How am I supposed to bot a new Cassandra node when I get this error?

    INFO [SSTableBatchOpen:1] 2014-02-25 01:51:17,132 SSTableReader.java (line 223) Opening /var/lib/cassandra/data/system/local/system-local-jb-5 (5725 bytes)
    ERROR [main] 2014-02-25 01:51:17,377 CassandraDaemon.java (line 237) Fatal exception during initialization
    org.apache.cassandra.exceptions.ConfigurationException: Saved cluster name Test Cluster != configured name thisisstupid
            at org.apache.cassandra.db.SystemKeyspace.checkHealth(SystemKeyspace.java:542)
            at org.apache.cassandra.service.CassandraDaemon.setup(CassandraDaemon.java:233)
            at org.apache.cassandra.service.CassandraDaemon.activate(CassandraDaemon.java:462)
            at org.apache.cassandra.service.CassandraDaemon.main(CassandraDaemon.java:552)


Name of cluster in the cassandra.yaml file is:


    cluster_name: &#39;thisisstupid&#39;


How do I resolve?

cassandra - Saved cluster name Test Cluster != configured name

We know that it is easy to create auto increment IDs in SQL databases, is there a good solution for it in Cassandra? The IDs should be for key or column name.

How to create auto increment IDs in Cassandra

I&#39;m looking for a way to delete all of the rows from a given column family in cassandra.

This is the equivalent of `TRUNCATE TABLE` in SQL.

How do I delete all data in a Cassandra column family?

For Cassandra, do `UPDATE`s become an implied `INSERT` if the selected row does not exist? That is, if I say

     UPDATE users SET name = &quot;Raedwald&quot; WHERE id = 545127

and `id` is the `PRIMARY KEY` of the `users` table, and the table has no row with a key of 545127, will that be equivalent to 

     INSERT INTO users (id, name) VALUES (545127, &quot;Raedwald&quot;)

I know that the opposite is true: an `INSERT` for an `id` that already exists becomes an `UPDATE` of the row with that `id`. Older Cassandra documentation talked about inserts actually being &quot;upserts&quot; for that reason.

I&#39;m interested in the case for CQL3, Cassandra version 1.2+.

Does an UPDATE become an implied INSERT

Just learning cassandra, is there a way to insert a UUID using CQL, ie

    create table stuff (uid uuid primary key, name varchar);
    insert into stuff (name) values(&#39;my name&#39;); // fails
    insert into stuff (uid, name) values(1, &#39;my name&#39;); // fails

Can you do something like

    insert into stuff (uid, name) values(nextuid(), &#39;my name&#39;);

How to auto generate uuid in cassandra CQL 3 command line

Suppose I have a column family:

    CREATE TABLE update_audit (
      scopeid bigint,
      formid bigint,
      time timestamp,
      record_link_id bigint,
      ipaddress text,
      user_zuid bigint,
      value text,
      PRIMARY KEY ((scopeid, formid), time)
      ) WITH CLUSTERING ORDER BY (time DESC)

With two secondary indexes, where `record_link_id` is a high-cardinality column:

    CREATE INDEX update_audit_id_idx ON update_audit (record_link_id);
    
    CREATE INDEX update_audit_user_zuid_idx ON update_audit (user_zuid);

According to my knowledge Cassandra will create two hidden column families like so:

    CREATE TABLE update_audit_id_idx(
        record_link_id bigint,
        scopeid bigint,
        formid bigint,
        time timestamp
        PRIMARY KEY ((record_link_id), scopeid, formid, time)
    );

    CREATE TABLE update_audit_user_zuid_idx(
        user_zuid bigint,
        scopeid bigint,
        formid bigint,
        time timestamp
        PRIMARY KEY ((user_zuid), scopeid, formid, time)
    );

Cassandra secondary indexes are implemented as local indexes rather than being distributed like normal tables. Each node only stores an index for the data it stores.

Consider the following query:

    select * from update_audit where scopeid=35 and formid=78005 and record_link_id=9897;

 1. How will this query execute &#39;under the hood&#39; in Cassandra?
 2. How will a high-cardinality column index (`record_link_id`) affect its performance?
 3. Will Cassandra touch all nodes for the above query? *Why?*
 4. Which criteria will be executed first, base table partition_key or secondary index partition_key? How will Cassandra intersect these two results?


How do secondary indexes work in Cassandra?

Would like to populate some static test data via a CQLsh script.

This doesn&#39;t work:  (device_id is UUID)

    insert into devices (device_id, geohash,name, external_identifier, measures, tags) 
    values (&#39;c37d661d-7e61-49ea-96a5-68c34e83db3a&#39;,&#39;9q9p3yyrn1&#39;, &#39;Acme1&#39;, &#39;936&#39;, {&#39;aparPower&#39;,&#39;actPower&#39;,&#39;actEnergy&#39;},{&#39;make&#39;:&#39;Acme&#39;});

&gt; Bad Request: Invalid STRING constant
&gt; (c37d661d-7e61-49ea-96a5-68c34e83db3a) for device_id of type uuid

I can&#39;t seem to find any CQL function to convert to proper type.  Do I need to do this from a python script?

Thanks,
Chris

Inserting a hard-coded UUID via CQLsh (Cassandra)

There has been a lot of talk related to [Cassandra][1] lately.

Twitter, Digg, Facebook, etc all use it.

When does it make sense to:

 - use Cassandra,
 - not use Cassandra, and
 - use a RDMS instead of Cassandra.

  [1]: http://cassandra.apache.org/

When NOT to use Cassandra?

I am newbie in Cassandra and trying to implement one toy application using Cassandra. I had created one keyspace and few column families in my Cassandra DB but I forgot the name of my cluster.

I am trying to find if there is any query which can list down all the available keyspaces.

Anybody knows such a query or command?

How to list all the available keyspaces in Cassandra?

I am evaluating what might be the best migration option.

Currently, I am on a sharded MySQL (horizontal partition), with most of my data stored in JSON blobs. I do not have any complex SQL queries (already migrated away after since I partitioned my db).

Right now, it seems like both MongoDB and Cassandra would be likely options. My situation:

- Lots of reads in every query, less regular writes
- Not worried about &quot;massive&quot; scalability
- More concerned about simple setup, maintenance and code
- Minimize hardware/server cost



MongoDB vs. Cassandra

I scaffold an app using jhipster which is microservice gateway using cassandra db and using maven to build which was building fine after scaffold.i ran gulp command to for the live reload of ui.

i made a change slighlty in navbar and home page of it.
which was also working file &amp; made some changes in the json files of home &amp; navbar &amp; do some minor changes as adding the search box and other.

it failed to reload. I stop the gulp &amp; maven &amp; restarted them.
maven is building but again not loading the site in localhost 

when i ran gulp it is showing me this error.

     gulp
    fs.js:952
      return binding.readdir(pathModule._makeLong(path), options.encoding);
                     ^
    
    Error: ENOENT: no such file or directory, scandir &#39;/home/hartron/foodnetteam/codebase/mandi/node_modules/node-sass/vendor&#39;
        at Error (native)
        at Object.fs.readdirSync (fs.js:952:18)
        at Object.getInstalledBinaries (/home/hartron/foodnetteam/codebase/mandi/node_modules/node-sass/lib/extensions.js:121:13)
        at foundBinariesList (/home/hartron/foodnetteam/codebase/mandi/node_modules/node-sass/lib/errors.js:20:15)
        at foundBinaries (/home/hartron/foodnetteam/codebase/mandi/node_modules/node-sass/lib/errors.js:15:5)
        at Object.module.exports.missingBinary (/home/hartron/foodnetteam/codebase/mandi/node_modules/node-sass/lib/errors.js:45:5)
        at module.exports (/home/hartron/foodnetteam/codebase/mandi/node_modules/node-sass/lib/binding.js:15:30)
        at Object.&lt;anonymous&gt; (/home/hartron/foodnetteam/codebase/mandi/node_modules/node-sass/lib/index.js:14:35)
        at Module._compile (module.js:570:32)
        at Object.Module._extensions..js (module.js:579:10)


Could anyone tell me solution for this

Error: ENOENT: no such file or directory, scandir

What does going with a document based NoSQL option buy you over a KV store, and vice-versa?

What does &quot;Document-oriented&quot; vs. Key-Value mean when talking about MongoDB vs Cassandra?

In BigTable/GFS and Cassandra terminology, what is the definition of a SSTable?


What is an SSTable?

I have been reading articles around the net to understand the differences between the following `key` types. But it just seems hard for me to grasp. Examples will definitely help  make understanding better.

    primary key,
    partition key, 
    composite key 
    clustering key

Difference between partition key, composite key and clustering key in Cassandra?

I am learning NoSQL and looking at different options for one of my client&#39;s requirements.  I have gone through various resources before putting up this question (a person with little knowledge in NoSQL)

 - I need to store data at faster rate and read data. 
 - Fully fail-safe and easily scalable.
 - Able to search through data for Analytics.

I ended up with a short list of: `Cassandra and Elasticsearch`

What I do understand is Cassandra is a perfect NoSQL storage solution for me, as I can write data and read data using indexes.  Where it fails or it could fail is on Analytics. In the future, if I want to get data from `from_date to to_date`, or more ways to get data for analytics, if I don&#39;t design the Data model properly or keeping long term sight, which might be quite hard in ever changing world.

While `Elastic Search` is best at indexing (backed by Lucene), and can search the data randomly by throwing some random text. But does it work the same for even if I want to retrieve data `from_date to to_date` (I expect it might be). But the real question is, is it a Search Engine, or perfect NoSQL data storage like Cassandra? If yes, why do we still need Cassandra?

If both of these are in different world, please explain that! How do we combine them to get a more effective solution?

Elasticsearch vs Cassandra vs Elasticsearch with Cassandra

I know there are three different, popular types of non-sql databases.

- Key/Value: Redis, Tokyo Cabinet, Memcached
- ColumnFamily: Cassandra, HBase
- Document: MongoDB, CouchDB

I have read long blogs about it without understanding so much.

I know relational databases and get the hang around document-based databases like MongoDB/CouchDB.

Could someone tell me what the major differences are between these and the 2 former on the list?

Difference between Document-based and Key/Value-based databases?

When experimenting with Cassandra I&#39;ve observed that Cassandra listens to the following ports:

* TCP *:8080
* TCP *:8888
* TCP *:57311
* TCP *:57312
* TCP 127.0.0.1:7000
* TCP 127.0.0.1:9160
* UDP 127.0.0.1:700

How does Cassandra use each of the ports listed?

Cassandra port usage - how are the ports used?

The three types of NoSQL databases I&#39;ve read about is key-value, column-oriented, and document-oriented.

Key-value is pretty straight forward - a key with a plain value.

I&#39;ve seen document-oriented databases described as like key-value, but the value can be a structure, like a JSON object. Each &quot;document&quot; can have all, some, or none of the same keys as another.

Column oriented seems to be very much like document oriented in that you don&#39;t specify a structure.

So what is the difference between these two, and why would you use one over the other?

I&#39;ve specifically looked at MongoDB and Cassandra. I basically need a dynamic structure that can change, but not affect other values. At the same time I need to be able to search/filter specific keys and run reports. With CAP, AP is the most important to me. The data can &quot;eventually&quot; be synced across nodes, just as long as there is no conflict or loss of data. Each user would get their own &quot;table&quot;.



How does column-oriented NoSQL differ from document-oriented?

Is there a command to all the rows present in a cql table in cassandra like the one in sql?
    
    delete from TABLE

Going by the documentation, I don&#39;t find any way to perform delete operation without a where condition.

    DELETE col1 FROM SomeTable WHERE userID = &#39;some_key_value&#39;; 

Deleting all rows from Cassandra cql table

I am nearly landed at Cassandra after my research on large scale data storage solutions. But its generally said that Hbase is better solution for large scale data processing and analysis. 

While both are same key/value storage and both are/can run (Cassandra recently) Hadoop layer then what makes Hadoop a better candidate when processing/analysis is required on large data.

I also found good details about both at
http://ria101.wordpress.com/2010/02/24/hbase-vs-cassandra-why-we-moved/ 

but I&#39;m still looking for concrete advantages of Hbase.

While I am more convinced about Cassandra because its simplicity for adding nodes and seamless replication and no point of failure features. And it also keeps secondary index feature so its a good plus.

Large scale data processing Hbase vs Cassandra

[Merkle Trees][1] are used as an anti-entropy mechanism in several distributed, replicated key/value stores:

* [Dynamo][2]
* [Riak][3]
* [Cassandra][4]

No doubt an anti-entropy mechanism is A Good Thing - transient failures just happen, in production.
I&#39;m just not sure I understand why Merkle _Trees_ are the popular approach.

* Sending a complete Merkle tree to a peer involves sending the local key-space to that peer, along with
  hashes of each key value, stored in the lowest levels of the tree.

* Diffing a Merkle tree sent from a peer requires having a Merkle tree of your own.

Since both peers must already have a sorted key / value-hash space on hand, why not do a linear merge to detect discrepancies?

I&#39;m just not convinced that the tree structure provides any kind of savings when you factor in upkeep costs, and the fact
that _linear passes over the tree leaves are already being done just to serialize the representation over the wire_.

To ground this out, a straw-man alternative might be to have nodes exchange arrays of hash digests,
which are incrementally updated and bucketed by modulo ring-position.

What am I missing?

  [1]: http://en.wikipedia.org/wiki/Hash_tree
  [2]: http://www.allthingsdistributed.com/files/amazon-dynamo-sosp2007.pdf
  [3]: http://doc.erlagner.org/riak_core/merkerl.html
  [4]: http://wiki.apache.org/cassandra/AntiEntropy


Explain Merkle Trees for use in Eventual Consistency

I&#39;m looking at both projects and I can&#39;t really see the difference

from Cassandra Site:
--------------------

&gt; Cassandra is a highly scalable, eventually consistent, distributed, structured key-value store...Cassandra is eventually consistent. Like BigTable, Cassandra provides a ColumnFamily-based data model richer than typical key/value systems.

from CouchDB Site:
------------------

&gt; Apache CouchDB is a distributed, fault-tolerant and schema-free document-oriented database accessible via a RESTful HTTP/JSON API. 


That said, I see the specific differences between each project as: access methods, written languages, etc. but to put AN EXAMPLE, when you talk about [SOLR][1] or [Sphinx][2] you know both are indexers with big differences but at the end are indexers.

Can I say here that Cassandra and CouchDB are non-relational databases that in some cases one can replace the other?


  [1]: http://lucene.apache.org/solr/
  [2]: http://sphinxsearch.com/

What is the difference between Cassandra and CouchDB?

We&#39;re developing a really big project and I was wondering if anyone can give me some advice about what DB backend should we pick.

Our system is compound by 1100 electronic devices that send a signal to a central server and then the server stores the signal info (the signal is about 35 bytes long). How ever these devices will be sending about 3 signals per minute each, so if we do de numbers, that&#39;ll be 4.752.000 new records/day on the database, and a total of 142.560.000 new records/month.

We need a DB Backend that is lighting fast and reliable. Of course we need to do some complex data mining on that DB. We&#39;re doing some research on the MongoDB/Cassandra/Redis/CouchDB, however the documentation websites are still on early stages.

Any help? Ideas?

Thanks a lot!

What should I choose: MongoDB/Cassandra/Redis/CouchDB?

Reading several papers and documents on internet, I found many contradictory information about the Cassandra data model. There are many which identify it as a column oriented database, other as a row-oriented and then who define it as a hybrid way of both.

According to what I know about how Cassandra stores file, it uses the *-Index.db  file to access at the right position of the *-Data.db file where it is stored the bloom filter, column index and then the columns of the required row.

In my opinion, this is strictly row-oriented. Is there something I&#39;m missing?

Why many refer to Cassandra as a Column oriented database?

Does anyone know the difference between the two CQL data types `text` and `varchar` in Cassandra? The Cassandra documentation describes both types as &quot;UTF-8 encoded string&quot; and nothing more.

Cassandra: text vs varchar

I&#39;m looking for some gui client for cassandra (like sqlDeveloper) to invoke some basic methods, and run cql queries

what is the recommend cassandra gui client for cassandra-1.1.2

I need to run a shell script file using nodeJS that executes a set of Cassandra DB commands. Can anybody please help me on this.

**inside db.sh file:** 

    create keyspace dummy with   replication = {&#39;class&#39;:&#39;SimpleStrategy&#39;,&#39;replication_factor&#39;:3}
    
    create table dummy (userhandle text, email text primary key , name text,profilepic)

How to run shell script file using nodejs?

I want to clarify very basic concept of replication factor and consistency level in Cassandra. Highly appreciate if someone can provide answer to below questions.

RF- Replication Factor
RC- Read Consistency
WC- Write Consistency

2 cassandra nodes (Ex: A, B) RF=1, RC=ONE, WC=ONE or ANY  

 - can I write data to node A and read from node B ?  
 - what will happen if A goes down ?

3 cassandra nodes (Ex: A, B, C) RF=2, RC=QUORUM, WC=QUORUM

 - can I write data to node A and read from node C ? 
 - what will happen if node A goes down ?

3 cassandra nodes (Ex: A, B, C) RF=3, RC=QUORUM, WC=QUORUM

 - can I write data to node A and read from node C ?  
 - what will happen if node A goes down ?

Understand cassandra replication factor versus consistency level

And what are the pitfalls to avoid? Are there any deal breaks for you? E.g., I&#39;ve heard that exporting/importing the Cassandra data is very difficult, making me wonder if that&#39;s going to hinder syncing production data to development environment.

BTW, it&#39;s very hard to find good tutorials on Cassandra, the only one I have http://arin.me/code/wtf-is-a-supercolumn-cassandra-data-model is still pretty basic.

Thanks.

What&#39;s The Best Practice In Designing A Cassandra Data Model?

I am trying to insert into my CQL table from the command line. I am able to insert everything. But I am wondering if I have a timestamp column, then how can I insert into timestamp column from the command line? Basically, I want to insert current timestamp whenever I am inserting into my CQL table - 

Currently, I am hardcoding the timestamp whenever I am inserting into my below CQL table -

    CREATE TABLE TEST (ID TEXT, NAME TEXT, VALUE TEXT, LAST_MODIFIED_DATE TIMESTAMP, PRIMARY KEY (ID));
    
    INSERT INTO TEST (ID, NAME, VALUE, LAST_MODIFIED_DATE) VALUES (&#39;1&#39;, &#39;elephant&#39;,  &#39;SOME_VALUE&#39;, 1382655211694);
    
Is there any way to get the current timestamp using some predefined functions in CQL so that while inserting into above table, I can use that method to get the current timestamp and then insert into above table?

How to get current timestamp with CQL while using Command Line?

The problem that I am having is that I want to run the following command (and I can&#39;t):

    cqlsh &lt; cql_directory/cql_create_stuff.cql

Because I have not logged in to cqlsh.

So I logged in:

    cqlsh -u &#39;my_username&#39; -p &#39;my_super_secret_password&#39;

and now I tried doing the command in cqlsh shell but It just responds with a syntax error.

**Basically, how do I login into cqlsh and run an external CQL script in my file system?** 

How to run cql files (.cql) from within cqlsh?

There are many tables in cassandra database, which contain column titled user_id. The values user_id are referred to user stored in table users. As some users are deleted, I would like to delete orphan records in all tables that contain column titled user_id.

Is there a way to list all tables using CassandraSQLContext or any other built-in method or custom procedure in order to avoid explicitly defining the list of tables?



How to list all cassandra tables

I&#39;ve just started working with Cassandra (datastax), version 2.1.3 and cqlsh version 5.0.1.

Cassandra starts up fine and the cluster is operational instantly.

Cqlsh is not working (on any of the nodes) and emits the following error:

&gt;Connection error: (&#39;Unable to connect to any servers&#39;, {&#39;127.0.0.1&#39;: error(111,
&quot;Tried connecting to [(&#39;127.0.0.1&#39;, 9042)]. Last error: Connection refused&quot;)})

I have tried starting cqlsh up with the hosts own ip, other hosts ip, different ports yet the result remains the same - always connection refused.

Cassandra cqlsh - connection refused

I&#39;m working on a real-time advertising platform with a heavy emphasis on performance. I&#39;ve always developed with MySQL, but I&#39;m open to trying something new like MongoDB or Cassandra if significant speed gains can be achieved. I&#39;ve been reading about both all day, but since both are being rapidly developed, a lot of the information appears somewhat dated.

The main data stored would be entries for each click, incremented rows for views, and information for each campaign (just some basic settings, etc). The speed gains need to be found in inserting clicks, updating view totals, and generating real-time statistic reports. The platform is developed with PHP.

Or maybe none of these?

MongoDB vs. Cassandra vs. MySQL for real-time advertising platform

For a bit of background - this question deals with a project running on a single small EC2 instance, and is about to migrate to a medium one. The main components are Django, MySQL and a large number of custom analysis tools written in python and java, which do the heavy
lifting. The same machine is running Apache as well.

The data model looks like the following - a large amount of real time data comes in streamed from various networked sensors, and ideally, I&#39;d like to establish a long-poll approach rather than the current poll every 15 minutes approach (a limitation of computing stats and writing into the database itself). Once the data comes in, I store the raw version in
MySQL, let the analysis tools loose on this data, and store statistics in another few tables. All of this is rendered using Django.

Relational features I would need -

 - Order by *[SliceRange in Cassandra&#39;s API seems to satisy this]*
 - Group by
 - Manytomany relations between multiple tables *[Cassandra SuperColumns seem to do well for one to many]*
 - Sphinx on this gives me a nice full text engine, so thats a necessity too. *[On Cassandra, the Lucandra project seems to satisfy this need]*

My major problem is that data reads are extremely slow (and writes aren&#39;t that hot either). I don&#39;t want to throw a lot of money and hardware on it right now, and I&#39;d prefer something that can scale easily with time. Vertically scaling MySQL is not trivial in that sense (or cheap).

So essentially, after having read a lot about NOSQL and experimented with things like MongoDB, Cassandra and Voldemort, my questions are,

- On a medium EC2 instance, ***would I gain any benefits in reads/writes by shifting to something like Cassandra***? [This article][1] (pdf) definitely seems to suggest that. Currently, I&#39;d say a few hundred writes per minute would be the norm. For reads - since the data changes every 5 minutes or so, cache invalidation has to happen pretty quickly. At some point, it should be able to handle a large number of concurrent users as well. The app performance currently gets killed on MySQL doing some joins on large tables even if indexes are created - something to the order of 32k rows takes more than a minute to render. (This may be an artifact of EC2 virtualized I/O as well). Size of tables is around 4-5 million rows, and there are about 5 such tables.

- Everyone talks about using Cassandra on multiple nodes, given the CAP theorem and eventual consistency. But, for a project that is just beginning to grow, ***does it make sense
to deploy a one node cassandra server***? Are there any caveats? For instance, can it replace MySQL as a backend for Django? [Is this recommended?]

- If I do shift, I&#39;m guessing I&#39;ll have to rewrite parts of the app to do a lot more &quot;administrivia&quot; since I&#39;d have to do multiple lookups to fetch rows.

- ***Would it make any sense to just use MySQL as a key value store*** rather than a relational engine, and go with that? That way I could utilize a large number of stable APIs available, as well as a stable engine (and go relational as needed). (Brett Taylor&#39;s post from Friendfeed on this - http://bret.appspot.com/entry/how-friendfeed-uses-mysql)

Any insights from people who&#39;ve done a shift would be greatly appreciated!

Thanks.

  [1]: http://static.last.fm/johan/nosql-20090611/cassandra_nosql.pdf

Switching from MySQL to Cassandra - Pros/Cons?

I&#39;m currently experimenting around with Cassandra. 

On the client-side (with Hector) I look up a few keys like this:

    ColumnFamilyResult&lt;String, String&gt; result = template.queryColumns(Arrays.asList(&quot;key1&quot;,&quot;key2&quot;,&quot;key3&quot;));

Most of the time it seems to work. But other times I get a timeout exception on the client:

	Caused by: me.prettyprint.hector.api.exceptions.HTimedOutException: TimedOutException()
		at me.prettyprint.cassandra.service.ExceptionsTranslatorImpl.translate(ExceptionsTranslatorImpl.java:35)
		at me.prettyprint.cassandra.service.template.ThriftColumnFamilyTemplate$1.execute(ThriftColumnFamilyTemplate.java:100)
		at me.prettyprint.cassandra.service.template.ThriftColumnFamilyTemplate$1.execute(ThriftColumnFamilyTemplate.java:88)
		at me.prettyprint.cassandra.service.Operation.executeAndSetResult(Operation.java:103)
		at me.prettyprint.cassandra.connection.HConnectionManager.operateWithFailover(HConnectionManager.java:258)
		at me.prettyprint.cassandra.model.ExecutingKeyspace.doExecuteOperation(ExecutingKeyspace.java:97)
		at me.prettyprint.cassandra.service.template.ThriftColumnFamilyTemplate.sliceInternal(ThriftColumnFamilyTemplate.java:88)
		at me.prettyprint.cassandra.service.template.ThriftColumnFamilyTemplate.doExecuteSlice(ThriftColumnFamilyTemplate.java:46)
		at me.prettyprint.cassandra.service.template.ColumnFamilyTemplate.queryColumns(ColumnFamilyTemplate.java:113)
		at info.gamlor.experiments.Cassandra.readObjectByKey(ComplexCassandra.java:255)

	Caused by: TimedOutException()
		at org.apache.cassandra.thrift.Cassandra$get_slice_result.read(Cassandra.java:7772)
		at org.apache.cassandra.thrift.Cassandra$Client.recv_get_slice(Cassandra.java:570)
		at org.apache.cassandra.thrift.Cassandra$Client.get_slice(Cassandra.java:542)
		at me.prettyprint.cassandra.service.template.ThriftColumnFamilyTemplate$1.execute(ThriftColumnFamilyTemplate.java:95)

And on the server this exception shows up:

	ERROR 11:33:55,312 Exception in thread Thread[ReadStage:91,5,main]
	java.lang.AssertionError: DecoratedKey(4948402862350542345439897754126541659, 6932) != DecoratedKey(132475956107784875457507977471906551877, 726f6f74) in C:\tem
	p\cassandra\lib\cassandra\data\CassandraPolepos\ComplexObjects\CassandraPolepos-ComplexObjects-hd-2-Data.db
			at org.apache.cassandra.db.columniterator.SSTableSliceIterator.&lt;init&gt;(SSTableSliceIterator.java:58)
			at org.apache.cassandra.db.filter.SliceQueryFilter.getSSTableColumnIterator(SliceQueryFilter.java:66)
			at org.apache.cassandra.db.filter.QueryFilter.getSSTableColumnIterator(QueryFilter.java:78)
			at org.apache.cassandra.db.CollationController.collectAllData(CollationController.java:256)
			at org.apache.cassandra.db.CollationController.getTopLevelColumns(CollationController.java:63)
			at org.apache.cassandra.db.ColumnFamilyStore.getTopLevelColumns(ColumnFamilyStore.java:1331)
			at org.apache.cassandra.db.ColumnFamilyStore.getColumnFamily(ColumnFamilyStore.java:1193)
			at org.apache.cassandra.db.ColumnFamilyStore.getColumnFamily(ColumnFamilyStore.java:1128)
			at org.apache.cassandra.db.Table.getRow(Table.java:378)
			at org.apache.cassandra.db.SliceFromReadCommand.getRow(SliceFromReadCommand.java:69)
			at org.apache.cassandra.service.StorageProxy$LocalReadRunnable.runMayThrow(StorageProxy.java:816)
			at org.apache.cassandra.service.StorageProxy$DroppableRunnable.run(StorageProxy.java:1250)
			at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
			at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
			at java.lang.Thread.run(Thread.java:722)


Sometimes the key-values in the DecoratedKey(...) part takes up pages.


Anyone a hint what I&#39;m doing wrong. Or how to investigate this issue. 

Thanks.

Cassandra server throws java.lang.AssertionError: DecoratedKey(...) != DecoratedKey

I&#39;m new in cassandra, and I have to export the result of a specific query to a csv file.

I found the `COPY` command, but (from what I understand) it allows you only to copy an already existing table to a csv file, and what I want is to copy directly the stdout of my query to the csv file. is there any way to do it with `COPY` command or with another way ?

My command is style (`select column1, column2 from table where condition = xy`) and I&#39;m using `cqlsh`.

Export cassandra query result to a csv file

Given that TimeUUID handily allows you to use `now()` in CQL, are there any reasons you wouldn&#39;t just go ahead and always use TimeUUID instead of plain old UUID?

Cassandra UUID vs TimeUUID benefits and disadvantages

This is a super basic question but it&#39;s actually been bugging me for days. Is there a good way to obtain the equivalent of a `COUNT(*)` of a given table in Cassandra? 

I will be moving several hundreds of millions of rows into C* for some load testing and I&#39;d like to at least get a row count on some sample ETL jobs before I move massive amounts of data over the network.

The best idea I have is to basically loop over each row with Python and auto increment a counter. Is there a better way to determine (or even estimate) the row size of a C* table? I&#39;ve also poked around Datastax Ops Center to see if I can determine the row size there. If you can, I don&#39;t see how it&#39;s possible.

Anyone else needed to get a `count(*)` of a table in C*? If so, how&#39;d you go about doing it? 

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