// $Id: MultiTableDeleteExecutor.java,v 1.2 2005/09/30 17:55:45 steveebersole Exp $
package org.hibernate.hql.ast.exec;

import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.util.Iterator;

import org.hibernate.HibernateException;
import org.hibernate.engine.QueryParameters;
import org.hibernate.engine.SessionImplementor;
import org.hibernate.exception.JDBCExceptionHelper;
import org.hibernate.hql.ast.HqlSqlWalker;
import org.hibernate.hql.ast.tree.DeleteStatement;
import org.hibernate.hql.ast.tree.FromElement;
import org.hibernate.param.ParameterSpecification;
import org.hibernate.persister.entity.Queryable;
import org.hibernate.sql.Delete;
import org.hibernate.util.StringHelper;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * Implementation of MultiTableDeleteExecutor.
 *
 * @author Steve Ebersole
 */
public class MultiTableDeleteExecutor extends AbstractStatementExecutor {
	private static final Log log = LogFactory.getLog( MultiTableDeleteExecutor.class );

	private final DeleteStatement deleteStatement;
	private final Queryable persister;
	private final String idInsertSelect;
	private final String[] deletes;

	public MultiTableDeleteExecutor(HqlSqlWalker walker) {
		super( walker, log );

		if ( !walker.getSessionFactoryHelper().getFactory().getDialect().supportsTemporaryTables() ) {
			throw new HibernateException( "cannot perform multi-table deletes using dialect not supporting temp tables" );
		}

		this.deleteStatement = ( DeleteStatement ) walker.getAST();

		FromElement fromElement = deleteStatement.getFromClause().getFromElement();
		this.persister = fromElement.getQueryable();

		this.idInsertSelect = generateIdInsertSelect( persister, ( ( DeleteStatement ) walker.getAST() ).getWhereClause() );
		log.trace( "Generated ID-INSERT-SELECT SQL (multi-table delete) : " +  idInsertSelect );

		String[] tableNames = persister.getConstraintOrderedTableNameClosure();
		String[][] columnNames = persister.getContraintOrderedTableKeyColumnClosure();
		String idSubselect = generateIdSubselect( persister );

		deletes = new String[tableNames.length];
		for ( int i = tableNames.length - 1; i >= 0; i-- ) {
			// TODO : an optimization here would be to consider cascade deletes and not gen those delete statements;
			//      the difficulty is the ordering of the tables here vs the cascade attributes on the persisters ->
			//          the table info gotten here should really be self-contained (i.e., a class representation
			//          defining all the needed attributes), then we could then get an array of those
			final Delete delete = new Delete()
					.setTableName( tableNames[i] )
					.setWhere( "(" + StringHelper.join( ", ", columnNames[i] ) + ") IN (" + idSubselect + ")" );
			if ( getFactory().getSettings().isCommentsEnabled() && getFactory().getDialect().supportsCommentOn() ) {
				delete.setComment( "bulk delete" );
			}

			deletes[i] = delete.toStatementString();
		}
	}

	public int execute(QueryParameters parameters, SessionImplementor session) throws HibernateException {
		coordinateSharedCacheCleanup( session );

		createTemporaryTableIfNecessary( persister, session );

		try {
			// First, save off the pertinent ids, saving the number of pertinent ids for return
			PreparedStatement ps = null;
			int resultCount = 0;
			try {
				try {
					ps = session.getBatcher().prepareStatement( idInsertSelect );
					Iterator paramSpecifications = getWalker().getParameters().iterator();
					int pos = 1;
					while ( paramSpecifications.hasNext() ) {
						final ParameterSpecification paramSpec = ( ParameterSpecification ) paramSpecifications.next();
						pos += paramSpec.bind( ps, parameters, session, pos );
					}
					resultCount = ps.executeUpdate();
				}
				finally {
					if ( ps != null ) {
						session.getBatcher().closeStatement( ps );
					}
				}
			}
			catch( SQLException e ) {
				throw JDBCExceptionHelper.convert(
						getFactory().getSQLExceptionConverter(),
						e,
						"could not insert/select ids for bulk delete",
						idInsertSelect
					);
			}

			// Start performing the deletes
			for ( int i = 0; i < deletes.length; i++ ) {
				try {
					try {
						ps = session.getBatcher().prepareStatement( deletes[i] );
						ps.executeUpdate();
					}
					finally {
						if ( ps != null ) {
							session.getBatcher().closeStatement( ps );
						}
					}
				}
				catch( SQLException e ) {
					throw JDBCExceptionHelper.convert(
							getFactory().getSQLExceptionConverter(),
							e,
							"error performing bulk delete",
							deletes[i]
						);
				}
			}

			return resultCount;
		}
		finally {
			dropTemporaryTableIfNecessary( persister, session );
		}
	}

	protected Queryable[] getAffectedQueryables() {
		return new Queryable[] { persister };
	}
}
