[jira] [Commented] (CASSANDRA-7107) General minor tidying of CollationController path

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

    [ https://issues.apache.org/jira/browse/CASSANDRA-7107?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13988852#comment-13988852 ] 

Aleksey Yeschenko commented on CASSANDRA-7107:
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Overall LGTM, some very welcome cleanup. Nice catch with the empty check in CollationController#collectTimeOrderedData(), too.

Squashed commit #1 and #3 together and added to extra commits with suggested changes, pushed to https://github.com/iamaleksey/cassandra/commits/7107

The second original commit is not included b/c I'm very uncomfortable with leaving a ColumnFamily#append() method around - it's going to be abused by some innocent sole, and there will be hard to debug suffering as a result. Inlined it into a new CF#maybeAppendColumn() method instead, that's less likely to be called by mistake (see the last commit).

The second commit has a bugfix, some improvements, nits fixed, some extra cleanup and prettiness:
- discovered only one bug - ABSC.CellCollection#size() was not calling maybeSortCells() - fixed in the commit #2
- refactored ABSC#slice() and ABTC#slice() for obviousness
- made the second binary search in ABSC#slice() use the updated lowerBound, reducing the range to search
- in CollationController#collectAllData(), in the memtable loop, using Iterables#transform() instead of copying the cells into a temporary ArrayList, to potentially reduce the amount of localCopy()-ing (esp. for low query LIMITs)
- rolled back MergeIterator#getSimple() - here, I don't think that 1-1 duplication of MergeIterator#get() is worth removing a little bit of indirection, sorry. Hope you don't have a strong opinion here, because I, weirdly, do.

> General minor tidying of CollationController path
> -------------------------------------------------
>
>                 Key: CASSANDRA-7107
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-7107
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Benedict
>            Assignee: Benedict
>            Priority: Minor
>             Fix For: 2.1 rc1
>
>
> There is a lot of unnecessary boiler plate when grabbing an iterator from an in-memory column family. This patch:
> * Removes FakeCellName
> * Avoids wrapping a non-OnDiskAtomIterator as an OnDiskAtomIterator except when the wrapping is useful
> * Removes ColumnSlice.NavigableSetIterator and creates a simpler more direct equivalent in ABTC
> * Does not construct a SliceIterator in either ABSC or ABTC if only one slice is requested (just returns that slice as an Iterator)
> * Does not construct multiple list indirections in ABSC when constructing a slice
> * Shares forward/reverse iterators in ABSC between slices and full-iteration
> * Avoids O(N) comparisons during collation of results into an ABSC, by using the knowledge that all columns are provided in insertion order from a merge iterator



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