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From Bill de hOra <>
Subject Re: list of columns
Date Mon, 17 May 2010 08:59:48 GMT
Agree with David, it's not there and thinking about how the data is laid 
out on disk, it can't be done without changing core code or harming 
something else.

 > if this is a performance concern

It's not, it was to supply an administrative function on SuperColumns, 
but it would be good to not crush a node.

 > a separate column family which just contains the column names and
 > timestamps with empty values.

Eventually, you'd want to ask a client library to do this, at the cost 
of two writes everytime you add a new column. But then you'd need 
re-ahead to check if the column is new, which would kill write performance.


Jonathan Shook wrote:
> I think you are correct, David. What Bill is asking for specifically
> is not in the API.
> Bill,
> if this is a performance concern (i.e., your column values are/could
> be vastly larger than your column names, and you need to query the
> namespace before loading the values), then you might consider keeping
> a separate column family which just contains the column names and
> timestamps with empty values.
> On Sun, May 16, 2010 at 4:37 AM, David Boxenhorn <> wrote:
>> Bill, I am a new user of Cassandra, so I've been following this discussion
>> with interest. I think the answer is "no", except for the brute force method
>> of looping through all your data. It's like asking for a list of all the
>> files on your C: drive. The term "column" is very misleading, since
>> "columns" are really leaves of a tree structure, not columns of a tabular
>> structure.
>> Anybody want to tell me I'm wrong?
>> BTW, Bill, I think we've corresponded before, here:
>> On Fri, May 14, 2010 at 2:23 AM, Bill de hOra <> wrote:
>>> A SlicePredicate/SliceRange can't exclude column values afaik.
>>> Bill
>>> Jonathan Shook wrote:
>>>> get_slice
>>>> see: under get_slice and
>>>> SlicePredicate
>>>> On Thu, May 13, 2010 at 9:45 AM, Bill de hOra <> wrote:
>>>>> get_count returns the number of columns, not the names of those columns?
>>>>> I
>>>>> should have been specific, by "list the columns", I meant "list the
>>>>> column
>>>>> names".
>>>>> Bill
>>>>> Gary Dusbabek wrote:
>>>>>> We have get_count at the thrift level.  You supply a predicate and
>>>>>> returns the number of columns that match.  There is also
>>>>>> multi_get_count, which is the same operation against multiple keys.
>>>>>> Gary.
>>>>>> On Thu, May 13, 2010 at 04:18, Bill de hOra <>
>>>>>>> Admin question - is there a way to list the columns for a particular
>>>>>>> key?
>>>>>>> Bill

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