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https://issues.apache.org/jira/browse/CASSANDRA-18134?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17688454#comment-17688454
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Benedict Elliott Smith commented on CASSANDRA-18134:
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We absolutely need to make the new features optional if they break downgrades -
and offering a downgrader is not the same thing. A downgrader is a costly
operation, which may not be desirable if some unexpected behaviour arises as
part of upgrade.
We might want to have some general purpose "ok, make my upgrade permanent"
function we attach these behavioural changes to. Or we might want to introduce
some general purpose nodetool feature for telling users what upgrade options
they have available to them to enable. But until those features become
incompatible with the next major they should remain optional, and NEWS.txt
should tell users how to enable them.
Berenguer's changes should be backwards compatible anyway, unless I missed
something? Isn't it just interpreting the in-memory ints as unsigned now, so
actually neutral for serialization?
> Improve handling of min/max clustering in sstable
> -------------------------------------------------
>
> Key: CASSANDRA-18134
> URL: https://issues.apache.org/jira/browse/CASSANDRA-18134
> Project: Cassandra
> Issue Type: Improvement
> Components: Local/SSTable
> Reporter: Jacek Lewandowski
> Assignee: Jacek Lewandowski
> Priority: Normal
> Fix For: 5.x
>
>
> This patch improves the following things:
> # SSTable metadata will store a covered slice instead of min/max clusterings.
> The difference is that for slices there is available the type of a bound
> rather than just a clustering. In particular it will provide the information
> whether the lower and upper bound of an sstable is opened or closed.
> # SSTable metadata will store a flag whether the SSTable contains any
> partition level deletions or not
> # The above two changes required to introduce a new major format for SSTables
> - {{oa}}
> # Single partition read command makes use of the above changes. In particular
> an sstable can be skipped when it does not intersect with the column filter,
> does not have partition level deletions and does not have statics; In case
> there are partition level deletions, but the other conditions are satisfied,
> only the partition header needs to be accessed (tests attached)
> # Skipping sstables assuming those three conditions are satisfied has been
> implemented also for partition range queries (tests attached). Also added
> minor separate statistics to record the number of accessed sstables in
> partition reads because now not all of them need to be accessed. That
> statistics is also needed in tests to confirm skipping.
> # Artificial lower bound marker is now an object on its own and is not
> implemented as a special case of range tombstone bound. Instead it sorts
> right before the lowest available bound in the data
> # Extended the lower bound optimization usage due the 1 and 2
> # Do not initialize iterator just to get a cached partition and associated
> columns index. The purpose of using lower bound optimization was to avoid
> opening an iterator of an sstable if possible.
> See also CASSANDRA-14861
> The changes in this patch include work of [~blambov], [~slebresne],
> [~jakubzytka] and [~jlewandowski]
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