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Andy Tolbert commented on CASSANDRA-8005:
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A new ticket has been opened, [CASSANDRA-14825], that revisits this concept.
This time CQL schema is exposed via virtual tables (i.e. {{select * from
system_views.describe_keyspace where keyspace_name = 'mykeyspace'}}). This
functionality is not meant to replace the structured schema information shared
via the {{system_schema}} keyspace, but to provide a means of getting the CQL
DDL, which is useful for tooling and backing up schema in such a way that can
be recreated. Today, both the java driver and python driver provide this
capability, but it has proven to be difficult to support multiple C* versions
simultaneously as new properties are changed and existing ones are replaced
release to release. I think it'd be much more useful to decouple a driver
implementation from providing this capability and should also be less
error-prone.
Does anyone see any reason to be hesitant about providing such capability via
virtual tables? The server already had the capability of emitting CQL schema
(although it had some issues which are addressed in this ticket) and we have a
functional patch available.
> Server-side DESCRIBE
> --------------------
>
> Key: CASSANDRA-8005
> URL: https://issues.apache.org/jira/browse/CASSANDRA-8005
> Project: Cassandra
> Issue Type: New Feature
> Components: CQL
> Reporter: Tyler Hobbs
> Priority: Minor
> Labels: client-impacting, cql3
>
> The various {{DESCRIBE}} commands are currently implemented by cqlsh, and
> nearly identical implementations exist in many drivers. There are several
> motivations for making {{DESCRIBE}} part of the CQL language:
> * Eliminate the (fairly complex) duplicate implementations across drivers and
> cqlsh
> * Get closer to allowing drivers to not have to fetch the schema tables.
> (Minor changes to prepared statements are also needed.)
> * Have instantaneous support for new schema features in cqlsh. (You
> currently have to update the bundled python driver.)
> * Support writing out schemas where it makes sense. One good example of this
> is backups. You need to restore the schema before restoring data in the case
> of total loss, so it makes sense to write out the schema alongside snapshots.
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