createconstant.java

非常棒的java数据库

/*
 * Copyright 2004-2008 H2 Group. Licensed under the H2 License, Version 1.0
 * (http://h2database.com/html/license.html).
 * Initial Developer: H2 Group
 */
package org.h2.command.ddl;

import java.sql.SQLException;

import org.h2.constant.ErrorCode;
import org.h2.engine.Database;
import org.h2.engine.Session;
import org.h2.expression.Expression;
import org.h2.message.Message;
import org.h2.schema.Constant;
import org.h2.schema.Schema;
import org.h2.value.Value;

/**
 * This class represents the statement
 * CREATE CONSTANT
 */
public class CreateConstant extends SchemaCommand {

    private String constantName;
    private Expression expression;
    private boolean ifNotExists;

    public CreateConstant(Session session, Schema schema) {
        super(session, schema);
    }

    public void setIfNotExists(boolean ifNotExists) {
        // TODO constant: if exists - probably better use 'or replace'
        this.ifNotExists = ifNotExists;
    }

    public int update() throws SQLException {
        session.commit(true);
        session.getUser().checkAdmin();
        Database db = session.getDatabase();
        if (getSchema().findConstant(constantName) != null) {
            if (ifNotExists) {
                return 0;
            }
            throw Message.getSQLException(ErrorCode.CONSTANT_ALREADY_EXISTS_1, constantName);
        }
        int id = getObjectId(false, true);
        Constant constant = new Constant(getSchema(), id, constantName);
        expression = expression.optimize(session);
        Value value = expression.getValue(session);
        constant.setValue(value);
        db.addSchemaObject(session, constant);
        return 0;
    }

    public void setConstantName(String constantName) {
        this.constantName = constantName;
    }

    public void setExpression(Expression expr) {
        this.expression = expr;
    }

}