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https://issues.apache.org/jira/browse/CASSANDRA-4988?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Sylvain Lebresne updated CASSANDRA-4988:
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Fix Version/s: (was: 1.2.2)
1.2.3
> Fix concurrent addition of collection columns
> ---------------------------------------------
>
> Key: CASSANDRA-4988
> URL: https://issues.apache.org/jira/browse/CASSANDRA-4988
> Project: Cassandra
> Issue Type: Bug
> Reporter: Sylvain Lebresne
> Fix For: 1.2.3
>
>
> It is currently not safe to update the schema by adding multiple collection
> columns to the same table. The reason is that with collections, the
> comparator embeds a map of names->comparator for each collection columns
> (since different maps can have different key type for example). And when
> serialized on disk in the schema table, the comparator is serialized as a
> string with that map as one column. So if new collection columns are added
> concurrently, the addition may not be merged correctly.
> One option to fix this would be to stop serializing the names->comparator map
> of ColumnToCollectionType in toString(), and do one of:
> # reconstruct that map from the information stores in the schema_columns. The
> downside I can see is that code-wise this may not be super clean to do.
> # change ColumnToCollectionType so that instead of having it's own
> names->comparator map, to just store a point to the CFMetaData that contains
> it and when it needs to find the exact comparator for a collection column, it
> would use CFMetadata.column_metadata directly. The downside is that creating
> a dependency from a comparator to a CFMetadata feels a bit backward.
> Note sure what's the best solution of the two honestly.
> While probably more anecdotal, we also now allow to change the type of the
> comparator in some cases (for example updating to BytesType is always
> allowed), and doing so concurrently on multiple components of a composite
> comparator is also not safe for a similar reason. I'm not sure how to fix
> that one.
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