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From "Michael Merickel (JIRA)" <j...@apache.org>
Subject [jira] Commented: (CASSANDRA-1087) load schema from schema.yaml or schema.xml if no schema is present and definition file exists in the classpath.
Date Fri, 21 May 2010 16:13:19 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-1087?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12870031#action_12870031
] 

Michael Merickel commented on CASSANDRA-1087:
---------------------------------------------

The motivation would be to simplify the creation of small non-production clusters (like everyone
tries when they want to see what Cassandra is all about). In this case the BadThings(tm) would
likely be the common case, where I just copy my schema.yaml to the new clusters because it
makes sense... that's how you setup the first node.

It feels similar to setting up bind9 in a distributed fashion where you change a zone file
and you need to update the timestamp or the file is ignored. If you want the node to read
your local changes to schema.yaml you need to provide a number or tag greater than what it
has, or it'll just be ignored. Thus you could put the same file everywhere, with the same
ID... it propagates through the system but it's simply ignored by nodes that already have
read the schema defined by that ID. Easy way to solve a lot of potential conflicts in the
schema file.

Anyway when a patch comes with an ACHTUNG! flag from a core developer, I feel the likelihood
that a new user may fall into this trap is almost a guarantee.

> load schema from schema.yaml or schema.xml if no schema is present and definition file
exists in the classpath.
> ---------------------------------------------------------------------------------------------------------------
>
>                 Key: CASSANDRA-1087
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-1087
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Gary Dusbabek
>            Assignee: Gary Dusbabek
>             Fix For: 0.7
>
>         Attachments: 0001-load-schema-from-schema.yaml-if-on-the-classpath.patch, 0002-remove-loadSchemaFromYaml-from-StorageServiceMBean.patch
>
>
> While I'm at it, this would be a good time to update http://wiki.apache.org/cassandra/API
to include documentation about the system_* calls.

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