What is the upper limit on the number of super columns? Is it pretty much the
same as for columns in general?
On Apr 28, 2010, at 10:09 PM, Schubert Zhang wrote:
> key : stock ID, e.g. AAPL+year
> column family: closting price and valume, tow CFs.
> colum name: timestamp LongType
>
> AAPL+2010-> CF:closingPrice -> {'04-13' : 242, '04-14': 245}
> AAPL+2010-> CF:volume -> {'04-13' : 242, '04-14': 245}
>
>
> On Thu, Apr 22, 2010 at 2:00 AM, Miguel Verde <miguelitov...@gmail.com> wrote:
> On Wed, Apr 21, 2010 at 12:17 PM, Steve Lihn <stevel...@gmail.com> wrote:
> [...]
>
> Design 1: Each attribute is a super column. Therefore each date is a column.
> So we have:
>
> AAPL -> closingPrice -> { '2010-04-13' : 242, '2010-04-14': 245 }
> AAPL -> volume -> { '2010-04-13' : 10.9m, '2010-04-14': 14.4m }
> etc.
> I would suggest not using this design, as each query involving an attribute
> will pull all dates for that attribute into memory on the server. i.e.
> getting the closingPrice for AAPL on '2010-04-13' would pull all closing
> prices for AAPL across all dates into memory.
>
>
> Design 2: Each date is a super column. Therefore each attribute is a column.
> So we have:
>
> AAPL -> '2010-04-13' -> { closingPrice -> 242, volume -> 10.9m }
> AAPL -> '2010-04-14' -> {closingPrice -> 245, volume -> 14.4m }
> etc.
>
> The date column / superColumn will need Order Perserving Partitioner since we
> are going to do a lot of range queries.
>
> Partitioners split up keys between nodes, the partitioner you use has no
> effect on your ability to query columns in a row.
>
> Examples are:
> Query 1: Give me the data between date1 and date2 for a set of tickers (say,
> the 100 tickers in QQQ).
> You could use http://wiki.apache.org/cassandra/API#multiget_slice for this.
>
> Query 2: More often than not, the query is: Give me the data for the max
> available dates (for each ticker) between date1 and date2 in a set of tickers.
> (Since not every day is traded, and we only want the most recent data, given
> a range of dates.)
> A http://wiki.apache.org/cassandra/API#SliceRange allows you to specify
> limits and ordering for columns you are slicing.
>
>
>
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