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Chris Lohfink commented on CASSANDRA-7622:
------------------------------------------
> I do think it would be worth separating the discussion on the system
> view/virtual table mechanism from the one on the exact schema of metrics
> tables for the sake of focus
agreed, I removed table_stats from system_view and it can be discussed in
another ticket. That leaves {{settings}}, {{compaction_stats}}, {{ring_state}}.
Thats 2 essentially copies of the nodetool output and a new table that lets you
see current state of the configuration (with a few updatable).
> I am strongly in favor of not shipping syntax for creating virtual tables
Removing CQL syntax change and {{CreateTableStatement}} changes. Will build the
tablemetadata from builder instead in the {{SystemViewKeyspace}}.
> The patch seems to disable the {{ALLOW FILTERING}} check for virtual tables
The patch allows each virtual table to enable or disable the restrictions that
normally would require {{ALLOW FILTERING}} to make
{code:java}
/**
* If the table allows unrestricted queries (ie filter on clustering key
with no partition). Since These tables are
* not backed by the C* data model, this restriction isnt always necessary.
*/
public boolean allowFiltering()
{
return true;
}
{code}
I will change default to have same behavior as normal C* tables, but I actually
really would like to remove those restrictions on queries for the
{{SystemView}} tables since they dont need them and it makes querying
interesting things a lot easier.
> naming is important
agreed but its hard to have 100% foresight, the goal of this ticket shifted
dramatically through its lifetime even. I went with {{VirtualTable}} being the
base abstract class for a custom backend, but the one implementation provided
is a {{SystemView}} to make it easier to make internal system state/metrics
tables.
> Implement virtual tables
> ------------------------
>
> Key: CASSANDRA-7622
> URL: https://issues.apache.org/jira/browse/CASSANDRA-7622
> Project: Cassandra
> Issue Type: Improvement
> Components: CQL
> Reporter: Tupshin Harper
> Assignee: Chris Lohfink
> Priority: Major
> Fix For: 4.x
>
> Attachments: screenshot-1.png
>
>
> There are a variety of reasons to want virtual tables, which would be any
> table that would be backed by an API, rather than data explicitly managed and
> stored as sstables.
> One possible use case would be to expose JMX data through CQL as a
> resurrection of CASSANDRA-3527.
> Another is a more general framework to implement the ability to expose yaml
> configuration information. So it would be an alternate approach to
> CASSANDRA-7370.
> A possible implementation would be in terms of CASSANDRA-7443, but I am not
> presupposing.
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