Christian Spriegel created CASSANDRA-4304:
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Summary: Add bytes-limit clause to queries
Key: CASSANDRA-4304
URL: https://issues.apache.org/jira/browse/CASSANDRA-4304
Project: Cassandra
Issue Type: New Feature
Components: API, Core
Reporter: Christian Spriegel
Fix For: 1.2
Idea is to add a second limit clause to (slice)queries. This would allow easy
loading of batches, even if content is variable sized.
Imagine the following use case:
You want to load a batch of XMLs, where each is between 100bytes and 5MB large.
Currently you can load either
- a large number of XMLs, but risk OOMs or timeouts
or
- a small number of XMLs, and do too many queries where each query usually
retrieves very little data.
With cassandra being able to limit by size and not just count, we could do a
single query which would never OOM but always return a decent amount of data --
with no extra overhead for multiple queries.
Few thoughts from my side:
- The limit should be a soft limit, not a hard limit. Therefore it will always
return at least one row/column, even if that one large than the limit specifies.
- HintedHandoffManager:303 is already doing a
InMemoryCompactionLimit/averageColumnSize to avoid OOM. It could then simply
use the new limit clause :-)
- A bytes-limit on a range- or indexed-query should always return a complete row
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