cms/drupal/includes/database/database.inc
changeset 541 e756a8c72c3d
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/cms/drupal/includes/database/database.inc	Fri Sep 08 12:04:06 2017 +0200
@@ -0,0 +1,3098 @@
+<?php
+
+/**
+ * @file
+ * Core systems for the database layer.
+ *
+ * Classes required for basic functioning of the database system should be
+ * placed in this file.  All utility functions should also be placed in this
+ * file only, as they cannot auto-load the way classes can.
+ */
+
+/**
+ * @defgroup database Database abstraction layer
+ * @{
+ * Allow the use of different database servers using the same code base.
+ *
+ * Drupal provides a database abstraction layer to provide developers with
+ * the ability to support multiple database servers easily. The intent of
+ * this layer is to preserve the syntax and power of SQL as much as possible,
+ * but also allow developers a way to leverage more complex functionality in
+ * a unified way. It also provides a structured interface for dynamically
+ * constructing queries when appropriate, and enforcing security checks and
+ * similar good practices.
+ *
+ * The system is built atop PHP's PDO (PHP Data Objects) database API and
+ * inherits much of its syntax and semantics.
+ *
+ * Most Drupal database SELECT queries are performed by a call to db_query() or
+ * db_query_range(). Module authors should also consider using the PagerDefault
+ * Extender for queries that return results that need to be presented on
+ * multiple pages (see https://drupal.org/node/508796), and the TableSort
+ * Extender for generating appropriate queries for sortable tables
+ * (see https://drupal.org/node/1848372).
+ *
+ * For example, one might wish to return a list of the most recent 10 nodes
+ * authored by a given user. Instead of directly issuing the SQL query
+ * @code
+ * SELECT n.nid, n.title, n.created FROM node n WHERE n.uid = $uid
+ *   ORDER BY n.created DESC LIMIT 0, 10;
+ * @endcode
+ * one would instead call the Drupal functions:
+ * @code
+ * $result = db_query_range('SELECT n.nid, n.title, n.created
+ *   FROM {node} n WHERE n.uid = :uid
+ *   ORDER BY n.created DESC', 0, 10, array(':uid' => $uid));
+ * foreach ($result as $record) {
+ *   // Perform operations on $record->title, etc. here.
+ * }
+ * @endcode
+ * Curly braces are used around "node" to provide table prefixing via
+ * DatabaseConnection::prefixTables(). The explicit use of a user ID is pulled
+ * out into an argument passed to db_query() so that SQL injection attacks
+ * from user input can be caught and nullified. The LIMIT syntax varies between
+ * database servers, so that is abstracted into db_query_range() arguments.
+ * Finally, note the PDO-based ability to iterate over the result set using
+ * foreach ().
+ *
+ * All queries are passed as a prepared statement string. A
+ * prepared statement is a "template" of a query that omits literal or variable
+ * values in favor of placeholders. The values to place into those
+ * placeholders are passed separately, and the database driver handles
+ * inserting the values into the query in a secure fashion. That means you
+ * should never quote or string-escape a value to be inserted into the query.
+ *
+ * There are two formats for placeholders: named and unnamed. Named placeholders
+ * are strongly preferred in all cases as they are more flexible and
+ * self-documenting. Named placeholders should start with a colon ":" and can be
+ * followed by one or more letters, numbers or underscores.
+ *
+ * Named placeholders begin with a colon followed by a unique string. Example:
+ * @code
+ * SELECT nid, title FROM {node} WHERE uid=:uid;
+ * @endcode
+ *
+ * ":uid" is a placeholder that will be replaced with a literal value when
+ * the query is executed. A given placeholder label cannot be repeated in a
+ * given query, even if the value should be the same. When using named
+ * placeholders, the array of arguments to the query must be an associative
+ * array where keys are a placeholder label (e.g., :uid) and the value is the
+ * corresponding value to use. The array may be in any order.
+ *
+ * Unnamed placeholders are simply a question mark. Example:
+ * @code
+ * SELECT nid, title FROM {node} WHERE uid=?;
+ * @endcode
+ *
+ * In this case, the array of arguments must be an indexed array of values to
+ * use in the exact same order as the placeholders in the query.
+ *
+ * Note that placeholders should be a "complete" value. For example, when
+ * running a LIKE query the SQL wildcard character, %, should be part of the
+ * value, not the query itself. Thus, the following is incorrect:
+ * @code
+ * SELECT nid, title FROM {node} WHERE title LIKE :title%;
+ * @endcode
+ * It should instead read:
+ * @code
+ * SELECT nid, title FROM {node} WHERE title LIKE :title;
+ * @endcode
+ * and the value for :title should include a % as appropriate. Again, note the
+ * lack of quotation marks around :title. Because the value is not inserted
+ * into the query as one big string but as an explicitly separate value, the
+ * database server knows where the query ends and a value begins. That is
+ * considerably more secure against SQL injection than trying to remember
+ * which values need quotation marks and string escaping and which don't.
+ *
+ * INSERT, UPDATE, and DELETE queries need special care in order to behave
+ * consistently across all different databases. Therefore, they use a special
+ * object-oriented API for defining a query structurally. For example, rather
+ * than:
+ * @code
+ * INSERT INTO node (nid, title, body) VALUES (1, 'my title', 'my body');
+ * @endcode
+ * one would instead write:
+ * @code
+ * $fields = array('nid' => 1, 'title' => 'my title', 'body' => 'my body');
+ * db_insert('node')->fields($fields)->execute();
+ * @endcode
+ * This method allows databases that need special data type handling to do so,
+ * while also allowing optimizations such as multi-insert queries. UPDATE and
+ * DELETE queries have a similar pattern.
+ *
+ * Drupal also supports transactions, including a transparent fallback for
+ * databases that do not support transactions. To start a new transaction,
+ * simply call $txn = db_transaction(); in your own code. The transaction will
+ * remain open for as long as the variable $txn remains in scope.  When $txn is
+ * destroyed, the transaction will be committed.  If your transaction is nested
+ * inside of another then Drupal will track each transaction and only commit
+ * the outer-most transaction when the last transaction object goes out out of
+ * scope, that is, all relevant queries completed successfully.
+ *
+ * Example:
+ * @code
+ * function my_transaction_function() {
+ *   // The transaction opens here.
+ *   $txn = db_transaction();
+ *
+ *   try {
+ *     $id = db_insert('example')
+ *       ->fields(array(
+ *         'field1' => 'mystring',
+ *         'field2' => 5,
+ *       ))
+ *       ->execute();
+ *
+ *     my_other_function($id);
+ *
+ *     return $id;
+ *   }
+ *   catch (Exception $e) {
+ *     // Something went wrong somewhere, so roll back now.
+ *     $txn->rollback();
+ *     // Log the exception to watchdog.
+ *     watchdog_exception('type', $e);
+ *   }
+ *
+ *   // $txn goes out of scope here.  Unless the transaction was rolled back, it
+ *   // gets automatically committed here.
+ * }
+ *
+ * function my_other_function($id) {
+ *   // The transaction is still open here.
+ *
+ *   if ($id % 2 == 0) {
+ *     db_update('example')
+ *       ->condition('id', $id)
+ *       ->fields(array('field2' => 10))
+ *       ->execute();
+ *   }
+ * }
+ * @endcode
+ *
+ * @see http://drupal.org/developing/api/database
+ */
+
+
+/**
+ * Base Database API class.
+ *
+ * This class provides a Drupal-specific extension of the PDO database
+ * abstraction class in PHP. Every database driver implementation must provide a
+ * concrete implementation of it to support special handling required by that
+ * database.
+ *
+ * @see http://php.net/manual/book.pdo.php
+ */
+abstract class DatabaseConnection extends PDO {
+
+  /**
+   * The database target this connection is for.
+   *
+   * We need this information for later auditing and logging.
+   *
+   * @var string
+   */
+  protected $target = NULL;
+
+  /**
+   * The key representing this connection.
+   *
+   * The key is a unique string which identifies a database connection. A
+   * connection can be a single server or a cluster of master and slaves (use
+   * target to pick between master and slave).
+   *
+   * @var string
+   */
+  protected $key = NULL;
+
+  /**
+   * The current database logging object for this connection.
+   *
+   * @var DatabaseLog
+   */
+  protected $logger = NULL;
+
+  /**
+   * Tracks the number of "layers" of transactions currently active.
+   *
+   * On many databases transactions cannot nest.  Instead, we track
+   * nested calls to transactions and collapse them into a single
+   * transaction.
+   *
+   * @var array
+   */
+  protected $transactionLayers = array();
+
+  /**
+   * Index of what driver-specific class to use for various operations.
+   *
+   * @var array
+   */
+  protected $driverClasses = array();
+
+  /**
+   * The name of the Statement class for this connection.
+   *
+   * @var string
+   */
+  protected $statementClass = 'DatabaseStatementBase';
+
+  /**
+   * Whether this database connection supports transactions.
+   *
+   * @var bool
+   */
+  protected $transactionSupport = TRUE;
+
+  /**
+   * Whether this database connection supports transactional DDL.
+   *
+   * Set to FALSE by default because few databases support this feature.
+   *
+   * @var bool
+   */
+  protected $transactionalDDLSupport = FALSE;
+
+  /**
+   * An index used to generate unique temporary table names.
+   *
+   * @var integer
+   */
+  protected $temporaryNameIndex = 0;
+
+  /**
+   * The connection information for this connection object.
+   *
+   * @var array
+   */
+  protected $connectionOptions = array();
+
+  /**
+   * The schema object for this connection.
+   *
+   * @var object
+   */
+  protected $schema = NULL;
+
+  /**
+   * The prefixes used by this database connection.
+   *
+   * @var array
+   */
+  protected $prefixes = array();
+
+  /**
+   * List of search values for use in prefixTables().
+   *
+   * @var array
+   */
+  protected $prefixSearch = array();
+
+  /**
+   * List of replacement values for use in prefixTables().
+   *
+   * @var array
+   */
+  protected $prefixReplace = array();
+
+  /**
+   * List of escaped database, table, and field names, keyed by unescaped names.
+   *
+   * @var array
+   */
+  protected $escapedNames = array();
+
+  /**
+   * List of escaped aliases names, keyed by unescaped aliases.
+   *
+   * @var array
+   */
+  protected $escapedAliases = array();
+
+  function __construct($dsn, $username, $password, $driver_options = array()) {
+    // Initialize and prepare the connection prefix.
+    $this->setPrefix(isset($this->connectionOptions['prefix']) ? $this->connectionOptions['prefix'] : '');
+
+    // Because the other methods don't seem to work right.
+    $driver_options[PDO::ATTR_ERRMODE] = PDO::ERRMODE_EXCEPTION;
+
+    // Call PDO::__construct and PDO::setAttribute.
+    parent::__construct($dsn, $username, $password, $driver_options);
+
+    // Set a Statement class, unless the driver opted out.
+    if (!empty($this->statementClass)) {
+      $this->setAttribute(PDO::ATTR_STATEMENT_CLASS, array($this->statementClass, array($this)));
+    }
+  }
+
+  /**
+   * Destroys this Connection object.
+   *
+   * PHP does not destruct an object if it is still referenced in other
+   * variables. In case of PDO database connection objects, PHP only closes the
+   * connection when the PDO object is destructed, so any references to this
+   * object may cause the number of maximum allowed connections to be exceeded.
+   */
+  public function destroy() {
+    // Destroy all references to this connection by setting them to NULL.
+    // The Statement class attribute only accepts a new value that presents a
+    // proper callable, so we reset it to PDOStatement.
+    $this->setAttribute(PDO::ATTR_STATEMENT_CLASS, array('PDOStatement', array()));
+    $this->schema = NULL;
+  }
+
+  /**
+   * Returns the default query options for any given query.
+   *
+   * A given query can be customized with a number of option flags in an
+   * associative array:
+   * - target: The database "target" against which to execute a query. Valid
+   *   values are "default" or "slave". The system will first try to open a
+   *   connection to a database specified with the user-supplied key. If one
+   *   is not available, it will silently fall back to the "default" target.
+   *   If multiple databases connections are specified with the same target,
+   *   one will be selected at random for the duration of the request.
+   * - fetch: This element controls how rows from a result set will be
+   *   returned. Legal values include PDO::FETCH_ASSOC, PDO::FETCH_BOTH,
+   *   PDO::FETCH_OBJ, PDO::FETCH_NUM, or a string representing the name of a
+   *   class. If a string is specified, each record will be fetched into a new
+   *   object of that class. The behavior of all other values is defined by PDO.
+   *   See http://php.net/manual/pdostatement.fetch.php
+   * - return: Depending on the type of query, different return values may be
+   *   meaningful. This directive instructs the system which type of return
+   *   value is desired. The system will generally set the correct value
+   *   automatically, so it is extremely rare that a module developer will ever
+   *   need to specify this value. Setting it incorrectly will likely lead to
+   *   unpredictable results or fatal errors. Legal values include:
+   *   - Database::RETURN_STATEMENT: Return the prepared statement object for
+   *     the query. This is usually only meaningful for SELECT queries, where
+   *     the statement object is how one accesses the result set returned by the
+   *     query.
+   *   - Database::RETURN_AFFECTED: Return the number of rows affected by an
+   *     UPDATE or DELETE query. Be aware that means the number of rows actually
+   *     changed, not the number of rows matched by the WHERE clause.
+   *   - Database::RETURN_INSERT_ID: Return the sequence ID (primary key)
+   *     created by an INSERT statement on a table that contains a serial
+   *     column.
+   *   - Database::RETURN_NULL: Do not return anything, as there is no
+   *     meaningful value to return. That is the case for INSERT queries on
+   *     tables that do not contain a serial column.
+   * - throw_exception: By default, the database system will catch any errors
+   *   on a query as an Exception, log it, and then rethrow it so that code
+   *   further up the call chain can take an appropriate action. To suppress
+   *   that behavior and simply return NULL on failure, set this option to
+   *   FALSE.
+   *
+   * @return
+   *   An array of default query options.
+   */
+  protected function defaultOptions() {
+    return array(
+      'target' => 'default',
+      'fetch' => PDO::FETCH_OBJ,
+      'return' => Database::RETURN_STATEMENT,
+      'throw_exception' => TRUE,
+    );
+  }
+
+  /**
+   * Returns the connection information for this connection object.
+   *
+   * Note that Database::getConnectionInfo() is for requesting information
+   * about an arbitrary database connection that is defined. This method
+   * is for requesting the connection information of this specific
+   * open connection object.
+   *
+   * @return
+   *   An array of the connection information. The exact list of
+   *   properties is driver-dependent.
+   */
+  public function getConnectionOptions() {
+    return $this->connectionOptions;
+  }
+
+  /**
+   * Set the list of prefixes used by this database connection.
+   *
+   * @param $prefix
+   *   The prefixes, in any of the multiple forms documented in
+   *   default.settings.php.
+   */
+  protected function setPrefix($prefix) {
+    if (is_array($prefix)) {
+      $this->prefixes = $prefix + array('default' => '');
+    }
+    else {
+      $this->prefixes = array('default' => $prefix);
+    }
+
+    // Set up variables for use in prefixTables(). Replace table-specific
+    // prefixes first.
+    $this->prefixSearch = array();
+    $this->prefixReplace = array();
+    foreach ($this->prefixes as $key => $val) {
+      if ($key != 'default') {
+        $this->prefixSearch[] = '{' . $key . '}';
+        $this->prefixReplace[] = $val . $key;
+      }
+    }
+    // Then replace remaining tables with the default prefix.
+    $this->prefixSearch[] = '{';
+    $this->prefixReplace[] = $this->prefixes['default'];
+    $this->prefixSearch[] = '}';
+    $this->prefixReplace[] = '';
+  }
+
+  /**
+   * Appends a database prefix to all tables in a query.
+   *
+   * Queries sent to Drupal should wrap all table names in curly brackets. This
+   * function searches for this syntax and adds Drupal's table prefix to all
+   * tables, allowing Drupal to coexist with other systems in the same database
+   * and/or schema if necessary.
+   *
+   * @param $sql
+   *   A string containing a partial or entire SQL query.
+   *
+   * @return
+   *   The properly-prefixed string.
+   */
+  public function prefixTables($sql) {
+    return str_replace($this->prefixSearch, $this->prefixReplace, $sql);
+  }
+
+  /**
+   * Find the prefix for a table.
+   *
+   * This function is for when you want to know the prefix of a table. This
+   * is not used in prefixTables due to performance reasons.
+   */
+  public function tablePrefix($table = 'default') {
+    if (isset($this->prefixes[$table])) {
+      return $this->prefixes[$table];
+    }
+    else {
+      return $this->prefixes['default'];
+    }
+  }
+
+  /**
+   * Prepares a query string and returns the prepared statement.
+   *
+   * This method caches prepared statements, reusing them when
+   * possible. It also prefixes tables names enclosed in curly-braces.
+   *
+   * @param $query
+   *   The query string as SQL, with curly-braces surrounding the
+   *   table names.
+   *
+   * @return DatabaseStatementInterface
+   *   A PDO prepared statement ready for its execute() method.
+   */
+  public function prepareQuery($query) {
+    $query = $this->prefixTables($query);
+
+    // Call PDO::prepare.
+    return parent::prepare($query);
+  }
+
+  /**
+   * Tells this connection object what its target value is.
+   *
+   * This is needed for logging and auditing. It's sloppy to do in the
+   * constructor because the constructor for child classes has a different
+   * signature. We therefore also ensure that this function is only ever
+   * called once.
+   *
+   * @param $target
+   *   The target this connection is for. Set to NULL (default) to disable
+   *   logging entirely.
+   */
+  public function setTarget($target = NULL) {
+    if (!isset($this->target)) {
+      $this->target = $target;
+    }
+  }
+
+  /**
+   * Returns the target this connection is associated with.
+   *
+   * @return
+   *   The target string of this connection.
+   */
+  public function getTarget() {
+    return $this->target;
+  }
+
+  /**
+   * Tells this connection object what its key is.
+   *
+   * @param $target
+   *   The key this connection is for.
+   */
+  public function setKey($key) {
+    if (!isset($this->key)) {
+      $this->key = $key;
+    }
+  }
+
+  /**
+   * Returns the key this connection is associated with.
+   *
+   * @return
+   *   The key of this connection.
+   */
+  public function getKey() {
+    return $this->key;
+  }
+
+  /**
+   * Associates a logging object with this connection.
+   *
+   * @param $logger
+   *   The logging object we want to use.
+   */
+  public function setLogger(DatabaseLog $logger) {
+    $this->logger = $logger;
+  }
+
+  /**
+   * Gets the current logging object for this connection.
+   *
+   * @return DatabaseLog
+   *   The current logging object for this connection. If there isn't one,
+   *   NULL is returned.
+   */
+  public function getLogger() {
+    return $this->logger;
+  }
+
+  /**
+   * Creates the appropriate sequence name for a given table and serial field.
+   *
+   * This information is exposed to all database drivers, although it is only
+   * useful on some of them. This method is table prefix-aware.
+   *
+   * @param $table
+   *   The table name to use for the sequence.
+   * @param $field
+   *   The field name to use for the sequence.
+   *
+   * @return
+   *   A table prefix-parsed string for the sequence name.
+   */
+  public function makeSequenceName($table, $field) {
+    return $this->prefixTables('{' . $table . '}_' . $field . '_seq');
+  }
+
+  /**
+   * Flatten an array of query comments into a single comment string.
+   *
+   * The comment string will be sanitized to avoid SQL injection attacks.
+   *
+   * @param $comments
+   *   An array of query comment strings.
+   *
+   * @return
+   *   A sanitized comment string.
+   */
+  public function makeComment($comments) {
+    if (empty($comments))
+      return '';
+
+    // Flatten the array of comments.
+    $comment = implode('; ', $comments);
+
+    // Sanitize the comment string so as to avoid SQL injection attacks.
+    return '/* ' . $this->filterComment($comment) . ' */ ';
+  }
+
+  /**
+   * Sanitize a query comment string.
+   *
+   * Ensure a query comment does not include strings such as "* /" that might
+   * terminate the comment early. This avoids SQL injection attacks via the
+   * query comment. The comment strings in this example are separated by a
+   * space to avoid PHP parse errors.
+   *
+   * For example, the comment:
+   * @code
+   * db_update('example')
+   *  ->condition('id', $id)
+   *  ->fields(array('field2' => 10))
+   *  ->comment('Exploit * / DROP TABLE node; --')
+   *  ->execute()
+   * @endcode
+   *
+   * Would result in the following SQL statement being generated:
+   * @code
+   * "/ * Exploit * / DROP TABLE node; -- * / UPDATE example SET field2=..."
+   * @endcode
+   *
+   * Unless the comment is sanitised first, the SQL server would drop the
+   * node table and ignore the rest of the SQL statement.
+   *
+   * @param $comment
+   *   A query comment string.
+   *
+   * @return
+   *   A sanitized version of the query comment string.
+   */
+  protected function filterComment($comment = '') {
+    return strtr($comment, array('*' => ' * '));
+  }
+
+  /**
+   * Executes a query string against the database.
+   *
+   * This method provides a central handler for the actual execution of every
+   * query. All queries executed by Drupal are executed as PDO prepared
+   * statements.
+   *
+   * @param $query
+   *   The query to execute. In most cases this will be a string containing
+   *   an SQL query with placeholders. An already-prepared instance of
+   *   DatabaseStatementInterface may also be passed in order to allow calling
+   *   code to manually bind variables to a query. If a
+   *   DatabaseStatementInterface is passed, the $args array will be ignored.
+   *   It is extremely rare that module code will need to pass a statement
+   *   object to this method. It is used primarily for database drivers for
+   *   databases that require special LOB field handling.
+   * @param $args
+   *   An array of arguments for the prepared statement. If the prepared
+   *   statement uses ? placeholders, this array must be an indexed array.
+   *   If it contains named placeholders, it must be an associative array.
+   * @param $options
+   *   An associative array of options to control how the query is run. See
+   *   the documentation for DatabaseConnection::defaultOptions() for details.
+   *
+   * @return DatabaseStatementInterface
+   *   This method will return one of: the executed statement, the number of
+   *   rows affected by the query (not the number matched), or the generated
+   *   insert ID of the last query, depending on the value of
+   *   $options['return']. Typically that value will be set by default or a
+   *   query builder and should not be set by a user. If there is an error,
+   *   this method will return NULL and may throw an exception if
+   *   $options['throw_exception'] is TRUE.
+   *
+   * @throws PDOException
+   */
+  public function query($query, array $args = array(), $options = array()) {
+
+    // Use default values if not already set.
+    $options += $this->defaultOptions();
+
+    try {
+      // We allow either a pre-bound statement object or a literal string.
+      // In either case, we want to end up with an executed statement object,
+      // which we pass to PDOStatement::execute.
+      if ($query instanceof DatabaseStatementInterface) {
+        $stmt = $query;
+        $stmt->execute(NULL, $options);
+      }
+      else {
+        $this->expandArguments($query, $args);
+        $stmt = $this->prepareQuery($query);
+        $stmt->execute($args, $options);
+      }
+
+      // Depending on the type of query we may need to return a different value.
+      // See DatabaseConnection::defaultOptions() for a description of each
+      // value.
+      switch ($options['return']) {
+        case Database::RETURN_STATEMENT:
+          return $stmt;
+        case Database::RETURN_AFFECTED:
+          return $stmt->rowCount();
+        case Database::RETURN_INSERT_ID:
+          return $this->lastInsertId();
+        case Database::RETURN_NULL:
+          return;
+        default:
+          throw new PDOException('Invalid return directive: ' . $options['return']);
+      }
+    }
+    catch (PDOException $e) {
+      if ($options['throw_exception']) {
+        // Add additional debug information.
+        if ($query instanceof DatabaseStatementInterface) {
+          $e->query_string = $stmt->getQueryString();
+        }
+        else {
+          $e->query_string = $query;
+        }
+        $e->args = $args;
+        throw $e;
+      }
+      return NULL;
+    }
+  }
+
+  /**
+   * Expands out shorthand placeholders.
+   *
+   * Drupal supports an alternate syntax for doing arrays of values. We
+   * therefore need to expand them out into a full, executable query string.
+   *
+   * @param $query
+   *   The query string to modify.
+   * @param $args
+   *   The arguments for the query.
+   *
+   * @return
+   *   TRUE if the query was modified, FALSE otherwise.
+   */
+  protected function expandArguments(&$query, &$args) {
+    $modified = FALSE;
+
+    // If the placeholder value to insert is an array, assume that we need
+    // to expand it out into a comma-delimited set of placeholders.
+    foreach (array_filter($args, 'is_array') as $key => $data) {
+      $new_keys = array();
+      foreach (array_values($data) as $i => $value) {
+        // This assumes that there are no other placeholders that use the same
+        // name.  For example, if the array placeholder is defined as :example
+        // and there is already an :example_2 placeholder, this will generate
+        // a duplicate key.  We do not account for that as the calling code
+        // is already broken if that happens.
+        $new_keys[$key . '_' . $i] = $value;
+      }
+
+      // Update the query with the new placeholders.
+      // preg_replace is necessary to ensure the replacement does not affect
+      // placeholders that start with the same exact text. For example, if the
+      // query contains the placeholders :foo and :foobar, and :foo has an
+      // array of values, using str_replace would affect both placeholders,
+      // but using the following preg_replace would only affect :foo because
+      // it is followed by a non-word character.
+      $query = preg_replace('#' . $key . '\b#', implode(', ', array_keys($new_keys)), $query);
+
+      // Update the args array with the new placeholders.
+      unset($args[$key]);
+      $args += $new_keys;
+
+      $modified = TRUE;
+    }
+
+    return $modified;
+  }
+
+  /**
+   * Gets the driver-specific override class if any for the specified class.
+   *
+   * @param string $class
+   *   The class for which we want the potentially driver-specific class.
+   * @param array $files
+   *   The name of the files in which the driver-specific class can be.
+   * @param $use_autoload
+   *   If TRUE, attempt to load classes using PHP's autoload capability
+   *   as well as the manual approach here.
+   * @return string
+   *   The name of the class that should be used for this driver.
+   */
+  public function getDriverClass($class, array $files = array(), $use_autoload = FALSE) {
+    if (empty($this->driverClasses[$class])) {
+      $driver = $this->driver();
+      $this->driverClasses[$class] = $class . '_' . $driver;
+      Database::loadDriverFile($driver, $files);
+      if (!class_exists($this->driverClasses[$class], $use_autoload)) {
+        $this->driverClasses[$class] = $class;
+      }
+    }
+    return $this->driverClasses[$class];
+  }
+
+  /**
+   * Prepares and returns a SELECT query object.
+   *
+   * @param $table
+   *   The base table for this query, that is, the first table in the FROM
+   *   clause. This table will also be used as the "base" table for query_alter
+   *   hook implementations.
+   * @param $alias
+   *   The alias of the base table of this query.
+   * @param $options
+   *   An array of options on the query.
+   *
+   * @return SelectQueryInterface
+   *   An appropriate SelectQuery object for this database connection. Note that
+   *   it may be a driver-specific subclass of SelectQuery, depending on the
+   *   driver.
+   *
+   * @see SelectQuery
+   */
+  public function select($table, $alias = NULL, array $options = array()) {
+    $class = $this->getDriverClass('SelectQuery', array('query.inc', 'select.inc'));
+    return new $class($table, $alias, $this, $options);
+  }
+
+  /**
+   * Prepares and returns an INSERT query object.
+   *
+   * @param $options
+   *   An array of options on the query.
+   *
+   * @return InsertQuery
+   *   A new InsertQuery object.
+   *
+   * @see InsertQuery
+   */
+  public function insert($table, array $options = array()) {
+    $class = $this->getDriverClass('InsertQuery', array('query.inc'));
+    return new $class($this, $table, $options);
+  }
+
+  /**
+   * Prepares and returns a MERGE query object.
+   *
+   * @param $options
+   *   An array of options on the query.
+   *
+   * @return MergeQuery
+   *   A new MergeQuery object.
+   *
+   * @see MergeQuery
+   */
+  public function merge($table, array $options = array()) {
+    $class = $this->getDriverClass('MergeQuery', array('query.inc'));
+    return new $class($this, $table, $options);
+  }
+
+
+  /**
+   * Prepares and returns an UPDATE query object.
+   *
+   * @param $options
+   *   An array of options on the query.
+   *
+   * @return UpdateQuery
+   *   A new UpdateQuery object.
+   *
+   * @see UpdateQuery
+   */
+  public function update($table, array $options = array()) {
+    $class = $this->getDriverClass('UpdateQuery', array('query.inc'));
+    return new $class($this, $table, $options);
+  }
+
+  /**
+   * Prepares and returns a DELETE query object.
+   *
+   * @param $options
+   *   An array of options on the query.
+   *
+   * @return DeleteQuery
+   *   A new DeleteQuery object.
+   *
+   * @see DeleteQuery
+   */
+  public function delete($table, array $options = array()) {
+    $class = $this->getDriverClass('DeleteQuery', array('query.inc'));
+    return new $class($this, $table, $options);
+  }
+
+  /**
+   * Prepares and returns a TRUNCATE query object.
+   *
+   * @param $options
+   *   An array of options on the query.
+   *
+   * @return TruncateQuery
+   *   A new TruncateQuery object.
+   *
+   * @see TruncateQuery
+   */
+  public function truncate($table, array $options = array()) {
+    $class = $this->getDriverClass('TruncateQuery', array('query.inc'));
+    return new $class($this, $table, $options);
+  }
+
+  /**
+   * Returns a DatabaseSchema object for manipulating the schema.
+   *
+   * This method will lazy-load the appropriate schema library file.
+   *
+   * @return DatabaseSchema
+   *   The DatabaseSchema object for this connection.
+   */
+  public function schema() {
+    if (empty($this->schema)) {
+      $class = $this->getDriverClass('DatabaseSchema', array('schema.inc'));
+      if (class_exists($class)) {
+        $this->schema = new $class($this);
+      }
+    }
+    return $this->schema;
+  }
+
+  /**
+   * Escapes a table name string.
+   *
+   * Force all table names to be strictly alphanumeric-plus-underscore.
+   * For some database drivers, it may also wrap the table name in
+   * database-specific escape characters.
+   *
+   * @return string
+   *   The sanitized table name string.
+   */
+  public function escapeTable($table) {
+    if (!isset($this->escapedNames[$table])) {
+      $this->escapedNames[$table] = preg_replace('/[^A-Za-z0-9_.]+/', '', $table);
+    }
+    return $this->escapedNames[$table];
+  }
+
+  /**
+   * Escapes a field name string.
+   *
+   * Force all field names to be strictly alphanumeric-plus-underscore.
+   * For some database drivers, it may also wrap the field name in
+   * database-specific escape characters.
+   *
+   * @return string
+   *   The sanitized field name string.
+   */
+  public function escapeField($field) {
+    if (!isset($this->escapedNames[$field])) {
+      $this->escapedNames[$field] = preg_replace('/[^A-Za-z0-9_.]+/', '', $field);
+    }
+    return $this->escapedNames[$field];
+  }
+
+  /**
+   * Escapes an alias name string.
+   *
+   * Force all alias names to be strictly alphanumeric-plus-underscore. In
+   * contrast to DatabaseConnection::escapeField() /
+   * DatabaseConnection::escapeTable(), this doesn't allow the period (".")
+   * because that is not allowed in aliases.
+   *
+   * @return string
+   *   The sanitized field name string.
+   */
+  public function escapeAlias($field) {
+    if (!isset($this->escapedAliases[$field])) {
+      $this->escapedAliases[$field] = preg_replace('/[^A-Za-z0-9_]+/', '', $field);
+    }
+    return $this->escapedAliases[$field];
+  }
+
+  /**
+   * Escapes characters that work as wildcard characters in a LIKE pattern.
+   *
+   * The wildcard characters "%" and "_" as well as backslash are prefixed with
+   * a backslash. Use this to do a search for a verbatim string without any
+   * wildcard behavior.
+   *
+   * For example, the following does a case-insensitive query for all rows whose
+   * name starts with $prefix:
+   * @code
+   * $result = db_query(
+   *   'SELECT * FROM person WHERE name LIKE :pattern',
+   *   array(':pattern' => db_like($prefix) . '%')
+   * );
+   * @endcode
+   *
+   * Backslash is defined as escape character for LIKE patterns in
+   * DatabaseCondition::mapConditionOperator().
+   *
+   * @param $string
+   *   The string to escape.
+   *
+   * @return
+   *   The escaped string.
+   */
+  public function escapeLike($string) {
+    return addcslashes($string, '\%_');
+  }
+
+  /**
+   * Determines if there is an active transaction open.
+   *
+   * @return
+   *   TRUE if we're currently in a transaction, FALSE otherwise.
+   */
+  public function inTransaction() {
+    return ($this->transactionDepth() > 0);
+  }
+
+  /**
+   * Determines current transaction depth.
+   */
+  public function transactionDepth() {
+    return count($this->transactionLayers);
+  }
+
+  /**
+   * Returns a new DatabaseTransaction object on this connection.
+   *
+   * @param $name
+   *   Optional name of the savepoint.
+   *
+   * @return DatabaseTransaction
+   *   A DatabaseTransaction object.
+   *
+   * @see DatabaseTransaction
+   */
+  public function startTransaction($name = '') {
+    $class = $this->getDriverClass('DatabaseTransaction');
+    return new $class($this, $name);
+  }
+
+  /**
+   * Rolls back the transaction entirely or to a named savepoint.
+   *
+   * This method throws an exception if no transaction is active.
+   *
+   * @param $savepoint_name
+   *   The name of the savepoint. The default, 'drupal_transaction', will roll
+   *   the entire transaction back.
+   *
+   * @throws DatabaseTransactionNoActiveException
+   *
+   * @see DatabaseTransaction::rollback()
+   */
+  public function rollback($savepoint_name = 'drupal_transaction') {
+    if (!$this->supportsTransactions()) {
+      return;
+    }
+    if (!$this->inTransaction()) {
+      throw new DatabaseTransactionNoActiveException();
+    }
+    // A previous rollback to an earlier savepoint may mean that the savepoint
+    // in question has already been accidentally committed.
+    if (!isset($this->transactionLayers[$savepoint_name])) {
+      throw new DatabaseTransactionNoActiveException();
+    }
+
+    // We need to find the point we're rolling back to, all other savepoints
+    // before are no longer needed. If we rolled back other active savepoints,
+    // we need to throw an exception.
+    $rolled_back_other_active_savepoints = FALSE;
+    while ($savepoint = array_pop($this->transactionLayers)) {
+      if ($savepoint == $savepoint_name) {
+        // If it is the last the transaction in the stack, then it is not a
+        // savepoint, it is the transaction itself so we will need to roll back
+        // the transaction rather than a savepoint.
+        if (empty($this->transactionLayers)) {
+          break;
+        }
+        $this->query('ROLLBACK TO SAVEPOINT ' . $savepoint);
+        $this->popCommittableTransactions();
+        if ($rolled_back_other_active_savepoints) {
+          throw new DatabaseTransactionOutOfOrderException();
+        }
+        return;
+      }
+      else {
+        $rolled_back_other_active_savepoints = TRUE;
+      }
+    }
+    parent::rollBack();
+    if ($rolled_back_other_active_savepoints) {
+      throw new DatabaseTransactionOutOfOrderException();
+    }
+  }
+
+  /**
+   * Increases the depth of transaction nesting.
+   *
+   * If no transaction is already active, we begin a new transaction.
+   *
+   * @throws DatabaseTransactionNameNonUniqueException
+   *
+   * @see DatabaseTransaction
+   */
+  public function pushTransaction($name) {
+    if (!$this->supportsTransactions()) {
+      return;
+    }
+    if (isset($this->transactionLayers[$name])) {
+      throw new DatabaseTransactionNameNonUniqueException($name . " is already in use.");
+    }
+    // If we're already in a transaction then we want to create a savepoint
+    // rather than try to create another transaction.
+    if ($this->inTransaction()) {
+      $this->query('SAVEPOINT ' . $name);
+    }
+    else {
+      parent::beginTransaction();
+    }
+    $this->transactionLayers[$name] = $name;
+  }
+
+  /**
+   * Decreases the depth of transaction nesting.
+   *
+   * If we pop off the last transaction layer, then we either commit or roll
+   * back the transaction as necessary. If no transaction is active, we return
+   * because the transaction may have manually been rolled back.
+   *
+   * @param $name
+   *   The name of the savepoint
+   *
+   * @throws DatabaseTransactionNoActiveException
+   * @throws DatabaseTransactionCommitFailedException
+   *
+   * @see DatabaseTransaction
+   */
+  public function popTransaction($name) {
+    if (!$this->supportsTransactions()) {
+      return;
+    }
+    // The transaction has already been committed earlier. There is nothing we
+    // need to do. If this transaction was part of an earlier out-of-order
+    // rollback, an exception would already have been thrown by
+    // Database::rollback().
+    if (!isset($this->transactionLayers[$name])) {
+      return;
+    }
+
+    // Mark this layer as committable.
+    $this->transactionLayers[$name] = FALSE;
+    $this->popCommittableTransactions();
+  }
+
+  /**
+   * Internal function: commit all the transaction layers that can commit.
+   */
+  protected function popCommittableTransactions() {
+    // Commit all the committable layers.
+    foreach (array_reverse($this->transactionLayers) as $name => $active) {
+      // Stop once we found an active transaction.
+      if ($active) {
+        break;
+      }
+
+      // If there are no more layers left then we should commit.
+      unset($this->transactionLayers[$name]);
+      if (empty($this->transactionLayers)) {
+        if (!parent::commit()) {
+          throw new DatabaseTransactionCommitFailedException();
+        }
+      }
+      else {
+        $this->query('RELEASE SAVEPOINT ' . $name);
+      }
+    }
+  }
+
+  /**
+   * Runs a limited-range query on this database object.
+   *
+   * Use this as a substitute for ->query() when a subset of the query is to be
+   * returned. User-supplied arguments to the query should be passed in as
+   * separate parameters so that they can be properly escaped to avoid SQL
+   * injection attacks.
+   *
+   * @param $query
+   *   A string containing an SQL query.
+   * @param $args
+   *   An array of values to substitute into the query at placeholder markers.
+   * @param $from
+   *   The first result row to return.
+   * @param $count
+   *   The maximum number of result rows to return.
+   * @param $options
+   *   An array of options on the query.
+   *
+   * @return DatabaseStatementInterface
+   *   A database query result resource, or NULL if the query was not executed
+   *   correctly.
+   */
+  abstract public function queryRange($query, $from, $count, array $args = array(), array $options = array());
+
+  /**
+   * Generates a temporary table name.
+   *
+   * @return
+   *   A table name.
+   */
+  protected function generateTemporaryTableName() {
+    return "db_temporary_" . $this->temporaryNameIndex++;
+  }
+
+  /**
+   * Runs a SELECT query and stores its results in a temporary table.
+   *
+   * Use this as a substitute for ->query() when the results need to stored
+   * in a temporary table. Temporary tables exist for the duration of the page
+   * request. User-supplied arguments to the query should be passed in as
+   * separate parameters so that they can be properly escaped to avoid SQL
+   * injection attacks.
+   *
+   * Note that if you need to know how many results were returned, you should do
+   * a SELECT COUNT(*) on the temporary table afterwards.
+   *
+   * @param $query
+   *   A string containing a normal SELECT SQL query.
+   * @param $args
+   *   An array of values to substitute into the query at placeholder markers.
+   * @param $options
+   *   An associative array of options to control how the query is run. See
+   *   the documentation for DatabaseConnection::defaultOptions() for details.
+   *
+   * @return
+   *   The name of the temporary table.
+   */
+  abstract function queryTemporary($query, array $args = array(), array $options = array());
+
+  /**
+   * Returns the type of database driver.
+   *
+   * This is not necessarily the same as the type of the database itself. For
+   * instance, there could be two MySQL drivers, mysql and mysql_mock. This
+   * function would return different values for each, but both would return
+   * "mysql" for databaseType().
+   */
+  abstract public function driver();
+
+  /**
+   * Returns the version of the database server.
+   */
+  public function version() {
+    return $this->getAttribute(PDO::ATTR_SERVER_VERSION);
+  }
+
+  /**
+   * Determines if this driver supports transactions.
+   *
+   * @return
+   *   TRUE if this connection supports transactions, FALSE otherwise.
+   */
+  public function supportsTransactions() {
+    return $this->transactionSupport;
+  }
+
+  /**
+   * Determines if this driver supports transactional DDL.
+   *
+   * DDL queries are those that change the schema, such as ALTER queries.
+   *
+   * @return
+   *   TRUE if this connection supports transactions for DDL queries, FALSE
+   *   otherwise.
+   */
+  public function supportsTransactionalDDL() {
+    return $this->transactionalDDLSupport;
+  }
+
+  /**
+   * Returns the name of the PDO driver for this connection.
+   */
+  abstract public function databaseType();
+
+
+  /**
+   * Gets any special processing requirements for the condition operator.
+   *
+   * Some condition types require special processing, such as IN, because
+   * the value data they pass in is not a simple value. This is a simple
+   * overridable lookup function. Database connections should define only
+   * those operators they wish to be handled differently than the default.
+   *
+   * @param $operator
+   *   The condition operator, such as "IN", "BETWEEN", etc. Case-sensitive.
+   *
+   * @return
+   *   The extra handling directives for the specified operator, or NULL.
+   *
+   * @see DatabaseCondition::compile()
+   */
+  abstract public function mapConditionOperator($operator);
+
+  /**
+   * Throws an exception to deny direct access to transaction commits.
+   *
+   * We do not want to allow users to commit transactions at any time, only
+   * by destroying the transaction object or allowing it to go out of scope.
+   * A direct commit bypasses all of the safety checks we've built on top of
+   * PDO's transaction routines.
+   *
+   * @throws DatabaseTransactionExplicitCommitNotAllowedException
+   *
+   * @see DatabaseTransaction
+   */
+  public function commit() {
+    throw new DatabaseTransactionExplicitCommitNotAllowedException();
+  }
+
+  /**
+   * Retrieves an unique id from a given sequence.
+   *
+   * Use this function if for some reason you can't use a serial field. For
+   * example, MySQL has no ways of reading of the current value of a sequence
+   * and PostgreSQL can not advance the sequence to be larger than a given
+   * value. Or sometimes you just need a unique integer.
+   *
+   * @param $existing_id
+   *   After a database import, it might be that the sequences table is behind,
+   *   so by passing in the maximum existing id, it can be assured that we
+   *   never issue the same id.
+   *
+   * @return
+   *   An integer number larger than any number returned by earlier calls and
+   *   also larger than the $existing_id if one was passed in.
+   */
+  abstract public function nextId($existing_id = 0);
+
+  /**
+   * Checks whether utf8mb4 support is configurable in settings.php.
+   *
+   * @return bool
+   */
+  public function utf8mb4IsConfigurable() {
+    // Since 4 byte UTF-8 is not supported by default, there is nothing to
+    // configure.
+    return FALSE;
+  }
+
+  /**
+   * Checks whether utf8mb4 support is currently active.
+   *
+   * @return bool
+   */
+  public function utf8mb4IsActive() {
+    // Since 4 byte UTF-8 is not supported by default, there is nothing to
+    // activate.
+    return FALSE;
+  }
+
+  /**
+   * Checks whether utf8mb4 support is available on the current database system.
+   *
+   * @return bool
+   */
+  public function utf8mb4IsSupported() {
+    // By default we assume that the database backend may not support 4 byte
+    // UTF-8.
+    return FALSE;
+  }
+}
+
+/**
+ * Primary front-controller for the database system.
+ *
+ * This class is uninstantiatable and un-extendable. It acts to encapsulate
+ * all control and shepherding of database connections into a single location
+ * without the use of globals.
+ */
+abstract class Database {
+
+  /**
+   * Flag to indicate a query call should simply return NULL.
+   *
+   * This is used for queries that have no reasonable return value anyway, such
+   * as INSERT statements to a table without a serial primary key.
+   */
+  const RETURN_NULL = 0;
+
+  /**
+   * Flag to indicate a query call should return the prepared statement.
+   */
+  const RETURN_STATEMENT = 1;
+
+  /**
+   * Flag to indicate a query call should return the number of affected rows.
+   */
+  const RETURN_AFFECTED = 2;
+
+  /**
+   * Flag to indicate a query call should return the "last insert id".
+   */
+  const RETURN_INSERT_ID = 3;
+
+  /**
+   * An nested array of all active connections. It is keyed by database name
+   * and target.
+   *
+   * @var array
+   */
+  static protected $connections = array();
+
+  /**
+   * A processed copy of the database connection information from settings.php.
+   *
+   * @var array
+   */
+  static protected $databaseInfo = NULL;
+
+  /**
+   * A list of key/target credentials to simply ignore.
+   *
+   * @var array
+   */
+  static protected $ignoreTargets = array();
+
+  /**
+   * The key of the currently active database connection.
+   *
+   * @var string
+   */
+  static protected $activeKey = 'default';
+
+  /**
+   * An array of active query log objects.
+   *
+   * Every connection has one and only one logger object for all targets and
+   * logging keys.
+   *
+   * array(
+   *   '$db_key' => DatabaseLog object.
+   * );
+   *
+   * @var array
+   */
+  static protected $logs = array();
+
+  /**
+   * Starts logging a given logging key on the specified connection.
+   *
+   * @param $logging_key
+   *   The logging key to log.
+   * @param $key
+   *   The database connection key for which we want to log.
+   *
+   * @return DatabaseLog
+   *   The query log object. Note that the log object does support richer
+   *   methods than the few exposed through the Database class, so in some
+   *   cases it may be desirable to access it directly.
+   *
+   * @see DatabaseLog
+   */
+  final public static function startLog($logging_key, $key = 'default') {
+    if (empty(self::$logs[$key])) {
+      self::$logs[$key] = new DatabaseLog($key);
+
+      // Every target already active for this connection key needs to have the
+      // logging object associated with it.
+      if (!empty(self::$connections[$key])) {
+        foreach (self::$connections[$key] as $connection) {
+          $connection->setLogger(self::$logs[$key]);
+        }
+      }
+    }
+
+    self::$logs[$key]->start($logging_key);
+    return self::$logs[$key];
+  }
+
+  /**
+   * Retrieves the queries logged on for given logging key.
+   *
+   * This method also ends logging for the specified key. To get the query log
+   * to date without ending the logger request the logging object by starting
+   * it again (which does nothing to an open log key) and call methods on it as
+   * desired.
+   *
+   * @param $logging_key
+   *   The logging key to log.
+   * @param $key
+   *   The database connection key for which we want to log.
+   *
+   * @return array
+   *   The query log for the specified logging key and connection.
+   *
+   * @see DatabaseLog
+   */
+  final public static function getLog($logging_key, $key = 'default') {
+    if (empty(self::$logs[$key])) {
+      return NULL;
+    }
+    $queries = self::$logs[$key]->get($logging_key);
+    self::$logs[$key]->end($logging_key);
+    return $queries;
+  }
+
+  /**
+   * Gets the connection object for the specified database key and target.
+   *
+   * @param $target
+   *   The database target name.
+   * @param $key
+   *   The database connection key. Defaults to NULL which means the active key.
+   *
+   * @return DatabaseConnection
+   *   The corresponding connection object.
+   */
+  final public static function getConnection($target = 'default', $key = NULL) {
+    if (!isset($key)) {
+      // By default, we want the active connection, set in setActiveConnection.
+      $key = self::$activeKey;
+    }
+    // If the requested target does not exist, or if it is ignored, we fall back
+    // to the default target. The target is typically either "default" or
+    // "slave", indicating to use a slave SQL server if one is available. If
+    // it's not available, then the default/master server is the correct server
+    // to use.
+    if (!empty(self::$ignoreTargets[$key][$target]) || !isset(self::$databaseInfo[$key][$target])) {
+      $target = 'default';
+    }
+
+    if (!isset(self::$connections[$key][$target])) {
+      // If necessary, a new connection is opened.
+      self::$connections[$key][$target] = self::openConnection($key, $target);
+    }
+    return self::$connections[$key][$target];
+  }
+
+  /**
+   * Determines if there is an active connection.
+   *
+   * Note that this method will return FALSE if no connection has been
+   * established yet, even if one could be.
+   *
+   * @return
+   *   TRUE if there is at least one database connection established, FALSE
+   *   otherwise.
+   */
+  final public static function isActiveConnection() {
+    return !empty(self::$activeKey) && !empty(self::$connections) && !empty(self::$connections[self::$activeKey]);
+  }
+
+  /**
+   * Sets the active connection to the specified key.
+   *
+   * @return
+   *   The previous database connection key.
+   */
+  final public static function setActiveConnection($key = 'default') {
+    if (empty(self::$databaseInfo)) {
+      self::parseConnectionInfo();
+    }
+
+    if (!empty(self::$databaseInfo[$key])) {
+      $old_key = self::$activeKey;
+      self::$activeKey = $key;
+      return $old_key;
+    }
+  }
+
+  /**
+   * Process the configuration file for database information.
+   */
+  final public static function parseConnectionInfo() {
+    global $databases;
+
+    $database_info = is_array($databases) ? $databases : array();
+    foreach ($database_info as $index => $info) {
+      foreach ($database_info[$index] as $target => $value) {
+        // If there is no "driver" property, then we assume it's an array of
+        // possible connections for this target. Pick one at random. That allows
+        //  us to have, for example, multiple slave servers.
+        if (empty($value['driver'])) {
+          $database_info[$index][$target] = $database_info[$index][$target][mt_rand(0, count($database_info[$index][$target]) - 1)];
+        }
+
+        // Parse the prefix information.
+        if (!isset($database_info[$index][$target]['prefix'])) {
+          // Default to an empty prefix.
+          $database_info[$index][$target]['prefix'] = array(
+            'default' => '',
+          );
+        }
+        elseif (!is_array($database_info[$index][$target]['prefix'])) {
+          // Transform the flat form into an array form.
+          $database_info[$index][$target]['prefix'] = array(
+            'default' => $database_info[$index][$target]['prefix'],
+          );
+        }
+      }
+    }
+
+    if (!is_array(self::$databaseInfo)) {
+      self::$databaseInfo = $database_info;
+    }
+
+    // Merge the new $database_info into the existing.
+    // array_merge_recursive() cannot be used, as it would make multiple
+    // database, user, and password keys in the same database array.
+    else {
+      foreach ($database_info as $database_key => $database_values) {
+        foreach ($database_values as $target => $target_values) {
+          self::$databaseInfo[$database_key][$target] = $target_values;
+        }
+      }
+    }
+  }
+
+  /**
+   * Adds database connection information for a given key/target.
+   *
+   * This method allows the addition of new connection credentials at runtime.
+   * Under normal circumstances the preferred way to specify database
+   * credentials is via settings.php. However, this method allows them to be
+   * added at arbitrary times, such as during unit tests, when connecting to
+   * admin-defined third party databases, etc.
+   *
+   * If the given key/target pair already exists, this method will be ignored.
+   *
+   * @param $key
+   *   The database key.
+   * @param $target
+   *   The database target name.
+   * @param $info
+   *   The database connection information, as it would be defined in
+   *   settings.php. Note that the structure of this array will depend on the
+   *   database driver it is connecting to.
+   */
+  public static function addConnectionInfo($key, $target, $info) {
+    if (empty(self::$databaseInfo[$key][$target])) {
+      self::$databaseInfo[$key][$target] = $info;
+    }
+  }
+
+  /**
+   * Gets information on the specified database connection.
+   *
+   * @param $connection
+   *   The connection key for which we want information.
+   */
+  final public static function getConnectionInfo($key = 'default') {
+    if (empty(self::$databaseInfo)) {
+      self::parseConnectionInfo();
+    }
+
+    if (!empty(self::$databaseInfo[$key])) {
+      return self::$databaseInfo[$key];
+    }
+  }
+
+  /**
+   * Rename a connection and its corresponding connection information.
+   *
+   * @param $old_key
+   *   The old connection key.
+   * @param $new_key
+   *   The new connection key.
+   * @return
+   *   TRUE in case of success, FALSE otherwise.
+   */
+  final public static function renameConnection($old_key, $new_key) {
+    if (empty(self::$databaseInfo)) {
+      self::parseConnectionInfo();
+    }
+
+    if (!empty(self::$databaseInfo[$old_key]) && empty(self::$databaseInfo[$new_key])) {
+      // Migrate the database connection information.
+      self::$databaseInfo[$new_key] = self::$databaseInfo[$old_key];
+      unset(self::$databaseInfo[$old_key]);
+
+      // Migrate over the DatabaseConnection object if it exists.
+      if (isset(self::$connections[$old_key])) {
+        self::$connections[$new_key] = self::$connections[$old_key];
+        unset(self::$connections[$old_key]);
+      }
+
+      return TRUE;
+    }
+    else {
+      return FALSE;
+    }
+  }
+
+  /**
+   * Remove a connection and its corresponding connection information.
+   *
+   * @param $key
+   *   The connection key.
+   * @return
+   *   TRUE in case of success, FALSE otherwise.
+   */
+  final public static function removeConnection($key) {
+    if (isset(self::$databaseInfo[$key])) {
+      self::closeConnection(NULL, $key);
+      unset(self::$databaseInfo[$key]);
+      return TRUE;
+    }
+    else {
+      return FALSE;
+    }
+  }
+
+  /**
+   * Opens a connection to the server specified by the given key and target.
+   *
+   * @param $key
+   *   The database connection key, as specified in settings.php. The default is
+   *   "default".
+   * @param $target
+   *   The database target to open.
+   *
+   * @throws DatabaseConnectionNotDefinedException
+   * @throws DatabaseDriverNotSpecifiedException
+   */
+  final protected static function openConnection($key, $target) {
+    if (empty(self::$databaseInfo)) {
+      self::parseConnectionInfo();
+    }
+
+    // If the requested database does not exist then it is an unrecoverable
+    // error.
+    if (!isset(self::$databaseInfo[$key])) {
+      throw new DatabaseConnectionNotDefinedException('The specified database connection is not defined: ' . $key);
+    }
+
+    if (!$driver = self::$databaseInfo[$key][$target]['driver']) {
+      throw new DatabaseDriverNotSpecifiedException('Driver not specified for this database connection: ' . $key);
+    }
+
+    // We cannot rely on the registry yet, because the registry requires an
+    // open database connection.
+    $driver_class = 'DatabaseConnection_' . $driver;
+    require_once DRUPAL_ROOT . '/includes/database/' . $driver . '/database.inc';
+    $new_connection = new $driver_class(self::$databaseInfo[$key][$target]);
+    $new_connection->setTarget($target);
+    $new_connection->setKey($key);
+
+    // If we have any active logging objects for this connection key, we need
+    // to associate them with the connection we just opened.
+    if (!empty(self::$logs[$key])) {
+      $new_connection->setLogger(self::$logs[$key]);
+    }
+
+    return $new_connection;
+  }
+
+  /**
+   * Closes a connection to the server specified by the given key and target.
+   *
+   * @param $target
+   *   The database target name.  Defaults to NULL meaning that all target
+   *   connections will be closed.
+   * @param $key
+   *   The database connection key. Defaults to NULL which means the active key.
+   */
+  public static function closeConnection($target = NULL, $key = NULL) {
+    // Gets the active connection by default.
+    if (!isset($key)) {
+      $key = self::$activeKey;
+    }
+    // To close a connection, it needs to be set to NULL and removed from the
+    // static variable. In all cases, closeConnection() might be called for a
+    // connection that was not opened yet, in which case the key is not defined
+    // yet and we just ensure that the connection key is undefined.
+    if (isset($target)) {
+      if (isset(self::$connections[$key][$target])) {
+        self::$connections[$key][$target]->destroy();
+        self::$connections[$key][$target] = NULL;
+      }
+      unset(self::$connections[$key][$target]);
+    }
+    else {
+      if (isset(self::$connections[$key])) {
+        foreach (self::$connections[$key] as $target => $connection) {
+          self::$connections[$key][$target]->destroy();
+          self::$connections[$key][$target] = NULL;
+        }
+      }
+      unset(self::$connections[$key]);
+    }
+  }
+
+  /**
+   * Instructs the system to temporarily ignore a given key/target.
+   *
+   * At times we need to temporarily disable slave queries. To do so, call this
+   * method with the database key and the target to disable. That database key
+   * will then always fall back to 'default' for that key, even if it's defined.
+   *
+   * @param $key
+   *   The database connection key.
+   * @param $target
+   *   The target of the specified key to ignore.
+   */
+  public static function ignoreTarget($key, $target) {
+    self::$ignoreTargets[$key][$target] = TRUE;
+  }
+
+  /**
+   * Load a file for the database that might hold a class.
+   *
+   * @param $driver
+   *   The name of the driver.
+   * @param array $files
+   *   The name of the files the driver specific class can be.
+   */
+  public static function loadDriverFile($driver, array $files = array()) {
+    static $base_path;
+
+    if (empty($base_path)) {
+      $base_path = dirname(realpath(__FILE__));
+    }
+
+    $driver_base_path = "$base_path/$driver";
+    foreach ($files as $file) {
+      // Load the base file first so that classes extending base classes will
+      // have the base class loaded.
+      foreach (array("$base_path/$file", "$driver_base_path/$file") as $filename) {
+        // The OS caches file_exists() and PHP caches require_once(), so
+        // we'll let both of those take care of performance here.
+        if (file_exists($filename)) {
+          require_once $filename;
+        }
+      }
+    }
+  }
+}
+
+/**
+ * Exception for when popTransaction() is called with no active transaction.
+ */
+class DatabaseTransactionNoActiveException extends Exception { }
+
+/**
+ * Exception thrown when a savepoint or transaction name occurs twice.
+ */
+class DatabaseTransactionNameNonUniqueException extends Exception { }
+
+/**
+ * Exception thrown when a commit() function fails.
+ */
+class DatabaseTransactionCommitFailedException extends Exception { }
+
+/**
+ * Exception to deny attempts to explicitly manage transactions.
+ *
+ * This exception will be thrown when the PDO connection commit() is called.
+ * Code should never call this method directly.
+ */
+class DatabaseTransactionExplicitCommitNotAllowedException extends Exception { }
+
+/**
+ * Exception thrown when a rollback() resulted in other active transactions being rolled-back.
+ */
+class DatabaseTransactionOutOfOrderException extends Exception { }
+
+/**
+ * Exception thrown for merge queries that do not make semantic sense.
+ *
+ * There are many ways that a merge query could be malformed.  They should all
+ * throw this exception and set an appropriately descriptive message.
+ */
+class InvalidMergeQueryException extends Exception {}
+
+/**
+ * Exception thrown if an insert query specifies a field twice.
+ *
+ * It is not allowed to specify a field as default and insert field, this
+ * exception is thrown if that is the case.
+ */
+class FieldsOverlapException extends Exception {}
+
+/**
+ * Exception thrown if an insert query doesn't specify insert or default fields.
+ */
+class NoFieldsException extends Exception {}
+
+/**
+ * Exception thrown if an undefined database connection is requested.
+ */
+class DatabaseConnectionNotDefinedException extends Exception {}
+
+/**
+ * Exception thrown if no driver is specified for a database connection.
+ */
+class DatabaseDriverNotSpecifiedException extends Exception {}
+
+
+/**
+ * A wrapper class for creating and managing database transactions.
+ *
+ * Not all databases or database configurations support transactions. For
+ * example, MySQL MyISAM tables do not. It is also easy to begin a transaction
+ * and then forget to commit it, which can lead to connection errors when
+ * another transaction is started.
+ *
+ * This class acts as a wrapper for transactions. To begin a transaction,
+ * simply instantiate it. When the object goes out of scope and is destroyed
+ * it will automatically commit. It also will check to see if the specified
+ * connection supports transactions. If not, it will simply skip any transaction
+ * commands, allowing user-space code to proceed normally. The only difference
+ * is that rollbacks won't actually do anything.
+ *
+ * In the vast majority of cases, you should not instantiate this class
+ * directly. Instead, call ->startTransaction(), from the appropriate connection
+ * object.
+ */
+class DatabaseTransaction {
+
+  /**
+   * The connection object for this transaction.
+   *
+   * @var DatabaseConnection
+   */
+  protected $connection;
+
+  /**
+   * A boolean value to indicate whether this transaction has been rolled back.
+   *
+   * @var Boolean
+   */
+  protected $rolledBack = FALSE;
+
+  /**
+   * The name of the transaction.
+   *
+   * This is used to label the transaction savepoint. It will be overridden to
+   * 'drupal_transaction' if there is no transaction depth.
+   */
+  protected $name;
+
+  public function __construct(DatabaseConnection $connection, $name = NULL) {
+    $this->connection = $connection;
+    // If there is no transaction depth, then no transaction has started. Name
+    // the transaction 'drupal_transaction'.
+    if (!$depth = $connection->transactionDepth()) {
+      $this->name = 'drupal_transaction';
+    }
+    // Within transactions, savepoints are used. Each savepoint requires a
+    // name. So if no name is present we need to create one.
+    elseif (!$name) {
+      $this->name = 'savepoint_' . $depth;
+    }
+    else {
+      $this->name = $name;
+    }
+    $this->connection->pushTransaction($this->name);
+  }
+
+  public function __destruct() {
+    // If we rolled back then the transaction would have already been popped.
+    if (!$this->rolledBack) {
+      $this->connection->popTransaction($this->name);
+    }
+  }
+
+  /**
+   * Retrieves the name of the transaction or savepoint.
+   */
+  public function name() {
+    return $this->name;
+  }
+
+  /**
+   * Rolls back the current transaction.
+   *
+   * This is just a wrapper method to rollback whatever transaction stack we are
+   * currently in, which is managed by the connection object itself. Note that
+   * logging (preferable with watchdog_exception()) needs to happen after a
+   * transaction has been rolled back or the log messages will be rolled back
+   * too.
+   *
+   * @see DatabaseConnection::rollback()
+   * @see watchdog_exception()
+   */
+  public function rollback() {
+    $this->rolledBack = TRUE;
+    $this->connection->rollback($this->name);
+  }
+}
+
+/**
+ * Represents a prepared statement.
+ *
+ * Some methods in that class are purposefully commented out. Due to a change in
+ * how PHP defines PDOStatement, we can't define a signature for those methods
+ * that will work the same way between versions older than 5.2.6 and later
+ * versions.  See http://bugs.php.net/bug.php?id=42452 for more details.
+ *
+ * Child implementations should either extend PDOStatement:
+ * @code
+ * class DatabaseStatement_oracle extends PDOStatement implements DatabaseStatementInterface {}
+ * @endcode
+ * or define their own class. If defining their own class, they will also have
+ * to implement either the Iterator or IteratorAggregate interface before
+ * DatabaseStatementInterface:
+ * @code
+ * class DatabaseStatement_oracle implements Iterator, DatabaseStatementInterface {}
+ * @endcode
+ */
+interface DatabaseStatementInterface extends Traversable {
+
+  /**
+   * Executes a prepared statement
+   *
+   * @param $args
+   *   An array of values with as many elements as there are bound parameters in
+   *   the SQL statement being executed.
+   * @param $options
+   *   An array of options for this query.
+   *
+   * @return
+   *   TRUE on success, or FALSE on failure.
+   */
+  public function execute($args = array(), $options = array());
+
+  /**
+   * Gets the query string of this statement.
+   *
+   * @return
+   *   The query string, in its form with placeholders.
+   */
+  public function getQueryString();
+
+  /**
+   * Returns the number of rows affected by the last SQL statement.
+   *
+   * @return
+   *   The number of rows affected by the last DELETE, INSERT, or UPDATE
+   *   statement executed.
+   */
+  public function rowCount();
+
+  /**
+   * Sets the default fetch mode for this statement.
+   *
+   * See http://php.net/manual/pdo.constants.php for the definition of the
+   * constants used.
+   *
+   * @param $mode
+   *   One of the PDO::FETCH_* constants.
+   * @param $a1
+   *   An option depending of the fetch mode specified by $mode:
+   *   - for PDO::FETCH_COLUMN, the index of the column to fetch
+   *   - for PDO::FETCH_CLASS, the name of the class to create
+   *   - for PDO::FETCH_INTO, the object to add the data to
+   * @param $a2
+   *   If $mode is PDO::FETCH_CLASS, the optional arguments to pass to the
+   *   constructor.
+   */
+  // public function setFetchMode($mode, $a1 = NULL, $a2 = array());
+
+  /**
+   * Fetches the next row from a result set.
+   *
+   * See http://php.net/manual/pdo.constants.php for the definition of the
+   * constants used.
+   *
+   * @param $mode
+   *   One of the PDO::FETCH_* constants.
+   *   Default to what was specified by setFetchMode().
+   * @param $cursor_orientation
+   *   Not implemented in all database drivers, don't use.
+   * @param $cursor_offset
+   *   Not implemented in all database drivers, don't use.
+   *
+   * @return
+   *   A result, formatted according to $mode.
+   */
+  // public function fetch($mode = NULL, $cursor_orientation = NULL, $cursor_offset = NULL);
+
+  /**
+   * Returns a single field from the next record of a result set.
+   *
+   * @param $index
+   *   The numeric index of the field to return. Defaults to the first field.
+   *
+   * @return
+   *   A single field from the next record, or FALSE if there is no next record.
+   */
+  public function fetchField($index = 0);
+
+  /**
+   * Fetches the next row and returns it as an object.
+   *
+   * The object will be of the class specified by DatabaseStatementInterface::setFetchMode()
+   * or stdClass if not specified.
+   */
+  // public function fetchObject();
+
+  /**
+   * Fetches the next row and returns it as an associative array.
+   *
+   * This method corresponds to PDOStatement::fetchObject(), but for associative
+   * arrays. For some reason PDOStatement does not have a corresponding array
+   * helper method, so one is added.
+   *
+   * @return
+   *   An associative array, or FALSE if there is no next row.
+   */
+  public function fetchAssoc();
+
+  /**
+   * Returns an array containing all of the result set rows.
+   *
+   * @param $mode
+   *   One of the PDO::FETCH_* constants.
+   * @param $column_index
+   *   If $mode is PDO::FETCH_COLUMN, the index of the column to fetch.
+   * @param $constructor_arguments
+   *   If $mode is PDO::FETCH_CLASS, the arguments to pass to the constructor.
+   *
+   * @return
+   *   An array of results.
+   */
+  // function fetchAll($mode = NULL, $column_index = NULL, array $constructor_arguments);
+
+  /**
+   * Returns an entire single column of a result set as an indexed array.
+   *
+   * Note that this method will run the result set to the end.
+   *
+   * @param $index
+   *   The index of the column number to fetch.
+   *
+   * @return
+   *   An indexed array, or an empty array if there is no result set.
+   */
+  public function fetchCol($index = 0);
+
+  /**
+   * Returns the entire result set as a single associative array.
+   *
+   * This method is only useful for two-column result sets. It will return an
+   * associative array where the key is one column from the result set and the
+   * value is another field. In most cases, the default of the first two columns
+   * is appropriate.
+   *
+   * Note that this method will run the result set to the end.
+   *
+   * @param $key_index
+   *   The numeric index of the field to use as the array key.
+   * @param $value_index
+   *   The numeric index of the field to use as the array value.
+   *
+   * @return
+   *   An associative array, or an empty array if there is no result set.
+   */
+  public function fetchAllKeyed($key_index = 0, $value_index = 1);
+
+  /**
+   * Returns the result set as an associative array keyed by the given field.
+   *
+   * If the given key appears multiple times, later records will overwrite
+   * earlier ones.
+   *
+   * @param $key
+   *   The name of the field on which to index the array.
+   * @param $fetch
+   *   The fetchmode to use. If set to PDO::FETCH_ASSOC, PDO::FETCH_NUM, or
+   *   PDO::FETCH_BOTH the returned value with be an array of arrays. For any
+   *   other value it will be an array of objects. By default, the fetch mode
+   *   set for the query will be used.
+   *
+   * @return
+   *   An associative array, or an empty array if there is no result set.
+   */
+  public function fetchAllAssoc($key, $fetch = NULL);
+}
+
+/**
+ * Default implementation of DatabaseStatementInterface.
+ *
+ * PDO allows us to extend the PDOStatement class to provide additional
+ * functionality beyond that offered by default. We do need extra
+ * functionality. By default, this class is not driver-specific. If a given
+ * driver needs to set a custom statement class, it may do so in its
+ * constructor.
+ *
+ * @see http://us.php.net/pdostatement
+ */
+class DatabaseStatementBase extends PDOStatement implements DatabaseStatementInterface {
+
+  /**
+   * Reference to the database connection object for this statement.
+   *
+   * The name $dbh is inherited from PDOStatement.
+   *
+   * @var DatabaseConnection
+   */
+  public $dbh;
+
+  protected function __construct($dbh) {
+    $this->dbh = $dbh;
+    $this->setFetchMode(PDO::FETCH_OBJ);
+  }
+
+  public function execute($args = array(), $options = array()) {
+    if (isset($options['fetch'])) {
+      if (is_string($options['fetch'])) {
+        // Default to an object. Note: db fields will be added to the object
+        // before the constructor is run. If you need to assign fields after
+        // the constructor is run, see http://drupal.org/node/315092.
+        $this->setFetchMode(PDO::FETCH_CLASS, $options['fetch']);
+      }
+      else {
+        $this->setFetchMode($options['fetch']);
+      }
+    }
+
+    $logger = $this->dbh->getLogger();
+    if (!empty($logger)) {
+      $query_start = microtime(TRUE);
+    }
+
+    $return = parent::execute($args);
+
+    if (!empty($logger)) {
+      $query_end = microtime(TRUE);
+      $logger->log($this, $args, $query_end - $query_start);
+    }
+
+    return $return;
+  }
+
+  public function getQueryString() {
+    return $this->queryString;
+  }
+
+  public function fetchCol($index = 0) {
+    return $this->fetchAll(PDO::FETCH_COLUMN, $index);
+  }
+
+  public function fetchAllAssoc($key, $fetch = NULL) {
+    $return = array();
+    if (isset($fetch)) {
+      if (is_string($fetch)) {
+        $this->setFetchMode(PDO::FETCH_CLASS, $fetch);
+      }
+      else {
+        $this->setFetchMode($fetch);
+      }
+    }
+
+    foreach ($this as $record) {
+      $record_key = is_object($record) ? $record->$key : $record[$key];
+      $return[$record_key] = $record;
+    }
+
+    return $return;
+  }
+
+  public function fetchAllKeyed($key_index = 0, $value_index = 1) {
+    $return = array();
+    $this->setFetchMode(PDO::FETCH_NUM);
+    foreach ($this as $record) {
+      $return[$record[$key_index]] = $record[$value_index];
+    }
+    return $return;
+  }
+
+  public function fetchField($index = 0) {
+    // Call PDOStatement::fetchColumn to fetch the field.
+    return $this->fetchColumn($index);
+  }
+
+  public function fetchAssoc() {
+    // Call PDOStatement::fetch to fetch the row.
+    return $this->fetch(PDO::FETCH_ASSOC);
+  }
+}
+
+/**
+ * Empty implementation of a database statement.
+ *
+ * This class satisfies the requirements of being a database statement/result
+ * object, but does not actually contain data.  It is useful when developers
+ * need to safely return an "empty" result set without connecting to an actual
+ * database.  Calling code can then treat it the same as if it were an actual
+ * result set that happens to contain no records.
+ *
+ * @see SearchQuery
+ */
+class DatabaseStatementEmpty implements Iterator, DatabaseStatementInterface {
+
+  public function execute($args = array(), $options = array()) {
+    return FALSE;
+  }
+
+  public function getQueryString() {
+    return '';
+  }
+
+  public function rowCount() {
+    return 0;
+  }
+
+  public function setFetchMode($mode, $a1 = NULL, $a2 = array()) {
+    return;
+  }
+
+  public function fetch($mode = NULL, $cursor_orientation = NULL, $cursor_offset = NULL) {
+    return NULL;
+  }
+
+  public function fetchField($index = 0) {
+    return NULL;
+  }
+
+  public function fetchObject() {
+    return NULL;
+  }
+
+  public function fetchAssoc() {
+    return NULL;
+  }
+
+  function fetchAll($mode = NULL, $column_index = NULL, array $constructor_arguments = array()) {
+    return array();
+  }
+
+  public function fetchCol($index = 0) {
+    return array();
+  }
+
+  public function fetchAllKeyed($key_index = 0, $value_index = 1) {
+    return array();
+  }
+
+  public function fetchAllAssoc($key, $fetch = NULL) {
+    return array();
+  }
+
+  /* Implementations of Iterator. */
+
+  public function current() {
+    return NULL;
+  }
+
+  public function key() {
+    return NULL;
+  }
+
+  public function rewind() {
+    // Nothing to do: our DatabaseStatement can't be rewound.
+  }
+
+  public function next() {
+    // Do nothing, since this is an always-empty implementation.
+  }
+
+  public function valid() {
+    return FALSE;
+  }
+}
+
+/**
+ * The following utility functions are simply convenience wrappers.
+ *
+ * They should never, ever have any database-specific code in them.
+ */
+
+/**
+ * Executes an arbitrary query string against the active database.
+ *
+ * Use this function for SELECT queries if it is just a simple query string.
+ * If the caller or other modules need to change the query, use db_select()
+ * instead.
+ *
+ * Do not use this function for INSERT, UPDATE, or DELETE queries. Those should
+ * be handled via db_insert(), db_update() and db_delete() respectively.
+ *
+ * @param $query
+ *   The prepared statement query to run. Although it will accept both named and
+ *   unnamed placeholders, named placeholders are strongly preferred as they are
+ *   more self-documenting.
+ * @param $args
+ *   An array of values to substitute into the query. If the query uses named
+ *   placeholders, this is an associative array in any order. If the query uses
+ *   unnamed placeholders (?), this is an indexed array and the order must match
+ *   the order of placeholders in the query string.
+ * @param $options
+ *   An array of options to control how the query operates.
+ *
+ * @return DatabaseStatementInterface
+ *   A prepared statement object, already executed.
+ *
+ * @see DatabaseConnection::defaultOptions()
+ */
+function db_query($query, array $args = array(), array $options = array()) {
+  if (empty($options['target'])) {
+    $options['target'] = 'default';
+  }
+
+  return Database::getConnection($options['target'])->query($query, $args, $options);
+}
+
+/**
+ * Executes a query against the active database, restricted to a range.
+ *
+ * @param $query
+ *   The prepared statement query to run. Although it will accept both named and
+ *   unnamed placeholders, named placeholders are strongly preferred as they are
+ *   more self-documenting.
+ * @param $from
+ *   The first record from the result set to return.
+ * @param $count
+ *   The number of records to return from the result set.
+ * @param $args
+ *   An array of values to substitute into the query. If the query uses named
+ *   placeholders, this is an associative array in any order. If the query uses
+ *   unnamed placeholders (?), this is an indexed array and the order must match
+ *   the order of placeholders in the query string.
+ * @param $options
+ *   An array of options to control how the query operates.
+ *
+ * @return DatabaseStatementInterface
+ *   A prepared statement object, already executed.
+ *
+ * @see DatabaseConnection::defaultOptions()
+ */
+function db_query_range($query, $from, $count, array $args = array(), array $options = array()) {
+  if (empty($options['target'])) {
+    $options['target'] = 'default';
+  }
+
+  return Database::getConnection($options['target'])->queryRange($query, $from, $count, $args, $options);
+}
+
+/**
+ * Executes a SELECT query string and saves the result set to a temporary table.
+ *
+ * The execution of the query string happens against the active database.
+ *
+ * @param $query
+ *   The prepared SELECT statement query to run. Although it will accept both
+ *   named and unnamed placeholders, named placeholders are strongly preferred
+ *   as they are more self-documenting.
+ * @param $args
+ *   An array of values to substitute into the query. If the query uses named
+ *   placeholders, this is an associative array in any order. If the query uses
+ *   unnamed placeholders (?), this is an indexed array and the order must match
+ *   the order of placeholders in the query string.
+ * @param $options
+ *   An array of options to control how the query operates.
+ *
+ * @return
+ *   The name of the temporary table.
+ *
+ * @see DatabaseConnection::defaultOptions()
+ */
+function db_query_temporary($query, array $args = array(), array $options = array()) {
+  if (empty($options['target'])) {
+    $options['target'] = 'default';
+  }
+
+  return Database::getConnection($options['target'])->queryTemporary($query, $args, $options);
+}
+
+/**
+ * Returns a new InsertQuery object for the active database.
+ *
+ * @param $table
+ *   The table into which to insert.
+ * @param $options
+ *   An array of options to control how the query operates.
+ *
+ * @return InsertQuery
+ *   A new InsertQuery object for this connection.
+ */
+function db_insert($table, array $options = array()) {
+  if (empty($options['target']) || $options['target'] == 'slave') {
+    $options['target'] = 'default';
+  }
+  return Database::getConnection($options['target'])->insert($table, $options);
+}
+
+/**
+ * Returns a new MergeQuery object for the active database.
+ *
+ * @param $table
+ *   The table into which to merge.
+ * @param $options
+ *   An array of options to control how the query operates.
+ *
+ * @return MergeQuery
+ *   A new MergeQuery object for this connection.
+ */
+function db_merge($table, array $options = array()) {
+  if (empty($options['target']) || $options['target'] == 'slave') {
+    $options['target'] = 'default';
+  }
+  return Database::getConnection($options['target'])->merge($table, $options);
+}
+
+/**
+ * Returns a new UpdateQuery object for the active database.
+ *
+ * @param $table
+ *   The table to update.
+ * @param $options
+ *   An array of options to control how the query operates.
+ *
+ * @return UpdateQuery
+ *   A new UpdateQuery object for this connection.
+ */
+function db_update($table, array $options = array()) {
+  if (empty($options['target']) || $options['target'] == 'slave') {
+    $options['target'] = 'default';
+  }
+  return Database::getConnection($options['target'])->update($table, $options);
+}
+
+/**
+ * Returns a new DeleteQuery object for the active database.
+ *
+ * @param $table
+ *   The table from which to delete.
+ * @param $options
+ *   An array of options to control how the query operates.
+ *
+ * @return DeleteQuery
+ *   A new DeleteQuery object for this connection.
+ */
+function db_delete($table, array $options = array()) {
+  if (empty($options['target']) || $options['target'] == 'slave') {
+    $options['target'] = 'default';
+  }
+  return Database::getConnection($options['target'])->delete($table, $options);
+}
+
+/**
+ * Returns a new TruncateQuery object for the active database.
+ *
+ * @param $table
+ *   The table from which to delete.
+ * @param $options
+ *   An array of options to control how the query operates.
+ *
+ * @return TruncateQuery
+ *   A new TruncateQuery object for this connection.
+ */
+function db_truncate($table, array $options = array()) {
+  if (empty($options['target']) || $options['target'] == 'slave') {
+    $options['target'] = 'default';
+  }
+  return Database::getConnection($options['target'])->truncate($table, $options);
+}
+
+/**
+ * Returns a new SelectQuery object for the active database.
+ *
+ * @param $table
+ *   The base table for this query. May be a string or another SelectQuery
+ *   object. If a query object is passed, it will be used as a subselect.
+ * @param $alias
+ *   The alias for the base table of this query.
+ * @param $options
+ *   An array of options to control how the query operates.
+ *
+ * @return SelectQuery
+ *   A new SelectQuery object for this connection.
+ */
+function db_select($table, $alias = NULL, array $options = array()) {
+  if (empty($options['target'])) {
+    $options['target'] = 'default';
+  }
+  return Database::getConnection($options['target'])->select($table, $alias, $options);
+}
+
+/**
+ * Returns a new transaction object for the active database.
+ *
+ * @param string $name
+ *   Optional name of the transaction.
+ * @param array $options
+ *   An array of options to control how the transaction operates:
+ *   - target: The database target name.
+ *
+ * @return DatabaseTransaction
+ *   A new DatabaseTransaction object for this connection.
+ */
+function db_transaction($name = NULL, array $options = array()) {
+  if (empty($options['target'])) {
+    $options['target'] = 'default';
+  }
+  return Database::getConnection($options['target'])->startTransaction($name);
+}
+
+/**
+ * Sets a new active database.
+ *
+ * @param $key
+ *   The key in the $databases array to set as the default database.
+ *
+ * @return
+ *   The key of the formerly active database.
+ */
+function db_set_active($key = 'default') {
+  return Database::setActiveConnection($key);
+}
+
+/**
+ * Restricts a dynamic table name to safe characters.
+ *
+ * Only keeps alphanumeric and underscores.
+ *
+ * @param $table
+ *   The table name to escape.
+ *
+ * @return
+ *   The escaped table name as a string.
+ */
+function db_escape_table($table) {
+  return Database::getConnection()->escapeTable($table);
+}
+
+/**
+ * Restricts a dynamic column or constraint name to safe characters.
+ *
+ * Only keeps alphanumeric and underscores.
+ *
+ * @param $field
+ *   The field name to escape.
+ *
+ * @return
+ *   The escaped field name as a string.
+ */
+function db_escape_field($field) {
+  return Database::getConnection()->escapeField($field);
+}
+
+/**
+ * Escapes characters that work as wildcard characters in a LIKE pattern.
+ *
+ * The wildcard characters "%" and "_" as well as backslash are prefixed with
+ * a backslash. Use this to do a search for a verbatim string without any
+ * wildcard behavior.
+ *
+ * For example, the following does a case-insensitive query for all rows whose
+ * name starts with $prefix:
+ * @code
+ * $result = db_query(
+ *   'SELECT * FROM person WHERE name LIKE :pattern',
+ *   array(':pattern' => db_like($prefix) . '%')
+ * );
+ * @endcode
+ *
+ * Backslash is defined as escape character for LIKE patterns in
+ * DatabaseCondition::mapConditionOperator().
+ *
+ * @param $string
+ *   The string to escape.
+ *
+ * @return
+ *   The escaped string.
+ */
+function db_like($string) {
+  return Database::getConnection()->escapeLike($string);
+}
+
+/**
+ * Retrieves the name of the currently active database driver.
+ *
+ * @return
+ *   The name of the currently active database driver.
+ */
+function db_driver() {
+  return Database::getConnection()->driver();
+}
+
+/**
+ * Closes the active database connection.
+ *
+ * @param $options
+ *   An array of options to control which connection is closed. Only the target
+ *   key has any meaning in this case.
+ */
+function db_close(array $options = array()) {
+  if (empty($options['target'])) {
+    $options['target'] = NULL;
+  }
+  Database::closeConnection($options['target']);
+}
+
+/**
+ * Retrieves a unique id.
+ *
+ * Use this function if for some reason you can't use a serial field. Using a
+ * serial field is preferred, and InsertQuery::execute() returns the value of
+ * the last ID inserted.
+ *
+ * @param $existing_id
+ *   After a database import, it might be that the sequences table is behind, so
+ *   by passing in a minimum ID, it can be assured that we never issue the same
+ *   ID.
+ *
+ * @return
+ *   An integer number larger than any number returned before for this sequence.
+ */
+function db_next_id($existing_id = 0) {
+  return Database::getConnection()->nextId($existing_id);
+}
+
+/**
+ * Returns a new DatabaseCondition, set to "OR" all conditions together.
+ *
+ * @return DatabaseCondition
+ */
+function db_or() {
+  return new DatabaseCondition('OR');
+}
+
+/**
+ * Returns a new DatabaseCondition, set to "AND" all conditions together.
+ *
+ * @return DatabaseCondition
+ */
+function db_and() {
+  return new DatabaseCondition('AND');
+}
+
+/**
+ * Returns a new DatabaseCondition, set to "XOR" all conditions together.
+ *
+ * @return DatabaseCondition
+ */
+function db_xor() {
+  return new DatabaseCondition('XOR');
+}
+
+/**
+ * Returns a new DatabaseCondition, set to the specified conjunction.
+ *
+ * Internal API function call.  The db_and(), db_or(), and db_xor()
+ * functions are preferred.
+ *
+ * @param $conjunction
+ *   The conjunction to use for query conditions (AND, OR or XOR).
+ * @return DatabaseCondition
+ */
+function db_condition($conjunction) {
+  return new DatabaseCondition($conjunction);
+}
+
+/**
+ * @} End of "defgroup database".
+ */
+
+
+/**
+ * @addtogroup schemaapi
+ * @{
+ */
+
+/**
+ * Creates a new table from a Drupal table definition.
+ *
+ * @param $name
+ *   The name of the table to create.
+ * @param $table
+ *   A Schema API table definition array.
+ */
+function db_create_table($name, $table) {
+  return Database::getConnection()->schema()->createTable($name, $table);
+}
+
+/**
+ * Returns an array of field names from an array of key/index column specifiers.
+ *
+ * This is usually an identity function but if a key/index uses a column prefix
+ * specification, this function extracts just the name.
+ *
+ * @param $fields
+ *   An array of key/index column specifiers.
+ *
+ * @return
+ *   An array of field names.
+ */
+function db_field_names($fields) {
+  return Database::getConnection()->schema()->fieldNames($fields);
+}
+
+/**
+ * Checks if an index exists in the given table.
+ *
+ * @param $table
+ *   The name of the table in drupal (no prefixing).
+ * @param $name
+ *   The name of the index in drupal (no prefixing).
+ *
+ * @return
+ *   TRUE if the given index exists, otherwise FALSE.
+ */
+function db_index_exists($table, $name) {
+  return Database::getConnection()->schema()->indexExists($table, $name);
+}
+
+/**
+ * Checks if a table exists.
+ *
+ * @param $table
+ *   The name of the table in drupal (no prefixing).
+ *
+ * @return
+ *   TRUE if the given table exists, otherwise FALSE.
+ */
+function db_table_exists($table) {
+  return Database::getConnection()->schema()->tableExists($table);
+}
+
+/**
+ * Checks if a column exists in the given table.
+ *
+ * @param $table
+ *   The name of the table in drupal (no prefixing).
+ * @param $field
+ *   The name of the field.
+ *
+ * @return
+ *   TRUE if the given column exists, otherwise FALSE.
+ */
+function db_field_exists($table, $field) {
+  return Database::getConnection()->schema()->fieldExists($table, $field);
+}
+
+/**
+ * Finds all tables that are like the specified base table name.
+ *
+ * @param $table_expression
+ *   An SQL expression, for example "simpletest%" (without the quotes).
+ *   BEWARE: this is not prefixed, the caller should take care of that.
+ *
+ * @return
+ *   Array, both the keys and the values are the matching tables.
+ */
+function db_find_tables($table_expression) {
+  return Database::getConnection()->schema()->findTables($table_expression);
+}
+
+function _db_create_keys_sql($spec) {
+  return Database::getConnection()->schema()->createKeysSql($spec);
+}
+
+/**
+ * Renames a table.
+ *
+ * @param $table
+ *   The current name of the table to be renamed.
+ * @param $new_name
+ *   The new name for the table.
+ */
+function db_rename_table($table, $new_name) {
+  return Database::getConnection()->schema()->renameTable($table, $new_name);
+}
+
+/**
+ * Drops a table.
+ *
+ * @param $table
+ *   The table to be dropped.
+ */
+function db_drop_table($table) {
+  return Database::getConnection()->schema()->dropTable($table);
+}
+
+/**
+ * Adds a new field to a table.
+ *
+ * @param $table
+ *   Name of the table to be altered.
+ * @param $field
+ *   Name of the field to be added.
+ * @param $spec
+ *   The field specification array, as taken from a schema definition. The
+ *   specification may also contain the key 'initial'; the newly-created field
+ *   will be set to the value of the key in all rows. This is most useful for
+ *   creating NOT NULL columns with no default value in existing tables.
+ * @param $keys_new
+ *   (optional) Keys and indexes specification to be created on the table along
+ *   with adding the field. The format is the same as a table specification, but
+ *   without the 'fields' element. If you are adding a type 'serial' field, you
+ *   MUST specify at least one key or index including it in this array. See
+ *   db_change_field() for more explanation why.
+ *
+ * @see db_change_field()
+ */
+function db_add_field($table, $field, $spec, $keys_new = array()) {
+  return Database::getConnection()->schema()->addField($table, $field, $spec, $keys_new);
+}
+
+/**
+ * Drops a field.
+ *
+ * @param $table
+ *   The table to be altered.
+ * @param $field
+ *   The field to be dropped.
+ */
+function db_drop_field($table, $field) {
+  return Database::getConnection()->schema()->dropField($table, $field);
+}
+
+/**
+ * Sets the default value for a field.
+ *
+ * @param $table
+ *   The table to be altered.
+ * @param $field
+ *   The field to be altered.
+ * @param $default
+ *   Default value to be set. NULL for 'default NULL'.
+ */
+function db_field_set_default($table, $field, $default) {
+  return Database::getConnection()->schema()->fieldSetDefault($table, $field, $default);
+}
+
+/**
+ * Sets a field to have no default value.
+ *
+ * @param $table
+ *   The table to be altered.
+ * @param $field
+ *   The field to be altered.
+ */
+function db_field_set_no_default($table, $field) {
+  return Database::getConnection()->schema()->fieldSetNoDefault($table, $field);
+}
+
+/**
+ * Adds a primary key to a database table.
+ *
+ * @param $table
+ *   Name of the table to be altered.
+ * @param $fields
+ *   Array of fields for the primary key.
+ */
+function db_add_primary_key($table, $fields) {
+  return Database::getConnection()->schema()->addPrimaryKey($table, $fields);
+}
+
+/**
+ * Drops the primary key of a database table.
+ *
+ * @param $table
+ *   Name of the table to be altered.
+ */
+function db_drop_primary_key($table) {
+  return Database::getConnection()->schema()->dropPrimaryKey($table);
+}
+
+/**
+ * Adds a unique key.
+ *
+ * @param $table
+ *   The table to be altered.
+ * @param $name
+ *   The name of the key.
+ * @param $fields
+ *   An array of field names.
+ */
+function db_add_unique_key($table, $name, $fields) {
+  return Database::getConnection()->schema()->addUniqueKey($table, $name, $fields);
+}
+
+/**
+ * Drops a unique key.
+ *
+ * @param $table
+ *   The table to be altered.
+ * @param $name
+ *   The name of the key.
+ */
+function db_drop_unique_key($table, $name) {
+  return Database::getConnection()->schema()->dropUniqueKey($table, $name);
+}
+
+/**
+ * Adds an index.
+ *
+ * @param $table
+ *   The table to be altered.
+ * @param $name
+ *   The name of the index.
+ * @param $fields
+ *   An array of field names.
+ */
+function db_add_index($table, $name, $fields) {
+  return Database::getConnection()->schema()->addIndex($table, $name, $fields);
+}
+
+/**
+ * Drops an index.
+ *
+ * @param $table
+ *   The table to be altered.
+ * @param $name
+ *   The name of the index.
+ */
+function db_drop_index($table, $name) {
+  return Database::getConnection()->schema()->dropIndex($table, $name);
+}
+
+/**
+ * Changes a field definition.
+ *
+ * IMPORTANT NOTE: To maintain database portability, you have to explicitly
+ * recreate all indices and primary keys that are using the changed field.
+ *
+ * That means that you have to drop all affected keys and indexes with
+ * db_drop_{primary_key,unique_key,index}() before calling db_change_field().
+ * To recreate the keys and indices, pass the key definitions as the optional
+ * $keys_new argument directly to db_change_field().
+ *
+ * For example, suppose you have:
+ * @code
+ * $schema['foo'] = array(
+ *   'fields' => array(
+ *     'bar' => array('type' => 'int', 'not null' => TRUE)
+ *   ),
+ *   'primary key' => array('bar')
+ * );
+ * @endcode
+ * and you want to change foo.bar to be type serial, leaving it as the primary
+ * key. The correct sequence is:
+ * @code
+ * db_drop_primary_key('foo');
+ * db_change_field('foo', 'bar', 'bar',
+ *   array('type' => 'serial', 'not null' => TRUE),
+ *   array('primary key' => array('bar')));
+ * @endcode
+ *
+ * The reasons for this are due to the different database engines:
+ *
+ * On PostgreSQL, changing a field definition involves adding a new field and
+ * dropping an old one which causes any indices, primary keys and sequences
+ * (from serial-type fields) that use the changed field to be dropped.
+ *
+ * On MySQL, all type 'serial' fields must be part of at least one key or index
+ * as soon as they are created. You cannot use
+ * db_add_{primary_key,unique_key,index}() for this purpose because the ALTER
+ * TABLE command will fail to add the column without a key or index
+ * specification. The solution is to use the optional $keys_new argument to
+ * create the key or index at the same time as field.
+ *
+ * You could use db_add_{primary_key,unique_key,index}() in all cases unless you
+ * are converting a field to be type serial. You can use the $keys_new argument
+ * in all cases.
+ *
+ * @param $table
+ *   Name of the table.
+ * @param $field
+ *   Name of the field to change.
+ * @param $field_new
+ *   New name for the field (set to the same as $field if you don't want to
+ *   change the name).
+ * @param $spec
+ *   The field specification for the new field.
+ * @param $keys_new
+ *   (optional) Keys and indexes specification to be created on the table along
+ *   with changing the field. The format is the same as a table specification
+ *   but without the 'fields' element.
+ */
+function db_change_field($table, $field, $field_new, $spec, $keys_new = array()) {
+  return Database::getConnection()->schema()->changeField($table, $field, $field_new, $spec, $keys_new);
+}
+
+/**
+ * @} End of "addtogroup schemaapi".
+ */
+
+/**
+ * Sets a session variable specifying the lag time for ignoring a slave server.
+ */
+function db_ignore_slave() {
+  $connection_info = Database::getConnectionInfo();
+  // Only set ignore_slave_server if there are slave servers being used, which
+  // is assumed if there are more than one.
+  if (count($connection_info) > 1) {
+    // Five minutes is long enough to allow the slave to break and resume
+    // interrupted replication without causing problems on the Drupal site from
+    // the old data.
+    $duration = variable_get('maximum_replication_lag', 300);
+    // Set session variable with amount of time to delay before using slave.
+    $_SESSION['ignore_slave_server'] = REQUEST_TIME + $duration;
+  }
+}