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https://issues.apache.org/jira/browse/CASSANDRA-9975?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Benedict updated CASSANDRA-9975:
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Attachment: before - schema query.png
before - limit query.png
after - schema query.png
after - limit query.png
Aleksey suggested you may be looking for some screenshots of debug points for
comparison. It's hard to convey the improved clarity, so I suggest you try
debugging for yourself, but attached are a couple of example comparisons.
They're not the most egregious, just easy to generate equivalents.
> Flatten Iterator call hierarchy with a shared Transformer
> ---------------------------------------------------------
>
> Key: CASSANDRA-9975
> URL: https://issues.apache.org/jira/browse/CASSANDRA-9975
> Project: Cassandra
> Issue Type: Sub-task
> Components: Core
> Reporter: Benedict
> Assignee: Benedict
> Fix For: 3.0.0
>
> Attachments: after - limit query.png, after - schema query.png,
> before - limit query.png, before - schema query.png
>
>
> Stepping through a read response is made exceedingly difficult by the sheer
> depth of the call hierarchy, and how rapidly your context jumps around. This
> ticket intend to partially address that, by flattening one of the main causes
> of this: iterator transformations.
> I have a patch that attempts to mitigate (but not entirely eliminate) this,
> through the introduction of a {{RowTransformer}} class that all
> transformations are applied through. If a transformation has already been
> applied, the {{RowTransformer}} class does not wrap a new iterator, but
> instead returns a new {{RowTransformer}} that wraps the original underlying
> (untransformed) iterator and both transformations. This can accumulate an
> arbitrary number of transformations and, quite importantly, can apply the
> filtration step {{Unfiltered -> Row}} in the same instance as well. The
> intention being that a majority of control flow happens inside this
> {{RowTransformer}}, so there is far less context jumping to cope with.
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