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From "Jonathan Ellis (JIRA)" <>
Subject [jira] Created: (CASSANDRA-1339) add support for GT, GTE index expressions
Date Thu, 29 Jul 2010 22:09:18 GMT
add support for GT, GTE index expressions

                 Key: CASSANDRA-1339
             Project: Cassandra
          Issue Type: New Feature
          Components: Core
            Reporter: Jonathan Ellis
             Fix For: 0.7.0

this will require hitting every node in the cluster and merging results, unlike with EQ.

For instance, say we have the following index rows for some hypothetical column C1:

Node 1, ('' - M]
4: A G K 
5: B F J M

Node 2, (M - '']
4: N P X
5: Q R T

Because we store the index columns sorted in partitioner order, queries for C1=4 can scan
first node 1, then if insufficient data is found, proceed to node 2.  But for GT or GTE queries
we have to scan everyone and merge.  (Since we don't know what the next value after 4 is.
 So an alternative would be for each node to send back, along with the data for the first
row, the row key that comes next.  This would be very very messy.)

Note that since we don't yet support range scans backwards, we can't support LT or LTE queries.
 The easiest workaround there would be to add a way to specify that you want to create an
index on the comparator, reversed.  This is also worth doing for optimizations within normal
columns -- see CASSANDRA-1338.

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