- Patch #1464940 by amateescu: move database.inc to proper location.

core/includes/database.inc

+<?php
+
+use Drupal\Core\Database\Database;
+use Drupal\Core\Database\Query\Condition;
+
+/**
+ * @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, and the Tablesort Extender for generating appropriate queries
+ * for sortable tables.
+ *
+ * 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 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', 0, 10, array(':uid' => $uid));
+ * foreach ($result as $record) {
+ *   // Perform operations on $node->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
+ *
+ * @link http://drupal.org/developing/api/database
+ */
+
+
+/**
+ * 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 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 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.
+ *
+ * You must use a query builder like db_select() in order to use db_like() on
+ * all supported database systems. Using db_like() with db_query() or
+ * db_query_range() is not supported.
+ *
+ * For example, the following does a case-insensitive query for all rows whose
+ * name starts with $prefix:
+ * @code
+ * $result = db_select('person', 'p')
+ *   ->fields('p')
+ *   ->condition('name', db_like($prefix) . '%', 'LIKE')
+ *   ->execute()
+ *   ->fetchAll();
+ * @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 Condition
+ */
+function db_or() {
+  return new Condition('OR');
+}
+
+/**
+ * Returns a new DatabaseCondition, set to "AND" all conditions together.
+ *
+ * @return Condition
+ */
+function db_and() {
+  return new Condition('AND');
+}
+
+/**
+ * Returns a new DatabaseCondition, set to "XOR" all conditions together.
+ *
+ * @return Condition
+ */
+function db_xor() {
+  return new Condition('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 $conjunction
+ *   The conjunction to use for query conditions (AND, OR or XOR).
+ * @return Condition
+ */
+function db_condition($conjunction) {
+  return new Condition($conjunction);
+}
+
+/**
+ * @} End of "defgroup database".
+ */
+
+
+/**
+ * @ingroup 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 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 "ingroup 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;
+  }
+}