database.inc

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.

File

drupal/core/includes/database.inc
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<?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
 * Drupal\Core\Database\Query\PagerSelectExtender 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 $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
 *
 * @link http://drupal.org/developing/api/database @endlink
 */

/**
 * 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".
 */

/**
 * @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;
  }
}

Functions

Namesort descending Description
db_add_field Adds a new field to a table.
db_add_index Adds an index.
db_add_primary_key Adds a primary key to a database table.
db_add_unique_key Adds a unique key.
db_and Returns a new DatabaseCondition, set to "AND" all conditions together.
db_change_field Changes a field definition.
db_close Closes the active database connection.
db_condition Returns a new DatabaseCondition, set to the specified conjunction.
db_create_table Creates a new table from a Drupal table definition.
db_delete Returns a new DeleteQuery object for the active database.
db_driver Retrieves the name of the currently active database driver.
db_drop_field Drops a field.
db_drop_index Drops an index.
db_drop_primary_key Drops the primary key of a database table.
db_drop_table Drops a table.
db_drop_unique_key Drops a unique key.
db_escape_field Restricts a dynamic column or constraint name to safe characters.
db_escape_table Restricts a dynamic table name to safe characters.
db_field_exists Checks if a column exists in the given table.
db_field_names Returns an array of field names from an array of key/index column specifiers.
db_field_set_default Sets the default value for a field.
db_field_set_no_default Sets a field to have no default value.
db_find_tables Finds all tables that are like the specified base table name.
db_ignore_slave Sets a session variable specifying the lag time for ignoring a slave server.
db_index_exists Checks if an index exists in the given table.
db_insert Returns a new InsertQuery object for the active database.
db_like Escapes characters that work as wildcard characters in a LIKE pattern.
db_merge Returns a new MergeQuery object for the active database.
db_next_id Retrieves a unique id.
db_or Returns a new DatabaseCondition, set to "OR" all conditions together.
db_query Executes an arbitrary query string against the active database.
db_query_range Executes a query against the active database, restricted to a range.
db_query_temporary Executes a query string and saves the result set to a temporary table.
db_rename_table Renames a table.
db_select Returns a new SelectQuery object for the active database.
db_set_active Sets a new active database.
db_table_exists Checks if a table exists.
db_transaction Returns a new transaction object for the active database.
db_truncate Returns a new TruncateQuery object for the active database.
db_update Returns a new UpdateQuery object for the active database.
db_xor Returns a new DatabaseCondition, set to "XOR" all conditions together.
_db_create_keys_sql