[jira] [Commented] (CASSANDRA-11072) Further unify Partition access methods, by removing searchIterator()

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

    [ https://issues.apache.org/jira/browse/CASSANDRA-11072?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15117159#comment-15117159 ] 

Benedict commented on CASSANDRA-11072:
--------------------------------------

Initial patch available [here|https://github.com/belliottsmith/cassandra/tree/11072]

[~slebresne], entirely up to you if we proceed or not, and which approach you prefer.

> Further unify Partition access methods, by removing searchIterator()
> --------------------------------------------------------------------
>
>                 Key: CASSANDRA-11072
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-11072
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Benedict
>            Assignee: Benedict
>            Priority: Minor
>             Fix For: 3.x
>
>
> After CASSANDRA-9986, the access paths can be further incrementally simplified.  In particular, the {{searchIterator}} method is only not trivially replaced in one location, and by removing it we can simplify the {{SearchIterator}} hierarchy, and merge the {{ClusteringIndexFilter}} hierarchy, as both use {{Slices}} now.
> In the one remaining location, three approaches are possible (of which I have implemented two in the attached patch; one in the first diff, one in the last):
> # Apply a transformation to the UnfilteredRowIterator composed of a slices query
> # Call {{getRow}} repeatedly
> # Provide access to an {{unfilteredSearchIterator}} for this method only, since we do not need to perform the complex filtration for this access path
> These are in decreasing order of costliness (CPU-wise); I don't have a fixed preference.
> This is just a step towards further necessary improvements. IMO, this should be followed by:
> # Supporting efficient "slicing" of a SearchIterator, so that the internal iteration of slices within {{unfilteredRowIterator}} is made cheap enough to not warrant a separate path (this would help all slice queries)
> ## Merging Slice and Clustering hierarchies, perhaps by making Slice an interface and having Clustering implement it.
> ## Specialising Slices when it contains only Clustering, so that it can implement NavigableSet<Clustering> (most likely by having it backed by, or extend, BTreeSet)
> ## Thus, saving a lot of shuffling and reconstruction costs around our filters, and reducing the duplication of concepts in {{ClusteringIndexNamesFilter}}



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