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From "Patrick McFadin (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-9200) Sequences
Date Wed, 01 Jul 2015 17:17:05 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-9200?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14610660#comment-14610660
] 

Patrick McFadin commented on CASSANDRA-9200:
--------------------------------------------

Bugs, user error, sun spots, anything that may cause values to become overlapping. You get
the safety of unique checks in RDBMS to stop you from overwriting. If I were to advise someone
to use a sequence on a partition key, always use IF NOT EXISTS on insert. If it were a 32
bit value, what do you get after inserting 4 billion keys? 

If these were scoped per partition, the chance of data loss is much less. In addition, I can
see the general usefullness of having an increasing number for ordering in partition without
the need for something like a timeUUID or timestamp. 

[~tupshin] not sure if this matches with your IMAP use case. Seems like it would. 

> Sequences
> ---------
>
>                 Key: CASSANDRA-9200
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-9200
>             Project: Cassandra
>          Issue Type: New Feature
>            Reporter: Jonathan Ellis
>            Assignee: Robert Stupp
>             Fix For: 3.x
>
>
> UUIDs are usually the right choice for surrogate keys, but sometimes application constraints
dictate an increasing numeric value.
> We could do this by using LWT to reserve "blocks" of the sequence for each member of
the cluster, which would eliminate paxos contention at the cost of not being strictly increasing.
> PostgreSQL syntax: http://www.postgresql.org/docs/9.4/static/sql-createsequence.html



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