[jira] [Commented] (CASSANDRA-9975) Flatten RowIterator call hierarchy with a shared RowTransformer

["Aleksey Yeschenko (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-9975?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14729392#comment-14729392 ] 

Aleksey Yeschenko commented on CASSANDRA-9975:
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Will do the first round of review before tomorrow morning. Will relabel back to b2 if we end up committing in time, though.

> Flatten RowIterator call hierarchy with a shared RowTransformer
> ---------------------------------------------------------------
>
>                 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 rc1
>
>
> 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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