/*
* Copyright 2004-2023 H2 Group. Multiple-Licensed under the MPL 2.0,
* and the EPL 1.0 (https://h2database.com/html/license.html).
* Initial Developer: H2 Group
*/
package org.h2.engine;
import java.sql.Connection;
import org.h2.message.DbException;
/**
* Level of isolation.
*/
public enum IsolationLevel {
/**
* Dirty reads, non-repeatable reads and phantom reads are allowed.
*/
READ_UNCOMMITTED(Connection.TRANSACTION_READ_UNCOMMITTED, Constants.LOCK_MODE_OFF),
/**
* Dirty reads aren't allowed; non-repeatable reads and phantom reads are
* allowed.
*/
READ_COMMITTED(Connection.TRANSACTION_READ_COMMITTED, Constants.LOCK_MODE_READ_COMMITTED),
/**
* Dirty reads and non-repeatable reads aren't allowed; phantom reads are
* allowed.
*/
REPEATABLE_READ(Connection.TRANSACTION_REPEATABLE_READ, Constants.LOCK_MODE_TABLE),
/**
* Dirty reads, non-repeatable reads and phantom reads are'n allowed.
*/
SNAPSHOT(Constants.TRANSACTION_SNAPSHOT, Constants.LOCK_MODE_TABLE),
/**
* Dirty reads, non-repeatable reads and phantom reads are'n allowed.
* Concurrent and serial execution of transactions with this isolation level
* should have the same effect.
*/
SERIALIZABLE(Connection.TRANSACTION_SERIALIZABLE, Constants.LOCK_MODE_TABLE);
/**
* Returns the isolation level from LOCK_MODE equivalent for PageStore and
* old versions of H2.
*
* @param level
* the LOCK_MODE value
* @return the isolation level
*/
public static IsolationLevel fromJdbc(int level) {
switch (level) {
case Connection.TRANSACTION_READ_UNCOMMITTED:
return IsolationLevel.READ_UNCOMMITTED;
case Connection.TRANSACTION_READ_COMMITTED:
return IsolationLevel.READ_COMMITTED;
case Connection.TRANSACTION_REPEATABLE_READ:
return IsolationLevel.REPEATABLE_READ;
case Constants.TRANSACTION_SNAPSHOT:
return IsolationLevel.SNAPSHOT;
case Connection.TRANSACTION_SERIALIZABLE:
return IsolationLevel.SERIALIZABLE;
default:
throw DbException.getInvalidValueException("isolation level", level);
}
}
/**
* Returns the isolation level from LOCK_MODE equivalent for PageStore and
* old versions of H2.
*
* @param lockMode
* the LOCK_MODE value
* @return the isolation level
*/
public static IsolationLevel fromLockMode(int lockMode) {
switch (lockMode) {
case Constants.LOCK_MODE_OFF:
return IsolationLevel.READ_UNCOMMITTED;
case Constants.LOCK_MODE_READ_COMMITTED:
default:
return IsolationLevel.READ_COMMITTED;
case Constants.LOCK_MODE_TABLE:
case Constants.LOCK_MODE_TABLE_GC:
return IsolationLevel.SERIALIZABLE;
}
}
/**
* Returns the isolation level from its SQL name.
*
* @param sql
* the SQL name
* @return the isolation level from its SQL name
*/
public static IsolationLevel fromSql(String sql) {
switch (sql) {
case "READ UNCOMMITTED":
return READ_UNCOMMITTED;
case "READ COMMITTED":
return READ_COMMITTED;
case "REPEATABLE READ":
return REPEATABLE_READ;
case "SNAPSHOT":
return SNAPSHOT;
case "SERIALIZABLE":
return SERIALIZABLE;
default:
throw DbException.getInvalidValueException("isolation level", sql);
}
}
private final String sql;
private final int jdbc, lockMode;
private IsolationLevel(int jdbc, int lockMode) {
sql = name().replace('_', ' ').intern();
this.jdbc = jdbc;
this.lockMode = lockMode;
}
/**
* Returns the SQL representation of this isolation level.
*
* @return SQL representation of this isolation level
*/
public String getSQL() {
return sql;
}
/**
* Returns the JDBC constant for this isolation level.
*
* @return the JDBC constant for this isolation level
*/
public int getJdbc() {
return jdbc;
}
/**
* Returns the LOCK_MODE equivalent for PageStore and old versions of H2.
*
* @return the LOCK_MODE equivalent
*/
public int getLockMode() {
return lockMode;
}
/**
* Returns whether a non-repeatable read phenomena is allowed.
*
* @return whether a non-repeatable read phenomena is allowed
*/
public boolean allowNonRepeatableRead() {
return ordinal() < REPEATABLE_READ.ordinal();
}
}