Does not matter to much but are you looking to get all the columns for some know keys (get_slice, multiget_slice) ? Or are you getting the columns for keys within a range (get_range_slices)?
If you provide do a reversed query the server will skip to the "end" of the column range. Here is some info I wrote about how the the different slice predicates work http://thelastpickle.com/2011/07/04/Cassandra-Query-Plans/ Hope that helps. ----------------- Aaron Morton Freelance Cassandra Developer @aaronmorton http://www.thelastpickle.com On 27/09/2011, at 5:51 AM, Ramesh Natarajan wrote: > Hi, > > I am trying to use the range query to retrieve a bunch of columns in reverse > order. The API documentation has a parameter bool reversed which should > return the results when queried using keys in a reverse order. > > Lets say my row has about 1500 columns with column names 1 to 1500, and I > query asking for columns 1500 (start ) - 1400 (end ) with reverse set to > true. > > Does cassandra read the entire row 1 - 1500 columns and then return the > result 1400 - 1500 or it is optimized to look directly into the 1400 - 1500 > columns? > > thanks > Ramesh > > > SliceRange > A SliceRange is a structure that stores basic range, ordering and limit > information for a query that will return multiple columns. It could be > thought of as Cassandra's version of LIMIT and ORDER BY. > > Attribute > Type > Default > Required > Description > start > binary > n/a > Y > The column name to start the slice with. This attribute is not required, > though there is no default value, and can be safely set to '', i.e., an empty > byte array, to start with the first column name. Otherwise, it must be a > valid value under the rules of the Comparator defined for the given > ColumnFamily. > finish > binary > n/a > Y > The column name to stop the slice at. This attribute is not required, though > there is no default value, and can be safely set to an empty byte array to > not stop until count results are seen. Otherwise, it must also be a valid > value to the ColumnFamily Comparator. > reversed > bool > false > Y > Whether the results should be ordered in reversed order. Similar to ORDER BY > blah DESC in SQL. > count > integer > 100 > Y > How many columns to return. Similar to LIMIT 100 in SQL. May be arbitrarily > large, but Thrift will materialize the whole result into memory before > returning it to the client, so be aware that you may be better served by > iterating through slices by passing the last value of one call in as the > start of the next instead of increasing count arbitrarily large.
