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From "Carl Yeksigian (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-7409) Allow multiple overlapping sstables in L1
Date Mon, 28 Jul 2014 23:55:41 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-7409?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14077156#comment-14077156
] 

Carl Yeksigian commented on CASSANDRA-7409:
-------------------------------------------

I have a first cut of this working now at https://github.com/carlyeks/cassandra/tree/overlapping

This adds a new compaction strategy called 'Overlapping', which operates mostly the same as
'Leveled' when max_overlapping_level is configured to 0, except L0 does not do any STCS. When
max_overlapping_level is set to non-zero, it will compact without selecting non-overlapping
sstables, and will not include any sstables from an upper level.

Also, added a new nodetool command to list the sstables in each level for both leveled and
overlapping. 

I haven't benchmarked this strategy yet to compare with regular leveled; that's going to be
what I work on next for this.

> Allow multiple overlapping sstables in L1
> -----------------------------------------
>
>                 Key: CASSANDRA-7409
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-7409
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Carl Yeksigian
>            Assignee: Carl Yeksigian
>
> Currently, when a normal L0 compaction takes place (not STCS), we take up to MAX_COMPACTING_L0
L0 sstables and all of the overlapping L1 sstables and compact them together. If we didn't
have to deal with the overlapping L1 tables, we could compact a higher number of L0 sstables
together into a set of non-overlapping L1 sstables.
> This could be done by delaying the invariant that L1 has no overlapping sstables. Going
from L1 to L2, we would be compacting fewer sstables together which overlap.
> When reading, we will not have the same one sstable per level (except L0) guarantee,
but this can be bounded (once we have too many sets of sstables, either compact them back
into the same level, or compact them up to the next level).
> This could be generalized to allow any level to be the maximum for this overlapping strategy.



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