Generic implementation of red-black binary tree. It's planned to use in

several places, but for now only GIN uses it during index creation.
Using self-balanced tree greatly speeds up index creation in corner cases
with preordered data.

1 files changed, 790 insertions, 0 deletions

diff --git a/src/backend/utils/misc/rbtree.c b/src/backend/utils/misc/rbtree.c
new file mode 100644
index 00000000000..d7b129fcb24
--- /dev/null
+++ b/src/backend/utils/misc/rbtree.c
@@ -0,0 +1,790 @@
+/*-------------------------------------------------------------------------
+ *
+ * rbtree.c
+ *	  implementation for PostgreSQL generic Red-Black binary tree package
+ *	  Adopted from http://algolist.manual.ru/ds/rbtree.php
+ *
+ * This code comes from Thomas Niemann's "Sorting and Searching Algorithms:
+ * a Cookbook".
+ *
+ * See http://www.cs.auckland.ac.nz/software/AlgAnim/niemann/s_man.htm for
+ * license terms: "Source code, when part of a software project, may be used
+ * freely without reference to the author."
+ *
+ * Red-black trees are a type of balanced binary tree wherein (1) any child of
+ * a red node is always black, and (2) every path from root to leaf traverses
+ * an equal number of black nodes.  From these properties, it follows that the
+ * longest path from root to leaf is only about twice as long as the shortest,
+ * so lookups are guaranteed to run in O(lg n) time.
+ *
+ * Copyright (c) 1996-2009, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  $PostgreSQL: pgsql/src/backend/utils/misc/rbtree.c,v 1.1 2010/02/11 14:29:50 teodor Exp $
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "utils/rbtree.h"
+
+/**********************************************************************
+ *						 Declarations								  *
+ **********************************************************************/
+
+/*
+ * Values for RBNode->iteratorState
+ */
+#define InitialState 	(0)
+#define FirstStepDone	(1)
+#define SecondStepDone	(2)
+#define ThirdStepDone	(3)
+
+/*
+ * Colors of node
+ */
+#define RBBLACK		(0)
+#define RBRED		(1)
+
+typedef struct RBNode
+{
+	uint32		iteratorState:2,
+				color:	1 ,
+				unused: 29;
+	struct RBNode *left;
+	struct RBNode *right;
+	struct RBNode *parent;
+	void	   *data;
+}	RBNode;
+
+struct RBTree
+{
+	RBNode	   *root;
+	rb_comparator comparator;
+	rb_appendator appendator;
+	rb_freefunc freefunc;
+	void	   *arg;
+};
+
+struct RBTreeIterator
+{
+	RBNode	   *node;
+	void	   *(*iterate) (RBTreeIterator *iterator);
+};
+
+/*
+ * all leafs are sentinels, use customized NIL name to prevent
+ * collision with sytem-wide NIL which is actually NULL
+ */
+#define RBNIL &sentinel
+
+RBNode		sentinel = {InitialState, RBBLACK, 0, RBNIL, RBNIL, NULL, NULL};
+
+/**********************************************************************
+ *						  Create									  *
+ **********************************************************************/
+
+RBTree *
+rb_create(rb_comparator comparator, rb_appendator appendator,
+				  rb_freefunc freefunc, void *arg)
+{
+	RBTree	   *tree = palloc(sizeof(RBTree));
+
+	tree->root = RBNIL;
+	tree->comparator = comparator;
+	tree->appendator = appendator;
+	tree->freefunc = freefunc;
+	tree->arg = arg;
+
+	return tree;
+}
+
+/**********************************************************************
+ *						  Search									  *
+ **********************************************************************/
+
+void *
+rb_find(RBTree *rb, void *data)
+{
+	RBNode	   *node = rb->root;
+	int			cmp;
+
+	while (node != RBNIL)
+	{
+		cmp = rb->comparator(data, node->data, rb->arg);
+
+		if (cmp == 0)
+			return node->data;
+		else if (cmp < 0)
+			node = node->left;
+		else
+			node = node->right;
+	}
+
+	return NULL;
+}
+
+/**********************************************************************
+ *							  Insertion								  *
+ **********************************************************************/
+
+/*
+ * Rotate node x to left.
+ *
+ * x's right child takes its place in the tree, and x becomes the left
+ * child of that node.
+ */
+static void
+rb_rotate_left(RBTree *rb, RBNode *x)
+{
+	RBNode	   *y = x->right;
+
+	/* establish x->right link */
+	x->right = y->left;
+	if (y->left != RBNIL)
+		y->left->parent = x;
+
+	/* establish y->parent link */
+	if (y != RBNIL)
+		y->parent = x->parent;
+	if (x->parent)
+	{
+		if (x == x->parent->left)
+			x->parent->left = y;
+		else
+			x->parent->right = y;
+	}
+	else
+	{
+		rb->root = y;
+	}
+
+	/* link x and y */
+	y->left = x;
+	if (x != RBNIL)
+		x->parent = y;
+}
+
+/*
+ * Rotate node x to right.
+ *
+ * x's left right child takes its place in the tree, and x becomes the right
+ * child of that node.
+ */
+static void
+rb_rotate_right(RBTree *rb, RBNode *x)
+{
+	RBNode	   *y = x->left;
+
+	/* establish x->left link */
+	x->left = y->right;
+	if (y->right != RBNIL)
+		y->right->parent = x;
+
+	/* establish y->parent link */
+	if (y != RBNIL)
+		y->parent = x->parent;
+	if (x->parent)
+	{
+		if (x == x->parent->right)
+			x->parent->right = y;
+		else
+			x->parent->left = y;
+	}
+	else
+	{
+		rb->root = y;
+	}
+
+	/* link x and y */
+	y->right = x;
+	if (x != RBNIL)
+		x->parent = y;
+}
+
+/*
+ * Maintain Red-Black tree balance after inserting node x.
+ *
+ * The newly inserted node is always initially marked red.  That may lead to
+ * a situation where a red node has a red child, which is prohibited.  We can
+ * always fix the problem by a series of color changes and/or "rotations",
+ * which move the problem progressively higher up in the tree.  If one of the
+ * two red nodes is the root, we can always fix the problem by changing the
+ * root from red to black.
+ *
+ * (This does not work lower down in the tree because we must also maintain
+ * the invariant that every leaf has equal black-height.)
+ */
+static void
+rb_insert_fixup(RBTree *rb, RBNode *x)
+{
+	/*
+	 * x is always a red node.  Initially, it is the newly inserted node.
+	 * Each iteration of this loop moves it higher up in the tree.
+	 */
+	while (x != rb->root && x->parent->color == RBRED)
+	{
+		/*
+		 * x and x->parent are both red.  Fix depends on whether x->parent is
+		 * a left or right child.  In either case, we define y to be the
+		 * "uncle" of x, that is, the other child of x's grandparent.
+		 *
+		 * If the uncle is red, we flip the grandparent to red and its two
+		 * children to black.  Then we loop around again to check whether the
+		 * grandparent still has a problem.
+		 *
+		 * If the uncle is black, we will perform one or two "rotations" to
+		 * balance the tree.  Either x or x->parent will take the grandparent's
+		 * position in the tree and recolored black, and the original
+		 * grandparent will be recolored red and become a child of that node.
+		 * This always leaves us with a valid red-black tree, so the loop
+		 * will terminate.
+		 */
+		if (x->parent == x->parent->parent->left)
+		{
+			RBNode	   *y = x->parent->parent->right;
+
+			if (y->color == RBRED)
+			{
+				/* uncle is RBRED */
+				x->parent->color = RBBLACK;
+				y->color = RBBLACK;
+				x->parent->parent->color = RBRED;
+				x = x->parent->parent;
+			}
+			else
+			{
+				/* uncle is RBBLACK */
+				if (x == x->parent->right)
+				{
+					/* make x a left child */
+					x = x->parent;
+					rb_rotate_left(rb, x);
+				}
+
+				/* recolor and rotate */
+				x->parent->color = RBBLACK;
+				x->parent->parent->color = RBRED;
+				rb_rotate_right(rb, x->parent->parent);
+			}
+		}
+		else
+		{
+			/* mirror image of above code */
+			RBNode	   *y = x->parent->parent->left;
+
+			if (y->color == RBRED)
+			{
+				/* uncle is RBRED */
+				x->parent->color = RBBLACK;
+				y->color = RBBLACK;
+				x->parent->parent->color = RBRED;
+				x = x->parent->parent;
+			}
+			else
+			{
+				/* uncle is RBBLACK */
+				if (x == x->parent->left)
+				{
+					x = x->parent;
+					rb_rotate_right(rb, x);
+				}
+				x->parent->color = RBBLACK;
+				x->parent->parent->color = RBRED;
+				rb_rotate_left(rb, x->parent->parent);
+			}
+		}
+	}
+
+	/*
+	 * The root may already have been black; if not, the black-height of every
+	 * node in the tree increases by one.
+	 */
+	rb->root->color = RBBLACK;
+}
+
+/*
+ * Allocate node for data and insert in tree.
+ *
+ * Return old data (or result of appendator method) if it exists and NULL
+ * otherwise.
+ */
+void *
+rb_insert(RBTree *rb, void *data)
+{
+	RBNode	   *current,
+			   *parent,
+			   *x;
+	int			cmp;
+
+	/* find where node belongs */
+	current = rb->root;
+	parent = NULL;
+	while (current != RBNIL)
+	{
+		cmp = rb->comparator(data, current->data, rb->arg);
+		if (cmp == 0)
+		{
+			/*
+			 * Found node with given key.  If appendator method is provided,
+			 * call it to join old and new data; else, new data replaces old
+			 * data.
+			 */
+			if (rb->appendator)
+			{
+				current->data = rb->appendator(current->data, data, rb->arg);
+				return current->data;
+			}
+			else
+			{
+				void	   *old = current->data;
+
+				current->data = data;
+				return old;
+			}
+		}
+		parent = current;
+		current = (cmp < 0) ? current->left : current->right;
+	}
+
+	/* setup new node in tree */
+	x = palloc(sizeof(RBNode));
+	x->data = data;
+	x->parent = parent;
+	x->left = RBNIL;
+	x->right = RBNIL;
+	x->color = RBRED;
+	x->iteratorState = InitialState;
+
+	/* insert node in tree */
+	if (parent)
+	{
+		if (cmp < 0)
+			parent->left = x;
+		else
+			parent->right = x;
+	}
+	else
+	{
+		rb->root = x;
+	}
+
+	rb_insert_fixup(rb, x);
+	return NULL;
+}
+
+/**********************************************************************
+ *							Deletion								  *
+ **********************************************************************/
+
+/*
+ * Maintain Red-Black tree balance after deleting a black node.
+ */
+static void
+rb_delete_fixup(RBTree *rb, RBNode *x)
+{
+	/*
+	 * x is always a black node.  Initially, it is the former child of the
+	 * deleted node.  Each iteration of this loop moves it higher up in the
+	 * tree.
+	 */
+	while (x != rb->root && x->color == RBBLACK)
+	{
+		/*
+		 * Left and right cases are symmetric.  Any nodes that are children
+		 * of x have a black-height one less than the remainder of the nodes
+		 * in the tree.  We rotate and recolor nodes to move the problem up
+		 * the tree: at some stage we'll either fix the problem, or reach the
+		 * root (where the black-height is allowed to decrease).
+		 */
+		if (x == x->parent->left)
+		{
+			RBNode	   *w = x->parent->right;
+
+			if (w->color == RBRED)
+			{
+				w->color = RBBLACK;
+				x->parent->color = RBRED;
+				rb_rotate_left(rb, x->parent);
+				w = x->parent->right;
+			}
+
+			if (w->left->color == RBBLACK && w->right->color == RBBLACK)
+			{
+				w->color = RBRED;
+				x = x->parent;
+			}
+			else
+			{
+				if (w->right->color == RBBLACK)
+				{
+					w->left->color = RBBLACK;
+					w->color = RBRED;
+					rb_rotate_right(rb, w);
+					w = x->parent->right;
+				}
+				w->color = x->parent->color;
+				x->parent->color = RBBLACK;
+				w->right->color = RBBLACK;
+				rb_rotate_left(rb, x->parent);
+				x = rb->root;		/* Arrange for loop to terminate. */
+			}
+		}
+		else
+		{
+			RBNode	   *w = x->parent->left;
+
+			if (w->color == RBRED)
+			{
+				w->color = RBBLACK;
+				x->parent->color = RBRED;
+				rb_rotate_right(rb, x->parent);
+				w = x->parent->left;
+			}
+
+			if (w->right->color == RBBLACK && w->left->color == RBBLACK)
+			{
+				w->color = RBRED;
+				x = x->parent;
+			}
+			else
+			{
+				if (w->left->color == RBBLACK)
+				{
+					w->right->color = RBBLACK;
+					w->color = RBRED;
+					rb_rotate_left(rb, w);
+					w = x->parent->left;
+				}
+				w->color = x->parent->color;
+				x->parent->color = RBBLACK;
+				w->left->color = RBBLACK;
+				rb_rotate_right(rb, x->parent);
+				x = rb->root;		/* Arrange for loop to terminate. */
+			}
+		}
+	}
+	x->color = RBBLACK;
+}
+
+/*
+ * Delete node z from tree.
+ */
+static void
+rb_delete_node(RBTree *rb, RBNode *z)
+{
+	RBNode	   *x,
+			   *y;
+
+	if (!z || z == RBNIL)
+		return;
+
+	/*
+	 * y is the node that will actually be removed from the tree.  This will
+	 * be z if z has fewer than two children, or the tree successor of z
+	 * otherwise.
+	 */
+	if (z->left == RBNIL || z->right == RBNIL)
+	{
+		/* y has a RBNIL node as a child */
+		y = z;
+	}
+	else
+	{
+		/* find tree successor */
+		y = z->right;
+		while (y->left != RBNIL)
+			y = y->left;
+	}
+
+	/* x is y's only child */
+	if (y->left != RBNIL)
+		x = y->left;
+	else
+		x = y->right;
+
+	/* Remove y from the tree. */
+	x->parent = y->parent;
+	if (y->parent)
+	{
+		if (y == y->parent->left)
+			y->parent->left = x;
+		else
+			y->parent->right = x;
+	}
+	else
+	{
+		rb->root = x;
+	}
+
+	/*
+	 * If we removed the tree successor of z rather than z itself, then
+	 * attach the data for the removed node to the one we were supposed to
+	 * remove.
+	 */
+	if (y != z)
+		z->data = y->data;
+
+	/*
+	 * Removing a black node might make some paths from root to leaf contain
+	 * fewer black nodes than others, or it might make two red nodes adjacent.
+	 */
+	if (y->color == RBBLACK)
+		rb_delete_fixup(rb, x);
+
+	pfree(y);
+}
+
+extern void
+rb_delete(RBTree *rb, void *data)
+{
+	RBNode	   *node = rb->root;
+	int			cmp;
+
+	while (node != RBNIL)
+	{
+		cmp = rb->comparator(data, node->data, rb->arg);
+
+		if (cmp == 0)
+		{
+			/* found node to delete */
+			if (rb->freefunc)
+				rb->freefunc(node->data);
+			node->data = NULL;
+			rb_delete_node(rb, node);
+			return;
+		}
+		else if (cmp < 0)
+			node = node->left;
+		else
+			node = node->right;
+	}
+}
+
+/*
+ * Return data on left most node and delete
+ * that node
+ */
+extern void *
+rb_leftmost(RBTree *rb)
+{
+	RBNode	   *node = rb->root;
+	RBNode	   *leftmost = rb->root;
+	void	   *res = NULL;
+
+	while (node != RBNIL)
+	{
+		leftmost = node;
+		node = node->left;
+	}
+
+	if (leftmost != RBNIL)
+	{
+		res = leftmost->data;
+		leftmost->data = NULL;
+		rb_delete_node(rb, leftmost);
+	}
+
+	return res;
+}
+
+/**********************************************************************
+ *						  Traverse									  *
+ **********************************************************************/
+
+static void *
+rb_next_node(RBTreeIterator *iterator, RBNode *node)
+{
+	node->iteratorState = InitialState;
+	iterator->node = node;
+	return iterator->iterate(iterator);
+}
+
+static void *
+rb_left_right_iterator(RBTreeIterator *iterator)
+{
+	RBNode	   *node = iterator->node;
+
+	switch (node->iteratorState)
+	{
+		case InitialState:
+			if (node->left != RBNIL)
+			{
+				node->iteratorState = FirstStepDone;
+				return rb_next_node(iterator, node->left);
+			}
+		case FirstStepDone:
+			node->iteratorState = SecondStepDone;
+			return node->data;
+		case SecondStepDone:
+			if (node->right != RBNIL)
+			{
+				node->iteratorState = ThirdStepDone;
+				return rb_next_node(iterator, node->right);
+			}
+		case ThirdStepDone:
+			if (node->parent)
+			{
+				iterator->node = node->parent;
+				return iterator->iterate(iterator);
+			}
+			break;
+		default:
+			elog(ERROR, "Unknow node state: %d", node->iteratorState);
+	}
+
+	return NULL;
+}
+
+static void *
+rb_right_left_iterator(RBTreeIterator *iterator)
+{
+	RBNode	   *node = iterator->node;
+
+	switch (node->iteratorState)
+	{
+		case InitialState:
+			if (node->right != RBNIL)
+			{
+				node->iteratorState = FirstStepDone;
+				return rb_next_node(iterator, node->right);
+			}
+		case FirstStepDone:
+			node->iteratorState = SecondStepDone;
+			return node->data;
+		case SecondStepDone:
+			if (node->left != RBNIL)
+			{
+				node->iteratorState = ThirdStepDone;
+				return rb_next_node(iterator, node->left);
+			}
+		case ThirdStepDone:
+			if (node->parent)
+			{
+				iterator->node = node->parent;
+				return iterator->iterate(iterator);
+			}
+			break;
+		default:
+			elog(ERROR, "Unknow node state: %d", node->iteratorState);
+	}
+
+	return NULL;
+}
+
+static void *
+rb_direct_iterator(RBTreeIterator *iterator)
+{
+	RBNode	   *node = iterator->node;
+
+	switch (node->iteratorState)
+	{
+		case InitialState:
+			node->iteratorState = FirstStepDone;
+			return node->data;
+		case FirstStepDone:
+			if (node->left != RBNIL)
+			{
+				node->iteratorState = SecondStepDone;
+				return rb_next_node(iterator, node->left);
+			}
+		case SecondStepDone:
+			if (node->right != RBNIL)
+			{
+				node->iteratorState = ThirdStepDone;
+				return rb_next_node(iterator, node->right);
+			}
+		case ThirdStepDone:
+			if (node->parent)
+			{
+				iterator->node = node->parent;
+				return iterator->iterate(iterator);
+			}
+			break;
+		default:
+			elog(ERROR, "Unknow node state: %d", node->iteratorState);
+	}
+
+	return NULL;
+}
+
+static void *
+rb_inverted_iterator(RBTreeIterator *iterator)
+{
+	RBNode	   *node = iterator->node;
+
+	switch (node->iteratorState)
+	{
+		case InitialState:
+			if (node->left != RBNIL)
+			{
+				node->iteratorState = FirstStepDone;
+				return rb_next_node(iterator, node->left);
+			}
+		case FirstStepDone:
+			if (node->right != RBNIL)
+			{
+				node->iteratorState = SecondStepDone;
+				return rb_next_node(iterator, node->right);
+			}
+		case SecondStepDone:
+			node->iteratorState = ThirdStepDone;
+			return node->data;
+		case ThirdStepDone:
+			if (node->parent)
+			{
+				iterator->node = node->parent;
+				return iterator->iterate(iterator);
+			}
+			break;
+		default:
+			elog(ERROR, "Unknow node state: %d", node->iteratorState);
+	}
+
+	return NULL;
+}
+
+RBTreeIterator *
+rb_begin_iterate(RBTree *rb, RBOrderControl ctrl)
+{
+	RBTreeIterator *iterator = palloc(sizeof(RBTreeIterator));
+
+	iterator->node = rb->root;
+	if (iterator->node != RBNIL)
+		iterator->node->iteratorState = InitialState;
+
+	switch (ctrl)
+	{
+		case LeftRightWalk:			/* visit left, then self, then right */
+			iterator->iterate = rb_left_right_iterator;
+			break;
+		case RightLeftWalk:			/* visit right, then self, then left */
+			iterator->iterate = rb_right_left_iterator;
+			break;
+		case DirectWalk:			/* visit self, then left, then right */
+			iterator->iterate = rb_direct_iterator;
+			break;
+		case InvertedWalk:			/* visit left, then right, then self */
+			iterator->iterate = rb_inverted_iterator;
+			break;
+		default:
+			elog(ERROR, "Unknown iterator order: %d", ctrl);
+	}
+
+	return iterator;
+}
+
+void *
+rb_iterate(RBTreeIterator *iterator)
+{
+	if (iterator->node == RBNIL)
+		return NULL;
+
+	return iterator->iterate(iterator);
+}
+
+void
+rb_free_iterator(RBTreeIterator *iterator)
+{
+	pfree(iterator);
+}