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https://issues.apache.org/jira/browse/CASSANDRA-18134?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17691425#comment-17691425
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Jacek Lewandowski commented on CASSANDRA-18134:
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Regarding upgrading/downgrading discussion and the ability to support multiple
formats - we should consider also CEP-17 here as when it is merged, we will
have the ability to define separate formats with their own identifiers. If we
agree, we can follow up it with extending its functionality to define separate
implementations for version ranges - like we have one implementation for BIG
format from {{ma-nz}} and different for {{oa+}}. All in all that would allow us
to not mix the implementation with several ifs to handle downgrading.
> 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: 4.x
>
>
> This patch improves the following things:
> # SSTable metadata will store a covered slice in addition 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. The legacy min/max clustering will be stored until a new major format
> {{o}} to ensure backward compatibility
> # SSTable metadata will store a flag whether the SSTable contains any
> partition level deletions or not
> # SSTable metadata will store the first and the last keys of the sstable.
> This is mostly for consistency - key range is logically a part of stats
> metadata. So far it is stored at the end of the index summary. After this
> change, index summary will be no longer needed to read key range of an
> sstable (although we will keep storing key range as before for compatibility
> reasons)
> # The above two changes required to introduce a new minor format for SSTables
> - {{nc}}
> # 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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