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https://issues.apache.org/jira/browse/CASSANDRA-7622?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15315917#comment-15315917
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Jeff Jirsa edited comment on CASSANDRA-7622 at 6/5/16 3:25 PM:
---------------------------------------------------------------
Hey [~snazy], really appreciate any feedback.
{quote}
Don't get me wrong, I really like virtual tables, but I am not a fan of a
{{CREATE TABLE}} for metrics - instead, I think it is better to provide
predefined, virtual tables for what we have in a "virtual keyspace" like
{{system_metrics}} or {{system_management}}.
{quote}
Totally agree that we should pre-define the tables we care about and will
support/maintain in the tree, but even traditional system tables get created by
{{CREATE TABLE}} throughout the code base - why would virtual be any
different? We can still bake it in by default as we do with {{SchemaKeyspace}}
and {{SystemDistributedKeyspace}}, but allowing arbitrary virtual table
creation by {{CREATE TABLE}} also lets users create their own.
{quote}
Some administrative operations probably require additional CQL commands (e.g.
{{ALTER SYSTEM DRAIN;}} ).
{quote}
What you're proposing makes sense, and seems reasonable, but also extends the
DDL in ways that may not be necessary - we could alternatively use {{ALTER
system_virtual.actions SET drain=true;}} and let whatever virtual table handler
controls {{system_virtual.actions}} run drain and shut down, getting the same
impact without extending the DDL?
was (Author: jjirsa):
Hey [~snazy], really appreciate any feedback.
{quote}
Don't get me wrong, I really like virtual tables, but I am not a fan of a
{{CREATE TABLE}} for metrics - instead, I think it is better to provide
predefined, virtual tables for what we have in a "virtual keyspace" like
{{system_metrics}} or {{system_management}}.
{quote}
Totally agree that we should pre-define the tables we care about and will
support/maintain in the tree, but even traditional system tables get created by
{{CREATE TABLE}} throughout the code base - why would virtual be any
different? We can still bake it in by default as we do with {{SchemaKeyspace}}
and {{SystemDistributedKeyspace}}, but allowing arbitrary virtual table
creation by {{CREATE TABLE}} also lets users create their own.
{quote}
Some administrative operations probably require additional CQL commands (e.g.
{{ALTER SYSTEM DRAIN;}} ).
{quote}
What you're proposing makes sense, and seems reasonable, but also extends the
DDL in ways that may not be necessary - we could alternatively use {{ALTER
system_virtual.actions SET drain=true; }} and let whatever virtual table
handler controls {{system_virtual.actions}} run drain and shut down, getting
the same impact without extending the DDL?
> Implement virtual tables
> ------------------------
>
> Key: CASSANDRA-7622
> URL: https://issues.apache.org/jira/browse/CASSANDRA-7622
> Project: Cassandra
> Issue Type: Improvement
> Reporter: Tupshin Harper
> Assignee: Jeff Jirsa
> Fix For: 3.x
>
>
> 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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