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Jeff Jirsa commented on CASSANDRA-7622:
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{quote}
No disagreement here. We don't want it to be exposed in regular DDL. However,
we would like this to be at least a little bit generic, so that one could
plug-in extra virtual keyspaces on C* startup, similar to how some folks/forks
add extra system keyspaces and system tables. There are some use cases for
virtual tables that we want to experiment with (Jeff Jirsa gave a few examples
in his NGCC talk) that are compelling enough to at least allow this possibility.
{quote}
Just to expand on this: the metrics/config stuff I think is a no brainer and
not really contentious. There are a few other things I think are useful to
operators that we'll likely be experimenting with (privately) in the near
future, as a proof-of-concept before we attempt to suggest they're suitable or
relevent for the larger audience. An example in this space is something like a
table that inspects unfiltered cells of a partition (a la {{sstabledump}} , but
over CQL) for troubleshooting purposes ('which sstables have this key' and 'why
does this partition have so many tombstones?' type virtual table
implementations). Further down the road (in the 6.x/7.x timeframe), leaving
these as virtual tables instead of system views may allow future uses like
https://wiki.postgresql.org/wiki/Foreign_data_wrappers , so long term I'd like
to consider leaving the door open for that if possible, but I'm happy to set
that desire aside if necessary in order to get the first two steps
(metrics/config and an extension point for the debugging tables/views) in
properly.
> 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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