The phrase is defensible, but that is the root of the problem. Take
for example a skateboard.
"A skateboard is like a bike because it has wheels and you ride on it."
That is true and defensively true. :) However with not much more text
you can accurately describe what it is, as opposed to something it is
"A skateboard is a thin piece of wood on top of four small wheels that
you stand on and ride"
The old sentence Cassandra statement was something to the effect of
"with the storage model of big table and the consistency model of
dynamo". This accurately described the system and gave reference to
specific known quantities (bigtable/dynamo) in which white papers
existed for further reading.
On Mon, Oct 3, 2016 at 6:24 AM, Benedict Elliott Smith
<bened...@apache.org <mailto:bened...@apache.org>> wrote:
While that sentence leaves a lot to be desired (for me because it
confers a different meaning on row store), it doesn't say
"Cassandra is like a RDBMS" - it says "like an RDBMS, it organises
data by rows and columns" - i.e., in this regard only it is like
an RDBMS, not more generally.
I believe it was meant to help people, especially those afraid of
the NoSQL thrift world, understand that it still uses the basic
concept of a rows and columns they are used to. I agree it could
be improved to minimise the chance of misreading it, and I'm
certain contributions would be welcome here.
I don't personally want to get bogged down in analysing every
piece of text anyone has ever written, so I'll bow out of further
discussion on this. These phrases may all be suboptimal, but they
are certainly defensible. Column store is not, that's all I
wanted to contribute here.
On 1 October 2016 at 19:35, Peter Lin <wool...@gmail.com
I'll second Ed's comment.
The documentation should be more careful when using phrases
"like relational databases". When we look at the history of
relational databases, people expect certain things like ACID
transactions, primary/foriegn key constraints, query planners,
joins and relational algebra. Clearly Cassandra's storage
engine does not follow most of those principals for a good reason.
The term row oriented storage would be more descriptive and
appropriate. It avoids conflating Cassandra storage engine
with "traditional" relational storage engines. Those of us
that have spent over a decade using IBM DB2, Oracle, Sql
Server and Sybase tend to think of relational databases in a
certain way. If we go back to 1998, most RDBMS storage engine
had a max row size limit. Databases like Sybase before version
9 preferred RAW disk for optimal performance. I can go on and
on, but there's no point really.
Cassandra's storage engine is "row oriented", but it's not
relational in RDBMS sense. We do everyone a huge disservice by
using confusing terminology and then making fun of those who
get confused. No one wins when that happens. At the end of the
day, what differentiates cassandra's storage engine is it
support static and dynamic columns, which traditional RDBMS
don't support today. Calling Cassandra storage "distributed
tables" doesn't really help in my bias opinion.
For example, if you tell a SqlServer or Oracle RAC admin
"cassandra uses distributed tables" they might answer "so
what, sql server and oracle can do that too." The difference
is with RDBMS the partitioning is optional and requires more
work to configure. Whereas with Cassandra you can have
everything in 1 node, which means there is only 1 partition
and no different to 1 instance of sql server. Where you win is
when you need to add 2 more nodes, Cassandra makes this easier
whereas with SqlServer and Oracle you have to do a little bit
more work. I've lost count of how many times I've to explained
noSql databases to RDBMS admins and had to explain the
official docs are stupid.
On Sat, Oct 1, 2016 at 11:31 AM, Edward Capriolo
<edlinuxg...@gmail.com <mailto:edlinuxg...@gmail.com>> wrote:
<http://wiki.apache.org/cassandra/DataModel> means that
like relational databases, Cassandra organizes data by
rows and columns. The Cassandra Query Language (CQL) is a
close relative of SQL.
I generally do not know what to say about these high level
"oversimplifications" like "firewalls block hackers". Are
there "firewalls" or do they mean IP routers with layer 4
packet inspections and layer 3 Access Control Lists?
We say (and I catch myself doing it all the time) "like
relational databases" often as if all relational databases
work alike. A columnar store like HP Vertica is a
relational database.MySql has different storage engines
does MyIsam work like InnoDB?
Google docs organizes data by rows and columns as well.
You can wrap any storage system into an API that makes
them look like rows and columns. Microsoft LINQ can
enumerate your network cars and query them
that really does not make your network cards a "row store"
"Theoretically a row can have 2 billion columns, but in
practice it shouldn't have more than 100 million columns."
In practice (In my experience) the number is much lower
than 100 million, and if the data actually is deleted and
readded frequently the number of live columns(rows,
whatever) you can use happily is even lower
I believe on twitter (I am unable to find the tweet)
someone was trying to convince me Cassandra was a
"columnar analytic database". ROFL
I believe telling someone it "row store" "like a
database", is not a good idea. They might away content
with that explanation. You are setting them up to walk
into an anti-pattern. Like a case where the user is
attempting to write and deleting 1 row and 1 column 6
billion times a day. Then you end up explaining to them
and how the cassandra storage model is not "like a
On Fri, Sep 30, 2016 at 9:22 PM, Edward Capriolo
<edlinuxg...@gmail.com <mailto:edlinuxg...@gmail.com>> wrote:
I can iterate over JSON data stored in mongo and
present it as a table with rows and columns. It does
not make mongo a rowstore.
On Fri, Sep 30, 2016 at 9:16 PM, Edward Capriolo
The problem with calling it a row store:
In the context of a relational database
a *row*—also called a record
single, implicitly structured data
<https://en.wikipedia.org/wiki/Data> item in a
In simple terms, a database table can be thought
of as consisting of /rows/ andcolumns
Each row in a table represents a set of related
data, and every row in the table has the same
When you have static columns and rows with maps,
and lists, it is hard to argue that every row has
the same structure. Physically at the storage
layer they do not have the same structure and
logically when accessing the data they barely have
the same structure, as the static column is just
appearing inside each row it is actually not
On Fri, Sep 30, 2016 at 4:47 PM, Jonathan Haddad
<j...@jonhaddad.com <mailto:j...@jonhaddad.com>> wrote:
+1000 to what Benedict says. I usually call it
a "partitioned row store" which usually needs
some extra explanation but is more accurate
than "column family" or whatever other thrift
era terminology people still use.
On Fri, Sep 30, 2016 at 1:53 PM DuyHai Doan
I used to present Cassandra as a NoSQL
datastore with "distributed" table. This
definition is closer to CQL and has some
academic background (distributed hash table).
On Fri, Sep 30, 2016 at 7:43 PM, Benedict
Elliott Smith <bened...@apache.org
Cassandra is not a "wide column store"
anymore. It has a schema. Only thrift
users no longer think they have a
schema (though they do), and thrift is
I really wish everyone would kill the
term "wide column store" with fire.
It seems to have never meant anything
beyond "schema-less, row-oriented",
and a "column store" means literally
the opposite of this.
Not only that, but people don't even
seem to realise the term "column
store" existed long before "wide
column store" and the latter is often
abbreviated to the former, as here:
Since it no longer applies, let's all
agree as a community to forget this
awful nomenclature ever existed.
On 30 September 2016 at 18:09, Joaquin
I can help clarify a few things.
As Carlos said, Cassandra is a
Wide Column Store. Theoretically a
row can have 2 billion columns,
but in practice it shouldn't have
more than 100 million columns.
Cassandra partitions data to
certain nodes based on the
partition key(s), but does provide
the option of setting zero or more
clustering keys. Together,
the partition key(s) and
clustering key(s) form the primary
When writing to Cassandra, you
will need to provide the full
primary key, however, when reading
from Cassandra, you only need to
provide the full partition key.
When you only provide the
partition key for a read
operation, you're able to return
all columns that exist on that
partition with low latency. These
columns are displayed as "CQL
rows" to make it easier to reason
Consider the schema:
CREATE TABLE foo (
PRIMARY KEY ((bar, boz), baz)
When you write to Cassandra you
will need to send bar, boz, and
baz and optionally data*, if it's
relevant for that CQL row. If you
chose not to define a data* field
for a particular CQL row, then
nothing is stored nor allocated on
disk. But I wouldn't consider that
caveat to be "schema-less".
However, all writes to the same
bar/boz will end up on the same
Cassandra replica set (a
configurable number of nodes) and
be stored on the same place(s) on
disk within the SSTable(s). And on
disk, each field that's not a
partition key is stored as a
column, including clustering keys
(this is optimized in Cassandra
3+, but now we're getting deep
In this way you can get fast
responses for all activity for
bar/boz either over time, or for a
specific time, with roughly the
same number of disk seeks, with
varying lengths on the disk scans.
Hope that helps!
Apache Cassandra Consulting
On Fri, Sep 30, 2016 at 11:40 AM,
Carlos Alonso <i...@mrcalonso.com
Cassandra is a Wide Column
Carlos Alonso | Software
Engineer | @calonso
On 30 September 2016 at 18:24,
I have a theoritical
- Is Apache Cassandra
really a column store?
Column store mean storing
the data as column rather
than as a rows.
In fact C* store the data
as row, and data is
partionned with row key.
Finally, for me, Cassandra
is a row oriented schema
less DBMS.... Is it true
for you also???
Many thanks in advance for
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