks, Gokul
