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https://issues.apache.org/jira/browse/CASSANDRA-14538?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16522474#comment-16522474
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Aleksey Yeschenko commented on CASSANDRA-14538:
-----------------------------------------------
I think this might be too big to materialize fully in memory, and probably
shouldn't be using {{SimpleDataSet}}.
> Add virtual table to view cache information
> -------------------------------------------
>
> Key: CASSANDRA-14538
> URL: https://issues.apache.org/jira/browse/CASSANDRA-14538
> Project: Cassandra
> Issue Type: Improvement
> Reporter: Chris Lohfink
> Assignee: Chris Lohfink
> Priority: Minor
> Labels: virtual-tables
>
> Add a couple tables, one for displaying the general cache information (like
> in {{nodetool info}}) and another to view the contents (ish) of keycache.
> This would be pretty useful in tests to tell if things are in the cache and
> in finding wide partitions and performance issues.
> Possibility to discuss: DELETE on the key cache to evict specific records, I
> wrote the code to do it but im not sure if its valuable or worth complexity.
> TRUNCATE support on virtual tables might be nice as a way to clear the
> keycache as well. These can be followup tickets though if it seems like a
> good idea as truncate and delete are currently disabled in virtual tables and
> that behavior should maybe be its own ticket/discussion.
>
> {code}
> cqlsh> SELECT * FROM system_views.caches;
> name | entries | hit_ratio | hits | recent_hits_per_sec |
> recent_requests_per_sec | requests | size_max | size_used
> ---------+---------+-----------+------+---------------------+-------------------------+----------+----------+-----------
> counter | 0 | NaN | 0 | 0 |
> 0 | 0 | 12582912 | 0
> key | 19 | 0.922509 | 250 | 11 |
> 13 | 271 | 25165824 | 1728
> row | 0 | NaN | 0 | 0 |
> 0 | 0 | 16777216 | 0
> (3 rows)
> cqlsh> SELECT * FROM system_views.key_cache;
> keyspace_name | table_name | key | sstable | size
> ---------------+------------------+---------------------+---------+------
> basic | wide | row1 | 5 | 64
> basic | wide | row1 | 6 | 64
> system | local | local | 15 | 24
> system | local | local | 16 | 24
> system | local | local | 17 | 24
> system | sstable_activity | system_auth:roles:1 | 13 | 24
> system_auth | roles | cassandra | 1 | 24
> system_schema | tables | basic | 13 | 24
> system_schema | tables | system_auth | 13 | 24
> system_schema | tables | system_distributed | 13 | 24
> system_schema | tables | system_traces | 13 | 24
> system_schema | columns | basic | 13 | 24
> system_schema | columns | system_auth | 13 | 24
> system_schema | columns | system_distributed | 13 | 24
> system_schema | columns | system_traces | 13 | 24
> system_schema | keyspaces | basic | 13 | 24
> system_schema | keyspaces | system_auth | 13 | 24
> system_schema | keyspaces | system_distributed | 13 | 24
> system_schema | keyspaces | system_traces | 13 | 24
> (19 rows)
> {code}
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