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From "Jeff Jirsa (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (CASSANDRA-7622) Implement virtual tables
Date Sun, 05 Jun 2016 15:25:59 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-7622?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15315917#comment-15315917
] 

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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