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From Keith Freeman <8fo...@gmail.com>
Subject Re: token(), limit and wide rows
Date Fri, 16 Aug 2013 16:08:39 GMT
I've run into the same problem, surprised nobody's responded to you.  
Any time someone asks "how do I page through all the rows of a table in 
CQL3?", the standard answer is token() and limit.  But as you point out, 
this method will often miss some data from wide rows.

Maybe a Cassandra expert will chime in if we're wrong.

Your suggestion is possible if you know how to find the previous value 
of 'name' field (and are willing to filter out repeated rows), but 
wouldn't that be difficult/impossible with some keys?  So then, is there 
a way to do paging queries that get ALL of the rows, even in wide rows?


On 08/13/2013 02:46 PM, Jan Algermissen wrote:
> HI,
>
> ok, so I found token() [1], and that it is an option for paging through randomly partitioned
data.
>
> I take it that combining token() and LIMIT is the CQL3 idiom for paging (set aside the
fact that one shouldn't raelly want to page and use C*)
>
> Now, when I page through a CF with wide rows, limitting each 'page' to, for example,
100 I end up in situations where not all 'sub'rows that have the same result for token() are
returned because LIMIT chops off the result after 100 'sub'rows, not neccessarily at the boundary
to the next wide row.
>
> Obvious ... but inconvenient.
>
> The solution would be to throw away the last token returned (because it's wide row could
have been chopped off) and do the next query with the token before.
>
> So instead of doing
>
>       SELECT * FROM users WHERE token(name) > token(last-name-of-prev-result) LIMIT
100;
>
> I'd be doing
>
>      SELECT * FROM users WHERE token(name) > token(one-befoe-the-last-name-of-prev-result)
LIMIT 100;
>
>
> Question: Is that what I have to do or is there a way to make token() and limit work
together to return complete wide rows?
>
>
> Jan
>
>
>
> [1] token() and how it relates to paging is actually quite hard to grasp from the docs.


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