cassandra-commits mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Alex Petrov (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-10698) Static column performance with DISTINCT
Date Mon, 18 Apr 2016 10:38:25 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-10698?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15245445#comment-15245445
] 

Alex Petrov commented on CASSANDRA-10698:
-----------------------------------------

[~masterzen] could you post a bit more information on the data layout? I've tried running
simiar queries on the mentioned version with relatively small partition sizes, although everything
works as expected. 
What's the normal amount of rows in the partition? 

> Static column performance with DISTINCT
> ---------------------------------------
>
>                 Key: CASSANDRA-10698
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-10698
>             Project: Cassandra
>          Issue Type: Bug
>         Environment: Linux, cassandra 2.1.11
>            Reporter: Brice Figureau
>            Priority: Critical
>              Labels: performance
>         Attachments: bug-slow-distinct.tar.gz
>
>
> As described on the mailing list, with the following schema:
> {code:sql}
> CREATE TABLE akka.messages (
>     persistence_id text,
>     partition_nr bigint,
>     sequence_nr bigint,
>     message blob,
>     used boolean static,
>     PRIMARY KEY ((persistence_id, partition_nr), sequence_nr)
> ) WITH CLUSTERING ORDER BY (sequence_nr 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 = 216000
>     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';
> {code}
> The following query:
> {code:sql}
> SELECT used from akka.messages WHERE
>       persistence_id = 'player-SW11f03e20b8802000' AND
>       partition_nr = 0;
> {code}
> is quite slow, and as slow as the {{distinct}} version:
> {code:sql}
> SELECT DISTINCT used from akka.messages WHERE
>       persistence_id = 'player-SW11f03e20b8802000' AND
>       partition_nr = 0;
> {code}
> As shown with this tracing from a small unloaded 3 nodes cluster:
> {noformat}
>  activity                                                                           
              | timestamp                  | source         | source_elapsed
> ---------------------------------------------------------------------------------------------------+----------------------------+----------------+----------------
>                                                                                 Execute
CQL3 query | 2015-11-13 11:04:41.771000 | 192.168.168.12 |              0
>  Parsing SELECT DISTINCT used ....                                           [SharedPool-Worker-1]
| 2015-11-13 11:04:41.771000 | 192.168.168.12 |             78
>             READ message received from /192.168.168.12 [MessagingService-Incoming-/192.168.168.12]
| 2015-11-13 11:04:41.772000 | 192.168.168.29 |             22
>                                                          Preparing statement [SharedPool-Worker-1]
| 2015-11-13 11:04:41.772000 | 192.168.168.12 |            271
>                                 Executing single-partition query on messages [SharedPool-Worker-4]
| 2015-11-13 11:04:41.772000 | 192.168.168.29 |            424
>                                            reading data from /192.168.168.29 [SharedPool-Worker-1]
| 2015-11-13 11:04:41.772000 | 192.168.168.12 |            642
>                                                 Acquiring sstable references [SharedPool-Worker-4]
| 2015-11-13 11:04:41.772000 | 192.168.168.29 |            445
>                Sending READ message to /192.168.168.29 [MessagingService-Outgoing-/192.168.168.29]
| 2015-11-13 11:04:41.772000 | 192.168.168.12 |            738
>                                                  Merging memtable tombstones [SharedPool-Worker-4]
| 2015-11-13 11:04:41.772000 | 192.168.168.29 |            476
>                                               Key cache hit for sstable 1126 [SharedPool-Worker-4]
| 2015-11-13 11:04:41.773000 | 192.168.168.29 |            560
>                                  Seeking to partition beginning in data file [SharedPool-Worker-4]
| 2015-11-13 11:04:41.773000 | 192.168.168.29 |            592
>    Skipped 0/1 non-slice-intersecting sstables, included 0 due to tombstones [SharedPool-Worker-4]
| 2015-11-13 11:04:41.773000 | 192.168.168.29 |            960
>                                   Merging data from memtables and 1 sstables [SharedPool-Worker-4]
| 2015-11-13 11:04:41.774000 | 192.168.168.29 |            971
>                                            Read 1 live and 0 tombstone cells [SharedPool-Worker-4]
| 2015-11-13 11:04:47.301000 | 192.168.168.29 |         529270
>                                        Enqueuing response to /192.168.168.12 [SharedPool-Worker-4]
| 2015-11-13 11:04:47.316000 | 192.168.168.29 |         544885
>    Sending REQUEST_RESPONSE message to /192.168.168.12 [MessagingService-Outgoing-/192.168.168.12]
| 2015-11-13 11:04:47.317000 | 192.168.168.29 |         545042
> REQUEST_RESPONSE message received from /192.168.168.29 [MessagingService-Incoming-/192.168.168.29]
| 2015-11-13 11:04:47.429000 | 192.168.168.12 |         657918
>                                     Processing response from /192.168.168.29 [SharedPool-Worker-2]
| 2015-11-13 11:04:47.429000 | 192.168.168.12 |         658224
>                                                                                   Request
complete | 2015-11-13 11:04:47.525892 | 192.168.168.12 |         754892
> {noformat}
> As you can see, there's a 5 seconds delay between "Merging data" and "Read 1 live and
0 tombstones" steps.
> Note that this row in particular is quite large, and has certainly a lots of tombstones.
But I understood that when querying for a static column,  cassandra shouldn't have to read
everything, as the static column value exists in one place.
> Note that if the row cache is enabled, the row is then cached and it is very fast on
subsequent request.
> I've attached the sstable in question, that exhibits the issue for this specific large
row.
> Note that I didn't run any compaction on the sstable, because I'm not sure if the problem
is coming from the tombstones on the said record.



--
This message was sent by Atlassian JIRA
(v6.3.4#6332)

Mime
View raw message