[jira] [Commented] (CASSANDRA-12443) Remove alter type support

["Aleksey Yeschenko (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-12443?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15417689#comment-15417689 ] 

Aleksey Yeschenko commented on CASSANDRA-12443:
-----------------------------------------------

Yup.

Another similar, but more subtle problem is with dropping columns repeatedly. Drop column foo (text), re-add it as foo (int), drop it again, and sstables where foo was still text would cause real issues on reading.

> Remove alter type support
> -------------------------
>
>                 Key: CASSANDRA-12443
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-12443
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Carl Yeksigian
>             Fix For: 4.x
>
>
> Currently, we allow altering of types. However, because we no longer store the length for all types anymore, switching from a fixed-width to variable-width type causes issues. commitlog playback breaking startup, queries currently in flight getting back bad results, and special casing required to handle the changes. In addition, this would solve CASSANDRA-10309, as there is no possibility of the types changing while an SSTableReader is open.
> For fixed-length, compatible types, the alter also doesn't add much over a cast, so users could use that in order to retrieve the altered type.



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