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From "Aleksey Yeschenko (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-9975) Flatten RowIterator call hierarchy with a shared RowTransformer
Date Sat, 12 Sep 2015 13:23:45 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-9975?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14742053#comment-14742053
] 

Aleksey Yeschenko commented on CASSANDRA-9975:
----------------------------------------------

Relabeling as 3.0.x, as it's strictly speaking not rc-blocking, not user-visible, and yet
not too intrusive to put it into 3.0.0 final or even 3.0.1, worst case. Might still make it
into rc1 however.

> 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.x
>
>
> 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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