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 >
