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https://issues.apache.org/jira/browse/DERBY-3022?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Kathey Marsden updated DERBY-3022:
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Urgency: Normal (was: Urgent)
Changing to normal urgency. This is an improvement and won't make it for 10.5.2
> Index Split stops right after restarting to split the parent node
> -----------------------------------------------------------------
>
> Key: DERBY-3022
> URL: https://issues.apache.org/jira/browse/DERBY-3022
> Project: Derby
> Issue Type: Improvement
> Components: Store
> Affects Versions: 10.3.1.4
> Environment: windows
> Reporter: Kangmo Kim
>
> Whle I was analyzing source code, I found that
> at org.apache.derby.impl.store.access.btree.BranchControlRow
> splitFor method tries to split the branch node.
> But, as soon as it finds that the parent node does not have enough space to
> insert
> the split branch row (the mid row in the page to be splitted),
> it calls restartSplitFor to restart split...
> // At this point we have guaranteed there is space in the parent
> // page for splitrow, but it could be the case that the new
> // "newbranchrow" does not fit on the parent page.
> if (!parent.page.spaceForInsert(
> newbranchrow.getRow(), (FormatableBitSet) null,
>
> AccessFactoryGlobals.BTREE_OVERFLOW_THRESHOLD))
> {
> // There is no room on the parent page to complete a split at
> // the current level, so restart the split at top with the
> // branchrow that did not fit. On return from this routine
> // there is no way to know the state of the tree, so the
> // current split pass recursion must end.
> return(
> parent.restartSplitFor(
> open_btree, template, parent, this,
> newbranchrow.getRow(), splitrow, flag));
> }
> Right before following the code, what I guessed was that
> restartSplitFor would insert newbranchrow into parent, and continue to split
> nodes to reserve space insert splitrow at leaf node of b-tree.
> public static long restartSplitFor(
> OpenBTree open_btree,
> DataValueDescriptor[] template,
> BranchControlRow parent,
> ControlRow child,
> DataValueDescriptor[] newbranchrow,
> DataValueDescriptor[] splitrow,
> int flag)
> throws StandardException
> {
> // release parent and current latch
> parent.release();
> child.release();
> parent = null;
> child = null;
> // Get the root page back, and perform a split following the
> // branch row which would not fit.
> ControlRow root = ControlRow.get(open_btree, BTree.ROOTPAGEID);
> if (SanityManager.DEBUG)
> SanityManager.ASSERT(root.page.isLatched());
> return(root.splitFor(open_btree, template, null, newbranchrow, flag));
> }
> But what I found was...
> It just inserts the split branch row into the parent,
> and ends...
> restartSplitFor should continue to split nodes to reserve space to insert
> splitrow at leaf level.
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