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/*
* Copyright 2004-2011 H2 Group. Multiple-Licensed under the H2 License,
* Version 1.0, and under the Eclipse Public License, Version 1.0
* (http://h2database.com/html/license.html).
* Initial Developer: H2 Group
*/
package org.h2.index;
import java.util.Arrays;
import org.h2.api.DatabaseEventListener;
import org.h2.constant.ErrorCode;
import org.h2.constant.SysProperties;
import org.h2.engine.Session;
import org.h2.message.DbException;
import org.h2.result.Row;
import org.h2.store.Data;
import org.h2.store.Page;
import org.h2.store.PageStore;
import org.h2.util.Utils;
/**
* A leaf page that contains data of one or multiple rows. Format:
*
*
page type: byte (0)
*
checksum: short (1-2)
*
parent page id (0 for root): int (3-6)
*
table id: varInt
*
count of all children (-1 if not known): int
*
entry count: short
*
rightmost child page id: int
*
entries (child page id: int, key: varLong)
*
* The key is the largest key of the respective child, meaning key[0] is the
* largest key of child[0].
*/
public class PageDataNode extends PageData {
/**
* The page ids of the children.
*/
private int[] childPageIds;
private int rowCountStored = UNKNOWN_ROWCOUNT;
private int rowCount = UNKNOWN_ROWCOUNT;
/**
* The number of bytes used in the page
*/
private int length;
private PageDataNode(PageDataIndex index, int pageId, Data data) {
super(index, pageId, data);
}
/**
* Create a new page.
*
* @param index the index
* @param pageId the page id
* @param parentPageId the parent
* @return the page
*/
static PageDataNode create(PageDataIndex index, int pageId, int parentPageId) {
PageDataNode p = new PageDataNode(index, pageId, index.getPageStore().createData());
index.getPageStore().logUndo(p, null);
p.parentPageId = parentPageId;
p.writeHead();
// 4 bytes for the rightmost child page id
p.length = p.data.length() + 4;
return p;
}
/**
* Read a data node page.
*
* @param index the index
* @param data the data
* @param pageId the page id
* @return the page
*/
public static Page read(PageDataIndex index, Data data, int pageId) {
PageDataNode p = new PageDataNode(index, pageId, data);
p.read();
return p;
}
private void read() {
data.reset();
data.readByte();
data.readShortInt();
this.parentPageId = data.readInt();
int indexId = data.readVarInt();
if (indexId != index.getId()) {
throw DbException.get(ErrorCode.FILE_CORRUPTED_1,
"page:" + getPos() + " expected index:" + index.getId() +
"got:" + indexId);
}
rowCount = rowCountStored = data.readInt();
entryCount = data.readShortInt();
childPageIds = new int[entryCount + 1];
childPageIds[entryCount] = data.readInt();
keys = Utils.newLongArray(entryCount);
for (int i = 0; i < entryCount; i++) {
childPageIds[i] = data.readInt();
keys[i] = data.readVarLong();
}
length = data.length();
check();
written = true;
}
private void addChild(int x, int childPageId, long key) {
index.getPageStore().logUndo(this, data);
written = false;
changeCount = index.getPageStore().getChangeCount();
childPageIds = insert(childPageIds, entryCount + 1, x + 1, childPageId);
keys = insert(keys, entryCount, x, key);
entryCount++;
length += 4 + Data.getVarLongLen(key);
}
int addRowTry(Row row) {
index.getPageStore().logUndo(this, data);
int keyOffsetPairLen = 4 + Data.getVarLongLen(row.getKey());
while (true) {
int x = find(row.getKey());
PageData page = index.getPage(childPageIds[x], getPos());
int splitPoint = page.addRowTry(row);
if (splitPoint == -1) {
break;
}
if (length + keyOffsetPairLen > index.getPageStore().getPageSize()) {
return entryCount / 2;
}
long pivot = splitPoint == 0 ? row.getKey() : page.getKey(splitPoint - 1);
PageData page2 = page.split(splitPoint);
index.getPageStore().update(page);
index.getPageStore().update(page2);
addChild(x, page2.getPos(), pivot);
index.getPageStore().update(this);
}
updateRowCount(1);
return -1;
}
private void updateRowCount(int offset) {
if (rowCount != UNKNOWN_ROWCOUNT) {
rowCount += offset;
}
if (rowCountStored != UNKNOWN_ROWCOUNT) {
rowCountStored = UNKNOWN_ROWCOUNT;
index.getPageStore().logUndo(this, data);
if (written) {
writeHead();
}
index.getPageStore().update(this);
}
}
Cursor find(Session session, long minKey, long maxKey, boolean multiVersion) {
int x = find(minKey);
int child = childPageIds[x];
return index.getPage(child, getPos()).find(session, minKey, maxKey, multiVersion);
}
PageData split(int splitPoint) {
int newPageId = index.getPageStore().allocatePage();
PageDataNode p2 = PageDataNode.create(index, newPageId, parentPageId);
int firstChild = childPageIds[splitPoint];
for (int i = splitPoint; i < entryCount;) {
p2.addChild(p2.entryCount, childPageIds[splitPoint + 1], keys[splitPoint]);
removeChild(splitPoint);
}
int lastChild = childPageIds[splitPoint - 1];
removeChild(splitPoint - 1);
childPageIds[splitPoint - 1] = lastChild;
p2.childPageIds[0] = firstChild;
p2.remapChildren(getPos());
return p2;
}
protected void remapChildren(int old) {
for (int i = 0; i < entryCount + 1; i++) {
int child = childPageIds[i];
PageData p = index.getPage(child, old);
p.setParentPageId(getPos());
index.getPageStore().update(p);
}
}
/**
* Initialize the page.
*
* @param page1 the first child page
* @param pivot the pivot key
* @param page2 the last child page
*/
void init(PageData page1, long pivot, PageData page2) {
entryCount = 1;
childPageIds = new int[] { page1.getPos(), page2.getPos() };
keys = new long[] { pivot };
length += 4 + Data.getVarLongLen(pivot);
check();
}
long getLastKey() {
return index.getPage(childPageIds[entryCount], getPos()).getLastKey();
}
/**
* Get the next leaf page.
*
* @param key the last key of the current page
* @return the next leaf page
*/
PageDataLeaf getNextPage(long key) {
int i = find(key) + 1;
if (i > entryCount) {
if (parentPageId == PageData.ROOT) {
return null;
}
PageDataNode next = (PageDataNode) index.getPage(parentPageId, -1);
return next.getNextPage(key);
}
PageData page = index.getPage(childPageIds[i], getPos());
return page.getFirstLeaf();
}
PageDataLeaf getFirstLeaf() {
int child = childPageIds[0];
return index.getPage(child, getPos()).getFirstLeaf();
}
boolean remove(long key) {
int at = find(key);
// merge is not implemented to allow concurrent usage
// TODO maybe implement merge
PageData page = index.getPage(childPageIds[at], getPos());
boolean empty = page.remove(key);
index.getPageStore().logUndo(this, data);
updateRowCount(-1);
if (!empty) {
// the first row didn't change - nothing to do
return false;
}
// this child is now empty
index.getPageStore().free(page.getPos());
if (entryCount < 1) {
// no more children - this page is empty as well
return true;
}
removeChild(at);
index.getPageStore().update(this);
return false;
}
void freeRecursive() {
index.getPageStore().logUndo(this, data);
index.getPageStore().free(getPos());
for (int i = 0; i < entryCount + 1; i++) {
int child = childPageIds[i];
index.getPage(child, getPos()).freeRecursive();
}
}
Row getRowWithKey(long key) {
int at = find(key);
PageData page = index.getPage(childPageIds[at], getPos());
return page.getRowWithKey(key);
}
int getRowCount() {
if (rowCount == UNKNOWN_ROWCOUNT) {
int count = 0;
for (int i = 0; i < entryCount + 1; i++) {
int child = childPageIds[i];
PageData page = index.getPage(child, getPos());
if (getPos() == page.getPos()) {
throw DbException.throwInternalError("Page it its own child: " + getPos());
}
count += page.getRowCount();
index.getDatabase().setProgress(DatabaseEventListener.STATE_SCAN_FILE,
index.getTable() + "." + index.getName(), count, Integer.MAX_VALUE);
}
rowCount = count;
}
return rowCount;
}
void setRowCountStored(int rowCount) {
this.rowCount = rowCount;
if (rowCountStored != rowCount) {
rowCountStored = rowCount;
index.getPageStore().logUndo(this, data);
if (written) {
changeCount = index.getPageStore().getChangeCount();
writeHead();
}
index.getPageStore().update(this);
}
}
private void check() {
if (SysProperties.CHECK) {
for (int i = 0; i < entryCount + 1; i++) {
int child = childPageIds[i];
if (child == 0) {
DbException.throwInternalError();
}
}
}
}
public void write() {
writeData();
index.getPageStore().writePage(getPos(), data);
}
private void writeHead() {
data.reset();
data.writeByte((byte) Page.TYPE_DATA_NODE);
data.writeShortInt(0);
if (SysProperties.CHECK2) {
if (data.length() != START_PARENT) {
DbException.throwInternalError();
}
}
data.writeInt(parentPageId);
data.writeVarInt(index.getId());
data.writeInt(rowCountStored);
data.writeShortInt(entryCount);
}
private void writeData() {
if (written) {
return;
}
check();
writeHead();
data.writeInt(childPageIds[entryCount]);
for (int i = 0; i < entryCount; i++) {
data.writeInt(childPageIds[i]);
data.writeVarLong(keys[i]);
}
if (length != data.length()) {
DbException.throwInternalError("expected pos: " + length + " got: " + data.length());
}
written = true;
}
private void removeChild(int i) {
index.getPageStore().logUndo(this, data);
written = false;
changeCount = index.getPageStore().getChangeCount();
int removedKeyIndex = i < entryCount ? i : i - 1;
entryCount--;
length -= 4 + Data.getVarLongLen(keys[removedKeyIndex]);
if (entryCount < 0) {
DbException.throwInternalError();
}
keys = remove(keys, entryCount + 1, removedKeyIndex);
childPageIds = remove(childPageIds, entryCount + 2, i);
}
public String toString() {
return "page[" + getPos() + "] data node table:" + index.getId() +
" entries:" + entryCount + " " + Arrays.toString(childPageIds);
}
public void moveTo(Session session, int newPos) {
PageStore store = index.getPageStore();
// load the pages into the cache, to ensure old pages
// are written
for (int i = 0; i < entryCount + 1; i++) {
int child = childPageIds[i];
store.getPage(child);
}
if (parentPageId != ROOT) {
store.getPage(parentPageId);
}
store.logUndo(this, data);
PageDataNode p2 = PageDataNode.create(index, newPos, parentPageId);
p2.rowCountStored = rowCountStored;
p2.rowCount = rowCount;
p2.childPageIds = childPageIds;
p2.keys = keys;
p2.entryCount = entryCount;
p2.length = length;
store.update(p2);
if (parentPageId == ROOT) {
index.setRootPageId(session, newPos);
} else {
PageDataNode p = (PageDataNode) store.getPage(parentPageId);
p.moveChild(getPos(), newPos);
}
for (int i = 0; i < entryCount + 1; i++) {
int child = childPageIds[i];
PageData p = (PageData) store.getPage(child);
p.setParentPageId(newPos);
store.update(p);
}
store.free(getPos());
}
/**
* One of the children has moved to another page.
*
* @param oldPos the old position
* @param newPos the new position
*/
void moveChild(int oldPos, int newPos) {
for (int i = 0; i < entryCount + 1; i++) {
if (childPageIds[i] == oldPos) {
index.getPageStore().logUndo(this, data);
written = false;
changeCount = index.getPageStore().getChangeCount();
childPageIds[i] = newPos;
index.getPageStore().update(this);
return;
}
}
throw DbException.throwInternalError();
}
}
