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From aaron morton <aa...@thelastpickle.com>
Subject Re: Astyanax empty column check
Date Thu, 18 Oct 2012 11:10:24 GMT
Very slim reason to link to my favourite Joe Celko (http://en.wikipedia.org/wiki/Joe_Celko)
quote:

"
'LOL! My wife is an ordained Soto Zen priest. I would say after 30 years together, I'd go
with her.  She is the only person who understood NULLs immediately.
http://www.simple-talk.com/opinion/geek-of-the-week/geek-of-the-week-joe-celko/
"

>>> a. A row which has only key without columns
>>> b. No this row in database.
From the point of view of the API a row with zero *live* columns is the same as a row that
does not exist. 

A row may exist on disk, but be made up of non-live columns. These are a combination of expired
TTL columns and columns overwritten by (row or column) tombstones. Eventually a row with 0
live columns, with >0 non live columns will be compacted and purged from disk.

Hope that helps. 


-----------------
Aaron Morton
Freelance Developer
@aaronmorton
http://www.thelastpickle.com

On 18/10/2012, at 1:34 AM, "Hiller, Dean" <Dean.Hiller@nrel.gov> wrote:

> What specifically are you trying to achieve?  The business requirement might help as
there are other ways of solving it such that you do not need to know the difference.
> 
> Dean
> 
> From: Xu Renjie <xrjxrjxrjnet@gmail.com<mailto:xrjxrjxrjnet@gmail.com>>
> Reply-To: "user@cassandra.apache.org<mailto:user@cassandra.apache.org>" <user@cassandra.apache.org<mailto:user@cassandra.apache.org>>
> Date: Wednesday, October 17, 2012 4:48 AM
> To: "user@cassandra.apache.org<mailto:user@cassandra.apache.org>" <user@cassandra.apache.org<mailto:user@cassandra.apache.org>>
> Subject: Re: Astyanax empty column check
> 
> So what you mean is essentially there is *no* way to differentiate it because what they
"appear" is the same?
> 
> On Wed, Oct 17, 2012 at 5:58 PM, rohit bhatia <rohit2412@gmail.com<mailto:rohit2412@gmail.com>>
wrote:
> See
> "If you attempt to retrieve an entire row and it returns a result with
> no columns, it effectively means that row does not exist."
> Essentially a row without co
> 
> http://stackoverflow.com/questions/8072253/is-there-a-difference-between-an-empty-key-and-a-key-that-doesnt-exist
> 
> lumns doesn't exist.. (except those with tombstones)
> from here
> On Wed, Oct 17, 2012 at 2:17 PM, Xu Renjie <xrjxrjxrjnet@gmail.com<mailto:xrjxrjxrjnet@gmail.com>>
wrote:
>> Sorry for the version, I am using 1.0.1 Astyanax.
>> 
>> 
>> On Wed, Oct 17, 2012 at 4:44 PM, Xu Renjie <xrjxrjxrjnet@gmail.com<mailto:xrjxrjxrjnet@gmail.com>>
wrote:
>>> 
>>> hello guys,
>>>   I am currently using Astyanax as a client(new to Astyanax). But I am
>>> not clear how to differentiate the following 2 situations:
>>> a. A row which has only key without columns
>>> b. No this row in database.
>>> 
>>> Since when I use RowQuery to query Cassandra with given key, both the
>>> above two situations will return a ColumnList
>>> with size 0. And also I didn't find other api can handle this.
>>> Do you have any better way for this? Thanks in advance.
>>> Cheers,
>>> Xu
>> 
>> 
> 


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