Re: Data migration from Oracle to Cassandra

[Chidambaran Subramanian]

More curious than answering the question. Would it be possible to even
design something generic here? Would it not depend on the schema?

On Thu, Nov 17, 2016 at 8:21 PM, Shashidhar Rao 
wrote:

> Hi,
>
> Has anyone done data migration from Oracle to Cassandra taking care of
> Change data capture.
>
> Kindly share the experience about the tools used. Golden Gate, IBM CDC or
> any tools.
>
> Recommendation of any Open Source tools would be highly useful. I need to
> constantly capture the commits from Oracle to Cassandra.
>
>
> Regards
> shashi
>

Re: Buggy JRE error

[Chidambaran Subramanian]

I got this error today.
INFO 11:16:08,067 Enqueuing flush of Memtable-LocationInfo@8820986(41/51
serialized/live bytes, 1 ops)
 INFO 11:16:08,068 Writing Memtable-LocationInfo@8820986(41/51
serialized/live bytes, 1 ops)
ERROR 11:16:08,077 Exception in thread Thread[COMMIT-LOG-ALLOCATOR,5,main]
java.io.IOError: java.io.IOException: Map failed
at
org.apache.cassandra.db.commitlog.CommitLogSegment.init(CommitLogSegment.java:127)
at
org.apache.cassandra.db.commitlog.CommitLogAllocator$3.run(CommitLogAllocator.java:203)
at
org.apache.cassandra.db.commitlog.CommitLogAllocator$1.runMayThrow(CommitLogAllocator.java:95)
at org.apache.cassandra.utils.WrappedRunnable.run(WrappedRunnable.java:30)
at java.lang.Thread.run(Thread.java:679)
Caused by: java.io.IOException: Map failed
at sun.nio.ch.FileChannelImpl.map(FileChannelImpl.java:803)
at
org.apache.cassandra.db.commitlog.CommitLogSegment.init(CommitLogSegment.java:119)
... 4 more
Caused by: java.lang.OutOfMemoryError: Map failed
at sun.nio.ch.FileChannelImpl.map0(Native Method)
at sun.nio.ch.FileChannelImpl.map(FileChannelImpl.java:800)
... 5 more
ERROR 11:16:08,082 Exception in thread
Thread[StorageServiceShutdownHook,5,main]
java.lang.NullPointerException
at org.apache.cassandra.gms.Gossiper.stop(Gossiper.java:1132)
at
org.apache.cassandra.service.StorageService$2.runMayThrow(StorageService.java:489)
at org.apache.cassandra.utils.WrappedRunnable.run(WrappedRunnable.java:30)
at java.lang.Thread.run(Thread.java:679)


Are the two issues related?

On Mon, May 27, 2013 at 1:50 PM, Kais Ahmed k...@neteck-fr.com wrote:

 Hi chiddu,

 You have to configure your operating system to use the Oracle JRE instead
 of OpenJDK.

 http://www.datastax.com/docs/1.0/install/install_jre



 2013/5/27 S Chidambaran chi...@gmail.com

 I get these errors frequently as Cassandra starts up. I'm using the
 official Java distribution from Ubuntu.


 WARN 08:11:48,145 MemoryMeter uninitialized (jamm not specified as java
 agent); assuming liveRatio of 10.0.  Usually this means cassandra-env.sh
 disabled jamm because you are using a buggy JRE; upgrade to the Sun JRE
 instead



 java version 1.6.0_27
 OpenJDK Runtime Environment (IcedTea6 1.12.5)
 (6b27-1.12.5-0ubuntu0.12.04.1)
 OpenJDK Server VM (build 20.0-b12, mixed mode)


 Any idea on how to fix this?

 Regards
 Chiddu

Exporting all data within a keyspace

[Chidambaran Subramanian]

Is there any easy way of exporting all data for a keyspace (and conversely)
importing it.

Regards
Chiddu

Re: Exporting all data within a keyspace

[Chidambaran Subramanian]

Thanks guys,both are good pointers

Regards
Chiddu

On Tue, Apr 30, 2013 at 7:09 PM, Brian O'Neill b...@alumni.brown.eduwrote:


 You could always do something like this as well:

 http://brianoneill.blogspot.com/2012/05/dumping-data-from-cassandra-like.html

 -brian

 ---

 Brian O'Neill

 Lead Architect, Software Development

 *Health Market Science*

 *The Science of Better Results*

 2700 Horizon Drive • King of Prussia, PA • 19406

 M: 215.588.6024 • @boneill42 http://www.twitter.com/boneill42  •

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 From: Kumar Ranjan winnerd...@gmail.com
 Reply-To: user@cassandra.apache.org
 Date: Tuesday, April 30, 2013 9:11 AM
 To: user@cassandra.apache.org user@cassandra.apache.org
 Subject: Re: Exporting all data within a keyspace

 Try sstable2json and json2sstable. But it works on column family so you
 can fetch all column family and iterate over list of CF and use
 sstable2json tool to extract data. Remember this will only fetch on disk
 data do anything in memtable/cache which is to be flushed will be missed.
 So run compaction and then run the written script.

 On Tuesday, April 30, 2013, Chidambaran Subramanian wrote:

 Is there any easy way of exporting all data for a keyspace (and
 conversely) importing it.

 Regards
 Chiddu

Re: Blob vs. normal columns (internals) difference?

[Chidambaran Subramanian]

On Thu, Apr 4, 2013 at 6:58 AM, aaron morton aa...@thelastpickle.comwrote:

  1. Is size getting bigger in either one in storing one Tweet?
 If you store the data in one blob then we only store one column name and
 the blob. If they are in different cols then we store the column names and
 their values.

  2. Has either choice have impact on read/write performance on large
 scale?
 If you store data in a blob you can only read and update it as a blob, so
 chances are you will be wasting effort as you do read-modify-write
 operations. Unless you have a good reason split things up and store them as
 columns.

 If its mostly read only data that can be cached outside Cassandra, storing
it in one column looks like a good idea to me. What is the downside, anyway?



 cheers

 -
 Aaron Morton
 Freelance Cassandra Consultant
 New Zealand

 @aaronmorton
 http://www.thelastpickle.com

 On 3/04/2013, at 1:08 PM, Alan Ristić alan.ris...@gmail.com wrote:

  Hi guys,
 
  Here is example (fictional) model I have for learning purposes...
 
  I'm currently storing the User object in a Tweet as blob value. So
 taking JSON of 'User' and storing it as blob. I'm wondering why is this
 better vs. just prefixing and flattening column names?
 
  Tweet {
   id uuid,
   user blob
  }
 
  vs.
 
  Tweet {
   id uuid,
   user_id uuid,
   user_name text,
   
  }
 
  In one or other
 
  1. Is size getting bigger in either one in storing one Tweet?
  2. Has either choice have impact on read/write performance on large
 scale?
  3. Anything else I should be considering here? Your view/thinking would
 be great.
 
  Here is my understanding:
  For 'ease' of update if for example user changes its name I'm aware I
 need to (re)write whole object in all Tweets in first blob example and
 only user_name column in second 'flattened' example. Which brings me that
 If I'd wanted to actually do this updating/rewriting for every Tweet I'd
 use second 'flattened' example since payload of only user_name is smaller
 than whole User blob for every Tweet right?
 
  Nothing urgent, any input is valuable, tnx guys :)
 
 
 
  Hvala in lp,
  Alan Ristić
 
  w: personal blog
   t: @alanristic
   l: linkedin.com/alanristic
  m: ​068 15 73 88​

Reading a counter column value

[Chidambaran Subramanian]

I created a CounterColumnType column family .

create column family counter1 with
 default_validation_class=CounterColumnType and replicate_on_write=true;

Unfortunately I could not figure out a way to read the column value. I am
using the Thrift API , and I couldn't make out any sense. I can't use
anything else right now, since I have a bunch of stuff already written
using Thrift. Any help is really appreciated.

Regards
Chiddu