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From "Sylvain Lebresne (JIRA)" <>
Subject [jira] [Resolved] (CASSANDRA-13027) Questions on compaction process
Date Mon, 12 Dec 2016 08:32:58 GMT


Sylvain Lebresne resolved CASSANDRA-13027.
    Resolution: Invalid

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> Questions on compaction process
> -------------------------------
>                 Key: CASSANDRA-13027
>                 URL:
>             Project: Cassandra
>          Issue Type: Task
>          Components: Compaction
>         Environment: ubuntu, centos
>            Reporter: Arvind Viswanathan
>             Fix For: 2.2.5
> I have the following schema ( a raw table and index table to look up data from the raw
table) and I notice the following problem:
> create table raw_table( 
> key uuid PRIMARY KEY,
> value text) ;
> create table index_table_1(
> time int,
> index_field1 text,
> col1 text,
> value uuid); PRIMARY_KEY(int, text)
> My usage involves continuous writes( no updates, just new data with TTL of 48 hrs) and
very less reads. I use STCS. I noticed the reads to the raw_table are failing whereas the
one to index tables where succeeding. I took a look at the compaction history of the different
table and here is what I observe
> Raw table has low completedcompactions (from the nodetool compactionhistory) but high
number of SSTable count (from nodetool cfstats), whereas the index table has lot of completed
compactions and low SSTable count. I can understand that high SSTable count can lead to read
failures, but I don't understand why the compactions are not able to complete as fast in the
raw tables. The cassandra version I use is 2.2.5.
> Also what is the impact of compaction on append only tables? 

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