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From "Patrick McFadin (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-9200) Sequences
Date Mon, 18 May 2015 17:16:01 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-9200?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14548314#comment-14548314
] 

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

Can somebody expound a bit on the use case dictating this change? In an RDBMS they are critical
for unique PKs and scanning sequential records. A UUID vs a numeric is going to be just as
random once it is hashed. Are we talking about the ability for a application to scan based
on a sequence?

Twitter Snowflake tried to accomplish something similar with Zookeeper. I know there were
failure modes difficult to manage and is now no longer available on GitHub. I can't think
of any project that has done this without introducing very restrictive failure modes. 

> 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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