It sounds like you want this:
create table data ( pk int, colname blob, value blob, primary key (pk,
colname));
that gives you arbitrary columns (cleverly labeled colname) in a single row,
where the value is "value".
If you don't want the overhead of storing "colname" in every row, try with
compact storage.
Does this solve the problem, or am I missing something?
On Aug 30, 2013, at 11:45 AM, Peter Lin <wool...@gmail.com> wrote:
>
> you could dynamically create new tables at runtime and insert rows into the
> new table, but is that better than using thrift and putting it into a regular
> dynamic column with the exact name type and value type?
>
> that would mean if there's 20 dynamic columns of different types, you'd have
> to execute 21 queries to rebuild the data. That's basically the same as using
> EVA tables in relational databases.
>
> Having used that approach in the past to build temporal databases, it doesn't
> scale well.
>
>
>
> On Fri, Aug 30, 2013 at 2:40 PM, Vivek Mishra <mishra.v...@gmail.com> wrote:
> create a column family as:
>
> create table dynamicTable(key text, nameAsDouble double, valueAsBlob blob);
>
> insert into dynamicTable(key, nameAsDouble, valueAsBlob) values ( "key",
> double(102.211), textAsBlob('valueInBytes').
>
> Do you think, it will work in case column name are double?
>
> -Vivek
>
>
> On Sat, Aug 31, 2013 at 12:03 AM, Peter Lin <wool...@gmail.com> wrote:
>
> In the interest of education and discussion.
>
> I didn't mean to say CQL3 doesn't support dynamic columns. The example from
> the page shows default type defined in the create statement.
> create column family data
> with key_validation_class=Int32Type
> and comparator=DateType
> and default_validation_class=FloatType;
>
>
> If I try to insert a dynamic column that uses double for column name and
> string for column value, it will throw an error. The kind of use case I'm
> talking about defines a minimum number of static columns. Most of the columns
> that are added at runtime are different name and value type. This is specific
> to my use case.
>
> Having said that, I believe it "would" be possible to provide that kind of
> feature in CQL, but the trade off is it deviates from SQL. The grammar would
> have to allow type declaration in the columns list and functions in the
> values. Something like
>
> insert into mytable (KEY, doubleType(newcol1), string(newcol2)) values
> ('abc123', "some string", double(102.211))
>
> doubleType(newcol1) and string(newcol2) are dynamic columns.
>
> I know many people find thrift hard to grok and struggle with it, but I'm a
> firm believer in taking time to learn. Every developer should take time to
> read cassandra source code and the source code for the driver they're using.
>
>
>
> On Fri, Aug 30, 2013 at 2:18 PM, Jonathan Ellis <jbel...@gmail.com> wrote:
> http://www.datastax.com/dev/blog/does-cql-support-dynamic-columns-wide-rows
>
>
> On Fri, Aug 30, 2013 at 12:53 PM, Peter Lin <wool...@gmail.com> wrote:
>
> my bias perspective, I find the sweet spot is thrift for insert/update and
> CQL for select queries.
>
> CQL is too limiting and negates the power of storing arbitrary data types in
> dynamic columns.
>
>
> On Fri, Aug 30, 2013 at 1:45 PM, Jon Haddad <j...@jonhaddad.com> wrote:
> If you're going to work with CQL, work with CQL. If you're going to work
> with Thrift, work with Thrift. Don't mix.
>
> On Aug 30, 2013, at 10:38 AM, Vivek Mishra <mishra.v...@gmail.com> wrote:
>
>> Hi,
>> If i a create a table with CQL3 as
>>
>> create table user(user_id text PRIMARY KEY, first_name text, last_name text,
>> emailid text);
>>
>> and create index as:
>> create index on user(first_name);
>>
>> then inserted some data as:
>> insert into user(user_id,first_name,last_name,"emailId")
>> values('@mevivs','vivek','mishra','vivek.mis...@impetus.co.in');
>>
>>
>> Then if update same column family using Cassandra-cli as:
>>
>> update column family user with key_validation_class='UTF8Type' and
>> column_metadata=[{column_name:last_name, validation_class:'UTF8Type',
>> index_type:KEYS},{column_name:first_name, validation_class:'UTF8Type',
>> index_type:KEYS}];
>>
>>
>> Now if i connect via cqlsh and explore user table, i can see column
>> first_name,last_name are not part of table structure anymore. Here is the
>> output:
>>
>> CREATE TABLE user (
>> key text PRIMARY KEY
>> ) WITH
>> bloom_filter_fp_chance=0.010000 AND
>> caching='KEYS_ONLY' AND
>> comment='' AND
>> dclocal_read_repair_chance=0.000000 AND
>> gc_grace_seconds=864000 AND
>> read_repair_chance=0.100000 AND
>> replicate_on_write='true' AND
>> populate_io_cache_on_flush='false' AND
>> compaction={'class': 'SizeTieredCompactionStrategy'} AND
>> compression={'sstable_compression': 'SnappyCompressor'};
>>
>> cqlsh:cql3usage> select * from user;
>>
>> user_id
>> ---------
>> @mevivs
>>
>>
>>
>>
>>
>> I understand that, CQL3 and thrift interoperability is an issue. But this
>> looks to me a very basic scenario.
>>
>>
>>
>> Any suggestions? Or If anybody can explain a reason behind this?
>>
>> -Vivek
>>
>>
>>
>>
>
>
>
>
>
> --
> Jonathan Ellis
> Project Chair, Apache Cassandra
> co-founder, http://www.datastax.com
> @spyced
>
>
>
