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From "Aleksey Yeschenko (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-14538) Add virtual table to view cache information
Date Mon, 25 Jun 2018 16:16:00 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-14538?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16522474#comment-16522474
] 

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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