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https://issues.apache.org/jira/browse/CASSANDRA-172?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12710500#action_12710500
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Jonathan Ellis commented on CASSANDRA-172:
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> For the CF wrapper, I need to resolve a column at a time so that I know when
> I have enough columns to return (since a column could be deleted).
It's O(N^2) to do a "for 1..N: L.add(cf2); resolve(L)" so that really needs to
be avoided. (even just removeDeleted is O(N) so don't nest that either.) SC
removeDeleted in particular does a ton of allocations, it's not intended to be
called repeatedly.
Since we are only concerned about counting top-level IColumns (even if this is
called on a super CF) then manually resolving is easy: "if column is live:
cf.addColumn(column)"
> I am not exactly sure how to apply your addColumn suggestion, since there is
> no place to call a single final resolve.
I don't understand the dillemma. building up a CF as described and then
"return removeDeleted(cf)" takes care of it. There is no resolving to do this
way.
> If all iterators are empty, an empty CF will be returned. I don't really need
> to update the tombstone in the CF unless for read-repair considerations.
> However, the current read-repair logic doesn't deal with CF removal.
Better to preserve correct behavior re CF tombstones when returning a CF than
be surprised by it later, especially when there is no pain in doing so. No?
> A improved and more general version of get_slice
> ------------------------------------------------
>
> Key: CASSANDRA-172
> URL: https://issues.apache.org/jira/browse/CASSANDRA-172
> Project: Cassandra
> Issue Type: New Feature
> Reporter: Jun Rao
> Assignee: Jun Rao
> Fix For: 0.4
>
> Attachments: get_slice_from.patchv1, get_slice_from.patchv2
>
>
> Today, get_slice has to scan through all columns in every memtable and
> sstable to get a slice of columns. This becomes inefficient when the number
> of columns in a row is large. We need a more efficient API.
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