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From "Ariel Weisberg (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-9779) Append-only optimization
Date Fri, 12 Feb 2016 15:00:24 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-9779?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15144665#comment-15144665
] 

Ariel Weisberg commented on CASSANDRA-9779:
-------------------------------------------

For tables that are marked append only it would be nice to have some best effort warnings
or feedback if updates do occur. Checking the memtable when writing might be cheap/free and
during compaction we can warn and log a conflict if an update is encountered. We could do
the same thing on read.

This would give people with a buggy application (or a bug in Cassandra) rapid feedback rather
then silently giving them inconsistent results.

> Append-only optimization
> ------------------------
>
>                 Key: CASSANDRA-9779
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-9779
>             Project: Cassandra
>          Issue Type: New Feature
>          Components: CQL
>            Reporter: Jonathan Ellis
>             Fix For: 3.x
>
>
> Many common workloads are append-only: that is, they insert new rows but do not update
existing ones.  However, Cassandra has no way to infer this and so it must treat all tables
as if they may experience updates in the future.
> If we added syntax to tell Cassandra about this ({{WITH INSERTS ONLY}} for instance)
then we could do a number of optimizations:
> - Compaction would only need to worry about defragmenting partitions, not rows.  We could
default to DTCS or similar.
> - CollationController could stop scanning sstables as soon as it finds a matching row
> - Most importantly, materialized views wouldn't need to worry about deleting prior values,
which would eliminate the majority of the MV overhead



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