engine/schema/src/com/cloud/upgrade/dao/DatabaseAccessObject.java

// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.
package com.cloud.upgrade.dao;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;

import org.apache.log4j.Logger;

public class DatabaseAccessObject {

    private static Logger s_logger = Logger.getLogger(DatabaseAccessObject.class);

    public void dropKey(Connection conn, String tableName, String key, boolean isForeignKey) {
        PreparedStatement pstmt = null;
        try {
            if (isForeignKey) {
                pstmt = conn.prepareStatement("ALTER TABLE " + tableName + " DROP FOREIGN KEY " + key);
            } else {
                pstmt = conn.prepareStatement("ALTER TABLE " + tableName + " DROP KEY " + key);
            }
            pstmt.executeUpdate();
            s_logger.debug("Key " + key + " is dropped successfully from the table " + tableName);
        } catch (SQLException e) {
            s_logger.warn("Ignored SQL Exception when trying to drop " + (isForeignKey ? "foreign " : "") + "key " + key + " on table " + tableName, e);
        } finally {
            closePreparedStatement(pstmt, "Ignored SQL Exception when trying to close PreparedStatement atfer dropping " + (isForeignKey ? "foreign " : "") + "key " + key
                    + " on table " + tableName);
        }
    }

    public void dropPrimaryKey(Connection conn, String tableName) {
        PreparedStatement pstmt = null;
        try {
            pstmt = conn.prepareStatement("ALTER TABLE " + tableName + " DROP PRIMARY KEY ");
            pstmt.executeUpdate();
            s_logger.debug("Primary key is dropped successfully from the table " + tableName);
        } catch (SQLException e) {
            s_logger.warn("Ignored SQL Exception when trying to drop primary key on table " + tableName, e);
        } finally {
            closePreparedStatement(pstmt, "Ignored SQL Exception when trying to close PreparedStatement atfer dropping primary key on table " + tableName);
        }
    }

    public void dropColumn(Connection conn, String tableName, String columnName) {
        PreparedStatement pstmt = null;
        try {
            pstmt = conn.prepareStatement("ALTER TABLE " + tableName + " DROP COLUMN " + columnName);
            pstmt.executeUpdate();
            s_logger.debug("Column " + columnName + " is dropped successfully from the table " + tableName);
        } catch (SQLException e) {
            s_logger.warn("Unable to drop columns using query " + pstmt + " due to exception", e);
        } finally {
            closePreparedStatement(pstmt, "Ignored SQL Exception when trying to close PreparedStatement after dropping column " + columnName + " on table " + tableName);
        }
    }

    public boolean columnExists(Connection conn, String tableName, String columnName) {
        boolean columnExists = false;
        PreparedStatement pstmt = null;
        try {
            pstmt = conn.prepareStatement("SELECT " + columnName + " FROM " + tableName);
            pstmt.executeQuery();
            columnExists = true;
        } catch (SQLException e) {
            s_logger.warn("Field " + columnName + " doesn't exist in " + tableName, e);
        } finally {
            closePreparedStatement(pstmt, "Ignored SQL Exception when trying to close PreparedStatement atfer checking if column " + columnName + " existed on table " + tableName);
        }

        return columnExists;
    }

    protected static void closePreparedStatement(PreparedStatement pstmt, String errorMessage) {
        try {
            if (pstmt != null) {
                pstmt.close();
            }
        } catch (SQLException e) {
            s_logger.warn(errorMessage, e);
        }
    }

}