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https://issues.apache.org/jira/browse/CALCITE-1941?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16147866#comment-16147866
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Maryann Xue commented on CALCITE-1941:
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Committed changes in PR. I removed {{contentsHaveChangedSince}} but kept
{{CachingCalciteSchema}}, which can be useful sometimes (e.g., for
AbstractSchema, JsonSchema, etc.). Except that I had to make changes to
{{JdbcTest#testSchemaCaching()}}, all tests are fine. Let me know if I can go
ahead and commit, [~julianhyde].
> Refine interface Schema#snapshot()
> ----------------------------------
>
> Key: CALCITE-1941
> URL: https://issues.apache.org/jira/browse/CALCITE-1941
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Affects Versions: 1.13.0
> Reporter: Maryann Xue
> Assignee: Maryann Xue
> Priority: Minor
> Fix For: 1.14.0
>
>
> The current Schema#snapshot(long timestamp) interface is limited, for it
> assumes that users only use timestamp for schema version control, thus we
> need something new to replace the "timestamp" parameter.
> So we'll introduce a SchemaVersion interface with a partial ordering contract
> that is:
> 1) Irreflexive: !a.isBefore(a), which means a cannot happen before itself;
> 2) Transitive: if a.isBefore(b) and b.isBefore(c) then a.isBefore(c);
> and 3) anti-symmetric: if a.isBefore(b) then !b.isBefore(a);
> User can implement their own SchemaVersion, which, aside from following the
> partial ordering contract, must also override {{equals()}}, {{hashCode()}}
> and {{toString()}}, so that user can, through overriding
> {{CalciteConnection#createPrepareContext()}}, create a Schema snapshot of a
> specific SchemaVersion used by the prepare context.
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