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https://issues.apache.org/jira/browse/CASSANDRA-9989?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16591169#comment-16591169
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Jay Zhuang commented on CASSANDRA-9989:
---------------------------------------
Sorry, I missed {{point 1.}} (I thought it's something else), but you already
get it:
{noformat}
int childrenNum = (size + childSize + 1) / (childSize +1)
==> int childrenNum = size / (childSize + 1) + (childSize + 1) / (childSize +
1)
==> int childrenNum = size / (childSize + 1) + 1
{noformat}
We can make it more clear with: {{(size / (childSize + 1)) + 1}}.
{quote}I think it might be nicer in this case to make the TREE_SIZE logically
more obvious, so that its accessors (which are rather more complicated) are
simplified, rather than its calculation? I don't think this is very tricky
anyway - just set TREE_SIZE[0] = FAN_FACTOR, and leave the loop as it is, I
think?
{quote}
It's also used here:
[{{TREE_SIZE[level-2]}}|https://github.com/cooldoger/cassandra/commit/8369dc8b7be3ccf8d1972e9c8cff95adb3493005#diff-4b911b7d0959c6219175e2349968f3cdR196].
Which needs to be changed to: {{int grandchildSize = level == 1 ? 0 :
TREE_SIZE[level - 2];}}. I prefer avoiding this check while building every node
(will add a comment that leaf node is level 1). But I'm fine with either way.
{quote}I think this is also more easily done by an incrementing counter, rather
than decrementing?
{quote}
Sure, I'll update the patch for that.
> Optimise BTree.Buider
> ---------------------
>
> Key: CASSANDRA-9989
> URL: https://issues.apache.org/jira/browse/CASSANDRA-9989
> Project: Cassandra
> Issue Type: Sub-task
> Reporter: Benedict
> Assignee: Jay Zhuang
> Priority: Minor
> Fix For: 4.x
>
> Attachments: 9989-trunk.txt
>
>
> BTree.Builder could reduce its copying, and exploit toArray more efficiently,
> with some work. It's not very important right now because we don't make as
> much use of its bulk-add methods as we otherwise might, however over time
> this work will become more useful.
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