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https://issues.apache.org/jira/browse/CASSANDRA-15413?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16981478#comment-16981478
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Alex Petrov commented on CASSANDRA-15413:
-----------------------------------------
I wrote a simple in-jvm dtest that reproduced it in all versions (2.1, 2.2,
3.0, 3.11, and trunk) last week and have started working on the patch. I'll
post it here as soon as it's ready, unless [~spodi] would like to post a full
patch.
> Missing results on reading large frozen text map
> ------------------------------------------------
>
> Key: CASSANDRA-15413
> URL: https://issues.apache.org/jira/browse/CASSANDRA-15413
> Project: Cassandra
> Issue Type: Bug
> Components: Local/SSTable
> Reporter: Tyler Codispoti
> Assignee: Alex Petrov
> Priority: Normal
>
> Cassandra version: 2.2.15
> I have been running into a case where, when fetching the results from a table
> with a frozen<map<text, text>>, if the number of results is greater than the
> fetch size (default 5000), we can end up with missing data.
> Side note: The table schema comes from using KairosDB, but we've isolated
> this issue to Cassandra itself. But it looks like this can cause problems for
> users of KairosDB as well.
> Repro case. Tested against fresh install of Cassandra 2.2.15.
> 1. Create table (csqlsh)
> {code:sql}
> CREATE KEYSPACE test
> WITH REPLICATION = {
> 'class' : 'SimpleStrategy',
> 'replication_factor' : 1
> };
> CREATE TABLE test.test (
> name text,
> tags frozen<map<text, text>>,
> PRIMARY KEY (name, tags)
> ) WITH CLUSTERING ORDER BY (tags ASC);
> {code}
> 2. Insert data (python3)
> {code:python}
> import time
> from cassandra.cluster import Cluster
> cluster = Cluster(['127.0.0.1'])
> session = cluster.connect('test')
> for i in range(0, 20000):
> session.execute(
> """
> INSERT INTO test (name, tags)
> VALUES (%s, %s)
> """,
> ("test_name", {'id':str(i)})
> )
> {code}
>
> 3. Flush
>
> {code:java}
> nodetools flush{code}
>
>
> 4. Fetch data (python3)
> {code:python}
> import time
> from cassandra.cluster import Cluster
> cluster = Cluster(['127.0.0.1'], control_connection_timeout=5000)
> session = cluster.connect('test')
> session.default_fetch_size = 5000
> session.default_timeout = 120
> count = 0
> rows = session.execute("select tags from test where name='test_name'")
> for row in rows:
> count += 1
> print(count)
> {code}
> Result: 10111 (expected 20000)
>
> Changing the page size changes the result count. Some quick samples:
>
> ||default_fetch_size||count||
> |5000|10111|
> |1000|1830|
> |999|1840|
> |998|1850|
> |20000|20000|
> |100000|20000|
>
>
> In short, I cannot guarantee I'll get all the results back unless the page
> size > number of rows.
> This seems to get worse with multiple SSTables (eg nodetool flush between
> some of the insert batches). When using replication, the issue can get
> disgustingly bad - potentially giving a different result on each query.
> Interesting, if we pad the values on the tag map ("id" in this repro case) so
> that the insertion is in lexicographical order, there is no issue. I believe
> the issue also does not repro if I do not call "nodetools flush" before
> querying.
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