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From "Sylvain Lebresne (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-5715) CAS on 'primary key only' table
Date Mon, 01 Jul 2013 14:56:20 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-5715?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13696860#comment-13696860
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Sylvain Lebresne commented on CASSANDRA-5715:
---------------------------------------------

I understand that, but CQL doesn't ever allow a PK column to be in the SET clause contrarily
to SQL. So allowing it in just that case wouldn't make sense unless we start allowing PK columns
in the SET clause in general. Note sure it's worth going there.
                
> CAS on 'primary key only' table
> -------------------------------
>
>                 Key: CASSANDRA-5715
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-5715
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Sylvain Lebresne
>            Priority: Minor
>
> Given a table with only a primary key, like
> {noformat}
> CREATE TABLE test (k int PRIMARY KEY)
> {noformat}
> there is currently no way to CAS a row in that table into existing because:
> # INSERT doesn't currently support IF
> # UPDATE has no way to update such table
> So we should probably allow IF conditions on INSERT statements.
> In addition (or alternatively), we could work on allowing UPDATE to update such table.
One motivation for that could be to make UPDATE always be more general to INSERT. That is
currently, there is a bunch of operation that INSERT cannot do (counter increments, collection
appends), but that "primary key table" case is, afaik, the only case where you *need* to use
INSERT. However, because CQL forces segregation of PK value to the WHERE clause and not to
the SET one, the only syntax that I can see work would be:
> {noformat}
> UPDATE WHERE k=0;
> {noformat}
> which maybe is too ugly to allow?
>  

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