Class SortBuffer
- java.lang.Object
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- org.apache.derby.impl.store.access.sort.SortBuffer
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class SortBuffer extends java.lang.Object
This class implements an in-memory ordered set based on the balanced binary tree algorithm from Knuth Vol. 3, Sec. 6.2.3, pp. 451-471. Nodes are always maintained in order, so that inserts and deletes can be intermixed.This algorithm will insert/delete N elements in O(N log(N)) time using O(N) space.
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Field Summary
Fields Modifier and Type Field Description private NodeAllocator
allocator
Where to allocate nodes from.private DataValueDescriptor[]
deletedKey
Set, as a side effect of deleteLeftMost (only), to the key from the node that was deleted from the tree.private Node
head
Special head node for the tree.private int
height
The current height of the tree.static int
INSERT_DUPLICATE
Returned from insert when the row which was inserted was a duplicate.static int
INSERT_FULL
Returned from insert when the row was not able to be inserted because the set was full.static int
INSERT_OK
Returned from insert when the row was inserted without incident.private int
lastAux
Read by the getLastAux() method.private int
nextAux
Set by the setNextAux() method.private MergeSort
sort
The sort this set is associated with.private boolean
subtreeShrunk
Set, as a side effect of deleteLeftMost and rotateRight, if the subtree they're working on decreased in height.
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Constructor Summary
Constructors Constructor Description SortBuffer(MergeSort sort)
Construct doesn't do anything, callers must call init and check its return code.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description (package private) int
capacity()
Return the number of elements this sorter can sort.void
check()
private java.lang.String
checkNode(Node n)
(package private) void
close()
private void
debug(java.lang.String s)
private Node
deleteLeftmost(Node thisNode)
Delete the node with the lowest key from the subtree defined by 'thisNode', maintaining balance in the subtree.private int
depth(Node n)
(package private) int
getLastAux()
Retrieve the aux value from the last node deallocated from the tree.(package private) void
grow(int percent)
Grow by a certain percent if we can(package private) boolean
init()
Initialize.(package private) int
insert(DataValueDescriptor[] k)
Insert a key k into the tree.void
print()
private void
printRecursive(Node n, int depth)
(package private) DataValueDescriptor[]
removeFirst()
Return the lowest key and delete it from the tree, preserving the balance of the tree.(package private) void
reset()
private Node
rotateRight(Node thisNode)
Perform either a single or double rotation, as appropriate, to get the subtree 'thisNode' back in balance, assuming that the right subtree of 'thisNode' is higher than the left subtree.(package private) void
setNextAux(int aux)
Arrange that the next node allocated in the tree have it's aux field set to the argument.
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Field Detail
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INSERT_OK
public static final int INSERT_OK
Returned from insert when the row was inserted without incident.- See Also:
- Constant Field Values
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INSERT_DUPLICATE
public static final int INSERT_DUPLICATE
Returned from insert when the row which was inserted was a duplicate. The set will have aggregated it in.- See Also:
- Constant Field Values
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INSERT_FULL
public static final int INSERT_FULL
Returned from insert when the row was not able to be inserted because the set was full.- See Also:
- Constant Field Values
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sort
private MergeSort sort
The sort this set is associated with.
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allocator
private NodeAllocator allocator
Where to allocate nodes from.
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head
private Node head
Special head node for the tree. Head.rightLink is the root of the tree.
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height
private int height
The current height of the tree.
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deletedKey
private DataValueDescriptor[] deletedKey
Set, as a side effect of deleteLeftMost (only), to the key from the node that was deleted from the tree. This field is only valid after a call to deleteLeftMost.
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subtreeShrunk
private boolean subtreeShrunk
Set, as a side effect of deleteLeftMost and rotateRight, if the subtree they're working on decreased in height. This field is only valid after a call to deleteLeftMost or rotateRight.
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nextAux
private int nextAux
Set by the setNextAux() method. This value is stuffed into the aux field of the next node that's allocated.
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lastAux
private int lastAux
Read by the getLastAux() method. This value is read out of the last node that was deallocated from the tree.
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Constructor Detail
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SortBuffer
SortBuffer(MergeSort sort)
Construct doesn't do anything, callers must call init and check its return code.
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Method Detail
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setNextAux
void setNextAux(int aux)
Arrange that the next node allocated in the tree have it's aux field set to the argument.
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getLastAux
int getLastAux()
Retrieve the aux value from the last node deallocated from the tree.
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init
boolean init()
Initialize. Returns false if the allocator couldn't be initialized.
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reset
void reset()
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close
void close()
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grow
void grow(int percent)
Grow by a certain percent if we can
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capacity
int capacity()
Return the number of elements this sorter can sort. It's the capacity of the node allocator minus one because the sorter uses one node for the head.
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insert
int insert(DataValueDescriptor[] k) throws StandardException
Insert a key k into the tree. Returns true if the key was inserted, false if the tree is full. Silently ignores duplicate keys.See Knuth Vol. 3, Sec. 6.2.3, pp. 455-457 for the algorithm.
- Throws:
StandardException
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removeFirst
DataValueDescriptor[] removeFirst()
Return the lowest key and delete it from the tree, preserving the balance of the tree.
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deleteLeftmost
private Node deleteLeftmost(Node thisNode)
Delete the node with the lowest key from the subtree defined by 'thisNode', maintaining balance in the subtree. Returns the node that should be the new root of the subtree. This method sets this.subtreeShrunk if the subtree of thisNode decreased in height. Saves the key that was in the deleted node in 'deletedKey'.
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rotateRight
private Node rotateRight(Node thisNode)
Perform either a single or double rotation, as appropriate, to get the subtree 'thisNode' back in balance, assuming that the right subtree of 'thisNode' is higher than the left subtree. Returns the node that should be the new root of the subtree.These are the cases depicted in diagrams (1) and (2) of Knuth (p. 454), and the node names reflect these diagrams. However, in deletion, the single rotation may encounter a case where the "beta" and "gamma" subtrees are the same height (b.balance == 0), so the resulting does not always shrink.
Note: This code will not do the "mirror image" cases. It only works when the right subtree is the higher one (this is the only case encountered when deleting leftmost nodes from the tree).
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check
public void check()
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checkNode
private java.lang.String checkNode(Node n)
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depth
private int depth(Node n)
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print
public void print()
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printRecursive
private void printRecursive(Node n, int depth)
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debug
private void debug(java.lang.String s)
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