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From "Sylvain Lebresne (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (CASSANDRA-4734) Move CQL3 consistency to protocol
Date Mon, 01 Oct 2012 15:17:07 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-4734?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Sylvain Lebresne updated CASSANDRA-4734:
----------------------------------------

    Attachment: 0002-Remove-remains-of-4448.txt
                0001-Move-consistency-level-to-the-protocol-level.txt

Attaching patches to do that.

There is the question of thrift. The current patch choses to introduce two new, CQL3 only,
execute_cql3_query and execute_prepared_cql3_query methods and start refusing CQL3 queries
in the old methods. This may or may not be what we want to do, and even if it is, we probably
can do some cleanups if we start separating the calls for CQL2 and CQL3.


                
> Move CQL3 consistency to protocol
> ---------------------------------
>
>                 Key: CASSANDRA-4734
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-4734
>             Project: Cassandra
>          Issue Type: Task
>          Components: API
>            Reporter: Jonathan Ellis
>            Assignee: Sylvain Lebresne
>             Fix For: 1.2.0 beta 2
>
>         Attachments: 0001-Move-consistency-level-to-the-protocol-level.txt, 0002-Remove-remains-of-4448.txt
>
>
> Currently, in CQL3, you set the consistency level of an operation in
> the language, eg 'SELECT * FROM foo USING CONSISTENCY QUORUM'.  It now
> looks like this was a mistake, and that consistency should be set at
> the protocol level, i.e. as a separate parameter along with the query.
> The reasoning is that the CL applies to the guarantee provided by the
> operation being successful, not to the query itself.  Specifically,
> having the CL being part of the language means that CL is opaque to
> low level client libraries without themselves parsing the CQL, which
> we want to avoid.  Thus,
> - Those libraries can't implement automatic retries policy, where a query would be retried
with a smaller CL.  (I'm aware that this is often a Bad Idea, but it does have legitimate
uses and not having that available is seen as a regression from the Thrift api.)
> - We had to introduce CASSANDRA-4448 to allow the client to configure some  form of default
CL since the library can't handle that anymore, which is  hackish.
> - Executing prepared statements with different CL requires preparing multiple statements.
> - CL only makes sense for BATCH operations as a whole, not the sub-statements within
the batch. Currently CQL3 "fixes" that by validating the given CLs match, but it would be
much more clear if the CL was on the protocol side.

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