To keep the terminology clear, your “row_key” is actually the “partition key”,
and “wide_row_column” is actually a “clustering column”, and the combination of
your row_key and wide_row_column is a “compound primary key”.
-- Jack Krupansky
From: Aaron Morton
Sent: Tuesday, May 20, 2014 3:06 AM
To: Cassandra User
Subject: Re: CQL 3 and wide rows
In a CQL 3 table the only **column** names are the ones defined in the table,
in the example below there are three column names.
CREATE TABLE keyspace.widerow (
row_key text,
wide_row_column text,
data_column text,
PRIMARY KEY (row_key, wide_row_column));
Check out, for example,
http://www.datastax.com/dev/blog/schema-in-cassandra-1-1.
Internally there may be more **cells** ( as we now call the internal columns).
In the example above each value for row_key will create a single partition (as
we now call internal storage engine rows). In each of those partitions there
will be cells for each CQL 3 row that has the same row_key, those cells will
use a Composite for the name. The first part of the composite will be the value
of the wide_row_column and the second will be the literal name of the non
primary key columns.
IMHO Wide partitions (storage engine rows) are more prevalent in CQL3 than
thrift models.
But still - I do not see Iteration, so it looks to me that CQL 3 is limited
when compared to CLI/Hector.
Now days you can do pretty much everything you can in cli. Provide an example
and we may be able to help.
Cheers
Aaron
-----------------
Aaron Morton
New Zealand
@aaronmorton
Co-Founder & Principal Consultant
Apache Cassandra Consulting
http://www.thelastpickle.com
On 20/05/2014, at 8:18 am, Maciej Miklas <mac.mik...@gmail.com> wrote:
Hi James,
Clustering is based on rows. I think that you meant not clustering columns,
but compound columns. Still all columns belong to single table and are stored
within single folder on one computer. And it looks to me (but I’am not sure)
that CQL 3 driver loads all column names into memory - which is confusing to
me. From one side we have wide row, but we load whole into ram…..
My understanding of wide row is a row that supports millions of columns, or
similar things like map or set. In CLI you would generate column names (or use
compound columns) to simulate set or map, in CQL 3 you would use some static
names plus Map or Set structures, or you could still alter table and have large
number of columns. But still - I do not see Iteration, so it looks to me that
CQL 3 is limited when compared to CLI/Hector.
Regards,
Maciej
On 19 May 2014, at 17:30, James Campbell <ja...@breachintelligence.com> wrote:
Maciej,
In CQL3 "wide rows" are expected to be created using clustering columns.
So while the schema will have a relatively smaller number of named columns, the
effect is a wide row. For example:
CREATE TABLE keyspace.widerow (
row_key text,
wide_row_column text,
data_column text,
PRIMARY KEY (row_key, wide_row_column));
Check out, for example,
http://www.datastax.com/dev/blog/schema-in-cassandra-1-1.
James
----------------------------------------------------------------------------
From: Maciej Miklas <mac.mik...@gmail.com>
Sent: Monday, May 19, 2014 11:20 AM
To: user@cassandra.apache.org
Subject: CQL 3 and wide rows
Hi *,
I’ve checked DataStax driver code for CQL 3, and it looks like the column
names for particular table are fully loaded into memory, it this true?
Cassandra should support wide rows, meaning tables with millions of
columns. Knowing that, I would expect kind of iterator for column names. Am I
missing something here?
Regards,
Maciej Miklas
