[jira] Updated: (DERBY-3022) Index Split stops right after restarting to split the parent node

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

     [ https://issues.apache.org/jira/browse/DERBY-3022?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Kathey Marsden updated DERBY-3022:
----------------------------------

    Issue Type: Improvement  (was: Bug)

Changing to improvement. User did not indicate a failing case with the issue.


> 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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