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https://issues.apache.org/jira/browse/CASSANDRA-6654?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13914935#comment-13914935
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Russ Hatch commented on CASSANDRA-6654:
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[~krummas] -- Thanks for the details on tombstone dropping during compaction.
Can you confirm this is the intended functionality of the system? -- I agree
with Keith that this seems peculiar.
I'm a bit confused by the maxDeletionTime logic because it presumably works for
rows with several columns but only one column with a TTL (so every column has a
TTL of infinity, except the one with a specific TTL). Though I guess maybe this
only applies to explicit TTL's and not the implied "forever" TTL.
If the current functionality is as-designed and won't be fixed, then is the
DroppableTombstoneRatio calculation incorrect since these tombstones aren't
actually droppable?
For the use case targeted by [~keithwrightbos] would the best workaround is to
stick with the implied forever TTL on most columns (don't specify one) and just
set TTL for these shorter lived values? (Perhaps using an additional
record_write_time column to reference later and manually prune records at 6
months.)
> Droppable tombstones are not being removed from LCS table despite being above
> 20%
> ---------------------------------------------------------------------------------
>
> Key: CASSANDRA-6654
> URL: https://issues.apache.org/jira/browse/CASSANDRA-6654
> Project: Cassandra
> Issue Type: Bug
> Components: Core
> Environment: 1.2.13 VNodes with murmur3
> Reporter: Keith Wright
> Assignee: Marcus Eriksson
> Attachments: Screen Shot 2014-02-05 at 9.38.20 AM.png, dtrlog.txt,
> repro3.py
>
>
> JMX is showing that one of our CQL3 LCS tables has a droppable tombstone
> ratio above 20% and increasing (currently at 28%). Compactions are not
> falling behind and we are using the OOTB setting for this feature so I would
> expect not to go above 20% (will attach screen shot from JMX). Table
> description:
> CREATE TABLE global_user (
> user_id timeuuid,
> app_id int,
> type text,
> name text,
> extra_param map<text, text>,
> last timestamp,
> paid boolean,
> sku_time map<text, timestamp>,
> values map<timestamp, float>,
> PRIMARY KEY (user_id, app_id, type, name)
> ) WITH
> bloom_filter_fp_chance=0.100000 AND
> caching='KEYS_ONLY' AND
> comment='' AND
> dclocal_read_repair_chance=0.000000 AND
> gc_grace_seconds=86400 AND
> read_repair_chance=0.100000 AND
> replicate_on_write='true' AND
> populate_io_cache_on_flush='false' AND
> compaction={'sstable_size_in_mb': '160', 'class':
> 'LeveledCompactionStrategy'} AND
> compression={'chunk_length_kb': '8', 'crc_check_chance': '0.1',
> 'sstable_compression': 'LZ4Compressor'};
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