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From Peter Lin <wool...@gmail.com>
Subject Re: CQL & Thrift
Date Fri, 30 Aug 2013 18:45:11 GMT
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.vivs@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 <woolfel@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 <jbellis@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 <woolfel@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 <jon@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.vivs@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.mishra@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
>>>
>>
>>
>

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