/*
 * Copyright 2004-2010 H2 Group. Multiple-Licensed under the H2 License,
 * Version 1.0, and under the Eclipse Public License, Version 1.0
 * (http://h2database.com/html/license.html).
 * Initial Developer: H2 Group
 */
package org.h2.constant;

import java.sql.ResultSet;
import org.h2.engine.Constants;
import org.h2.message.TraceSystem;
import org.h2.util.MathUtils;

/**
 * The constants defined in this class are initialized from system properties.
 * Some system properties are per machine settings, and others are as a last
 * resort and temporary solution to work around a problem in the application or
 * database engine. Also, there are system properties to enable features that
 * are not yet fully tested or that are not backward compatible.
 * <p>
 * System properties can be set when starting the virtual machine:
 * </p>
 *
 * <pre>
 * java -Dh2.baseDir=/temp
 * </pre>
 *
 * They can be set within the application, but this must be done before loading
 * any classes of this database (before loading the JDBC driver):
 *
 * <pre>
 * System.setProperty(&quot;h2.baseDir&quot;, &quot;/temp&quot;);
 * </pre>
 */
public class SysProperties {

    /**
     * INTERNAL
     */
    public static final String H2_SCRIPT_DIRECTORY = "h2.scriptDirectory";

    /**
     * INTERNAL
     */
    public static final String H2_MAX_QUERY_TIMEOUT = "h2.maxQueryTimeout";

    /**
     * INTERNAL
     */
    public static final String H2_COLLATOR_CACHE_SIZE = "h2.collatorCacheSize";

    /**
     * System property <code>file.encoding</code> (default: Cp1252).<br />
     * It is usually set by the system and is the default encoding used for the
     * RunScript and CSV tool.
     */
    public static final String FILE_ENCODING = getStringSetting("file.encoding", "Cp1252");

    /**
     * System property <code>file.separator</code> (default: /).<br />
     * It is usually set by the system, and used to build absolute file names.
     */
    public static final String FILE_SEPARATOR = getStringSetting("file.separator", "/");

    /**
     * System property <code>java.specification.version</code>.<br />
     * It is set by the system. Examples: 1.4, 1.5, 1.6.
     */
    public static final String JAVA_SPECIFICATION_VERSION = getStringSetting("java.specification.version", "1.4");

    /**
     * System property <code>line.separator</code> (default: \n).<br />
     * It is usually set by the system, and used by the script and trace tools.
     */
    public static final String LINE_SEPARATOR = getStringSetting("line.separator", "\n");

    /**
     * System property <code>user.home</code> (empty string if not set).<br />
     * It is usually set by the system, and used as a replacement for ~ in file
     * names.
     */
    public static final String USER_HOME = getStringSetting("user.home", "");

    /**
     * System property <code>h2.analyzeSample</code> (default: 10000).<br />
     * The default sample size when analyzing a table.
     */
    public static final int ANALYZE_SAMPLE = getIntSetting("h2.analyzeSample", 10000);

    /**
     * System property <code>h2.analyzeAuto</code> (default: 0).<br />
     * After changing this many rows, ANALYZE is automatically run for a table.
     * Automatically running ANALYZE is disabled if set to 0. If set to 1000,
     * then ANALYZE will run against each user table after about 1000 changes to
     * that table. The time between running ANALYZE doubles each time since
     * starting the database. It is not run on local temporary tables, and
     * tables that have a trigger on SELECT.
     */
    public static final int ANALYZE_AUTO = getIntSetting("h2.analyzeAuto", 0);

    /**
     * System property <code>h2.aliasColumnName</code> (default: false).<br />
     * When enabled, aliased columns (as in SELECT ID AS I FROM TEST) return the
     * alias (I in this case) in ResultSetMetaData.getColumnName() and 'null' in
     * getTableName(). If disabled, the real column name (ID in this case) and
     * table name is returned. This setting only affects the default mode.
     * <br />
     * When using different modes, this feature is disabled for compatibility
     * for all databases except MySQL. For MySQL, it is always enabled.
     */
    public static final boolean ALIAS_COLUMN_NAME = getBooleanSetting("h2.aliasColumnName", false);

    /**
     * System property <code>h2.allowBigDecimalExtensions</code> (default:
     * false).<br />
     * When enabled, classes that extend BigDecimal are supported in
     * PreparedStatement.setBigDecimal.
     */
    public static final boolean ALLOW_BIG_DECIMAL_EXTENSIONS = getBooleanSetting("h2.allowBigDecimalExtensions", false);

    /**
     * System property <code>h2.allowedClasses</code> (default: *).<br />
     * Comma separated list of class names or prefixes.
     */
    public static final String ALLOWED_CLASSES = getStringSetting("h2.allowedClasses", "*");

    /**
     * System property <code>h2.browser</code> (default: null).<br />
     * The preferred browser to use. If not set, the default browser is used.
     * For Windows, to use the Internet Explorer, set this property to 'explorer'.
     * For Mac OS, if the default browser is not Safari and you want to use Safari,
     * use: <code>java -Dh2.browser="open,-a,Safari,%url" ...</code>.
     */
    public static final String BROWSER = getStringSetting("h2.browser", null);

    /**
     * System property <code>h2.enableAnonymousSSL</code> (default: true).<br />
     * When using SSL connection, the anonymous cipher suite
     * SSL_DH_anon_WITH_RC4_128_MD5 should be enabled.
     */
    public static final boolean ENABLE_ANONYMOUS_SSL = getBooleanSetting("h2.enableAnonymousSSL", true);

    /**
     * System property <code>h2.bindAddress</code> (default: null).<br />
     * Comma separated list of class names or prefixes.
     */
    public static final String BIND_ADDRESS = getStringSetting("h2.bindAddress", null);

    /**
     * System property <code>h2.cacheSizeDefault</code> (default: 16384).<br />
     * The default cache size in KB.
     */
    public static final int CACHE_SIZE_DEFAULT = getIntSetting("h2.cacheSizeDefault", 16 * 1024);

    /**
     * System property <code>h2.cacheTypeDefault</code> (default: LRU).<br />
     * How many time the cache size value is divided by two to get the index
     * cache size. The index cache size is calculated like this: cacheSize >>
     * cacheSizeIndexShift.
     */
    public static final String CACHE_TYPE_DEFAULT = getStringSetting("h2.cacheTypeDefault", "LRU");

    /**
     * System property <code>h2.check</code> (default: true).<br />
     * Assertions in the database engine.
     */
    public static final boolean CHECK = getBooleanSetting("h2.check", true);

    /**
     * System property <code>h2.check2</code> (default: true).<br />
     * Additional assertions in the database engine.
     */
    public static final boolean CHECK2 = getBooleanSetting("h2.check2", false);

    /**
     * System property <code>h2.clientTraceDirectory</code> (default:
     * trace.db/).<br />
     * Directory where the trace files of the JDBC client are stored (only for
     * client / server).
     */
    public static final String CLIENT_TRACE_DIRECTORY = getStringSetting("h2.clientTraceDirectory", "trace.db/");

    /**
     * System property <code>h2.commandCacheSize</code> (default: 0).<br />
     * The size of the query cache. Each session has it's own cache with the
     * given size. The cache is only used if the SQL statement and all
     * parameters match. Only the last returned result per query is cached. Only
     * SELECT statements are cached (excluding UNION and FOR UPDATE statements).
     * This works for both statements and prepared statement.
     */
    public static final int QUERY_CACHE_SIZE = getIntSetting("h2.queryCacheSize", 0);

    /**
     * System property <code>h2.consoleStream</code> (default: true).<br />
     * H2 Console: stream query results.
     */
    public static final boolean CONSOLE_STREAM = getBooleanSetting("h2.consoleStream", true);

    /**
     * System property <code>h2.databaseToUpper</code> (default: true).<br />
     * Database short names are converted to uppercase for the DATABASE()
     * function, and in the CATALOG column of all database meta data methods.
     * Setting this to "false" is experimental.
     */
    public static final boolean DATABASE_TO_UPPER = getBooleanSetting("h2.databaseToUpper", true);

    /**
     * System property <code>h2.defaultEscape</code> (default: \).<br />
     * The default escape character for LIKE comparisons. To select no escape
     * character, use an empty string.
     */
    public static final String DEFAULT_ESCAPE = getStringSetting("h2.defaultEscape", "\\");

    /**
     * System property <code>h2.defaultMaxOperationMemory</code> (default:
     * 100000).<br />
     * The default for the setting MAX_OPERATION_MEMORY.
     */
    public static final int DEFAULT_MAX_OPERATION_MEMORY = getIntSetting("h2.defaultMaxOperationMemory", 100000);

    /**
     * System property <code>h2.defaultMaxLengthInplaceLob</code>
     * (default: 4096).<br />
     * The default maximum length of an LOB that is stored in the database file.
     */
    public static final int DEFAULT_MAX_LENGTH_INPLACE_LOB = getIntSetting("h2.defaultMaxLengthInplaceLob", 4096);

    /**
     * System property <code>h2.defaultMaxLengthInplaceLob2</code>
     * (default: 128).<br />
     * The default maximum length of an LOB that is stored with the record itself.
     * Only used if h2.lobInDatabase is enabled.
     */
    public static final int DEFAULT_MAX_LENGTH_INPLACE_LOB2 = getIntSetting("h2.defaultMaxLengthInplaceLob2", 128);

    /**
     * System property <code>h2.defaultResultSetConcurrency</code> (default:
     * ResultSet.CONCUR_READ_ONLY).<br />
     * The default result set concurrency for statements created with
     * Connection.createStatement() or prepareStatement(String sql).
     */
    public static final int DEFAULT_RESULT_SET_CONCURRENCY = getIntSetting("h2.defaultResultSetConcurrency", ResultSet.CONCUR_READ_ONLY);

    /**
     * System property <code>h2.dataSourceTraceLevel</code> (default: 1).<br />
     * The trace level of the data source implementation. Default is 1 for
     * error.
     */
    public static final int DATASOURCE_TRACE_LEVEL = getIntSetting("h2.dataSourceTraceLevel", TraceSystem.ERROR);

    /**
     * System property <code>h2.defaultMaxMemoryUndo</code> (default: 50000).<br />
     * The default value for the MAX_MEMORY_UNDO setting.
     */
    public static final int DEFAULT_MAX_MEMORY_UNDO = getIntSetting("h2.defaultMaxMemoryUndo", 50000);

    /**
     * System property <code>h2.defaultLockMode</code> (default: 3).<br />
     * The default value for the LOCK_MODE setting.
     */
    public static final int DEFAULT_LOCK_MODE = getIntSetting("h2.defaultLockMode", Constants.LOCK_MODE_READ_COMMITTED);

    /**
     * System property <code>h2.delayWrongPasswordMin</code> (default: 250).<br />
     * The minimum delay in milliseconds before an exception is thrown for using
     * the wrong user name or password. This slows down brute force attacks. The
     * delay is reset to this value after a successful login. Unsuccessful
     * logins will double the time until DELAY_WRONG_PASSWORD_MAX.
     * To disable the delay, set this system property to 0.
     */
    public static final int DELAY_WRONG_PASSWORD_MIN = getIntSetting("h2.delayWrongPasswordMin", 250);

    /**
     * System property <code>h2.delayWrongPasswordMax</code> (default: 4000).<br />
     * The maximum delay in milliseconds before an exception is thrown for using
     * the wrong user name or password. This slows down brute force attacks. The
     * delay is reset after a successful login. The value 0 means there is no
     * maximum delay.
     */
    public static final int DELAY_WRONG_PASSWORD_MAX = getIntSetting("h2.delayWrongPasswordMax", 4000);

    /**
     * System property <code>h2.dropRestrict</code> (default: false).<br />
     * Whether the default action for DROP TABLE and DROP VIEW is RESTRICT. For
     * most databases, the default action is RESTRICT, but for compatibility
     * with older versions of H2 the default action is currently CASCADE. This will
     * change in a future version of H2.
     */
    public static final boolean DROP_RESTRICT = getBooleanSetting("h2.dropRestrict", false);

    /**
     * System property <code>h2.estimatedFunctionTableRows</code> (default:
     * 1000).<br />
     * The estimated number of rows in a function table (for example, CSVREAD or
     * FTL_SEARCH). This value is used by the optimizer.
     */
    public static final int ESTIMATED_FUNCTION_TABLE_ROWS = getIntSetting("h2.estimatedFunctionTableRows", 1000);

    /**
     * System property <code>h2.functionsInSchema</code> (default:
     * false).<br />
     * If set, all functions are stored in a schema. Specially, the SCRIPT statement
     * will always include the schema name in the CREATE ALIAS statement.
     * This is not backward compatible with H2 versions 1.2.134 and older.
     */
    public static final boolean FUNCTIONS_IN_SCHEMA = getBooleanSetting("h2.functionsInSchema", false);

    /**
     * System property <code>h2.identifiersToUpper</code> (default: true).<br />
     * Unquoted identifiers in SQL statements are case insensitive and converted
     * to uppercase.
     */
    public static final boolean IDENTIFIERS_TO_UPPER = getBooleanSetting("h2.identifiersToUpper", true);
    /**
     * System property <code>h2.largeResultBufferSize</code> (default: 4096).<br />
     * Buffer size for large result sets. Set this value to 0 to disable the
     * buffer.
     */
    public static final int LARGE_RESULT_BUFFER_SIZE = getIntSetting("h2.largeResultBufferSize", 4 * 1024);

    /**
     * System property <code>h2.largeTransactions</code> (default: false).<br />
     * Support very large transactions
     */
    public static final boolean LARGE_TRANSACTIONS = getBooleanSetting("h2.largeTransactions", false);

    /**
     * System property <code>h2.lobCloseBetweenReads</code> (default: false).<br />
     * Close LOB files between read operations.
     */
    public static boolean lobCloseBetweenReads = getBooleanSetting("h2.lobCloseBetweenReads", false);

    /**
     * System property <code>h2.lobFilesPerDirectory</code> (default: 256).<br />
     * Maximum number of LOB files per directory.
     */
    public static final int LOB_FILES_PER_DIRECTORY = getIntSetting("h2.lobFilesPerDirectory", 256);

    /**
     * System property <code>h2.lobInDatabase</code> (default: false).<br />
     * Store LOB files in the database.
     */
    public static final boolean LOB_IN_DATABASE = getBooleanSetting("h2.lobInDatabase", false);

    /**
     * System property <code>h2.logAllErrors</code> (default: false).<br />
     * Write stack traces of any kind of error to a file.
     */
    public static final boolean LOG_ALL_ERRORS = getBooleanSetting("h2.logAllErrors", false);

    /**
     * System property <code>h2.logAllErrorsFile</code> (default:
     * h2errors.txt).<br />
     * File name to log errors.
     */
    public static final String LOG_ALL_ERRORS_FILE = getStringSetting("h2.logAllErrorsFile", "h2errors.txt");

    /**
     * System property <code>h2.maxCompactCount</code>
     * (default: Integer.MAX_VALUE).<br />
     * The maximum number of pages to move when closing a database.
     */
    public static final int MAX_COMPACT_COUNT = getIntSetting("h2.maxCompactCount", Integer.MAX_VALUE);

    /**
     * System property <code>h2.maxCompactTime</code> (default: 1000).<br />
     * The maximum time in milliseconds used to compact a database when closing.
     */
    public static final int MAX_COMPACT_TIME = getIntSetting("h2.maxCompactTime", 1000);

    /**
     * System property <code>h2.maxFileRetry</code> (default: 16).<br />
     * Number of times to retry file delete and rename. in Windows, files can't
     * be deleted if they are open. Waiting a bit can help (sometimes the
     * Windows Explorer opens the files for a short time) may help. Sometimes,
     * running garbage collection may close files if the user forgot to call
     * Connection.close() or InputStream.close().
     */
    public static final int MAX_FILE_RETRY = Math.max(1, getIntSetting("h2.maxFileRetry", 16));

    /**
     * System property <code>h2.maxMemoryRowsDistinct</code> (default:
     * Integer.MAX_VALUE).<br />
     * The maximum number of rows kept in-memory for SELECT DISTINCT queries. If
     * more than this number of rows are in a result set, a temporary table is
     * used.
     */
    public static final int MAX_MEMORY_ROWS_DISTINCT = getIntSetting("h2.maxMemoryRowsDistinct", Integer.MAX_VALUE);

    /**
     * System property <code>h2.maxReconnect</code> (default: 3).<br />
     * The maximum number of tries to reconnect in a row.
     */
    public static final int MAX_RECONNECT = getIntSetting("h2.maxReconnect", 3);

    /**
     * System property <code>h2.maxTraceDataLength</code> (default: 65535).<br />
     * The maximum size of a LOB value that is written as data to the trace system.
     */
    public static final long MAX_TRACE_DATA_LENGTH = getIntSetting("h2.maxTraceDataLength", 65535);

    /**
     * System property <code>h2.minColumnNameMap</code> (default: 3).<br />
     * The minimum number of columns where a hash table is created when result set
     * methods with column name (instead of column index) parameter are called.
     */
    public static final int MIN_COLUMN_NAME_MAP = getIntSetting("h2.minColumnNameMap", 3);

    /**
     * System property <code>h2.minWriteDelay</code> (default: 5).<br />
     * The minimum write delay that causes commits to be delayed.
     */
    public static final int MIN_WRITE_DELAY = getIntSetting("h2.minWriteDelay", 5);

    /**
     * System property <code>h2.nestedJoins</code> (default: false).<br />
     * Whether nested joins should be supported.
     */
    public static final boolean NESTED_JOINS = getBooleanSetting("h2.nestedJoins", false);

    /**
     * System property <code>h2.nioLoadMapped</code> (default: false).<br />
     * If the mapped buffer should be loaded when the file is opened.
     * This can improve performance.
     */
    public static final boolean NIO_LOAD_MAPPED = getBooleanSetting("h2.nioLoadMapped", false);

    /**
     * System property <code>h2.nioCleanerHack</code> (default: false).<br />
     * If enabled, use the reflection hack to un-map the mapped file if
     * possible. If disabled, System.gc() is called in a loop until the object
     * is garbage collected. See also
     * http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4724038
     */
    public static final boolean NIO_CLEANER_HACK = getBooleanSetting("h2.nioCleanerHack", false);

    /**
     * System property <code>h2.objectCache</code> (default: true).<br />
     * Cache commonly used values (numbers, strings). There is a shared cache
     * for all values.
     */
    public static final boolean OBJECT_CACHE = getBooleanSetting("h2.objectCache", true);

    /**
     * System property <code>h2.objectCacheMaxPerElementSize</code> (default:
     * 4096).<br />
     * The maximum size (precision) of an object in the cache.
     */
    public static final int OBJECT_CACHE_MAX_PER_ELEMENT_SIZE = getIntSetting("h2.objectCacheMaxPerElementSize", 4096);

    /**
     * System property <code>h2.objectCacheSize</code> (default: 1024).<br />
     * The maximum number of objects in the cache.
     * This value must be a power of 2.
     */
    public static final int OBJECT_CACHE_SIZE = MathUtils.nextPowerOf2(getIntSetting("h2.objectCacheSize", 1024));

    /**
     * System property <code>h2.optimizeDistinct</code> (default: true).<br />
     * Improve the performance of simple DISTINCT queries if an index is
     * available for the given column. The optimization is used if:
     * <ul>
     * <li>The select is a single column query without condition </li>
     * <li>The query contains only one table, and no group by </li>
     * <li>There is only one table involved </li>
     * <li>There is an ascending index on the column </li>
     * <li>The selectivity of the column is below 20 </li>
     * </ul>
     */
    public static final boolean OPTIMIZE_DISTINCT = getBooleanSetting("h2.optimizeDistinct", true);

    /**
     * System property <code>h2.optimizeUpdate</code> (default: true).<br />
     * Speed up inserts, updates, and deletes by not reading all rows from a
     * page unless necessary.
     */
    public static final boolean OPTIMIZE_UPDATE = getBooleanSetting("h2.optimizeUpdate", true);

    /**
     * System property <code>h2.optimizeEvaluatableSubqueries</code> (default:
     * true).<br />
     * Optimize subqueries that are not dependent on the outer query.
     */
    public static final boolean OPTIMIZE_EVALUATABLE_SUBQUERIES = getBooleanSetting("h2.optimizeEvaluatableSubqueries", true);

    /**
     * System property <code>h2.optimizeInList</code> (default: true).<br />
     * Optimize IN(...) and IN(SELECT ...) comparisons. This includes
     * optimization for SELECT, DELETE, and UPDATE.
     */
    public static final boolean OPTIMIZE_IN_LIST = getBooleanSetting("h2.optimizeInList", true);

    /**
     * System property <code>h2.optimizeIsNull</code> (default: false).<br />
     * Use an index for condition of the form columnName IS NULL.
     */
    public static final boolean OPTIMIZE_IS_NULL = getBooleanSetting("h2.optimizeIsNull", true);

    /**
     * System property <code>h2.optimizeOr</code> (default: false).<br />
     * Convert (C=? OR C=?) to (C IN(?, ?)).
     */
    public static final boolean OPTIMIZE_OR = getBooleanSetting("h2.optimizeOr", false);

    /**
     * System property <code>h2.optimizeSubqueryCache</code> (default: true).<br />
     * Cache subquery results.
     */
    public static final boolean OPTIMIZE_SUBQUERY_CACHE = getBooleanSetting("h2.optimizeSubqueryCache", true);

    /**
     * System property <code>h2.optimizeTwoEquals</code> (default: true).<br />
     * Optimize expressions of the form A=B AND B=1. In this case, AND A=1 is
     * added so an index on A can be used.
     */
    public static final boolean OPTIMIZE_TWO_EQUALS = getBooleanSetting("h2.optimizeTwoEquals", true);

    /**
     * System property <code>h2.pageSize</code> (default: 2048).<br />
     * The page size to use for new databases.
     */
    public static final int PAGE_SIZE = getIntSetting("h2.pageSize", 2048);

    /**
     * System property <code>h2.pageStoreTrim</code> (default: true).<br />
     * Trim the database size when closing.
     */
    public static final boolean PAGE_STORE_TRIM = getBooleanSetting("h2.pageStoreTrim", true);

    /**
     * System property <code>h2.pageStoreInternalCount</code> (default: false).<br />
     * Update the row counts on a node level.
     */
    public static final boolean PAGE_STORE_INTERNAL_COUNT = getBooleanSetting("h2.pageStoreInternalCount", false);

    /**
     * System property <code>h2.pgClientEncoding</code> (default: UTF-8).<br />
     * Default client encoding for PG server. It is used if the client does not
     * sends his encoding.
     */
    public static final String PG_DEFAULT_CLIENT_ENCODING = getStringSetting("h2.pgClientEncoding", "UTF-8");

    /**
     * System property <code>h2.prefixTempFile</code> (default: h2.temp).<br />
     * The prefix for temporary files in the temp directory.
     */
    public static final String PREFIX_TEMP_FILE = getStringSetting("h2.prefixTempFile", "h2.temp");

    /**
     * System property <code>h2.recompileAlways</code> (default: false).<br />
     * Always recompile prepared statements.
     */
    public static final boolean RECOMPILE_ALWAYS = getBooleanSetting("h2.recompileAlways", false);

    /**
     * System property <code>h2.reconnectCheckDelay</code> (default: 200).<br />
     * Check the .lock.db file every this many milliseconds to detect that the
     * database was changed. The process writing to the database must first
     * notify a change in the .lock.db file, then wait twice this many
     * milliseconds before updating the database.
     */
    public static final int RECONNECT_CHECK_DELAY = getIntSetting("h2.reconnectCheckDelay", 200);

    /**
     * System property <code>h2.redoBufferSize</code> (default: 262144).<br />
     * Size of the redo buffer (used at startup when recovering).
     */
    public static final int REDO_BUFFER_SIZE = getIntSetting("h2.redoBufferSize", 256 * 1024);

    /**
     * System property <code>h2.reserveMemory</code> (default: 524288).<br />
     * This many bytes in main memory are allocated as a reserve. This reserve
     * is freed up when if no memory is available, so that rolling back a large
     * transaction is easier.
     */
    public static final int RESERVE_MEMORY = getIntSetting("h2.reserveMemory", 512 * 1024);

    /**
     * System property <code>h2.returnLobObjects</code> (default: true).<br />
     * When true, ResultSet.getObject for CLOB or BLOB will return a
     * java.sql.Clob / java.sql.Blob object. When set to false, it will return a
     * java.io.Reader / java.io.InputStream.
     */
    public static final boolean RETURN_LOB_OBJECTS = getBooleanSetting("h2.returnLobObjects", true);

    /**
     * System property <code>h2.runFinalize</code> (default: true).<br />
     * Run finalizers to detect unclosed connections.
     */
    public static boolean runFinalize = getBooleanSetting("h2.runFinalize", true);

    /**
     * System property <code>h2.selectForUpdateMvcc</code> (default: false).<br />
     * If set, SELECT .. FOR UPDATE queries lock the rows when using MVCC.
     */
    public static final boolean SELECT_FOR_UPDATE_MVCC = getBooleanSetting("h2.selectForUpdateMvcc", false);

    /**
     * System property <code>h2.serverCachedObjects</code> (default: 64).<br />
     * TCP Server: number of cached objects per session.
     */
    public static final int SERVER_CACHED_OBJECTS = getIntSetting("h2.serverCachedObjects", 64);

    /**
     * System property <code>h2.serverResultSetFetchSize</code>
     * (default: 100).<br />
     * The default result set fetch size when using the server mode.
     */
    public static final int SERVER_RESULT_SET_FETCH_SIZE = getIntSetting("h2.serverResultSetFetchSize", 100);

    /**
     * System property <code>h2.shareLinkedConnections</code>
     * (default: true).<br />
     * Linked connections should be shared, that means connections to the same
     * database should be used for all linked tables that connect to the same
     * database.
     */
    public static final boolean SHARE_LINKED_CONNECTIONS = getBooleanSetting("h2.shareLinkedConnections", true);

    /**
     * System property <code>h2.socketConnectRetry</code> (default: 16).<br />
     * The number of times to retry opening a socket. Windows sometimes fails
     * to open a socket, see bug
     * http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6213296
     */
    public static final int SOCKET_CONNECT_RETRY = getIntSetting("h2.socketConnectRetry", 16);

    /**
     * System property <code>h2.socketConnectTimeout</code> (default: 2000).<br />
     * The timeout in milliseconds to connect to a server.
     */
    public static final int SOCKET_CONNECT_TIMEOUT = getIntSetting("h2.socketConnectTimeout", 2000);

    /**
     * System property <code>h2.sortNullsHigh</code> (default: false).<br />
     * Invert the default sorting behavior for NULL values, such that NULL
     * values are sorted to the end of a result set in an ascending sort and to
     * the beginning of a result set in a descending sort.
     */
    public static final boolean SORT_NULLS_HIGH = getBooleanSetting("h2.sortNullsHigh", false);

    /**
     * System property <code>h2.splitFileSizeShift</code> (default: 30).<br />
     * The maximum file size of a split file is 1L &lt;&lt; x.
     */
    public static final long SPLIT_FILE_SIZE_SHIFT = getIntSetting("h2.splitFileSizeShift", 30);

    /**
     * System property <code>h2.syncMethod</code> (default: sync).<br />
     * What method to call when closing the database, on checkpoint, and on
     * CHECKPOINT SYNC. The following options are supported:
     * "sync" (default): RandomAccessFile.getFD().sync();
     * "force": RandomAccessFile.getChannel().force(true);
     * "forceFalse": RandomAccessFile.getChannel().force(false);
     * "": do not call a method (fast but there is a risk of data loss
     * on power failure).
     */
    public static final String SYNC_METHOD = getStringSetting("h2.syncMethod", "sync");

    /**
     * System property <code>h2.traceIO</code> (default: false).<br />
     * Trace all I/O operations.
     */
    public static final boolean TRACE_IO = getBooleanSetting("h2.traceIO", false);

    /**
     * System property <code>h2.webMaxValueLength</code> (default: 100000).<br />
     * The H2 Console will abbreviate (truncate) result values larger than this size.
     * The data in the database is not truncated, it is only to avoid out of memory
     * in the H2 Console application.
     */
    public static final int WEB_MAX_VALUE_LENGTH = getIntSetting("h2.webMaxValueLength", 100000);

    private static final String H2_BASE_DIR = "h2.baseDir";

    private SysProperties() {
        // utility class
    }

    private static boolean getBooleanSetting(String name, boolean defaultValue) {
        String s = getProperty(name);
        if (s != null) {
            try {
                return Boolean.valueOf(s).booleanValue();
            } catch (NumberFormatException e) {
                // ignore
            }
        }
        return defaultValue;
    }

    private static String getProperty(String name) {
        try {
            return System.getProperty(name);
        } catch (Exception e) {
            // SecurityException
            // applets may not do that - ignore
            return null;
        }
    }

    /**
     * INTERNAL
     */
    public static String getStringSetting(String name, String defaultValue) {
        String s = getProperty(name);
        return s == null ? defaultValue : s;
    }

    /**
     * INTERNAL
     */
    public static int getIntSetting(String name, int defaultValue) {
        String s = getProperty(name);
        if (s != null) {
            try {
                return Integer.decode(s).intValue();
            } catch (NumberFormatException e) {
                // ignore
            }
        }
        return defaultValue;
    }

    /**
     * INTERNAL
     */
    public static void setBaseDir(String dir) {
        if (!dir.endsWith("/")) {
            dir += "/";
        }
        System.setProperty(H2_BASE_DIR, dir);
    }

    /**
     * INTERNAL
     */
    public static String getBaseDir() {
        return getStringSetting(H2_BASE_DIR, null);
    }

    /**
     * System property <code>h2.scriptDirectory</code> (default: empty
     * string).<br />
     * Relative or absolute directory where the script files are stored to or
     * read from.
     *
     * @return the current value
     */
    public static String getScriptDirectory() {
        return getStringSetting(H2_SCRIPT_DIRECTORY, "");
    }

    /**
     * System property <code>h2.maxQueryTimeout</code> (default: 0).<br />
     * The maximum timeout of a query. The default is 0, meaning no limit.
     *
     * @return the current value
     */
    public static int getMaxQueryTimeout() {
        return getIntSetting(H2_MAX_QUERY_TIMEOUT, 0);
    }

    /**
     * System property <code>h2.collatorCacheSize</code> (default: 32000).<br />
     * The cache size for collation keys (in elements). Used when a collator has
     * been set for the database.
     *
     * @return the current value
     */
    public static int getCollatorCacheSize() {
        return getIntSetting(H2_COLLATOR_CACHE_SIZE, 32000);
    }

}
