view src/main/java/nl/cwi/monetdb/jdbc/MonetConnection.java @ 172:60063c67f9e7 embedded

Merged with default
author Pedro Ferreira <pedro.ferreira@monetdbsolutions.com>
date Tue, 19 Sep 2017 13:49:34 +0200 (2017-09-19)
parents 6c74540a8e6b 89e954e7acbb
children 89c285fc0a49
line wrap: on
line source
package nl.cwi.monetdb.jdbc;

import nl.cwi.monetdb.mcl.connection.ControlCommands;
import nl.cwi.monetdb.mcl.connection.IMonetDBLanguage;
import nl.cwi.monetdb.mcl.connection.MCLException;
import nl.cwi.monetdb.mcl.connection.SenderThread;
import nl.cwi.monetdb.mcl.protocol.AbstractProtocol;
import nl.cwi.monetdb.mcl.protocol.ProtocolException;
import nl.cwi.monetdb.mcl.protocol.ServerResponses;
import nl.cwi.monetdb.mcl.protocol.StarterHeaders;
import nl.cwi.monetdb.mcl.responses.*;

import java.io.IOException;
import java.net.SocketException;
import java.net.SocketTimeoutException;
import java.sql.*;
import java.util.*;
import java.util.concurrent.Executor;

/**
 * A {@link Connection} suitable for the MonetDB database.
 *
 * This connection represents a connection (session) to a MonetDB
 * database. SQL statements are executed and results are returned within
 * the context of a connection. This Connection object holds a physical
 * connection to the MonetDB database.
 *
 * A Connection object's database should able to provide information
 * describing its tables, its supported SQL grammar, its stored
 * procedures, the capabilities of this connection, and so on. This
 * information is obtained with the getMetaData method.
 *
 * Note: By default a Connection object is in auto-commit mode, which
 * means that it automatically commits changes after executing each
 * statement. If auto-commit mode has been disabled, the method commit
 * must be called explicitly in order to commit changes; otherwise,
 * database changes will not be saved.
 *
 * The current state of this connection is that it nearly implements the
 * whole Connection interface.
 *
 * @author Fabian Groffen, Martin van Dinther, Pedro Ferreira
 * @version 1.3
 */
public abstract class MonetConnection extends MonetWrapper implements Connection, AutoCloseable {

	/** The sequence counter */
	private static int SeqCounter = 0;

	/**
	 * Gets the current sequence counter.
	 *
	 * @return The current sequence counter
	 */
	public static int getSeqCounter() {
		return SeqCounter;
	}

	/** The successful processed input properties */
	protected final Properties conn_props;
	/** The language to connect with */
	protected IMonetDBLanguage language;
	/** Authentication hash method */
	protected final String hash;
	/** An optional thread that is used for sending large queries */
	private SenderThread senderThread;
	/** Whether this Connection is closed (and cannot be used anymore) */
	private boolean closed;
	/** Whether this Connection is in autocommit mode */
	private boolean autoCommit = true;
	/** The stack of warnings for this Connection object */
	private SQLWarning warnings;
	/** The Connection specific mapping of user defined types to Java types */
	private Map<String,Class<?>> typeMap = new HashMap<String,Class<?>>() {
		private static final long serialVersionUID = 1L; {
			put("inet", MonetINET.class);
			put("url", MonetURL.class);
		}
	};

	// See javadoc for documentation about WeakHashMap if you don't know what it does !!!NOW!!!
	// (only when you deal with it of course)
	/** A Map containing all (active) Statements created from this Connection */
	private Map<Statement,?> statements = new WeakHashMap<>();
	/** The number of results we receive from the server at once */
	private int curReplySize = -1; // the server by default uses -1 (all)
	/** Whether or not BLOB is mapped to LONGVARBINARY within the driver */
	private final boolean blobIsBinary;
	/** Whether or not CLOB is mapped to LONGVARCHAR within the driver */
	private final boolean clobIsLongChar;
	/** The underlying proticol provided by the connection (MAPI or embedded) */
	protected AbstractProtocol protocol;
	/** Tells if the connection is embedded or not */
	private final boolean isEmbedded;

	/**
	 * Constructor of a Connection for MonetDB. At this moment the current implementation limits itself to storing the
	 * given host, database, username and password for later use by the createStatement() call.  This constructor is
	 * only accessible to classes from the jdbc package.
	 */
	public MonetConnection(Properties props, String hash, IMonetDBLanguage language, boolean blobIsBinary,
						   boolean clobIsLongChar) {
		this.conn_props = props;
		this.hash = hash;
		this.language = language;
		this.blobIsBinary = blobIsBinary;
		this.clobIsLongChar = clobIsLongChar;
		//"instance of" should be cleanner, but this is faster.
		this.isEmbedded = props.getProperty("embedded", "false").equals("true");
	}

	/**
	 * Checks if the conection is embedded or not
	 *
	 * @return If the connection is embedded
	 */
	public boolean isEmbedded() {
		return isEmbedded;
	}

	/**
	 * Gets the connection's language data.
	 *
	 * @return The connection's language data
	 */
	public IMonetDBLanguage getLanguage() {
		return language;
	}

	/**
	 * Gets the connection's protocol.
	 *
	 * @return The connection's protocol
	 */
	public AbstractProtocol getProtocol() {
		return this.protocol;
	}

	/**
	 * Connects to the server, authenticating the user.
	 *
	 * @param user The user name to authenticate
	 * @param pass The user's password
	 * @return A List with informational (warning) messages. If this list is empty; then there are no warnings.
	 * @throws IOException if an I/O error occurs when creating the socket
	 * @throws ProtocolException if bogus data is received
	 * @throws MCLException if an MCL related error occurs
	 */
	public abstract List<String> connect(String user, String pass) throws IOException, ProtocolException, MCLException;

	/**
	 * Gets the underlying connection block size length.
	 *
	 * @return The block size length
	 */
	public abstract int getBlockSize();

	/**
	 * Gets the underlying connection default fetch size for DataBlock responses.
	 *
	 * @return The default fetch size
	 */
	public abstract int getDefFetchsize();

	/**
	 * Gets the initial value for the StringBuilder size.
	 *
	 * @return The initial value for the StringBuilder size
	 */
	public abstract int initialStringBuilderSize();

	/**
	 * Gets the underlying connection socket timeout.
	 *
	 * @return The underlying connection socket timeout
	 */
	public abstract int getSoTimeout() throws SocketException;

	/**
	 * Sets the underlying connection socket timeout.
	 *
	 * @param timeout The specified timeout, in milliseconds. A timeout of zero is interpreted as an infinite timeout
	 */
	public abstract void setSoTimeout(int timeout) throws SocketException;

	/**
	 * Closes the underlying connection implementation.
	 *
	 * @throws IOException if an I/O error occurs while closing the connection
	 */
	public abstract void closeUnderlyingConnection() throws IOException;

	/**
	 * Gets the underlying connection JDBC String URL.
	 *
	 * @return The underlying connection JDBC String URL
	 */
	public abstract String getJDBCURL();

	/**
	 * Sends a control command to the server.
	 *
	 * @param commandID the command identifier according to {@link ControlCommands} listing
	 * @param data The integer to send according to the control command
	 * @throws SQLException if an IO exception or a database error occurs
	 */
	public abstract void sendControlCommand(int commandID, int data) throws SQLException;

	/**
	 * Releases this Connection object's database and JDBC resources immediately instead of waiting for them to be
	 * automatically released. All Statements created from this Connection will be closed when this method is called.
	 *
	 * Calling the method close on a Connection object that is already closed is a no-op.
	 */
	@Override
	public void close() {
		for (Statement st : statements.keySet()) {
			try {
				st.close();
			} catch (SQLException e) {
				// better luck next time!
			}
		}
		// close the socket or the embedded server
		try {
			this.closeUnderlyingConnection();
		} catch (IOException e) {
			// ignore it
		}
		// close active SendThread if any
		if (senderThread != null) {
			senderThread.shutdown();
			senderThread = null;
		}
		// report ourselves as closed
		closed = true;
	}

	/**
	 * Destructor called by garbage collector before destroying this object tries to disconnect the MonetDB connection
	 * if it has not been disconnected already.
	 */
	@Override
	protected void finalize() throws Throwable {
		this.close();
		super.finalize();
	}

	//== methods of interface Connection

	/**
	 * Clears all warnings reported for this Connection object. After a call to this method, the method getWarnings
	 * returns null until a new warning is reported for this Connection object.
	 */
	@Override
	public void clearWarnings() {
		warnings = null;
	}

	/**
	 * Makes all changes made since the previous commit/rollback permanent and releases any database locks currently
	 * held by this Connection object. This method should be used only when auto-commit mode has been disabled.
	 *
	 * @throws SQLException if a database access error occurs or this Connection object is in auto-commit mode
	 * @see #setAutoCommit(boolean)
	 */
	@Override
	public void commit() throws SQLException {
		// note: can't use sendIndependentCommand here because we need to process the auto_commit state the server gives
		this.sendTransactionCommand("COMMIT");
	}

	/**
	 * Creates a Statement object for sending SQL statements to the
	 * database.  SQL statements without parameters are normally
	 * executed using Statement objects. If the same SQL statement is
	 * executed many times, it may be more efficient to use a
	 * PreparedStatement object.
	 *
	 * Result sets created using the returned Statement object will by
	 * default be type TYPE_FORWARD_ONLY and have a concurrency level of
	 * CONCUR_READ_ONLY.
	 *
	 * @return a new default Statement object
	 * @throws SQLException if a database access error occurs
	 */
	@Override
	public Statement createStatement() throws SQLException {
		return createStatement(ResultSet.TYPE_FORWARD_ONLY, ResultSet.CONCUR_READ_ONLY, ResultSet.HOLD_CURSORS_OVER_COMMIT);
	}

	/**
	 * Creates a Statement object that will generate ResultSet objects
	 * with the given type and concurrency. This method is the same as
	 * the createStatement method above, but it allows the default
	 * result set type and concurrency to be overridden.
	 *
	 * @param resultSetType a result set type; one of
	 *        ResultSet.TYPE_FORWARD_ONLY, ResultSet.TYPE_SCROLL_INSENSITIVE,
	 *        or ResultSet.TYPE_SCROLL_SENSITIVE
	 * @param resultSetConcurrency a concurrency type; one of
	 *        ResultSet.CONCUR_READ_ONLY or ResultSet.CONCUR_UPDATABLE
	 * @return a new Statement object that will generate ResultSet objects with
	 *         the given type and concurrency
	 * @throws SQLException if a database access error occurs
	 */
	@Override
	public Statement createStatement(int resultSetType, int resultSetConcurrency) throws SQLException {
		return createStatement(resultSetType, resultSetConcurrency, ResultSet.HOLD_CURSORS_OVER_COMMIT);
	}

	/**
	 * Creates a Statement object that will generate ResultSet objects
	 * with the given type, concurrency, and holdability.  This method
	 * is the same as the createStatement method above, but it allows
	 * the default result set type, concurrency, and holdability to be
	 * overridden.
	 *
	 * @param resultSetType one of the following ResultSet constants:
	 * ResultSet.TYPE_FORWARD_ONLY, ResultSet.TYPE_SCROLL_INSENSITIVE,
	 * or ResultSet.TYPE_SCROLL_SENSITIVE
	 * @param resultSetConcurrency one of the following ResultSet
	 * constants: ResultSet.CONCUR_READ_ONLY or
	 * ResultSet.CONCUR_UPDATABLE
	 * @param resultSetHoldability one of the following ResultSet
	 * constants: ResultSet.HOLD_CURSORS_OVER_COMMIT or
	 * ResultSet.CLOSE_CURSORS_AT_COMMIT
	 *
	 * @return a new Statement      object that will generate ResultSet
	 * objects with the given type, concurrency, and holdability
	 * @throws SQLException if a database access error occurs or the
	 * given parameters are not ResultSet constants indicating type,
	 * concurrency, and holdability
	 */
	@Override
	public Statement createStatement(int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException {
		try {
			Statement ret = new MonetStatement(this, resultSetType, resultSetConcurrency, resultSetHoldability);
			// store it in the map for when we close...
			statements.put(ret, null);
			return ret;
		} catch (IllegalArgumentException e) {
			throw new SQLException(e.toString(), "M0M03");
		}
		// we don't have to catch SQLException because that is declared to
		// be thrown
	}

	/**
	 * Retrieves the current auto-commit mode for this Connection object.
	 *
	 * @return the current state of this Connection object's auto-commit mode
	 * @see #setAutoCommit(boolean)
	 */
	@Override
	public boolean getAutoCommit() throws SQLException {
		return autoCommit;
	}

	/**
	 * Retrieves this Connection object's current catalog name.
	 *
	 * @return the current catalog name or null if there is none
	 * @throws SQLException if a database access error occurs or the current language is not SQL
	 */
	@Override
	public String getCatalog() throws SQLException {
		// MonetDB does NOT support catalogs
		return null;
	}

	/**
	 * Retrieves the current holdability of ResultSet objects created using this Connection object.
	 *
	 * @return the holdability, one of ResultSet.HOLD_CURSORS_OVER_COMMIT or ResultSet.CLOSE_CURSORS_AT_COMMIT
	 */
	@Override
	public int getHoldability() {
		// TODO: perhaps it is better to have the server implement
		//       CLOSE_CURSORS_AT_COMMIT
		return ResultSet.HOLD_CURSORS_OVER_COMMIT;
	}

	/**
	 * Retrieves a DatabaseMetaData object that contains metadata about
	 * the database to which this Connection object represents a
	 * connection. The metadata includes information about the
	 * database's tables, its supported SQL grammar, its stored
	 * procedures, the capabilities of this connection, and so on.
	 *
	 * @throws SQLException if the current language is not SQL
	 * @return a DatabaseMetaData object for this Connection object
	 */
	@Override
	public DatabaseMetaData getMetaData() throws SQLException {
		if (!this.language.getRepresentation().equals("sql")) {
			throw new SQLException("This method is only supported in SQL mode", "M0M04");
		}
		return new MonetDatabaseMetaData(this);
	}

	/**
	 * Retrieves this Connection object's current transaction isolation level.
	 *
	 * @return the current transaction isolation level, which will be Connection.TRANSACTION_SERIALIZABLE
	 */
	@Override
	public int getTransactionIsolation() {
		return TRANSACTION_SERIALIZABLE;
	}

	/**
	 * Retrieves the Map object associated with this Connection object. Unless the application has added an entry,
	 * the type map returned will be empty.
	 *
	 * @return the java.util.Map object associated with this Connection object
	 */
	@Override
	public Map<String,Class<?>> getTypeMap() {
		return typeMap;
	}

	/**
	 * Retrieves the first warning reported by calls on this Connection
	 * object.  If there is more than one warning, subsequent warnings
	 * will be chained to the first one and can be retrieved by calling
	 * the method SQLWarning.getNextWarning on the warning that was
	 * retrieved previously.
	 *
	 * This method may not be called on a closed connection; doing so will cause an SQLException to be thrown.
	 *
	 * Note: Subsequent warnings will be chained to this SQLWarning.
	 *
	 * @return the first SQLWarning object or null if there are none
	 * @throws SQLException if a database access error occurs or this method is called on a closed connection
	 */
	@Override
	public SQLWarning getWarnings() throws SQLException {
		if (closed) {
			throw new SQLException("Cannot call on closed Connection", "M1M20");
		}
		// if there are no warnings, this will be null, which fits with the specification.
		return warnings;
	}

	/**
	 * Retrieves whether this Connection object has been closed.  A
	 * connection is closed if the method close has been called on it or
	 * if certain fatal errors have occurred.  This method is guaranteed
	 * to return true only when it is called after the method
	 * Connection.close has been called.
	 *
	 * This method generally cannot be called to determine whether a
	 * connection to a database is valid or invalid.  A typical client
	 * can determine that a connection is invalid by catching any
	 * exceptions that might be thrown when an operation is attempted.
	 *
	 * @return true if this Connection object is closed; false if it is still open
	 */
	@Override
	public boolean isClosed() {
		return closed;
	}

	/**
	 * Retrieves whether this Connection object is in read-only mode.
	 * MonetDB currently doesn't support updateable result sets, but
	 * updates are possible.  Hence the Connection object is never in
	 * read-only mode.
	 *
	 * @return true if this Connection object is read-only; false otherwise
	 */
	@Override
	public boolean isReadOnly() {
		return false;
	}

	@Override
	public String nativeSQL(String sql) {
		/* there is currently no way to get the native MonetDB rewritten SQL string back, so just return the original string */
		/* in future we may replace/remove the escape sequences { <escape-type> ...} before sending it to the server */
		return sql;
	}

	@Override
	public CallableStatement prepareCall(String sql) {
		/* not implemented yet */
		return null;
	}

	@Override
	public CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency) {
		/* not implemented yet */
		return null;
	}

	@Override
	public CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency, int resultSetHoldability) {
		/* not implemented yet */
		return null;
	}

	/**
	 * Creates a PreparedStatement object for sending parameterized SQL
	 * statements to the database.
	 *
	 * A SQL statement with or without IN parameters can be pre-compiled
	 * and stored in a PreparedStatement object. This object can then be
	 * used to efficiently execute this statement multiple times.
	 *
	 * Note: This method is optimized for handling parametric SQL
	 * statements that benefit from precompilation. If the driver
	 * supports precompilation, the method prepareStatement will send
	 * the statement to the database for precompilation. Some drivers
	 * may not support precompilation. In this case, the statement may
	 * not be sent to the database until the PreparedStatement object is
	 * executed. This has no direct effect on users; however, it does
	 * affect which methods throw certain SQLException objects.
	 *
	 * Result sets created using the returned PreparedStatement object
	 * will by default be type TYPE_FORWARD_ONLY and have a concurrency
	 * level of CONCUR_READ_ONLY.
	 *
	 * @param sql an SQL statement that may contain one or more '?' IN
	 *        parameter placeholders
	 * @return a new default PreparedStatement object containing the
	 *         pre-compiled SQL statement
	 * @throws SQLException if a database access error occurs
	 */
	@Override
	public PreparedStatement prepareStatement(String sql) throws SQLException {
		return prepareStatement(sql, ResultSet.TYPE_FORWARD_ONLY, ResultSet.CONCUR_READ_ONLY, ResultSet.HOLD_CURSORS_OVER_COMMIT);
	}

	/**
	 * Creates a PreparedStatement object that will generate ResultSet
	 * objects with the given type and concurrency.  This method is the
	 * same as the prepareStatement method above, but it allows the
	 * default result set type and concurrency to be overridden.
	 *
	 * @param sql a String object that is the SQL statement to be sent to the
	 *        database; may contain one or more ? IN parameters
	 * @param resultSetType a result set type; one of
	 *        ResultSet.TYPE_FORWARD_ONLY, ResultSet.TYPE_SCROLL_INSENSITIVE,
	 *        or ResultSet.TYPE_SCROLL_SENSITIVE
	 * @param resultSetConcurrency a concurrency type; one of
	 *        ResultSet.CONCUR_READ_ONLY or ResultSet.CONCUR_UPDATABLE
	 * @return a new PreparedStatement object containing the pre-compiled SQL
	 *         statement that will produce ResultSet objects with the given
	 *         type and concurrency
	 * @throws SQLException if a database access error occurs or the given
	 *         parameters are not ResultSet constants indicating
	 *         type and concurrency
	 */
	@Override
	public PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency) throws SQLException {
		return prepareStatement(sql, resultSetType, resultSetConcurrency, ResultSet.HOLD_CURSORS_OVER_COMMIT);
	}

	/**
	 * Creates a PreparedStatement object that will generate ResultSet
	 * objects with the given type, concurrency, and holdability.
	 *
	 * This method is the same as the prepareStatement method above, but
	 * it allows the default result set type, concurrency, and
	 * holdability to be overridden.
	 *
	 * @param sql a String object that is the SQL statement to be sent
	 * to the database; may contain one or more ? IN parameters
	 * @param resultSetType one of the following ResultSet constants:
	 * ResultSet.TYPE_FORWARD_ONLY, ResultSet.TYPE_SCROLL_INSENSITIVE,
	 * or ResultSet.TYPE_SCROLL_SENSITIVE
	 * @param resultSetConcurrency one of the following ResultSet
	 * constants: ResultSet.CONCUR_READ_ONLY or
	 * ResultSet.CONCUR_UPDATABLE
	 * @param resultSetHoldability one of the following ResultSet
	 * constants: ResultSet.HOLD_CURSORS_OVER_COMMIT or
	 * ResultSet.CLOSE_CURSORS_AT_COMMIT
	 * @return a new PreparedStatement object, containing the
	 * pre-compiled SQL statement, that will generate ResultSet objects
	 * with the given type, concurrency, and holdability
	 * @throws SQLException if a database access error occurs or the
	 * given parameters are not ResultSet constants indicating type,
	 * concurrency, and holdability
	 */
	@Override
	public PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency, int resultSetHoldability)
			throws SQLException {
		try {
			PreparedStatement ret = new MonetPreparedStatement(this, resultSetType, resultSetConcurrency,
					resultSetHoldability, sql);
			// store it in the map for when we close...
			statements.put(ret, null);
			return ret;
		} catch (IllegalArgumentException e) {
			throw new SQLException(e.toString(), "M0M03");
		}
		// we don't have to catch SQLException because that is declared to
		// be thrown
	}

	/**
	 * Creates a default PreparedStatement object that has the
	 * capability to retrieve auto-generated keys.  The given constant
	 * tells the driver whether it should make auto-generated keys
	 * available for retrieval.  This parameter is ignored if the SQL
	 * statement is not an INSERT statement.
	 *
	 * Note: This method is optimized for handling parametric SQL
	 * statements that benefit from precompilation.  If the driver
	 * supports precompilation, the method prepareStatement will send
	 * the statement to the database for precompilation. Some drivers
	 * may not support precompilation.  In this case, the statement may
	 * not be sent to the database until the PreparedStatement object is
	 * executed.  This has no direct effect on users; however, it does
	 * affect which methods throw certain SQLExceptions.
	 *
	 * Result sets created using the returned PreparedStatement object
	 * will by default be type TYPE_FORWARD_ONLY and have a concurrency
	 * level of CONCUR_READ_ONLY.
	 *
	 * @param sql an SQL statement that may contain one or more '?' IN
	 *        parameter placeholders
	 * @param autoGeneratedKeys a flag indicating whether auto-generated
	 *        keys should be returned; one of
	 *        Statement.RETURN_GENERATED_KEYS or
	 *        Statement.NO_GENERATED_KEYS
	 * @return a new PreparedStatement object, containing the
	 *         pre-compiled SQL statement, that will have the capability
	 *         of returning auto-generated keys
	 * @throws SQLException - if a database access error occurs or the
	 *         given parameter is not a Statement  constant indicating
	 *         whether auto-generated keys should be returned
	 */
	@Override
	public PreparedStatement prepareStatement(String sql, int autoGeneratedKeys) throws SQLException {
		if (autoGeneratedKeys != Statement.RETURN_GENERATED_KEYS &&
				autoGeneratedKeys != Statement.NO_GENERATED_KEYS)
			throw new SQLException("Invalid argument, expected RETURN_GENERATED_KEYS or NO_GENERATED_KEYS", "M1M05");

		/* MonetDB has no way to disable this, so just do the normal
		 * thing ;) */
		return prepareStatement(sql, ResultSet.TYPE_FORWARD_ONLY, ResultSet.CONCUR_READ_ONLY);
	}

	/**
	 * Creates a default PreparedStatement object capable of returning the auto-generated keys designated by the given array.
	 * This array contains the indexes of the columns in the target table that contain the auto-generated keys that should be made available.
	 * The driver will ignore the array if the SQL statement is not an INSERT statement, or an SQL statement able to
	 * return auto-generated keys (the list of such statements is vendor-specific).
	 *
	 * An SQL statement with or without IN parameters can be pre-compiled and stored in a PreparedStatement object.
	 * This object can then be used to efficiently execute this statement multiple times.
	 *
	 * Note: This method is optimized for handling parametric SQL statements that benefit from precompilation.
	 * If the driver supports precompilation, the method prepareStatement will send the statement to the database for precompilation.
	 * Some drivers may not support precompilation. In this case, the statement may not be sent to the database until the PreparedStatement
	 * object is executed. This has no direct effect on users; however, it does affect which methods throw certain SQLExceptions.
	 *
	 * Result sets created using the returned PreparedStatement object will by default be type TYPE_FORWARD_ONLY and have
	 * a concurrency level of CONCUR_READ_ONLY. The holdability of the created result sets can be determined by calling getHoldability().
	 *
	 * Parameters:
	 *     sql - an SQL statement that may contain one or more '?' IN parameter placeholders
	 *     columnIndexes - an array of column indexes indicating the columns that should be returned from the inserted row or rows
	 * Returns:
	 *     a new PreparedStatement object, containing the pre-compiled statement, that is capable of
	 *     returning the auto-generated keys designated by the given array of column indexes
	 * Throws:
	 *     SQLException - if a database access error occurs or this method is called on a closed connection
	 *     SQLFeatureNotSupportedException - if the JDBC driver does not support this method
	 */
	@Override
	public PreparedStatement prepareStatement(String sql, int[] columnIndexes) throws SQLException {
		throw new SQLFeatureNotSupportedException("prepareStatement(String sql, int[] columnIndexes) not supported", "0A000");
	}

	/**
	 * Creates a default PreparedStatement object capable of returning the auto-generated keys designated by the given array.
	 * This array contains the names of the columns in the target table that contain the auto-generated keys that should be returned.
	 * The driver will ignore the array if the SQL statement is not an INSERT statement, or an SQL statement able to
	 * return auto-generated keys (the list of such statements is vendor-specific).
	 *
	 * An SQL statement with or without IN parameters can be pre-compiled and stored in a PreparedStatement object.
	 * This object can then be used to efficiently execute this statement multiple times.
	 *
	 * Note: This method is optimized for handling parametric SQL statements that benefit from precompilation.
	 * If the driver supports precompilation, the method prepareStatement will send the statement to the database for precompilation.
	 * Some drivers may not support precompilation. In this case, the statement may not be sent to the database until the PreparedStatement
	 * object is executed. This has no direct effect on users; however, it does affect which methods throw certain SQLExceptions.
	 *
	 * Result sets created using the returned PreparedStatement object will by default be type TYPE_FORWARD_ONLY and have
	 * a concurrency level of CONCUR_READ_ONLY. The holdability of the created result sets can be determined by calling getHoldability().
	 *
	 * Parameters:
	 *     sql - an SQL statement that may contain one or more '?' IN parameter placeholders
	 *     columnNames - an array of column names indicating the columns that should be returned from the inserted row or rows
	 * Returns:
	 *     a new PreparedStatement object, containing the pre-compiled statement, that is capable of
	 *     returning the auto-generated keys designated by the given array of column names
	 * Throws:
	 *     SQLException - if a database access error occurs or this method is called on a closed connection
	 *     SQLFeatureNotSupportedException - if the JDBC driver does not support this method
	 */
	@Override
	public PreparedStatement prepareStatement(String sql, String[] columnNames) throws SQLException {
		throw new SQLFeatureNotSupportedException("prepareStatement(String sql, String[] columnNames) not supported", "0A000");
	}

	/**
	 * Removes the given Savepoint object from the current transaction.
	 * Any reference to the savepoint after it have been removed will
	 * cause an SQLException to be thrown.
	 *
	 * @param savepoint the Savepoint object to be removed
	 * @throws SQLException if a database access error occurs or the given
	 *         Savepoint object is not a valid savepoint in the current
	 *         transaction
	 */
	@Override
	public void releaseSavepoint(Savepoint savepoint) throws SQLException {
		if (!(savepoint instanceof MonetSavepoint)) {
			throw new SQLException("This driver can only handle savepoints it created itself", "M0M06");
		}
		MonetSavepoint sp = (MonetSavepoint) savepoint;
		// note: can't use sendIndependentCommand here because we need
		// to process the auto_commit state the server gives
		this.sendTransactionCommand("RELEASE SAVEPOINT " + sp.getName());
	}

	/**
	 * Undoes all changes made in the current transaction and releases
	 * any database locks currently held by this Connection object. This
	 * method should be used only when auto-commit mode has been
	 * disabled.
	 *
	 * @throws SQLException if a database access error occurs or this
	 *         Connection object is in auto-commit mode
	 * @see #setAutoCommit(boolean)
	 */
	@Override
	public void rollback() throws SQLException {
		// note: can't use sendIndependentCommand here because we need
		// to process the auto_commit state the server gives
		// create a container for the result
		this.sendTransactionCommand("ROLLBACK");
	}

	/**
	 * Undoes all changes made after the given Savepoint object was set.
	 *
	 * This method should be used only when auto-commit has been
	 * disabled.
	 *
	 * @param savepoint the Savepoint object to roll back to
	 * @throws SQLException if a database access error occurs, the
	 *         Savepoint object is no longer valid, or this Connection
	 *         object is currently in auto-commit mode
	 */
	@Override
	public void rollback(Savepoint savepoint) throws SQLException {
		if (!(savepoint instanceof MonetSavepoint)) {
			throw new SQLException("This driver can only handle savepoints it created itself", "M0M06");
		}

		MonetSavepoint sp = (MonetSavepoint)savepoint;
		// note: can't use sendIndependentCommand here because we need
		// to process the auto_commit state the server gives
		// create a container for the result
		this.sendTransactionCommand("ROLLBACK TO SAVEPOINT " + sp.getName());
	}

	/**
	 * Sets this connection's auto-commit mode to the given state. If a
	 * connection is in auto-commit mode, then all its SQL statements
	 * will be executed and committed as individual transactions.
	 * Otherwise, its SQL statements are grouped into transactions that
	 * are terminated by a call to either the method commit or the
	 * method rollback. By default, new connections are in auto-commit
	 * mode.
	 *
	 * The commit occurs when the statement completes or the next
	 * execute occurs, whichever comes first. In the case of statements
	 * returning a ResultSet object, the statement completes when the
	 * last row of the ResultSet object has been retrieved or the
	 * ResultSet object has been closed. In advanced cases, a single
	 * statement may return multiple results as well as output parameter
	 * values. In these cases, the commit occurs when all results and
	 * output parameter values have been retrieved.
	 *
	 * NOTE: If this method is called during a transaction, the
	 * transaction is committed.
	 *
	 * @param autoCommit true to enable auto-commit mode; false to disable it
	 * @throws SQLException if a database access error occurs
	 * @see #getAutoCommit()
	 */
	@Override
	public void setAutoCommit(boolean autoCommit) throws SQLException {
		if (this.autoCommit != autoCommit) {
			this.sendControlCommand(ControlCommands.AUTO_COMMIT, (autoCommit ? 1 : 0));
			this.autoCommit = autoCommit;
		}
	}

	/**
	 * Sets the given catalog name in order to select a subspace of this
	 * Connection object's database in which to work.  If the driver
	 * does not support catalogs, it will silently ignore this request.
	 */
	@Override
	public void setCatalog(String catalog) throws SQLException {
		throw new SQLFeatureNotSupportedException("setCatalog(String catalog) not supported", "0A000");
	}

	/**
	 * Changes the default holdability of ResultSet objects created using this
	 * Connection object to the given holdability. The default holdability of
	 * ResultSet objects can be be determined by invoking DatabaseMetaData.getResultSetHoldability().
	 *
	 * @param holdability - a ResultSet holdability constant; one of
	 *	ResultSet.HOLD_CURSORS_OVER_COMMIT or
	 *	ResultSet.CLOSE_CURSORS_AT_COMMIT
	 * @see #getHoldability()
	 */
	@Override
	public void setHoldability(int holdability) throws SQLException {
		// we only support ResultSet.HOLD_CURSORS_OVER_COMMIT
		if (holdability != ResultSet.HOLD_CURSORS_OVER_COMMIT)
			throw new SQLFeatureNotSupportedException("setHoldability(CLOSE_CURSORS_AT_COMMIT) not supported", "0A000");
	}

	/**
	 * Puts this connection in read-only mode as a hint to the driver to
	 * enable database optimizations.  MonetDB doesn't support any mode
	 * here, hence an SQLWarning is generated if attempted to set
	 * to true here.
	 *
	 * @param readOnly true enables read-only mode; false disables it
	 * @throws SQLException if a database access error occurs or this
	 *         method is called during a transaction.
	 */
	@Override
	public void setReadOnly(boolean readOnly) throws SQLException {
		if (readOnly) {
			addWarning("cannot setReadOnly(true): read-only Connection mode not supported", "01M08");
		}
	}

	/**
	 * Creates an unnamed savepoint in the current transaction and
	 * returns the new Savepoint object that represents it.
	 *
	 * @return the new Savepoint object
	 * @throws SQLException if a database access error occurs or this Connection
	 *         object is currently in auto-commit mode
	 */
	@Override
	public Savepoint setSavepoint() throws SQLException {
		// create a new Savepoint object
		MonetSavepoint sp = new MonetSavepoint();
		// note: can't use sendIndependentCommand here because we need
		// to process the auto_commit state the server gives
		// create a container for the result
		this.sendTransactionCommand("SAVEPOINT " + sp.getName());
		return sp;
	}

	/**
	 * Creates a savepoint with the given name in the current
	 * transaction and returns the new Savepoint object that represents
	 * it.
	 *
	 * @param name a String containing the name of the savepoint
	 * @return the new Savepoint object
	 * @throws SQLException if a database access error occurs or this Connection
	 *         object is currently in auto-commit mode
	 */
	@Override
	public Savepoint setSavepoint(String name) throws SQLException {
		// create a new Savepoint object
		MonetSavepoint sp;
		try {
			sp = new MonetSavepoint(name);
		} catch (IllegalArgumentException e) {
			throw new SQLException(e.getMessage(), "M0M03");
		}
		// note: can't use sendIndependentCommand here because we need
		// to process the auto_commit state the server gives
		// create a container for the result
		this.sendTransactionCommand("SAVEPOINT " + sp.getName());
		return sp;
	}

	/**
	 * Attempts to change the transaction isolation level for this
	 * Connection object to the one given.  The constants defined in the
	 * interface Connection are the possible transaction isolation
	 * levels.
	 *
	 * @param level one of the following Connection constants: Connection.TRANSACTION_READ_UNCOMMITTED,
	 *        Connection.TRANSACTION_READ_COMMITTED, Connection.TRANSACTION_REPEATABLE_READ, or
	 *        Connection.TRANSACTION_SERIALIZABLE.
	 */
	@Override
	public void setTransactionIsolation(int level) {
		if (level != TRANSACTION_SERIALIZABLE) {
			addWarning("MonetDB only supports fully serializable " +
					"transactions, continuing with transaction level raised to TRANSACTION_SERIALIZABLE", "01M09");
		}
	}

	/**
	 * Installs the given TypeMap object as the type map for this
	 * Connection object. The type map will be used for the custom
	 * mapping of SQL structured types and distinct types.
	 *
	 * @param map the java.util.Map object to install as the replacement for
	 *        this Connection  object's default type map
	 */
	@Override
	public void setTypeMap(Map<String, Class<?>> map) {
		typeMap = map;
	}

	/**
	 * Returns a string identifying this Connection to the MonetDB server.
	 *
	 * @return a String representing this Object
	 */
	@Override
	public String toString() {
		return "MonetDB Connection (" + this.getJDBCURL() + ") " + (closed ? "disconnected" : "connected");
	}

	/**
	 * Factory method for creating Array objects.
	 *
	 * Note: When createArrayOf is used to create an array object that
	 * maps to a primitive data type, then it is implementation-defined
	 * whether the Array object is an array of that primitive data type
	 * or an array of Object.
	 *
	 * Note: The JDBC driver is responsible for mapping the elements
	 * Object array to the default JDBC SQL type defined in
	 * java.sql.Types for the given class of Object. The default mapping
	 * is specified in Appendix B of the JDBC specification. If the
	 * resulting JDBC type is not the appropriate type for the given
	 * typeName then it is implementation defined whether an
	 * SQLException is thrown or the driver supports the resulting conversion.
	 *
	 * @param typeName the SQL name of the type the elements of the
	 *        array map to. The typeName is a database-specific name
	 *        which may be the name of a built-in type, a user-defined
	 *        type or a standard SQL type supported by this database.
	 *        This is the value returned by Array.getBaseTypeName
	 * @return an Array object whose elements map to the specified SQL type
	 * @throws SQLException if a database error occurs, the JDBC type
	 *         is not appropriate for the typeName and the conversion is
	 *         not supported, the typeName is null or this method is
	 *         called on a closed connection
	 * @throws SQLFeatureNotSupportedException the JDBC driver does
	 *         not support this data type
	 * @since 1.6
	 */
	@Override
	public java.sql.Array createArrayOf(String typeName, Object[] elements) throws SQLException {
		throw new SQLFeatureNotSupportedException("createArrayOf() not supported", "0A000");
	}


	//== end methods of interface java.sql.Connection

	/**
	 * Constructs an object that implements the Clob interface. The
	 * object returned initially contains no data. The setAsciiStream,
	 * setCharacterStream and setString methods of the Clob interface
	 * may be used to add data to the Clob.
	 *
	 * @return a MonetClob instance
	 * @throws SQLFeatureNotSupportedException the JDBC driver does
	 *         not support MonetClob objects that can be filled in
	 * @since 1.6
	 */
	@Override
	public java.sql.Clob createClob() throws SQLException {
		return new MonetClob("");
	}

	/**
	 * Constructs an object that implements the Blob interface. The
	 * object returned initially contains no data. The setBinaryStream
	 * and setBytes methods of the Blob interface may be used to add
	 * data to the Blob.
	 *
	 * @return a MonetBlob instance
	 * @throws SQLFeatureNotSupportedException the JDBC driver does
	 *         not support MonetBlob objects that can be filled in
	 * @since 1.6
	 */
	@Override
	public java.sql.Blob createBlob() throws SQLException {
		return new MonetBlob(new byte[1]);
	}

	/**
	 * Constructs an object that implements the NClob interface. The
	 * object returned initially contains no data. The setAsciiStream,
	 * setCharacterStream and setString methods of the NClob interface
	 * may be used to add data to the NClob.
	 *
	 * @return an NClob instance
	 * @throws SQLFeatureNotSupportedException the JDBC driver does
	 *         not support MonetNClob objects that can be filled in
	 * @since 1.6
	 */
	@Override
	public java.sql.NClob createNClob() throws SQLException {
		throw new SQLFeatureNotSupportedException("createNClob() not supported", "0A000");
	}

	/**
	 * Factory method for creating Struct objects.
	 *
	 * @param typeName the SQL type name of the SQL structured type that
	 *        this Struct object maps to. The typeName is the name of a
	 *        user-defined type that has been defined for this database.
	 *        It is the value returned by Struct.getSQLTypeName.
	 * @param attributes the attributes that populate the returned object
	 * @return a Struct object that maps to the given SQL type and is
	 *         populated with the given attributes
	 * @throws SQLException if a database error occurs, the typeName
	 *         is null or this method is called on a closed connection
	 * @throws SQLFeatureNotSupportedException the JDBC driver does
	 *         not support this data type
	 * @since 1.6
	 */
	@Override
	public java.sql.Struct createStruct(String typeName, Object[] attributes) throws SQLException {
		throw new SQLFeatureNotSupportedException("createStruct() not supported", "0A000");
	}

	/**
	 * Constructs an object that implements the SQLXML interface. The
	 * object returned initially contains no data. The
	 * createXmlStreamWriter object and setString method of the SQLXML
	 * interface may be used to add data to the SQLXML object.
	 *
	 * @return An object that implements the SQLXML interface
	 * @throws SQLFeatureNotSupportedException the JDBC driver does
	 *         not support this data type
	 * @since 1.6
	 */
	@Override
	public java.sql.SQLXML createSQLXML() throws SQLException {
		throw new SQLFeatureNotSupportedException("createSQLXML() not supported", "0A000");
	}

	/**
	 * Returns true if the connection has not been closed and is still
	 * valid. The driver shall submit a query on the connection or use
	 * some other mechanism that positively verifies the connection is
	 * still valid when this method is called.
	 *
	 * The query submitted by the driver to validate the connection
	 * shall be executed in the context of the current transaction.
	 *
	 * @param timeout The time in seconds to wait for the database
	 *        operation used to validate the connection to complete. If
	 *        the timeout period expires before the operation completes,
	 *        this method returns false. A value of 0 indicates a
	 *        timeout is not applied to the database operation.
	 * @return true if the connection is valid, false otherwise
	 * @throws SQLException if the value supplied for timeout is less than 0
	 * @since 1.6
	 */
	@Override
	public boolean isValid(int timeout) throws SQLException {
		if (timeout < 0)
			throw new SQLException("timeout is less than 0", "M1M05");
		if (closed)
			return false;

		// ping db using query: select 1;
		Statement stmt = null;
		ResultSet rs = null;
		boolean isValid = false;
		try {
			stmt = createStatement();
			if (stmt != null) {
				int original_timeout = stmt.getQueryTimeout();
				if (timeout > 0 && original_timeout != timeout) {
					// we need to change the requested timeout for this test query
					stmt.setQueryTimeout(timeout);
				}
				rs = stmt.executeQuery("SELECT 1");
				if (rs != null && rs.next()) {
					isValid = true;
				}
				if (timeout > 0 && original_timeout != timeout) {
					// restore the original server timeout value
					stmt.setQueryTimeout(original_timeout);
				}
			}
		} catch (SQLException se) {
			String msg = se.getMessage();
			if (msg != null && msg.equals("Current transaction is aborted (please ROLLBACK)")) {
				isValid = true;
			}
			/* ignore stmt errors/exceptions, we are only testing if the connection is still alive and usable */
		} finally {
			if (rs != null) {
				try {
					rs.close();
				} catch (Exception e2) { /* ignore error */ }
			}
			if (stmt != null) {
				try {
					stmt.close();
				} catch (Exception e2) { /* ignore error */ }
			}
		}
		return isValid;
	}

	/**
	 * Returns the value of the client info property specified by name.
	 * This method may return null if the specified client info property
	 * has not been set and does not have a default value.
	 * This method will also return null if the specified client info
	 * property name is not supported by the driver.
	 * Applications may use the DatabaseMetaData.getClientInfoProperties method
	 * to determine the client info properties supported by the driver.
	 *
	 * @param name - The name of the client info property to retrieve
	 * @return The value of the client info property specified or null
	 * @throws SQLException - if the database server returns an error
	 *	when fetching the client info value from the database
	 *	or this method is called on a closed connection
	 * @since 1.6
	 */
	@Override
	public String getClientInfo(String name) throws SQLException {
		if (name == null || name.isEmpty())
			return null;
		return conn_props.getProperty(name);
	}

	/**
	 * Returns a list containing the name and current value of each client info
	 * property supported by the driver. The value of a client info property may
	 * be null if the property has not been set and does not have a default value.
	 *
	 * @return A Properties object that contains the name and current value
	 *         of each of the client info properties supported by the driver.
	 * @throws SQLException - if the database server returns an error
	 *	when fetching the client info value from the database
	 *	or this method is called on a closed connection
	 * @since 1.6
	 */
	@Override
	public Properties getClientInfo() throws SQLException {
		// return a clone of the connection properties object
		return new Properties(conn_props);
	}

	/**
	 * Sets the value of the client info property specified by name to the value specified by value.
	 * Applications may use the DatabaseMetaData.getClientInfoProperties method to determine
	 * the client info properties supported by the driver and the maximum length that may be specified
	 * for each property.
	 *
	 * The driver stores the value specified in a suitable location in the database. For example
	 * in a special register, session parameter, or system table column. For efficiency the driver
	 * may defer setting the value in the database until the next time a statement is executed
	 * or prepared. Other than storing the client information in the appropriate place in the
	 * database, these methods shall not alter the behavior of the connection in anyway.
	 * The values supplied to these methods are used for accounting, diagnostics and debugging purposes only.
	 *
	 * The driver shall generate a warning if the client info name specified is not recognized by the driver.
	 *
	 * If the value specified to this method is greater than the maximum length for the property
	 * the driver may either truncate the value and generate a warning or generate a SQLClientInfoException.
	 * If the driver generates a SQLClientInfoException, the value specified was not set on the connection.
	 *
	 * The following are standard client info properties. Drivers are not required to support these
	 * properties however if the driver supports a client info property that can be described by one
	 * of the standard properties, the standard property name should be used.
	 *
	 *	ApplicationName - The name of the application currently utilizing the connection
	 *	ClientUser - The name of the user that the application using the connection is performing work for.
	 *		This may not be the same as the user name that was used in establishing the connection.
	 *	ClientHostname - The hostname of the computer the application using the connection is running on.
	 *
	 * @param name - The name of the client info property to set
	 * @param value - The value to set the client info property to. If the
	 *        value is null, the current value of the specified property is cleared.
	 * @throws SQLClientInfoException - if the database server returns an error
	 *         while setting the clientInfo values on the database server
	 *         or this method is called on a closed connection
	 * @since 1.6
	 */
	@Override
	public void setClientInfo(String name, String value) throws java.sql.SQLClientInfoException {
		if (name == null || name.isEmpty()) {
			addWarning("setClientInfo: missing property name", "01M07");
			return;
		}
		// If the value is null, the current value of the specified property is cleared.
		if (value == null) {
			if (conn_props.containsKey(name))
				conn_props.remove(name);
			return;
		}
		// only set value for supported property names
		if (name.equals("host") || name.equals("port") || name.equals("user") || name.equals("password") ||
				name.equals("database") || name.equals("language") || name.equals("so_timeout") ||
				name.equals("hash") || name.equals("treat_blob_as_binary") || name.equals("follow_redirects") ||
				name.equals("treat_clob_as_longvarchar") || name.equals("embedded") || name.equals("directory")) {
			conn_props.setProperty(name, value);
		} else {
			addWarning("setClientInfo: " + name + "is not a recognised property", "01M07");
		}
	}

	/**
	 * Sets the value of the connection's client info properties.
	 * The Properties object contains the names and values of the client info
	 * properties to be set. The set of client info properties contained in the
	 * properties list replaces the current set of client info properties on the connection.
	 * If a property that is currently set on the connection is not present in the
	 * properties list, that property is cleared. Specifying an empty properties list
	 * will clear all of the properties on the connection.
	 * See setClientInfo (String, String) for more information.
	 *
	 * If an error occurs in setting any of the client info properties, a
	 * SQLClientInfoException is thrown. The SQLClientInfoException contains information
	 * indicating which client info properties were not set. The state of the client
	 * information is unknown because some databases do not allow multiple client info
	 * properties to be set atomically. For those databases, one or more properties may
	 * have been set before the error occurred.
	 *
	 * @param props - The list of client info properties to set
	 * @throws SQLClientInfoException - if the database server returns an error
	 *	while setting the clientInfo values on the database server
	 *	or this method is called on a closed connection
	 * @since 1.6
	 */
	@Override
	public void setClientInfo(Properties props) throws java.sql.SQLClientInfoException {
		if (props != null) {
			for (Map.Entry<Object, Object> entry : props.entrySet()) {
				setClientInfo(entry.getKey().toString(), entry.getValue().toString());
			}
		}
	}

	/**
	 * Sets the given schema name to access.
	 *
	 * @param schema the name of a schema in which to work
	 * @throws SQLException if a database access error occurs or this method is called on a closed connection
	 * @since 1.7
	 */
	@Override
	public void setSchema(String schema) throws SQLException {
		if (closed)
			throw new SQLException("Cannot call on closed Connection", "M1M20");
		if (schema == null)
			throw new SQLException("Missing schema name", "M1M05");

		Statement st = createStatement();
		schema = schema.replaceAll("\\\\", "\\\\\\\\").replaceAll("'", "\\\\'");
		try {
			st.execute("SET SCHEMA \"" + schema + "\"");
		} finally {
			st.close();
		}
	}

	/**
	 * Retrieves this Connection object's current schema name.
	 *
	 * @return the current schema name or null if there is none
	 * @throws SQLException if a database access error occurs or this method is called on a closed connection
	 */
	@Override
	public String getSchema() throws SQLException {
		if (closed) {
			throw new SQLException("Cannot call on closed Connection", "M1M20");
		}
		String cur_schema;
		Statement st = createStatement();
		ResultSet rs = null;
		try {
			rs = st.executeQuery("SELECT CURRENT_SCHEMA");
			if (!rs.next())
				throw new SQLException("Row expected", "02000");
			cur_schema = rs.getString(1);
		} finally {
			if (rs != null)
				rs.close();
			st.close();
		}
		return cur_schema;
	}

	/**
	 * Terminates an open connection. Calling abort results in:
	 *  * The connection marked as closed
	 *  * Closes any physical connection to the database
	 *  * Releases resources used by the connection
	 *  * Insures that any thread that is currently accessing the
	 *    connection will either progress to completion or throw an
	 *    SQLException.
	 * Calling abort marks the connection closed and releases any
	 * resources. Calling abort on a closed connection is a no-op.
	 *
	 * @param executor The Executor implementation which will be used by abort
	 * @throws SQLException if a database access error occurs or the executor is null
	 * @throws SecurityException if a security manager exists and its checkPermission method denies calling abort
	 */
	@Override
	public void abort(Executor executor) throws SQLException {
		if (closed)
			return;
		if (executor == null)
			throw new SQLException("executor is null", "M1M05");
		// this is really the simplest thing to do, it destroys
		// everything (in particular the server connection)
		close();
	}

	/**
	 * Sets the maximum period a Connection or objects created from the
	 * Connection will wait for the database to reply to any one
	 * request. If any request remains unanswered, the waiting method
	 * will return with a SQLException, and the Connection or objects
	 * created from the Connection will be marked as closed. Any
	 * subsequent use of the objects, with the exception of the close,
	 * isClosed or Connection.isValid methods, will result in a
	 * SQLException.
	 *
	 * @param executor The Executor implementation which will be used by setNetworkTimeout
	 * @param millis The time in milliseconds to wait for the database operation to complete
	 * @throws SQLException if a database access error occurs, this method is called on a closed connection, the
	 * executor is null, or the value specified for seconds is less than 0.
	 */
	@Override
	public void setNetworkTimeout(Executor executor, int millis) throws SQLException {
		if (closed)
			throw new SQLException("Cannot call on closed Connection", "M1M20");
		if (executor == null)
			throw new SQLException("executor is null", "M1M05");
		if (millis < 0)
			throw new SQLException("milliseconds is less than zero", "M1M05");

		try {
			this.setSoTimeout(millis);
		} catch (SocketException e) {
			throw new SQLNonTransientConnectionException(e.getMessage(), "08000");
		}
	}

	/**
	 * Retrieves the number of milliseconds the driver will wait for a
	 * database request to complete. If the limit is exceeded, a
	 * SQLException is thrown.
	 *
	 * @return the current timeout limit in milliseconds; zero means
	 *         there is no limit
	 * @throws SQLException if a database access error occurs or
	 *         this method is called on a closed Connection
	 * @since 1.7
	 */
	@Override
	public int getNetworkTimeout() throws SQLException {
		if (closed)
			throw new SQLException("Cannot call on closed Connection", "M1M20");

		try {
			return this.getSoTimeout();
		} catch (SocketException e) {
			throw new SQLNonTransientConnectionException(e.getMessage(), "08000");
		}
	}

	//== end methods of interface Connection

	/**
	 * Returns whether the BLOB type should be mapped to BINARY type.
	 */
	public boolean getBlobAsBinary() {
		return blobIsBinary;
	}

	/**
	 * Returns whether the CLOB type should be mapped to LONGVARCHAR type.
	 */
	public boolean getClobAsLongChar() {
		return clobIsLongChar;
	}

	/**
	 * Sends the given string to MonetDB as special transaction command.
	 * All possible returned information is discarded.
	 * Encountered errors are reported.
	 *
	 * @param command the exact string to send to MonetDB
	 * @throws SQLException if an IO exception or a database error occurs
	 */
	private void sendTransactionCommand(String command) throws SQLException {
		// create a container for the result
		ResponseList l = new ResponseList(0, 0, ResultSet.FETCH_FORWARD, ResultSet.CONCUR_READ_ONLY);
		// send the appropriate query string to the database
		try {
			l.processQuery(command);
		} finally {
			l.close();
		}
	}

	/**
	 * Sends the given string to MonetDB as regular statement, making sure there is a prompt after the command is sent.
	 * All possible returned information is discarded. Encountered errors are reported.
	 *
	 * @param command the exact string to send to MonetDB
	 * @throws SQLException if an IO exception or a database error occurs
	 */
	void sendIndependentCommand(String command) throws SQLException {
		try {
			protocol.writeNextQuery(language.getQueryTemplateIndex(0), command, language.getQueryTemplateIndex(1));
			protocol.waitUntilPrompt();
			int csrh = protocol.getCurrentServerResponse();
			if (csrh == ServerResponses.ERROR) {
				String error = protocol.getRemainingStringLine(0);
				throw new SQLException(error.substring(6), error.substring(0, 5));
			}
		} catch (SocketTimeoutException e) {
			close(); // JDBC 4.1 semantics: abort()
			throw new SQLNonTransientConnectionException("connection timed out", "08M33");
		} catch (IOException e) {
			throw new SQLNonTransientConnectionException(e.getMessage(), "08000");
		}
	}

	/**
	 * Adds a warning to the pile of warnings this Connection object has. If there were no warnings (or clearWarnings
	 * was called) this warning will be the first, otherwise this warning will get appended to the current warning.
	 *
	 * @param reason the warning message
	 */
	void addWarning(String reason, String sqlstate) {
		if (warnings == null) {
			warnings = new SQLWarning(reason, sqlstate);
		} else {
			warnings.setNextWarning(new SQLWarning(reason, sqlstate));
		}
	}

	/**
	 * A list of Response objects. Responses are added to this list. Methods of this class are not synchronized. This is
	 * left as responsibility to the caller to prevent concurrent access.
	 */
	public class ResponseList {

		/** The cache size (number of rows in a DataBlockResponse object) */
		private final int cachesize;
		/** The maximum number of results for this query */
		private final int maxrows;
		/** The ResultSet type to produce */
		private final int rstype;
		/** The ResultSet concurrency to produce */
		private final int rsconcur;
		/** The sequence number of this ResponseList */
		private final int seqnr;
		/** A list of the Responses associated with the query, in the right order */
		private final List<IResponse> responses = new ArrayList<>();
		/** A map of ResultSetResponses, used for additional DataBlockResponse mapping */
		private Map<Integer, ResultSetResponse> rsresponses;
		/** The current header returned by getNextResponse() */
		private int curResponse = -1;

		/**
		 * Main constructor. The query argument can either be a String or List.  An SQLException is thrown if another
		 * object instance is supplied.
		 *
		 * @param cachesize overall cachesize to use
		 * @param maxrows maximum number of rows to allow in the set
		 * @param rstype the type of result sets to produce
		 * @param rsconcur the concurrency of result sets to produce
		 */
		ResponseList(int cachesize, int maxrows, int rstype, int rsconcur) {
			this.cachesize = cachesize;
			this.maxrows = maxrows;
			this.rstype = rstype;
			this.rsconcur = rsconcur;
			this.seqnr = SeqCounter++;
		}

		public int getCachesize() {
			return cachesize;
		}

		public int getRstype() {
			return rstype;
		}

		public int getRsconcur() {
			return rsconcur;
		}

		public int getMaxrows() {
			return maxrows;
		}

		/**
		 * Retrieves the next available response, or null if there are no more responses.
		 *
		 * @return the next Response available or null
		 */
		IResponse getNextResponse() throws SQLException {
			if (rstype == ResultSet.TYPE_FORWARD_ONLY) {
				// free resources if we're running forward only
				if (curResponse >= 0 && curResponse < responses.size()) {
					IResponse tmp = responses.get(curResponse);
					if (tmp != null) {
						tmp.close();
					}
					responses.set(curResponse, null);
				}
			}
			curResponse++;
			if (curResponse >= responses.size()) {
				// ResponseList is obviously completed so, there are no more responses
				return null;
			} else {
				// return this response
				return responses.get(curResponse);
			}
		}

		/**
		 * Closes the Response at index i, if not null.
		 *
		 * @param i the index position of the header to close
		 */
		void closeResponse(int i) {
			if (i < 0 || i >= responses.size()) return;
			IResponse tmp = responses.set(i, null);
			if (tmp != null)
				tmp.close();
		}

		/**
		 * Closes the current response.
		 */
		void closeCurrentResponse() {
			closeResponse(curResponse);
		}

		/**
		 * Closes the current and previous responses.
		 */
		void closeCurOldResponses() {
			for (int i = curResponse; i >= 0; i--) {
				closeResponse(i);
			}
		}

		/**
		 * Closes this ResponseList by closing all the Responses in this ResponseList.
		 */
		public void close() {
			for (int i = 0; i < responses.size(); i++) {
				closeResponse(i);
			}
		}

		/**
		 * Returns whether this ResponseList has still unclosed Responses.
		 */
		boolean hasUnclosedResponses() {
			for (IResponse r : responses) {
				if (r != null)
					return true;
			}
			return false;
		}

		/**
		 * Executes the query contained in this ResponseList, and stores the Responses resulting from this query in this
		 * ResponseList.
		 *
		 * @throws SQLException if a database error occurs
		 */
		void processQuery(String query) throws SQLException {
			this.executeQuery(language.getQueryTemplates(), query);
		}

		/**
		 * Internal executor of queries.
		 *
		 * @param templ the template to fill in
		 * @param query the query to execute
		 * @throws SQLException if a database error occurs
		 */
		@SuppressWarnings("fallthrough")
		public void executeQuery(String[] templ, String query) throws SQLException {
			String error = null;

			try {
				// make sure we're ready to send query; read data till we have the prompt it is possible (and most
				// likely) that we already have the prompt and do not have to skip any lines. Ignore errors from
				// previous result sets.
				protocol.waitUntilPrompt();

				// {{{ set reply size
				/*
				 * Change the reply size of the server.  If the given value is the same as the current value known
				 * to use, then ignore this call.  If it is set to 0 we get a prompt after the server sent it's
				 * header.
				 *
				 * 2017: For now, in the embedded connection, the value set cachesize will be always the default one.
				 */
				int size = (cachesize != 0 && !isEmbedded) ? cachesize : MonetConnection.this.getDefFetchsize();
				size = maxrows != 0 ? Math.min(maxrows, size) : size;
				// don't do work if it's not needed
				if (!isEmbedded && language.getRepresentation().equals("sql") && size != curReplySize &&
						!Arrays.deepEquals(templ, language.getCommandTemplates())) {
					sendControlCommand(ControlCommands.REPLY_SIZE, size);
					// store the reply size after a successful change
					curReplySize = size;
				}
				// }}} set reply size

				// If the query is larger than the TCP buffer size, use a special send thread to avoid deadlock with
				// the server due to blocking behaviour when the buffer is full. Because the server will be writing
				// back results to us, it will eventually block as well when its TCP buffer gets full, as we are
				// blocking an not consuming from it. The result is a state where both client and server want to
				// write, but block.
				if (query.length() > getBlockSize()) {
					// get a reference to the send thread
					if (senderThread == null) {
						senderThread = new SenderThread(protocol);
					}
					// tell it to do some work!
					senderThread.runQuery(templ, query);
				} else {
					// this is a simple call, which is a lot cheaper and will always succeed for small queries.
					protocol.writeNextQuery((templ[0] == null) ? "" : templ[0], query,
							(templ[1] == null) ? "" : templ[1]);
				}

				// go for new results
				protocol.fetchNextResponseData();
				int nextResponse = protocol.getCurrentServerResponse();
				IResponse res = null;
				while (nextResponse != ServerResponses.PROMPT) {
					// each response should start with a start of header (or error)
					switch (nextResponse) {
						case ServerResponses.SOHEADER:
							// make the response object, and fill it
							int nextStartHeader = protocol.getNextStarterHeader();
							try {
								switch (nextStartHeader) {
									case StarterHeaders.Q_PARSE:
										throw new ProtocolException("Q_PARSE header not allowed here");
									case StarterHeaders.Q_TABLE:
									case StarterHeaders.Q_PREPARE: {
										res = protocol.getNextResultSetResponse(MonetConnection.this,
												ResponseList.this, this.seqnr, this.maxrows);
										ResultSetResponse rsreponse = (ResultSetResponse) res;
										if (rsresponses == null) {
											rsresponses = new HashMap<>();
										}
										rsresponses.put(rsreponse.getId(), rsreponse);
									}
									break;
									case StarterHeaders.Q_UPDATE:
										res = protocol.getNextUpdateResponse();
										break;
									case StarterHeaders.Q_SCHEMA:
										res = protocol.getNextSchemaResponse();
										break;
									case StarterHeaders.Q_TRANS:
										res = protocol.getNextAutoCommitResponse();
										boolean isAutoCommit = ((AutoCommitResponse) res).isAutocommit();

										if (MonetConnection.this.getAutoCommit() && isAutoCommit) {
											MonetConnection.this.addWarning("Server enabled auto commit mode " +
													"while local state already was auto commit.", "01M11");
										}
										MonetConnection.this.autoCommit = isAutoCommit;
										break;
									case StarterHeaders.Q_BLOCK: {
										AbstractDataBlockResponse next = protocol.getNextDatablockResponse(rsresponses);
										if (next == null) {
											error = "M0M12!No ResultSetResponse for a DataBlock found";
											break;
										}
										res = next;
									}
									break;
								}
							} catch (ProtocolException e) {
								error = "M0M10!error while parsing start of header:\n" + e.getMessage() + " found: '"
										+ protocol.getRemainingStringLine(0).charAt(e.getErrorOffset()) + "'" +
										" in: \"" + protocol.getRemainingStringLine(0) + "\"" + " at pos: "
										+ e.getErrorOffset();
								// flush all the rest
								protocol.waitUntilPrompt();
								nextResponse = protocol.getCurrentServerResponse();
								break;
							}
							// immediately handle errors after parsing the header (res may be null)
							if (error != null) {
								protocol.waitUntilPrompt();
								nextResponse = protocol.getCurrentServerResponse();
								break;
							}
							// here we have a res object, which we can start filling
							if (res instanceof IIncompleteResponse) {
								IIncompleteResponse iter = (IIncompleteResponse) res;
								while (iter.wantsMore()) {
									try {
										protocol.fetchNextResponseData();
										iter.addLines(protocol);
									} catch (ProtocolException ex) {
										// right, some protocol violation, skip the rest of the result
										error = "M0M10!" + ex.getMessage();
										protocol.waitUntilPrompt();
										nextResponse = protocol.getCurrentServerResponse();
										break;
									}
								}
							}

							if (error != null) {
								break;
							}

							// it is of no use to store DataBlockResponses, you never want to retrieve them directly
							// anyway
							if (!(res instanceof AbstractDataBlockResponse)) {
								responses.add(res);
							}
							// read the next line (can be prompt, new result, error, etc.) before we start the loop over
							protocol.fetchNextResponseData();
							nextResponse = protocol.getCurrentServerResponse();
							break;
						case ServerResponses.INFO:
							addWarning(protocol.getRemainingStringLine(0), "01000");
							// read the next line (can be prompt, new result, error, etc.) before we start the loop over
							protocol.fetchNextResponseData();
							nextResponse = protocol.getCurrentServerResponse();
							break;
						case ServerResponses.ERROR:
							// read everything till the prompt (should be error) we don't know if we ignore some
							// garbage here... but the log should reveal that
							error = protocol.getRemainingStringLine(0);
							protocol.waitUntilPrompt();
							nextResponse = protocol.getCurrentServerResponse();
							break;
						default:
							throw new SQLException("Protocol violation, unexpected line!", "M0M10");
					}
				}

				// if we used the senderThread, make sure it has finished
				if (senderThread != null) {
					String tmp = senderThread.getErrors();
					if (tmp != null) {
						if (error == null) {
							error = "08000!" + tmp;
						} else {
							error += "\n08000!" + tmp;
						}
					}
				}
				if (error != null) {
					SQLException ret = null;
					String[] errorsList = error.split("\n");
					for (String singleError : errorsList) {
						SQLException newErr;
						String reason = isEmbedded() ? singleError : singleError.substring(6);
						String sqlState = isEmbedded() ? "M0M10" : singleError.substring(0, 5);
						if (singleError.length() >= 6) {
							newErr = new SQLException(reason, sqlState);
						} else {
							newErr = new SQLNonTransientConnectionException(singleError, "08000");
						}
						if (ret == null) {
							ret = newErr;
						} else {
							ret.setNextException(newErr);
						}
					}
					throw ret;
				}
			} catch (SocketTimeoutException e) {
				this.close(); // JDBC 4.1 semantics, abort()
				throw new SQLNonTransientConnectionException("connection timed out", "08M33");
			} catch (IOException e) {
				closed = true;
				throw new SQLNonTransientConnectionException(e.getMessage() + " (mserver5 still alive?)", "08006");
			}
		}
	}
}