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Posted to commits@cassandra.apache.org by "Aleksey Yeschenko (JIRA)" <ji...@apache.org> on 2017/01/27 22:22:24 UTC
[jira] [Comment Edited] (CASSANDRA-9425) Make node-local schema
fully immutable
[ https://issues.apache.org/jira/browse/CASSANDRA-9425?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15843582#comment-15843582 ]
Aleksey Yeschenko edited comment on CASSANDRA-9425 at 1/27/17 10:22 PM:
------------------------------------------------------------------------
Committed as [af3fe39dcabd9ef77a00309ce6741268423206df|https://github.com/apache/cassandra/commit/af3fe39dcabd9ef77a00309ce6741268423206df] to trunk. Will open up a separate follow up ticket for DDL statement rework, as the comment section for this JIRA has grown quite a bit.
Thanks again for the review.
was (Author: iamaleksey):
Committed as [af3fe39dcabd9ef77a00309ce6741268423206df|] to trunk. Will open up a separate follow up ticket for DDL statement rework, as the comment section for this JIRA has grown quite a bit.
Thanks again for the review.
> Make node-local schema fully immutable
> --------------------------------------
>
> Key: CASSANDRA-9425
> URL: https://issues.apache.org/jira/browse/CASSANDRA-9425
> Project: Cassandra
> Issue Type: Sub-task
> Reporter: Aleksey Yeschenko
> Assignee: Aleksey Yeschenko
> Fix For: 4.0
>
>
> The way we handle schema changes currently is inherently racy.
> All of our {{SchemaAlteringStatement}} s perform validation on a schema state that's won't necessarily be there when the statement gets executed and mutates schema.
> We should make all the *Metadata classes ({{KeyspaceMetadata, TableMetadata}}, {{ColumnMetadata}}, immutable, and local schema persistently snapshottable, with a single top-level {{AtomicReference}} to the current snapshot. Have DDL statements perform validation and transformation on the same state.
> In pseudo-code, think
> {code}
> public interface DDLStatement
> {
> /**
> * Validates that the DDL statement can be applied to the provided schema snapshot.
> *
> * @param schema snapshot of schema before executing CREATE KEYSPACE
> */
> void validate(SchemaSnapshot schema);
>
> /**
> * Applies the DDL statement to the provided schema snapshot.
> * Implies that validate() has already been called on the provided snapshot.
> *
> * @param schema snapshot of schema before executing the statement
> * @return snapshot of schema as it would be after executing the statement
> */
> SchemaSnapshot transform(SchemaSnapshot schema);
> }
> {code}
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