/*
* 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.schema;
import org.h2.engine.DbObject;
import org.h2.engine.Session;
import org.h2.message.DbException;
import org.h2.message.Trace;
import org.h2.table.Table;
/**
*A sequence is created using the statement
* CREATE SEQUENCE
*/
public class Sequence extends SchemaObjectBase {
/**
* The default cache size for sequences.
*/
public static final int DEFAULT_CACHE_SIZE = 32;
private long value = 1;
private long valueWithMargin;
private long increment = 1;
private long cacheSize = DEFAULT_CACHE_SIZE;
private boolean belongsToTable;
public Sequence(Schema schema, int id, String name, boolean belongsToTable) {
initSchemaObjectBase(schema, id, name, Trace.SEQUENCE);
this.belongsToTable = belongsToTable;
}
public synchronized void setStartValue(long value) {
this.value = value;
this.valueWithMargin = value;
}
public boolean getBelongsToTable() {
return belongsToTable;
}
public long getIncrement() {
return increment;
}
public void setIncrement(long inc) {
if (inc == 0) {
throw DbException.getInvalidValueException("INCREMENT", 0);
}
this.increment = inc;
}
public String getDropSQL() {
if (getBelongsToTable()) {
return null;
}
return "DROP SEQUENCE IF EXISTS " + getSQL();
}
public String getCreateSQLForCopy(Table table, String quotedName) {
throw DbException.throwInternalError();
}
public synchronized String getCreateSQL() {
StringBuilder buff = new StringBuilder("CREATE SEQUENCE ");
buff.append(getSQL()).append(" START WITH ").append(value);
if (increment != 1) {
buff.append(" INCREMENT BY ").append(increment);
}
if (cacheSize != DEFAULT_CACHE_SIZE) {
buff.append(" CACHE ").append(cacheSize);
}
if (belongsToTable) {
buff.append(" BELONGS_TO_TABLE");
}
return buff.toString();
}
/**
* Get the next value for this sequence.
*
* @param session the session
* @return the next value
*/
public synchronized long getNext(Session session) {
if ((increment > 0 && value >= valueWithMargin) || (increment < 0 && value <= valueWithMargin)) {
valueWithMargin += increment * cacheSize;
flush(session);
}
long v = value;
value += increment;
return v;
}
/**
* Flush the current value to disk.
*/
public void flushWithoutMargin() {
if (valueWithMargin != value) {
valueWithMargin = value;
flush(null);
}
}
/**
* Flush the current value, including the margin, to disk.
*
* @param session the session
*/
public synchronized void flush(Session session) {
Session sysSession = database.getSystemSession();
if (session == null || !database.isSysTableLocked()) {
// this session may not lock the sys table (except if it already has locked it)
// because it must be committed immediately
// otherwise other threads can not access the sys table.
session = sysSession;
}
synchronized (session) {
// just for this case, use the value with the margin for the script
long realValue = value;
try {
value = valueWithMargin;
database.update(session, this);
} finally {
value = realValue;
}
if (session == sysSession) {
// if the system session is used,
// the transaction must be committed immediately
sysSession.commit(false);
}
}
}
/**
* Flush the current value to disk and close this object.
*/
public void close() {
flushWithoutMargin();
}
public int getType() {
return DbObject.SEQUENCE;
}
public void removeChildrenAndResources(Session session) {
database.removeMeta(session, getId());
invalidate();
}
public void checkRename() {
// nothing to do
}
public synchronized long getCurrentValue() {
return value - increment;
}
public void setBelongsToTable(boolean b) {
this.belongsToTable = b;
}
public void setCacheSize(long cacheSize) {
this.cacheSize = cacheSize;
}
public long getCacheSize() {
return cacheSize;
}
}