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From "Keith Wright (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-6654) Droppable tombstones are not being removed from LCS table despite being above 20%
Date Thu, 27 Feb 2014 15:25:20 GMT


Keith Wright commented on CASSANDRA-6654:

So you're saying that even though we know we can compact away some columns due to their TTL,
we can't because some other columns have older TTLs?  This seems counter intuitive when we
are allowed to set per column TTLs.  In the end you have a row TTL that matches the column
that needs to live the longest.

This severely impacts our Cassandra usage case as we selected Cassandra specifically for its
ability to size data based on TTL to ensure we do not get wide rows.  

> Droppable tombstones are not being removed from LCS table despite being above 20%
> ---------------------------------------------------------------------------------
>                 Key: CASSANDRA-6654
>                 URL:
>             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,
> 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':

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