Add hyperdb

wp-content/db.php

+<?php
+
+// HyperDB
+// This file should be installed at ABSPATH/wp-content/db.php
+
+/** Load the wpdb class while preventing instantiation **/
+$wpdb = true;
+require_once( ABSPATH . WPINC . '/wp-db.php' );
+
+if ( defined('DB_CONFIG_FILE') && file_exists( DB_CONFIG_FILE ) ) {
+
+	/** The config file was defined earlier. **/
+
+} elseif ( file_exists( ABSPATH . 'db-config.php') ) {
+
+	/** The config file resides in ABSPATH. **/
+	define( 'DB_CONFIG_FILE', ABSPATH . 'db-config.php' );
+
+} elseif ( file_exists( dirname(ABSPATH) . '/db-config.php' ) && ! file_exists( dirname(ABSPATH) . '/wp-settings.php' ) ) {
+
+	/** The config file resides one level above ABSPATH but is not part of another install. **/
+	define( 'DB_CONFIG_FILE', dirname(ABSPATH) . '/db-config.php' );
+
+} else {
+
+	/** Lacking a config file, revert to the standard database class. **/
+	$wpdb = new wpdb( DB_USER, DB_PASSWORD, DB_NAME, DB_HOST );
+	return;
+
+}
+
+class hyperdb extends wpdb {
+	/**
+	 * The last table that was queried
+	 * @var string
+	 */
+	var $last_table;
+
+	/**
+	 * After any SQL_CALC_FOUND_ROWS query, the query "SELECT FOUND_ROWS()"
+	 * is sent and the mysql result resource stored here. The next query
+	 * for FOUND_ROWS() will retrieve this. We do this to prevent any
+	 * intervening queries from making FOUND_ROWS() inaccessible. You may
+	 * prevent this by adding "NO_SELECT_FOUND_ROWS" in a comment.
+	 * @var resource
+	 */
+	var $last_found_rows_result;
+
+	/**
+	 * Whether to store queries in an array. Useful for debugging and profiling.
+	 * @var bool
+	 */
+	var $save_queries = false;
+
+	/**
+	 * The current mysql link resource
+	 * @var resource
+	 */
+	var $dbh;
+
+	/**
+	 * Associative array (dbhname => dbh) for established mysql connections
+	 * @var array
+	 */
+	var $dbhs;
+
+	/**
+	 * The multi-dimensional array of datasets and servers
+	 * @var array
+	 */
+	var $hyper_servers = array();
+
+	/**
+	 * Optional directory of tables and their datasets
+	 * @var array
+	 */
+	var $hyper_tables = array();
+
+	/**
+	 * Optional directory of callbacks to determine datasets from queries
+	 * @var array
+	 */
+	var $hyper_callbacks = array();
+
+	/**
+	 * Custom callback to save debug info in $this->queries
+	 * @var callable
+	 */
+	var $save_query_callback = null;
+
+	/**
+	 * Whether to use mysql_pconnect instead of mysql_connect
+	 * @var bool
+	 */
+	var $persistent = false;
+
+	/**
+	 * The maximum number of db links to keep open. The least-recently used
+	 * link will be closed when the number of links exceeds this.
+	 * @var int
+	 */
+	var $max_connections = 10;
+
+	/**
+	 * Whether to check with fsockopen prior to mysql_connect.
+	 * @var bool
+	 */
+	var $check_tcp_responsiveness = true;
+
+	/**
+	 * Minimum number of connections to try before bailing
+	 * @var int
+	 */
+	var $min_tries = 3;
+
+	/**
+	 * Send Reads To Masters. This disables slave connections while true.
+	 * Otherwise it is an array of written tables.
+	 * @var array
+	 */
+	var $srtm = array();
+
+	/**
+	 * The log of db connections made and the time each one took
+	 * @var array
+	 */
+	var $db_connections;
+
+	/**
+	 * The list of unclosed connections sorted by LRU
+	 */
+	var $open_connections = array();
+
+	/**
+	 * The last server used and the database name selected
+	 * @var array
+	 */
+	var $last_used_server;
+
+	/**
+	 * Lookup array (dbhname => (server, db name) ) for re-selecting the db
+	 * when a link is re-used.
+	 * @var array
+	 */
+	var $used_servers = array();
+
+	/**
+	 * Triggers __construct() for backwards compatibility with PHP4
+	 */
+	function db( $args = null ) {
+		return $this->__construct($args);
+	}
+
+	/**
+	 * Gets ready to make database connections
+	 * @param array db class vars
+	 */
+	function __construct( $args = null ) {
+		if ( is_array($args) )
+			foreach ( get_class_vars(__CLASS__) as $var => $value )
+				if ( isset($args[$var]) )
+					$this->$var = $args[$var];
+	}
+
+	/**
+	 * Add the connection parameters for a database
+	 */
+	function add_database( $db ) {
+		extract($db, EXTR_SKIP);
+		isset($dataset) or $dataset = 'global';
+		isset($read)    or $read = 1;
+		isset($write)   or $write = 1;
+		unset($db['dataset']);
+		if ( $read )
+			$this->hyper_servers[ $dataset ][ 'read' ][ $read ][] = $db;
+		if ( $write )
+			$this->hyper_servers[ $dataset ][ 'write' ][ $write ][] = $db;
+	}
+
+	/**
+	 * Specify the dateset where a table is found
+	 */
+	function add_table( $dataset, $table ) {
+		$this->hyper_tables[ $table ] = $dataset;
+	}
+
+	/**
+	 * Add a callback to examine queries and determine dataset.
+	 */
+	function add_callback( $callback ) {
+		$this->hyper_callbacks[] = $callback;
+	}
+
+	/**
+	 * Find the first table name referenced in a query
+	 * @param string query
+	 * @return string table
+	 */
+	function get_table_from_query ( $q ) {
+		// Remove characters that can legally trail the table name
+		$q = rtrim($q, ';/-#');
+		// allow (select...) union [...] style queries. Use the first queries table name.
+		$q = ltrim($q, "\t ("); 
+
+		// Quickly match most common queries
+		if ( preg_match('/^\s*(?:'
+				. 'SELECT.*?\s+FROM'
+				. '|INSERT(?:\s+IGNORE)?(?:\s+INTO)?'
+				. '|REPLACE(?:\s+INTO)?'
+				. '|UPDATE(?:\s+IGNORE)?'
+				. '|DELETE(?:\s+IGNORE)?(?:\s+FROM)?'
+				. ')\s+`?(\w+)`?/is', $q, $maybe) )
+			return $maybe[1];
+
+		// Refer to the previous query
+		if ( preg_match('/^\s*SELECT.*?\s+FOUND_ROWS\(\)/is', $q) )
+			return $this->last_table;
+
+		// SHOW TABLE STATUS LIKE and SHOW TABLE STATUS WHERE Name = 
+		if ( preg_match('/^\s*'
+				. 'SHOW\s+TABLE\s+STATUS.+(?:LIKE\s+|WHERE\s+Name\s*=\s*)'
+				. '\W(\w+)\W/is', $q, $maybe) )
+			return $maybe[1];
+
+		// Big pattern for the rest of the table-related queries in MySQL 5.0
+		if ( preg_match('/^\s*(?:'
+				. '(?:EXPLAIN\s+(?:EXTENDED\s+)?)?SELECT.*?\s+FROM'
+				. '|INSERT(?:\s+LOW_PRIORITY|\s+DELAYED|\s+HIGH_PRIORITY)?(?:\s+IGNORE)?(?:\s+INTO)?'
+				. '|REPLACE(?:\s+LOW_PRIORITY|\s+DELAYED)?(?:\s+INTO)?'
+				. '|UPDATE(?:\s+LOW_PRIORITY)?(?:\s+IGNORE)?'
+				. '|DELETE(?:\s+LOW_PRIORITY|\s+QUICK|\s+IGNORE)*(?:\s+FROM)?'
+				. '|DESCRIBE|DESC|EXPLAIN|HANDLER'
+				. '|(?:LOCK|UNLOCK)\s+TABLE(?:S)?'
+				. '|(?:RENAME|OPTIMIZE|BACKUP|RESTORE|CHECK|CHECKSUM|ANALYZE|OPTIMIZE|REPAIR).*\s+TABLE'
+				. '|TRUNCATE(?:\s+TABLE)?'
+				. '|CREATE(?:\s+TEMPORARY)?\s+TABLE(?:\s+IF\s+NOT\s+EXISTS)?'
+				. '|ALTER(?:\s+IGNORE)?\s+TABLE'
+				. '|DROP\s+TABLE(?:\s+IF\s+EXISTS)?'
+				. '|CREATE(?:\s+\w+)?\s+INDEX.*\s+ON'
+				. '|DROP\s+INDEX.*\s+ON'
+				. '|LOAD\s+DATA.*INFILE.*INTO\s+TABLE'
+				. '|(?:GRANT|REVOKE).*ON\s+TABLE'
+				. '|SHOW\s+(?:.*FROM|.*TABLE)'
+				. ')\s+`?(\w+)`?/is', $q, $maybe) )
+			return $maybe[1];
+	}
+
+	/**
+	 * Determine the likelihood that this query could alter anything
+	 * @param string query
+	 * @return bool
+	 */
+	function is_write_query( $q ) {
+		// Quick and dirty: only SELECT statements are considered read-only.
+		$q = ltrim($q, "\t (");
+		$word = strtoupper( substr( trim( $q ), 0, 6 ) );
+		return 'SELECT' != $word;
+	}
+
+	/**
+	 * Set a flag to prevent reading from slaves which might be lagging after a write
+	 */
+	function send_reads_to_masters() {
+		$this->srtm = true;
+	}
+
+	/**
+	 * Callbacks are specified in the config. They must return a dataset
+	 * or an associative array with an element called 'dataset'.
+	 */
+	function run_callbacks( $query ) {
+		$args = array($query, &$this);
+		foreach ( $this->hyper_callbacks as $func ) {
+			$result = call_user_func_array($func, $args);
+			if ( isset($result) )
+				return $result;
+		}
+	}
+
+	/**
+	 * Figure out which database server should handle the query, and connect to it.
+	 * @param string query
+	 * @return resource mysql database connection
+	 */
+	function &db_connect( $query = '' ) {
+		$connect_function = $this->persistent ? 'mysql_pconnect' : 'mysql_connect';
+		if ( empty( $this->hyper_servers ) ) {
+			if ( is_resource( $this->dbh ) )
+				return $this->dbh;
+			if (
+				!defined('DB_HOST')
+				|| !defined('DB_USER')
+				|| !defined('DB_PASSWORD')
+				|| !defined('DB_NAME') )
+				return $this->bail("We were unable to query because there was no database defined.");
+			$this->dbh = @ $connect_function(DB_HOST, DB_USER, DB_PASSWORD, true);
+			if ( ! is_resource( $this->dbh ) )
+				return $this->bail("We were unable to connect to the database. (DB_HOST)");
+			if ( ! mysql_select_db(DB_NAME, $this->dbh) )
+				return $this->bail("We were unable to select the database.");
+			if ( ! empty( $this->charset ) ) {
+				$collation_query = "SET NAMES '$this->charset'";
+				if ( !empty( $this->collate ) )
+					$collation_query .= " COLLATE '$this->collate'";
+				mysql_query($collation_query, $this->dbh);
+			}
+			return $this->dbh;
+		}
+
+		if ( empty( $query ) )
+			return false;
+
+		$this->last_table = $this->table = $this->get_table_from_query($query);
+
+		if ( isset($this->hyper_tables[$this->table]) ) {
+			$dataset = $this->hyper_tables[$this->table];
+			$this->callback_result = null;
+		} elseif ( null !== $this->callback_result = $this->run_callbacks($query) ) {
+			if ( is_array($this->callback_result) )
+				extract( $this->callback_result, EXTR_OVERWRITE );
+			else
+				$dataset = $this->callback_result;
+		}
+
+		if ( !isset($dataset) )
+			$dataset = 'global';
+
+		if ( !$dataset )
+			return $this->bail("Unable to determine which dataset to query. ($this->table)");
+		else
+			$this->dataset = $dataset;
+
+		// Determine whether the query must be sent to the master (a writable server)
+		if ( $use_master || $this->srtm === true || isset($this->srtm[$this->table]) ) {
+			$use_master = true;
+		} elseif ( $is_write = $this->is_write_query($query) ) {
+			$use_master = true;
+			if ( is_array($this->srtm) )
+				$this->srtm[$this->table] = true;
+		} elseif ( !isset($use_master) && is_array($this->srtm) && !empty($this->srtm) ) {
+			// Detect queries that have a join in the srtm array.
+			$pattern = '/' . implode('|', array_keys($this->srtm)) . '/i';
+			if ( preg_match($pattern, substr($query, 0, 1000)) )
+				$use_master = true;
+			else
+				$use_master = false;
+		} else {
+			$use_master = false;
+		}
+
+		if ( $use_master ) {
+			$this->dbhname = $dbhname = $dataset . '__w';
+			$operation = 'write';
+		} else {
+			$this->dbhname = $dbhname = $dataset . '__r';
+			$operation = 'read';
+		}
+
+		// Try to reuse an existing connection
+		while ( is_resource($this->dbhs[$dbhname]) ) {
+			// Find the connection for incrementing counters
+			foreach ( array_keys($this->db_connections) as $i )
+				if ( $this->db_connections[$i]['dbhname'] == $dbhname )
+					$conn =& $this->db_connections[$i];
+
+			if ( isset($server['name']) ) {
+				$name = $server['name'];
+				// A callback has specified a database name so it's possible the existing connection selected a different one.
+				if ( $name != $this->used_servers[$dbhname]['name'] ) {
+					if ( !mysql_select_db($name, $this->dbhs[$dbhname]) ) {
+						// this can happen when the user varies and lacks permission on the $name database
+						++$conn['disconnect (select failed)'];
+						$this->disconnect($dbhname);
+						break;
+					}
+					$this->used_servers[$dbhname]['name'] = $name;
+				}
+			} else {
+				$name = $this->used_servers[$dbhname]['name'];
+			}
+
+			$this->current_host = $this->dbh2host[$dbhname];
+
+			// Keep this connection at the top of the stack to prevent disconnecting frequently-used connections
+			if ( $k = array_search($dbhname, $this->open_connections) ) {
+				unset($this->open_connections[$k]);
+				$this->open_connections[] = $dbhname;
+			}
+
+			$this->last_used_server = $this->used_servers[$dbhname];
+			$this->last_connection = compact('dbhname', 'name');
+
+			if ( !mysql_ping($this->dbhs[$dbhname]) ) {
+				++$conn['disconnect (ping failed)'];
+				$this->disconnect($dbhname);
+				break;
+			}
+
+			++$conn['queries'];
+
+			return $this->dbhs[$dbhname];
+		}
+
+		if ( $this->write && defined( "MASTER_DB_DEAD" ) ) {
+			return $this->bail("We're updating the database, please try back in 5 minutes. If you are posting to your blog please hit the refresh button on your browser in a few minutes to post the data again. It will be posted as soon as the database is back online again.");
+		}
+
+		if ( empty($this->hyper_servers[$dataset][$operation]) )
+			return $this->bail("No databases available with $this->table ($dataset)");
+
+		// Put the groups in order by priority
+		ksort($this->hyper_servers[$dataset][$operation]);
+
+		// Make a list of at least $this->min_tries connections to try, repeating as necessary.
+		$servers = array();
+		do {
+			foreach ( $this->hyper_servers[$dataset][$operation] as $group => $items ) {
+				$keys = array_keys($items);
+				shuffle($keys);
+				foreach ( $keys as $key ) {
+					$servers[] = compact('group', 'key');
+				}
+			}
+			$tries_remaining = count($servers);
+			if ( !$tries_remaining )
+				return $this->bail("No database servers were found to match the query. ($this->table, $dataset)");
+		} while ( $tries_remaining < $this->min_tries );
+
+		// Connect to a database server
+		foreach ( $servers as $group_key ) {
+			--$tries_remaining;
+
+			// $group, $key
+			extract($group_key, EXTR_OVERWRITE);
+
+			// $host, $user, $password, $name, $read, $write [ $connect_function, $timeout ]
+			extract($this->hyper_servers[$dataset][$operation][$group][$key], EXTR_OVERWRITE);
+
+			list($host, $port) = explode(':', $host);
+
+			// Split host:port into $host and $port
+			if ( strpos($host, ':') )
+				list($host, $port) = explode(':', $host);
+
+			// Overlay $server if it was extracted from a callback
+			if ( isset($server) && is_array($server) )
+				extract($server, EXTR_OVERWRITE);
+
+			// Split again in case $server had host:port
+			if ( strpos($host, ':') )
+				list($host, $port) = explode(':', $host);
+
+			// Make sure there's always a port number
+			if ( empty($port) )
+				$port = 3306;
+
+			// Use a default timeout of 200ms
+			if ( !isset($timeout) )
+				$timeout = 0.2;
+
+			$this->timer_start();
+
+			// Connect if necessary or possible
+			$tcp = null;
+			if ( $use_master || !$tries_remaining || !$this->check_tcp_responsiveness || true === $tcp = $this->check_tcp_responsiveness($host, $port, $timeout) ) {
+				$this->dbhs[$dbhname] = @ $connect_function( "$host:$port", $user, $password, true );
+			} else {
+				$this->dbhs[$dbhname] = false;
+			}
+
+			$elapsed = $this->timer_stop();
+
+			if ( is_resource($this->dbhs[$dbhname]) && mysql_select_db( $name, $this->dbhs[$dbhname] ) ) {
+				$success = true;
+				$this->current_host = "$host:$port";
+				$this->dbh2host[$dbhname] = "$host:$port";
+				$queries = 1;
+				$this->last_connection = compact('dbhname', 'host', 'port', 'user', 'name', 'tcp', 'elapsed', 'success', 'queries');
+				$this->db_connections[] = $this->last_connection;
+				$this->open_connections[] = $dbhname;
+				break;
+			} else {
+				$success = false;
+				$this->last_connection = compact('dbhname', 'host', 'port', 'user', 'name', 'tcp', 'elapsed', 'success');
+				$this->db_connections[] = $this->last_connection;
+				$error_details = array (
+					'referrer' => "{$_SERVER['HTTP_HOST']}{$_SERVER['REQUEST_URI']}",
+'server'=>$server,
+					'host' => $host,
+					'error' => mysql_error(),
+					'errno' => mysql_errno(),
+					'tcp_responsive' => $tcp === true ? 'true' : $tcp,
+				);
+				$msg = date( "Y-m-d H:i:s" ) . " Can't select $dbhname - ";
+				$msg .= "\n" . print_r($error_details, true);
+
+				$this->print_error( $msg );
+			}
+		}
+
+		if ( ! is_resource( $this->dbhs[$dbhname] ) )
+			return $this->bail("Unable to connect to $host:$port to $operation table '$this->table' ($dataset)");
+
+		if ( !empty($charset) )
+			$collation_query = "SET NAMES '$charset'";
+		elseif ( !empty($this->charset) )
+			$collation_query = "SET NAMES '$this->charset'";
+		if ( !empty($collation_query) && !empty($collate) )
+			$collation_query .= " COLLATE '$collate'";
+		if ( !empty($collation_query) && !empty($this->collation) )
+			$collation_query .= " COLLATE '$this->collation'";
+		mysql_query($collation_query, $this->dbhs[$dbhname]);
+
+		$this->last_used_server = compact('host', 'user', 'name', 'read', 'write');
+
+		$this->used_servers[$dbhname] = $this->last_used_server;
+
+		while ( !$this->persistent && count($this->open_connections) > $this->max_connections ) {
+			$oldest_connection = array_shift($this->open_connections);
+			if ( $this->dbhs[$oldest_connection] != $this->dbhs[$dbhname] )
+				$this->disconnect($oldest_connection);
+		}
+
+		return $this->dbhs[$dbhname];
+	}
+
+	/**
+	 * Disconnect and remove connection from open connections list
+	 * @param string $tdbhname
+	 */
+	function disconnect($dbhname) {
+		if ( $k = array_search($dbhname, $this->open_connections) )
+			unset($this->open_connections[$k]);
+
+		if ( is_resource($this->dbhs[$dbhname]) )
+			mysql_close($this->dbhs[$dbhname]);
+
+		unset($this->dbhs[$dbhname]);
+	}
+
+	/**
+	 * Kill cached query results
+	 */
+	function flush() {
+		$this->last_error = '';
+		$this->num_rows = 0;
+		parent::flush();
+	}
+
+	/**
+	 * Basic query. See docs for more details.
+	 * @param string $query
+	 * @return int number of rows
+	 */
+	function query($query) {
+		// some queries are made before the plugins have been loaded, and thus cannot be filtered with this method
+		if ( function_exists('apply_filters') )
+			$query = apply_filters('query', $query);
+
+		// initialise return
+		$return_val = 0;
+		$this->flush();
+
+		// Log how the function was called
+		$this->func_call = "\$db->query(\"$query\")";
+
+		// Keep track of the last query for debug..
+		$this->last_query = $query;
+
+		if ( preg_match('/^\s*SELECT\s+FOUND_ROWS(\s*)/i', $query) && is_resource($this->last_found_rows_result) ) {
+			$this->result = $this->last_found_rows_result;
+			$elapsed = 0;
+		} else {
+			$this->dbh = $this->db_connect( $query );
+
+			if ( ! is_resource($this->dbh) )
+				return false;
+
+			$this->timer_start();
+			$this->result = mysql_query($query, $this->dbh);
+			$elapsed = $this->timer_stop();
+			++$this->num_queries;
+
+			if ( preg_match('/^\s*SELECT\s+SQL_CALC_FOUND_ROWS\s/i', $query) ) {
+				if ( false === strpos($query, "NO_SELECT_FOUND_ROWS") ) {
+					$this->timer_start();
+					$this->last_found_rows_result = mysql_query("SELECT FOUND_ROWS()", $this->dbh);
+					$elapsed += $this->timer_stop();
+					++$this->num_queries;
+					$query .= "; SELECT FOUND_ROWS()";
+				}
+			} else {
+				$this->last_found_rows_result = null;
+			}
+
+			if ( $this->save_queries ) {
+				if ( is_callable($this->save_query_callback) )
+					$this->queries[] = call_user_func_array( $this->save_query_callback, array( $query, $elapsed, debug_backtrace(), &$this ) );
+				else
+					$this->queries[] = array( $query, $elapsed, $this->get_caller() );
+			}
+		}
+
+		// If there is an error then take note of it
+		if ( $this->last_error = mysql_error($this->dbh) ) {
+			$this->print_error($this->last_error);
+			return false;
+		}
+
+		if ( preg_match("/^\\s*(insert|delete|update|replace|alter) /i",$query) ) {
+			$this->rows_affected = mysql_affected_rows($this->dbh);
+
+			// Take note of the insert_id
+			if ( preg_match("/^\\s*(insert|replace) /i",$query) ) {
+				$this->insert_id = mysql_insert_id($this->dbh);
+			}
+			// Return number of rows affected
+			$return_val = $this->rows_affected;
+		} else {
+			$i = 0;
+			$this->col_info = array();
+			while ($i < @mysql_num_fields($this->result)) {
+				$this->col_info[$i] = @mysql_fetch_field($this->result);
+				$i++;
+			}
+			$num_rows = 0;
+			$this->last_result = array();
+			while ( $row = @mysql_fetch_object($this->result) ) {
+				$this->last_result[$num_rows] = $row;
+				$num_rows++;
+			}
+
+			@mysql_free_result($this->result);
+
+			// Log number of rows the query returned
+			$this->num_rows = $num_rows;
+
+			// Return number of rows selected
+			$return_val = $this->num_rows;
+		}
+
+		return $return_val;
+	}
+
+	/**
+	 * Whether or not MySQL database is at least the required minimum version.
+	 * The additional argument allows the caller to check a specific database.
+	 *
+	 * @since 2.5.0
+	 * @uses $wp_version
+	 *
+	 * @return WP_Error
+	 */
+	function check_database_version( $dbh_or_table = false ) {
+		global $wp_version;
+		// Make sure the server has MySQL 4.1.2
+		$mysql_version = preg_replace( '|[^0-9\.]|', '', $this->db_version( $dbh_or_table ) );
+		if ( version_compare($mysql_version, '4.1.2', '<') )
+			return new WP_Error( 'database_version', sprintf(__('<strong>ERROR</strong>: WordPress %s requires MySQL 4.1.2 or higher'), $wp_version) );
+	}
+
+	/**
+	 * This function is called when WordPress is generating the table schema to determine wether or not the current database
+	 * supports or needs the collation statements.
+	 * The additional argument allows the caller to check a specific database.
+	 * @return bool
+	 */
+	function supports_collation( $dbh_or_table = false ) {
+		return $this->has_cap( 'collation', $dbh_or_table );
+	}
+
+	/**
+	 * Generic function to determine if a database supports a particular feature
+	 * The additional argument allows the caller to check a specific database.
+	 * @param string $db_cap the feature
+	 * @param false|string|resource $dbh_or_table the databaese (the current database, the database housing the specified table, or the database of the mysql resource)
+	 * @return bool
+	 */
+	function has_cap( $db_cap, $dbh_or_table = false ) {
+		$version = $this->db_version( $dbh_or_table );
+
+		switch ( strtolower( $db_cap ) ) :
+		case 'collation' :
+		case 'group_concat' :
+		case 'subqueries' :
+			return version_compare($version, '4.1', '>=');
+			break;
+		endswitch;
+
+		return false;
+	}
+
+	/**
+	 * The database version number
+	 * @param false|string|resource $dbh_or_table the databaese (the current database, the database housing the specified table, or the database of the mysql resource)
+	 * @return false|string false on failure, version number on success
+	 */
+	function db_version( $dbh_or_table = false ) {
+		if ( !$dbh_or_table && $this->dbh )
+			$dbh =& $this->dbh;
+		elseif ( is_resource( $dbh_or_table ) )
+			$dbh =& $dbh_or_table;
+		else
+			$dbh = $this->db_connect( "SELECT FROM $dbh_or_table $this->users" );
+
+		if ( $dbh )
+			return preg_replace('/[^0-9.].*/', '', mysql_get_server_info( $dbh ));
+		return false;
+	}
+
+	/**
+	 * Get the name of the function that called wpdb.
+	 * @return string the name of the calling function
+	 */
+	function get_caller() {
+		// requires PHP 4.3+
+		if ( !is_callable('debug_backtrace') )
+			return '';
+
+		$bt = debug_backtrace();
+		$caller = '';
+
+		foreach ( (array) $bt as $trace ) {
+			if ( isset($trace['class']) && is_a( $this, $trace['class'] ) )
+				continue;
+			elseif ( !isset($trace['function']) )
+				continue;
+			elseif ( strtolower($trace['function']) == 'call_user_func_array' )
+				continue;
+			elseif ( strtolower($trace['function']) == 'apply_filters' )
+				continue;
+			elseif ( strtolower($trace['function']) == 'do_action' )
+				continue;
+
+			if ( isset($trace['class']) )
+				$caller = $trace['class'] . '::' . $trace['function'];
+			else
+				$caller = $trace['function'];
+			break;
+		}
+		return $caller;
+	}
+
+	/**
+	 * Check the responsiveness of a tcp/ip daemon
+	 * @return (bool) true when $host:$post responds within $float_timeout seconds, else (bool) false
+	 */
+	function check_tcp_responsiveness($host, $port, $float_timeout) {
+		if ( 1 == 2 && function_exists('apc_store') ) {
+			$use_apc = true;
+			$apc_key = "{$host}{$port}";
+			$apc_ttl = 10;
+		} else {
+			$use_apc = false;
+		}
+		if ( $use_apc ) {
+			$cached_value=apc_fetch($apc_key);
+			switch ( $cached_value ) {
+				case 'up':
+					$this->tcp_responsive = 'true';
+					return true;
+				case 'down':
+					$this->tcp_responsive = 'false';
+					return false;
+			}
+		}
+	        $socket = @ fsockopen($host, $port, $errno, $errstr, $float_timeout);
+	        if ( $socket === false ) {
+			if ( $use_apc )
+				apc_store($apc_key, 'down', $apc_ttl);
+			return "[ > $float_timeout ] ($errno) '$errstr'";
+		}
+		fclose($socket);
+		if ( $use_apc )
+			apc_store($apc_key, 'up', $apc_ttl);
+	        return true;
+	}
+
+	// Helper functions for configuration
+	
+} // class hyperdb
+
+$wpdb = new hyperdb();
+
+require( DB_CONFIG_FILE );
+
+?>