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

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

Benedict created CASSANDRA-11072:
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             Summary: 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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