Benedict created CASSANDRA-9708:
-----------------------------------
Summary: Serialize ClusteringPrefixes in batches
Key: CASSANDRA-9708
URL: https://issues.apache.org/jira/browse/CASSANDRA-9708
Project: Cassandra
Issue Type: Sub-task
Components: Core
Reporter: Benedict
Assignee: Benedict
Fix For: 3.0.0 rc1
Typically we will have very few clustering prefixes to serialize, however in
theory they are not constrained (or are they, just to a very large number?).
Currently we encode a fat header for all values up front (two bits per value),
however those bits will typically be zero, and typically we will have only a
handful (perhaps 1 or 2) of values.
This patch modifies the encoding to batch the prefixes in groups of up to 32,
along with a header that is vint encoded. Typically this will result in a
single byte per batch, but will consume up to 9 bytes if some of the values
have their flags set. If we have more than 32 columns, we just read another
header. This means we incur no garbage, and compress the data on disk in many
cases where we have more than 4 clustering components.
I do wonder if we shouldn't impose a limit on clustering columns, though: If
you have more than a handful merge performance is going to disintegrate. 32 is
probably well in excess of what we should be seeing in the wild anyway.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
