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https://issues.apache.org/jira/browse/CASSANDRA-11044?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15109430#comment-15109430
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Ivan Ryndin commented on CASSANDRA-11044:
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>From log it looks like most time is spent while merging memtables and
>sstables. I see that after messages like {{Merging data from memtables and 3
>sstables}} there is a big time gap before next message in log shows.
> query under certain partition key takes much more time than expected
> ---------------------------------------------------------------------
>
> Key: CASSANDRA-11044
> URL: https://issues.apache.org/jira/browse/CASSANDRA-11044
> Project: Cassandra
> Issue Type: Bug
> Components: Local Write-Read Paths
> Reporter: xiaost
> Attachments: tracing.log
>
>
> In my cluster, all the nodes is under low workload,
> but query under certain partition key (we found one) takes much more time
> than expected.
> we write & updates about 3 times per row in one day,
> reads are much more than writes.
> HARDWARD:
> 6*nodes(E5-2630, 1*ssd with 5GB data)
> TABLE DESCRIBE:
> {noformat}
> CREATE TABLE album.user_updates (
> user_id bigint,
> time_uuid bigint,
> key ascii,
> PRIMARY KEY (user_id, time_uuid)
> ) WITH CLUSTERING ORDER BY (time_uuid ASC)
> AND bloom_filter_fp_chance = 0.01
> AND caching = '{"keys":"ALL", "rows_per_partition":"NONE"}'
> AND comment = ''
> AND compaction = {'class':
> 'org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy'}
> AND compression = {'sstable_compression':
> 'org.apache.cassandra.io.compress.LZ4Compressor'}
> AND dclocal_read_repair_chance = 0.1
> AND default_time_to_live = 0
> AND gc_grace_seconds = 864000
> AND max_index_interval = 2048
> AND memtable_flush_period_in_ms = 0
> AND min_index_interval = 128
> AND read_repair_chance = 0.0
> AND speculative_retry = '99.0PERCENTILE';
> {noformat}
> QUERYs:
> {noformat}
> select * from user_updates where user_id = 1432138730701829 limit 100;
> select count(1) from user_updates where user_id = 1432138730701829;
> {noformat}
> RESULT: (takes about 3.5 minutes)
> {noformat}
> count
> -------
> 1058
> (1 rows)
> {noformat}
> check attachments for the tracing log
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