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https://issues.apache.org/jira/browse/CASSANDRA-8961?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14359995#comment-14359995
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Aleksey Yeschenko commented on CASSANDRA-8961:
----------------------------------------------
CASSANDRA-8099 will make that query not use range tombstones, but you'll have
to wait for 3.0 to get that.
> Data rewrite case causes almost non-functional compaction
> ---------------------------------------------------------
>
> Key: CASSANDRA-8961
> URL: https://issues.apache.org/jira/browse/CASSANDRA-8961
> Project: Cassandra
> Issue Type: Bug
> Environment: Centos 6.6, Cassandra 2.0.12 (Also seen in Cassandra 2.1)
> Reporter: Dan Kinder
> Priority: Minor
>
> There seems to be a bug of some kind where compaction grinds to a halt in
> this use case: from time to time we have a set of rows we need to "migrate",
> changing their primary key by deleting the row and inserting a new row with
> the same partition key and different cluster key. The python script below
> demonstrates this; it takes a bit of time to run (didn't try to optimize it)
> but when it's done it will be trying to compact a few hundred megs of data
> for a long time... on the order of days, or it will never finish.
> Not verified by this sandboxed experiment but it seems that compression
> settings do not matter and that this seems to happen to STCS as well, not
> just LCS. I am still testing if other patterns cause this terrible compaction
> performance, like deleting all rows then inserting or vice versa.
> Even if it isn't a "bug" per se, is there a way to fix or work around this
> behavior?
> {code}
> import string
> import random
> from cassandra.cluster import Cluster
> cluster = Cluster(['localhost'])
> db = cluster.connect('walker')
> db.execute("DROP KEYSPACE IF EXISTS trial")
> db.execute("""CREATE KEYSPACE trial
> WITH REPLICATION = { 'class': 'SimpleStrategy',
> 'replication_factor': 1 }""")
> db.execute("""CREATE TABLE trial.tbl (
> pk text,
> data text,
> PRIMARY KEY(pk, data)
> ) WITH compaction = { 'class' : 'LeveledCompactionStrategy' }
> AND compression = {'sstable_compression': ''}""")
> # Number of rows to insert and "move"
> n = 200000
>
> # Insert n rows with the same partition key, 1KB of unique data in cluster key
> for i in range(n):
> db.execute("INSERT INTO trial.tbl (pk, data) VALUES ('thepk', %s)",
> [str(i).zfill(1024)])
> # Update those n rows, deleting each and replacing with a very similar row
> for i in range(n):
> val = str(i).zfill(1024)
> db.execute("DELETE FROM trial.tbl WHERE pk = 'thepk' AND data = %s",
> [val])
> db.execute("INSERT INTO trial.tbl (pk, data) VALUES ('thepk', %s)", ["1"
> + val])
> {code}
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