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 *  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
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 *    http://www.apache.org/licenses/LICENSE-2.0
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package org.apache.cayenne.dba.sqlserver;

import java.sql.Connection;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Collections;

import org.apache.cayenne.access.OperationObserver;
import org.apache.cayenne.access.QueryLogger;
import org.apache.cayenne.access.jdbc.BatchAction;
import org.apache.cayenne.dba.DbAdapter;
import org.apache.cayenne.map.Attribute;
import org.apache.cayenne.map.DbAttribute;
import org.apache.cayenne.map.EntityResolver;
import org.apache.cayenne.query.BatchQuery;
import org.apache.cayenne.query.InsertBatchQuery;

/**
 * @since 1.2
 * @author Andrus Adamchik
 */
public class SQLServerBatchAction extends BatchAction {

    public SQLServerBatchAction(BatchQuery batchQuery, DbAdapter adapter,
            EntityResolver entityResolver) {
        super(batchQuery, adapter, entityResolver);
    }

    @Override
    public void performAction(Connection connection, OperationObserver observer)
            throws SQLException, Exception {

        // this condition checks if identity columns are present in the query and adapter
        // is not ready to process them... e.g. if we are using a MS driver...
        boolean identityOverride = expectsToOverrideIdentityColumns();
        if (identityOverride) {
            setIdentityInsert(connection, true);
        }

        try {
            super.performAction(connection, observer);
        }
        finally {

            // important: turn off IDENTITY_INSERT as SQL Server won't be able to process
            // other identity columns in the same transaction
            
            // TODO: if an error happens here this would mask the parent error
            if (identityOverride) {
                setIdentityInsert(connection, false);
            }
        }
    }
    
    protected void setIdentityInsert(Connection connection, boolean on)
            throws SQLException {

        String flag = on ? " ON" : " OFF";
        String configSQL = "SET IDENTITY_INSERT "
                + query.getDbEntity().getFullyQualifiedName()
                + flag;

        QueryLogger.logQuery(configSQL, Collections.EMPTY_LIST);

        Statement statement = connection.createStatement();
        try {
            statement.execute(configSQL);
        }
        finally {
            try {
                statement.close();
            }
            catch (Exception e) {
            }
        }
    }
 
    /**
     * Returns whether a table has identity columns.
     */
    protected boolean expectsToOverrideIdentityColumns() {
        // jTDS driver supports identity columns, no need for tricks...
        if (getAdapter().supportsGeneratedKeys()) {
            return false;
        }

        if (!(query instanceof InsertBatchQuery) || query.getDbEntity() == null) {
            return false;
        }

        // find identity attributes
        for (Attribute attribute : query.getDbEntity().getAttributes()) {
            if (((DbAttribute)attribute).isGenerated()) {
                return true;
            }
        }

        return false;
    }
}
