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org.h2.index.MultiVersionIndex Maven / Gradle / Ivy
/*
* Copyright 2004-2014 H2 Group. Multiple-Licensed under the MPL 2.0,
* and the EPL 1.0 (http://h2database.com/html/license.html).
* Initial Developer: H2 Group
*/
package org.h2.index;
import java.util.ArrayList;
import org.h2.api.ErrorCode;
import org.h2.engine.Database;
import org.h2.engine.DbObject;
import org.h2.engine.Session;
import org.h2.message.DbException;
import org.h2.result.Row;
import org.h2.result.SearchRow;
import org.h2.result.SortOrder;
import org.h2.schema.Schema;
import org.h2.table.Column;
import org.h2.table.IndexColumn;
import org.h2.table.RegularTable;
import org.h2.table.Table;
import org.h2.table.TableFilter;
import org.h2.value.Value;
import org.h2.value.ValueNull;
/**
* A multi-version index is a combination of a regular index,
* and a in-memory tree index that contains uncommitted changes.
* Uncommitted changes can include new rows, and deleted rows.
*/
public class MultiVersionIndex implements Index {
private final Index base;
private final TreeIndex delta;
private final RegularTable table;
private final Object sync;
private final Column firstColumn;
public MultiVersionIndex(Index base, RegularTable table) {
this.base = base;
this.table = table;
IndexType deltaIndexType = IndexType.createNonUnique(false);
if (base instanceof SpatialIndex) {
throw DbException.get(ErrorCode.FEATURE_NOT_SUPPORTED_1,
"MVCC & spatial index");
}
this.delta = new TreeIndex(table, -1, "DELTA", base.getIndexColumns(),
deltaIndexType);
delta.setMultiVersion(true);
this.sync = base.getDatabase();
this.firstColumn = base.getColumns()[0];
}
@Override
public void add(Session session, Row row) {
synchronized (sync) {
base.add(session, row);
if (removeIfExists(session, row)) {
// for example rolling back an delete operation
} else if (row.getSessionId() != 0) {
// don't insert rows that are added when creating an index
delta.add(session, row);
}
}
}
@Override
public void close(Session session) {
synchronized (sync) {
base.close(session);
}
}
@Override
public Cursor find(TableFilter filter, SearchRow first, SearchRow last) {
synchronized (sync) {
Cursor baseCursor = base.find(filter, first, last);
Cursor deltaCursor = delta.find(filter, first, last);
return new MultiVersionCursor(filter.getSession(), this,
baseCursor, deltaCursor, sync);
}
}
@Override
public Cursor find(Session session, SearchRow first, SearchRow last) {
synchronized (sync) {
Cursor baseCursor = base.find(session, first, last);
Cursor deltaCursor = delta.find(session, first, last);
return new MultiVersionCursor(session, this, baseCursor, deltaCursor, sync);
}
}
@Override
public Cursor findNext(Session session, SearchRow first, SearchRow last) {
throw DbException.throwInternalError();
}
@Override
public boolean canFindNext() {
// TODO possible, but more complicated
return false;
}
@Override
public boolean canGetFirstOrLast() {
return base.canGetFirstOrLast() && delta.canGetFirstOrLast();
}
@Override
public Cursor findFirstOrLast(Session session, boolean first) {
if (first) {
// TODO optimization: this loops through NULL elements
Cursor cursor = find(session, null, null);
while (cursor.next()) {
SearchRow row = cursor.getSearchRow();
Value v = row.getValue(firstColumn.getColumnId());
if (v != ValueNull.INSTANCE) {
return cursor;
}
}
return cursor;
}
Cursor baseCursor = base.findFirstOrLast(session, false);
Cursor deltaCursor = delta.findFirstOrLast(session, false);
MultiVersionCursor cursor = new MultiVersionCursor(session, this,
baseCursor, deltaCursor, sync);
cursor.loadCurrent();
// TODO optimization: this loops through NULL elements
while (cursor.previous()) {
SearchRow row = cursor.getSearchRow();
if (row == null) {
break;
}
Value v = row.getValue(firstColumn.getColumnId());
if (v != ValueNull.INSTANCE) {
return cursor;
}
}
return cursor;
}
@Override
public double getCost(Session session, int[] masks, TableFilter filter,
SortOrder sortOrder) {
return base.getCost(session, masks, filter, sortOrder);
}
@Override
public boolean needRebuild() {
return base.needRebuild();
}
/**
* Check if there is an uncommitted row with the given key
* within a different session.
*
* @param session the original session
* @param row the row (only the key is checked)
* @return true if there is an uncommitted row
*/
public boolean isUncommittedFromOtherSession(Session session, Row row) {
Cursor c = delta.find(session, row, row);
while (c.next()) {
Row r = c.get();
return r.getSessionId() != session.getId();
}
return false;
}
private boolean removeIfExists(Session session, Row row) {
// maybe it was inserted by the same session just before
Cursor c = delta.find(session, row, row);
while (c.next()) {
Row r = c.get();
if (r.getKey() == row.getKey() && r.getVersion() == row.getVersion()) {
if (r != row && table.getScanIndex(session).compareRows(r, row) != 0) {
row.setVersion(r.getVersion() + 1);
} else {
delta.remove(session, r);
return true;
}
}
}
return false;
}
@Override
public void remove(Session session, Row row) {
synchronized (sync) {
base.remove(session, row);
if (removeIfExists(session, row)) {
// added and deleted in the same transaction: no change
} else {
delta.add(session, row);
}
}
}
@Override
public void remove(Session session) {
synchronized (sync) {
base.remove(session);
}
}
@Override
public void truncate(Session session) {
synchronized (sync) {
delta.truncate(session);
base.truncate(session);
}
}
@Override
public void commit(int operation, Row row) {
synchronized (sync) {
removeIfExists(null, row);
}
}
@Override
public int compareRows(SearchRow rowData, SearchRow compare) {
return base.compareRows(rowData, compare);
}
@Override
public int getColumnIndex(Column col) {
return base.getColumnIndex(col);
}
@Override
public Column[] getColumns() {
return base.getColumns();
}
@Override
public IndexColumn[] getIndexColumns() {
return base.getIndexColumns();
}
@Override
public String getCreateSQL() {
return base.getCreateSQL();
}
@Override
public String getCreateSQLForCopy(Table forTable, String quotedName) {
return base.getCreateSQLForCopy(forTable, quotedName);
}
@Override
public String getDropSQL() {
return base.getDropSQL();
}
@Override
public IndexType getIndexType() {
return base.getIndexType();
}
@Override
public String getPlanSQL() {
return base.getPlanSQL();
}
@Override
public long getRowCount(Session session) {
return base.getRowCount(session);
}
@Override
public Table getTable() {
return base.getTable();
}
@Override
public int getType() {
return base.getType();
}
@Override
public void removeChildrenAndResources(Session session) {
synchronized (sync) {
table.removeIndex(this);
remove(session);
}
}
@Override
public String getSQL() {
return base.getSQL();
}
@Override
public Schema getSchema() {
return base.getSchema();
}
@Override
public void checkRename() {
base.checkRename();
}
@Override
public ArrayList getChildren() {
return base.getChildren();
}
@Override
public String getComment() {
return base.getComment();
}
@Override
public Database getDatabase() {
return base.getDatabase();
}
@Override
public int getId() {
return base.getId();
}
@Override
public String getName() {
return base.getName();
}
@Override
public boolean isTemporary() {
return base.isTemporary();
}
@Override
public void rename(String newName) {
base.rename(newName);
}
@Override
public void setComment(String comment) {
base.setComment(comment);
}
@Override
public void setTemporary(boolean temporary) {
base.setTemporary(temporary);
}
@Override
public long getRowCountApproximation() {
return base.getRowCountApproximation();
}
@Override
public long getDiskSpaceUsed() {
return base.getDiskSpaceUsed();
}
public Index getBaseIndex() {
return base;
}
@Override
public Row getRow(Session session, long key) {
return base.getRow(session, key);
}
@Override
public boolean isHidden() {
return base.isHidden();
}
@Override
public boolean isRowIdIndex() {
return base.isRowIdIndex() && delta.isRowIdIndex();
}
@Override
public boolean canScan() {
return base.canScan();
}
@Override
public void setSortedInsertMode(boolean sortedInsertMode) {
base.setSortedInsertMode(sortedInsertMode);
delta.setSortedInsertMode(sortedInsertMode);
}
}
