Jay Patel created CASSANDRA-8855:
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Summary: Batching SELECTs
Key: CASSANDRA-8855
URL: https://issues.apache.org/jira/browse/CASSANDRA-8855
Project: Cassandra
Issue Type: New Feature
Reporter: Jay Patel
SELECT’s IN clause allows to batch selects for multiple partition keys of a
given table. Can we consider supporting batch select for multiple column ranges
for a given partition key?
For instance, would like to batch below two or more SELECTs for a given
partition key “event_type” and the different ranges of the “time”:
SELECT value
FROM events
WHERE event_type = 'myEvent'
AND time > '2011-02-03'
AND time <= '2012-01-01'
SELECT value
FROM events
WHERE event_type = 'myEvent'
AND time > '2012-02-03'
AND time <= '2013-01-01’
One way to optimize these is to fire multiple SELECTs in parallel & async from
the application, but by batching them we can do further optimizations such as
avoid multiple round trips; from app server to C*, and even from coordinator to
the replicas. Once request is received by the target replicas, we can return
all the ranges requested for a particular partition key in one shot.
This will be very useful for some of the use cases we're working on. I can take
a first cut at this if no concerns.
In addition, how about supporting batch for multiple SELECTs across tables. I
think that will require more changes in ResultSet and may not have lot of
opportunities for optimizations. However, at least it will help to avoid
multiple round trips from app server to the C*.
Thoughts welcome. Thanks!
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