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From "Aleksey Yeschenko (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-8480) Update of primary key should be possible
Date Tue, 16 Dec 2014 15:50:13 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-8480?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14248388#comment-14248388
] 

Aleksey Yeschenko commented on CASSANDRA-8480:
----------------------------------------------

Don't get me wrong. We obviously want Cassandra to be as usable as possible, and CQL as expressive
as possible, too.

Yet, there are things that are fundamentally anti-Cassandra, and this request is one of those
things. One of the core principles of Cassandra is not introducing implicit reads to the write
path, thus having the write path have consistent performance characteristics.

Another ticket similar to this one is CASSANDRA-6750. That one would also be good to have.
We recognize that. That said, being a distributed database with a focus on scaling out, we
have to restrict certain functionality that doesn't fit the overall direction of the project
:(

> Update of primary key should be possible
> ----------------------------------------
>
>                 Key: CASSANDRA-8480
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-8480
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: API
>            Reporter: Jason Kania
>
> While attempting to update a column in a row, I encountered the error
> PRIMARY KEY part thingy found in SET part
> The error is not helpful as it doesn't state why this is problem so I looked on google
and encountered many, many entries from people who have experienced the issue including those
with single column table who have to hack to work around this.
> After looking around further in the documentation, I discovered that it is not possible
to update a primary key but I still have not found a good explanation. I suspect that that
this is because it would change the indexing location of the record effectively requiring
a delete followed by an insert. If the question is one of guaranteeing no update to a deleted
row, a client will have the same issue.
> To me, this really should be handled behind the API because:
> 1) it is an expected capability in a database to update all columns and having these
limitations only puts off potential users especially when they have to discover the limitation
after the fact
> 2) being able to use a column in a WHERE clause requires it to be part of the primary
key so what this limitation means is if you can update a column, you can't search for it,
or if you can search on a column, you can't update it which leaves a serious gap in handling
a wide number of use cases.
> 3) deleting and inserting a row with an updated primary key will mean sucking in all
the data from the row up to the client and sending it all back down even when a single column
in the primary key was all that was updated.
> Why not document the issue but make the interface more usable by supporting the operation?
> Jason



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