Chris@0: <?php
Chris@0: 
Chris@0: /**
Chris@0:  * @file
Chris@0:  * Hooks related to the Database system and the Schema API.
Chris@0:  */
Chris@0: 
Chris@0: use Drupal\Core\Database\Query\Condition;
Chris@0: 
Chris@0: /**
Chris@0:  * @defgroup database Database abstraction layer
Chris@0:  * @{
Chris@0:  * Allow the use of different database servers using the same code base.
Chris@0:  *
Chris@0:  * @section sec_intro Overview
Chris@0:  * Drupal's database abstraction layer provides a unified database query API
Chris@0:  * that can query different underlying databases. It is built upon PHP's
Chris@0:  * PDO (PHP Data Objects) database API, and inherits much of its syntax and
Chris@0:  * semantics. Besides providing a unified API for database queries, the
Chris@0:  * database abstraction layer also provides a structured way to construct
Chris@0:  * complex queries, and it protects the database by using good security
Chris@0:  * practices.
Chris@0:  *
Chris@0:  * For more detailed information on the database abstraction layer, see
Chris@0:  * https://www.drupal.org/developing/api/database.
Chris@0:  *
Chris@0:  * @section sec_entity Querying entities
Chris@0:  * Any query on Drupal entities or fields should use the Entity Query API. See
Chris@0:  * the @link entity_api entity API topic @endlink for more information.
Chris@0:  *
Chris@0:  * @section sec_simple Simple SELECT database queries
Chris@0:  * For simple SELECT queries that do not involve entities, the Drupal database
Chris@0:  * abstraction layer provides the functions db_query() and db_query_range(),
Chris@0:  * which execute SELECT queries (optionally with range limits) and return result
Chris@0:  * sets that you can iterate over using foreach loops. (The result sets are
Chris@0:  * objects implementing the \Drupal\Core\Database\StatementInterface interface.)
Chris@0:  * You can use the simple query functions for query strings that are not
Chris@0:  * dynamic (except for placeholders, see below), and that you are certain will
Chris@0:  * work in any database engine. See @ref sec_dynamic below if you have a more
Chris@0:  * complex query, or a query whose syntax would be different in some databases.
Chris@0:  *
Chris@0:  * As a note, db_query() and similar functions are wrappers on connection object
Chris@0:  * methods. In most classes, you should use dependency injection and the
Chris@0:  * database connection object instead of these wrappers; See @ref sec_connection
Chris@0:  * below for details.
Chris@0:  *
Chris@0:  * To use the simple database query functions, you will need to make a couple of
Chris@0:  * modifications to your bare SQL query:
Chris@0:  * - Enclose your table name in {}. Drupal allows site builders to use
Chris@0:  *   database table name prefixes, so you cannot be sure what the actual
Chris@0:  *   name of the table will be. So, use the name that is in the hook_schema(),
Chris@0:  *   enclosed in {}, and Drupal will calculate the right name.
Chris@0:  * - Instead of putting values for conditions into the query, use placeholders.
Chris@0:  *   The placeholders are named and start with :, and they take the place of
Chris@0:  *   putting variables directly into the query, to protect against SQL
Chris@0:  *   injection attacks.
Chris@0:  * - LIMIT syntax differs between databases, so if you have a ranged query,
Chris@0:  *   use db_query_range() instead of db_query().
Chris@0:  *
Chris@0:  * For example, if the query you want to run is:
Chris@0:  * @code
Chris@0:  * SELECT e.id, e.title, e.created FROM example e WHERE e.uid = $uid
Chris@0:  *   ORDER BY e.created DESC LIMIT 0, 10;
Chris@0:  * @endcode
Chris@0:  * you would do it like this:
Chris@0:  * @code
Chris@0:  * $result = db_query_range('SELECT e.id, e.title, e.created
Chris@0:  *   FROM {example} e
Chris@0:  *   WHERE e.uid = :uid
Chris@0:  *   ORDER BY e.created DESC',
Chris@0:  *   0, 10, array(':uid' => $uid));
Chris@0:  * foreach ($result as $record) {
Chris@0:  *   // Perform operations on $record->title, etc. here.
Chris@0:  * }
Chris@0:  * @endcode
Chris@0:  *
Chris@0:  * Note that if your query has a string condition, like:
Chris@0:  * @code
Chris@0:  * WHERE e.my_field = 'foo'
Chris@0:  * @endcode
Chris@0:  * when you convert it to placeholders, omit the quotes:
Chris@0:  * @code
Chris@0:  * WHERE e.my_field = :my_field
Chris@0:  * ... array(':my_field' => 'foo') ...
Chris@0:  * @endcode
Chris@0:  *
Chris@0:  * @section sec_dynamic Dynamic SELECT queries
Chris@0:  * For SELECT queries where the simple query API described in @ref sec_simple
Chris@0:  * will not work well, you need to use the dynamic query API. However, you
Chris@0:  * should still use the Entity Query API if your query involves entities or
Chris@0:  * fields (see the @link entity_api Entity API topic @endlink for more on
Chris@0:  * entity queries).
Chris@0:  *
Chris@0:  * As a note, db_select() and similar functions are wrappers on connection
Chris@0:  * object methods. In most classes, you should use dependency injection and the
Chris@0:  * database connection object instead of these wrappers; See @ref sec_connection
Chris@0:  * below for details.
Chris@0:  *
Chris@0:  * The dynamic query API lets you build up a query dynamically using method
Chris@0:  * calls. As an illustration, the query example from @ref sec_simple above
Chris@0:  * would be:
Chris@0:  * @code
Chris@0:  * $result = db_select('example', 'e')
Chris@0:  *   ->fields('e', array('id', 'title', 'created'))
Chris@0:  *   ->condition('e.uid', $uid)
Chris@0:  *   ->orderBy('e.created', 'DESC')
Chris@0:  *   ->range(0, 10)
Chris@0:  *   ->execute();
Chris@0:  * @endcode
Chris@0:  *
Chris@0:  * There are also methods to join to other tables, add fields with aliases,
Chris@0:  * isNull() to have a @code WHERE e.foo IS NULL @endcode condition, etc. See
Chris@0:  * https://www.drupal.org/developing/api/database for many more details.
Chris@0:  *
Chris@0:  * One note on chaining: It is common in the dynamic database API to chain
Chris@0:  * method calls (as illustrated here), because most of the query methods modify
Chris@0:  * the query object and then return the modified query as their return
Chris@0:  * value. However, there are some important exceptions; these methods (and some
Chris@0:  * others) do not support chaining:
Chris@0:  * - join(), innerJoin(), etc.: These methods return the joined table alias.
Chris@0:  * - addField(): This method returns the field alias.
Chris@0:  * Check the documentation for the query method you are using to see if it
Chris@0:  * returns the query or something else, and only chain methods that return the
Chris@0:  * query.
Chris@0:  *
Chris@0:  * @section_insert INSERT, UPDATE, and DELETE queries
Chris@0:  * INSERT, UPDATE, and DELETE queries need special care in order to behave
Chris@0:  * consistently across databases; you should never use db_query() to run
Chris@0:  * an INSERT, UPDATE, or DELETE query. Instead, use functions db_insert(),
Chris@0:  * db_update(), and db_delete() to obtain a base query on your table, and then
Chris@0:  * add dynamic conditions (as illustrated in @ref sec_dynamic above).
Chris@0:  *
Chris@0:  * As a note, db_insert() and similar functions are wrappers on connection
Chris@0:  * object methods. In most classes, you should use dependency injection and the
Chris@0:  * database connection object instead of these wrappers; See @ref sec_connection
Chris@0:  * below for details.
Chris@0:  *
Chris@0:  * For example, if your query is:
Chris@0:  * @code
Chris@0:  * INSERT INTO example (id, uid, path, name) VALUES (1, 2, 'path', 'Name');
Chris@0:  * @endcode
Chris@0:  * You can execute it via:
Chris@0:  * @code
Chris@0:  * $fields = array('id' => 1, 'uid' => 2, 'path' => 'path', 'name' => 'Name');
Chris@0:  * db_insert('example')
Chris@0:  *   ->fields($fields)
Chris@0:  *   ->execute();
Chris@0:  * @endcode
Chris@0:  *
Chris@0:  * @section sec_transaction Transactions
Chris@0:  * Drupal supports transactions, including a transparent fallback for
Chris@0:  * databases that do not support transactions. To start a new transaction,
Chris@0:  * call @code $txn = db_transaction(); @endcode The transaction will
Chris@0:  * remain open for as long as the variable $txn remains in scope; when $txn is
Chris@0:  * destroyed, the transaction will be committed. If your transaction is nested
Chris@0:  * inside of another then Drupal will track each transaction and only commit
Chris@0:  * the outer-most transaction when the last transaction object goes out out of
Chris@0:  * scope (when all relevant queries have completed successfully).
Chris@0:  *
Chris@0:  * Example:
Chris@0:  * @code
Chris@0:  * function my_transaction_function() {
Chris@0:  *   // The transaction opens here.
Chris@0:  *   $txn = db_transaction();
Chris@0:  *
Chris@0:  *   try {
Chris@0:  *     $id = db_insert('example')
Chris@0:  *       ->fields(array(
Chris@0:  *         'field1' => 'mystring',
Chris@0:  *         'field2' => 5,
Chris@0:  *       ))
Chris@0:  *       ->execute();
Chris@0:  *
Chris@0:  *     my_other_function($id);
Chris@0:  *
Chris@0:  *     return $id;
Chris@0:  *   }
Chris@0:  *   catch (Exception $e) {
Chris@0:  *     // Something went wrong somewhere, so roll back now.
Chris@0:  *     $txn->rollBack();
Chris@0:  *     // Log the exception to watchdog.
Chris@0:  *     watchdog_exception('type', $e);
Chris@0:  *   }
Chris@0:  *
Chris@0:  *   // $txn goes out of scope here.  Unless the transaction was rolled back, it
Chris@0:  *   // gets automatically committed here.
Chris@0:  * }
Chris@0:  *
Chris@0:  * function my_other_function($id) {
Chris@0:  *   // The transaction is still open here.
Chris@0:  *
Chris@0:  *   if ($id % 2 == 0) {
Chris@0:  *     db_update('example')
Chris@0:  *       ->condition('id', $id)
Chris@0:  *       ->fields(array('field2' => 10))
Chris@0:  *       ->execute();
Chris@0:  *   }
Chris@0:  * }
Chris@0:  * @endcode
Chris@0:  *
Chris@0:  * @section sec_connection Database connection objects
Chris@0:  * The examples here all use functions like db_select() and db_query(), which
Chris@0:  * can be called from any Drupal method or function code. In some classes, you
Chris@0:  * may already have a database connection object in a member variable, or it may
Chris@0:  * be passed into a class constructor via dependency injection. If that is the
Chris@0:  * case, you can look at the code for db_select() and the other functions to see
Chris@0:  * how to get a query object from your connection variable. For example:
Chris@0:  * @code
Chris@0:  * $query = $connection->select('example', 'e');
Chris@0:  * @endcode
Chris@0:  * would be the equivalent of
Chris@0:  * @code
Chris@0:  * $query = db_select('example', 'e');
Chris@0:  * @endcode
Chris@0:  * if you had a connection object variable $connection available to use. See
Chris@0:  * also the @link container Services and Dependency Injection topic. @endlink
Chris@0:  *
Chris@0:  * @see https://www.drupal.org/developing/api/database
Chris@0:  * @see entity_api
Chris@0:  * @see schemaapi
Chris@0:  *
Chris@0:  * @}
Chris@0:  */
Chris@0: 
Chris@0: /**
Chris@0:  * @defgroup schemaapi Schema API
Chris@0:  * @{
Chris@0:  * API to handle database schemas.
Chris@0:  *
Chris@0:  * A Drupal schema definition is an array structure representing one or
Chris@0:  * more tables and their related keys and indexes. A schema is defined by
Chris@0:  * hook_schema(), which usually lives in a modulename.install file.
Chris@0:  *
Chris@0:  * By implementing hook_schema() and specifying the tables your module
Chris@0:  * declares, you can easily create and drop these tables on all
Chris@0:  * supported database engines. You don't have to deal with the
Chris@0:  * different SQL dialects for table creation and alteration of the
Chris@0:  * supported database engines.
Chris@0:  *
Chris@0:  * hook_schema() should return an array with a key for each table that
Chris@0:  * the module defines.
Chris@0:  *
Chris@0:  * The following keys are defined:
Chris@0:  *   - 'description': A string in non-markup plain text describing this table
Chris@0:  *     and its purpose. References to other tables should be enclosed in
Chris@0:  *     curly-brackets. For example, the node_field_revision table
Chris@0:  *     description field might contain "Stores per-revision title and
Chris@0:  *     body data for each {node}."
Chris@0:  *   - 'fields': An associative array ('fieldname' => specification)
Chris@0:  *     that describes the table's database columns. The specification
Chris@0:  *     is also an array. The following specification parameters are defined:
Chris@0:  *     - 'description': A string in non-markup plain text describing this field
Chris@0:  *       and its purpose. References to other tables should be enclosed in
Chris@0:  *       curly-brackets. For example, the node table vid field
Chris@0:  *       description might contain "Always holds the largest (most
Chris@0:  *       recent) {node_field_revision}.vid value for this nid."
Chris@0:  *     - 'type': The generic datatype: 'char', 'varchar', 'text', 'blob', 'int',
Chris@0:  *       'float', 'numeric', or 'serial'. Most types just map to the according
Chris@0:  *       database engine specific datatypes. Use 'serial' for auto incrementing
Chris@0:  *       fields. This will expand to 'INT auto_increment' on MySQL.
Chris@0:  *       A special 'varchar_ascii' type is also available for limiting machine
Chris@0:  *       name field to US ASCII characters.
Chris@0:  *     - 'mysql_type', 'pgsql_type', 'sqlite_type', etc.: If you need to
Chris@0:  *       use a record type not included in the officially supported list
Chris@0:  *       of types above, you can specify a type for each database
Chris@0:  *       backend. In this case, you can leave out the type parameter,
Chris@0:  *       but be advised that your schema will fail to load on backends that
Chris@0:  *       do not have a type specified. A possible solution can be to
Chris@0:  *       use the "text" type as a fallback.
Chris@0:  *     - 'serialize': A boolean indicating whether the field will be stored as
Chris@0:  *       a serialized string.
Chris@0:  *     - 'size': The data size: 'tiny', 'small', 'medium', 'normal',
Chris@0:  *       'big'. This is a hint about the largest value the field will
Chris@0:  *       store and determines which of the database engine specific
Chris@0:  *       datatypes will be used (e.g. on MySQL, TINYINT vs. INT vs. BIGINT).
Chris@0:  *       'normal', the default, selects the base type (e.g. on MySQL,
Chris@0:  *       INT, VARCHAR, BLOB, etc.).
Chris@0:  *       Not all sizes are available for all data types. See
Chris@0:  *       DatabaseSchema::getFieldTypeMap() for possible combinations.
Chris@0:  *     - 'not null': If true, no NULL values will be allowed in this
Chris@0:  *       database column. Defaults to false.
Chris@0:  *     - 'default': The field's default value. The PHP type of the
Chris@0:  *       value matters: '', '0', and 0 are all different. If you
Chris@0:  *       specify '0' as the default value for a type 'int' field it
Chris@0:  *       will not work because '0' is a string containing the
Chris@0:  *       character "zero", not an integer.
Chris@0:  *     - 'length': The maximal length of a type 'char', 'varchar' or 'text'
Chris@0:  *       field. Ignored for other field types.
Chris@0:  *     - 'unsigned': A boolean indicating whether a type 'int', 'float'
Chris@0:  *       and 'numeric' only is signed or unsigned. Defaults to
Chris@0:  *       FALSE. Ignored for other field types.
Chris@0:  *     - 'precision', 'scale': For type 'numeric' fields, indicates
Chris@0:  *       the precision (total number of significant digits) and scale
Chris@0:  *       (decimal digits right of the decimal point). Both values are
Chris@0:  *       mandatory. Ignored for other field types.
Chris@0:  *     - 'binary': A boolean indicating that MySQL should force 'char',
Chris@0:  *       'varchar' or 'text' fields to use case-sensitive binary collation.
Chris@0:  *       This has no effect on other database types for which case sensitivity
Chris@0:  *       is already the default behavior.
Chris@0:  *     All parameters apart from 'type' are optional except that type
Chris@0:  *     'numeric' columns must specify 'precision' and 'scale', and type
Chris@0:  *     'varchar' must specify the 'length' parameter.
Chris@0:  *  - 'primary key': An array of one or more key column specifiers (see below)
Chris@0:  *    that form the primary key.
Chris@0:  *  - 'unique keys': An associative array of unique keys ('keyname' =>
Chris@0:  *    specification). Each specification is an array of one or more
Chris@0:  *    key column specifiers (see below) that form a unique key on the table.
Chris@0:  *  - 'foreign keys': An associative array of relations ('my_relation' =>
Chris@0:  *    specification). Each specification is an array containing the name of
Chris@0:  *    the referenced table ('table'), and an array of column mappings
Chris@0:  *    ('columns'). Column mappings are defined by key pairs ('source_column' =>
Chris@0:  *    'referenced_column'). This key is for documentation purposes only; foreign
Chris@0:  *    keys are not created in the database, nor are they enforced by Drupal.
Chris@0:  *  - 'indexes':  An associative array of indexes ('indexname' =>
Chris@0:  *    specification). Each specification is an array of one or more
Chris@0:  *    key column specifiers (see below) that form an index on the
Chris@0:  *    table.
Chris@0:  *
Chris@0:  * A key column specifier is either a string naming a column or an
Chris@0:  * array of two elements, column name and length, specifying a prefix
Chris@0:  * of the named column.
Chris@0:  *
Chris@0:  * As an example, here is a SUBSET of the schema definition for
Chris@0:  * Drupal's 'node' table. It show four fields (nid, vid, type, and
Chris@0:  * title), the primary key on field 'nid', a unique key named 'vid' on
Chris@0:  * field 'vid', and two indexes, one named 'nid' on field 'nid' and
Chris@0:  * one named 'node_title_type' on the field 'title' and the first four
Chris@0:  * bytes of the field 'type':
Chris@0:  *
Chris@0:  * @code
Chris@0:  * $schema['node'] = array(
Chris@0:  *   'description' => 'The base table for nodes.',
Chris@0:  *   'fields' => array(
Chris@0:  *     'nid'       => array('type' => 'serial', 'unsigned' => TRUE, 'not null' => TRUE),
Chris@0:  *     'vid'       => array('type' => 'int', 'unsigned' => TRUE, 'not null' => TRUE,'default' => 0),
Chris@0:  *     'type'      => array('type' => 'varchar','length' => 32,'not null' => TRUE, 'default' => ''),
Chris@0:  *     'language'  => array('type' => 'varchar','length' => 12,'not null' => TRUE,'default' => ''),
Chris@0:  *     'title'     => array('type' => 'varchar','length' => 255,'not null' => TRUE, 'default' => ''),
Chris@0:  *     'uid'       => array('type' => 'int', 'not null' => TRUE, 'default' => 0),
Chris@0:  *     'status'    => array('type' => 'int', 'not null' => TRUE, 'default' => 1),
Chris@0:  *     'created'   => array('type' => 'int', 'not null' => TRUE, 'default' => 0),
Chris@0:  *     'changed'   => array('type' => 'int', 'not null' => TRUE, 'default' => 0),
Chris@0:  *     'comment'   => array('type' => 'int', 'not null' => TRUE, 'default' => 0),
Chris@0:  *     'promote'   => array('type' => 'int', 'not null' => TRUE, 'default' => 0),
Chris@0:  *     'moderate'  => array('type' => 'int', 'not null' => TRUE,'default' => 0),
Chris@0:  *     'sticky'    => array('type' => 'int', 'not null' => TRUE, 'default' => 0),
Chris@0:  *     'translate' => array('type' => 'int', 'not null' => TRUE, 'default' => 0),
Chris@0:  *   ),
Chris@0:  *   'indexes' => array(
Chris@0:  *     'node_changed'        => array('changed'),
Chris@0:  *     'node_created'        => array('created'),
Chris@0:  *     'node_moderate'       => array('moderate'),
Chris@0:  *     'node_frontpage'      => array('promote', 'status', 'sticky', 'created'),
Chris@0:  *     'node_status_type'    => array('status', 'type', 'nid'),
Chris@0:  *     'node_title_type'     => array('title', array('type', 4)),
Chris@0:  *     'node_type'           => array(array('type', 4)),
Chris@0:  *     'uid'                 => array('uid'),
Chris@0:  *     'translate'           => array('translate'),
Chris@0:  *   ),
Chris@0:  *   'unique keys' => array(
Chris@0:  *     'vid' => array('vid'),
Chris@0:  *   ),
Chris@0:  *   // For documentation purposes only; foreign keys are not created in the
Chris@0:  *   // database.
Chris@0:  *   'foreign keys' => array(
Chris@0:  *     'node_revision' => array(
Chris@0:  *       'table' => 'node_field_revision',
Chris@0:  *       'columns' => array('vid' => 'vid'),
Chris@0:  *      ),
Chris@0:  *     'node_author' => array(
Chris@0:  *       'table' => 'users',
Chris@0:  *       'columns' => array('uid' => 'uid'),
Chris@0:  *      ),
Chris@0:  *    ),
Chris@0:  *   'primary key' => array('nid'),
Chris@0:  * );
Chris@0:  * @endcode
Chris@0:  *
Chris@0:  * @see drupal_install_schema()
Chris@0:  *
Chris@0:  * @}
Chris@0:  */
Chris@0: 
Chris@0: /**
Chris@0:  * @addtogroup hooks
Chris@0:  * @{
Chris@0:  */
Chris@0: 
Chris@0: /**
Chris@0:  * Perform alterations to a structured query.
Chris@0:  *
Chris@0:  * Structured (aka dynamic) queries that have tags associated may be altered by any module
Chris@0:  * before the query is executed.
Chris@0:  *
Chris@0:  * @param $query
Chris@0:  *   A Query object describing the composite parts of a SQL query.
Chris@0:  *
Chris@0:  * @see hook_query_TAG_alter()
Chris@0:  * @see node_query_node_access_alter()
Chris@0:  * @see AlterableInterface
Chris@0:  * @see SelectInterface
Chris@0:  *
Chris@0:  * @ingroup database
Chris@0:  */
Chris@0: function hook_query_alter(Drupal\Core\Database\Query\AlterableInterface $query) {
Chris@0:   if ($query->hasTag('micro_limit')) {
Chris@0:     $query->range(0, 2);
Chris@0:   }
Chris@0: }
Chris@0: 
Chris@0: /**
Chris@0:  * Perform alterations to a structured query for a given tag.
Chris@0:  *
Chris@0:  * @param $query
Chris@0:  *   An Query object describing the composite parts of a SQL query.
Chris@0:  *
Chris@0:  * @see hook_query_alter()
Chris@0:  * @see node_query_node_access_alter()
Chris@0:  * @see AlterableInterface
Chris@0:  * @see SelectInterface
Chris@0:  *
Chris@0:  * @ingroup database
Chris@0:  */
Chris@0: function hook_query_TAG_alter(Drupal\Core\Database\Query\AlterableInterface $query) {
Chris@0:   // Skip the extra expensive alterations if site has no node access control modules.
Chris@0:   if (!node_access_view_all_nodes()) {
Chris@0:     // Prevent duplicates records.
Chris@0:     $query->distinct();
Chris@0:     // The recognized operations are 'view', 'update', 'delete'.
Chris@0:     if (!$op = $query->getMetaData('op')) {
Chris@0:       $op = 'view';
Chris@0:     }
Chris@0:     // Skip the extra joins and conditions for node admins.
Chris@0:     if (!\Drupal::currentUser()->hasPermission('bypass node access')) {
Chris@0:       // The node_access table has the access grants for any given node.
Chris@0:       $access_alias = $query->join('node_access', 'na', '%alias.nid = n.nid');
Chris@0:       $or = new Condition('OR');
Chris@0:       // If any grant exists for the specified user, then user has access to the node for the specified operation.
Chris@0:       foreach (node_access_grants($op, $query->getMetaData('account')) as $realm => $gids) {
Chris@0:         foreach ($gids as $gid) {
Chris@0:           $or->condition((new Condition('AND'))
Chris@0:             ->condition($access_alias . '.gid', $gid)
Chris@0:             ->condition($access_alias . '.realm', $realm)
Chris@0:           );
Chris@0:         }
Chris@0:       }
Chris@0: 
Chris@0:       if (count($or->conditions())) {
Chris@0:         $query->condition($or);
Chris@0:       }
Chris@0: 
Chris@0:       $query->condition($access_alias . 'grant_' . $op, 1, '>=');
Chris@0:     }
Chris@0:   }
Chris@0: }
Chris@0: 
Chris@0: /**
Chris@0:  * Define the current version of the database schema.
Chris@0:  *
Chris@0:  * A Drupal schema definition is an array structure representing one or more
Chris@0:  * tables and their related keys and indexes. A schema is defined by
Chris@0:  * hook_schema() which must live in your module's .install file.
Chris@0:  *
Chris@0:  * The tables declared by this hook will be automatically created when the
Chris@0:  * module is installed, and removed when the module is uninstalled. This happens
Chris@0:  * before hook_install() is invoked, and after hook_uninstall() is invoked,
Chris@0:  * respectively.
Chris@0:  *
Chris@0:  * By declaring the tables used by your module via an implementation of
Chris@0:  * hook_schema(), these tables will be available on all supported database
Chris@0:  * engines. You don't have to deal with the different SQL dialects for table
Chris@0:  * creation and alteration of the supported database engines.
Chris@0:  *
Chris@0:  * See the Schema API Handbook at https://www.drupal.org/node/146843 for details
Chris@0:  * on schema definition structures. Note that foreign key definitions are for
Chris@0:  * documentation purposes only; foreign keys are not created in the database,
Chris@0:  * nor are they enforced by Drupal.
Chris@0:  *
Chris@0:  * @return array
Chris@0:  *   A schema definition structure array. For each element of the
Chris@0:  *   array, the key is a table name and the value is a table structure
Chris@0:  *   definition.
Chris@0:  *
Chris@0:  * @ingroup schemaapi
Chris@0:  */
Chris@0: function hook_schema() {
Chris@0:   $schema['node'] = [
Chris@0:     // Example (partial) specification for table "node".
Chris@0:     'description' => 'The base table for nodes.',
Chris@0:     'fields' => [
Chris@0:       'nid' => [
Chris@0:         'description' => 'The primary identifier for a node.',
Chris@0:         'type' => 'serial',
Chris@0:         'unsigned' => TRUE,
Chris@0:         'not null' => TRUE,
Chris@0:       ],
Chris@0:       'vid' => [
Chris@0:         'description' => 'The current {node_field_revision}.vid version identifier.',
Chris@0:         'type' => 'int',
Chris@0:         'unsigned' => TRUE,
Chris@0:         'not null' => TRUE,
Chris@0:         'default' => 0,
Chris@0:       ],
Chris@0:       'type' => [
Chris@0:         'description' => 'The type of this node.',
Chris@0:         'type' => 'varchar',
Chris@0:         'length' => 32,
Chris@0:         'not null' => TRUE,
Chris@0:         'default' => '',
Chris@0:       ],
Chris@0:       'title' => [
Chris@0:         'description' => 'The node title.',
Chris@0:         'type' => 'varchar',
Chris@0:         'length' => 255,
Chris@0:         'not null' => TRUE,
Chris@0:         'default' => '',
Chris@0:       ],
Chris@0:     ],
Chris@0:     'indexes' => [
Chris@0:       'node_changed'        => ['changed'],
Chris@0:       'node_created'        => ['created'],
Chris@0:     ],
Chris@0:     'unique keys' => [
Chris@0:       'nid_vid' => ['nid', 'vid'],
Chris@0:       'vid'     => ['vid'],
Chris@0:     ],
Chris@0:     // For documentation purposes only; foreign keys are not created in the
Chris@0:     // database.
Chris@0:     'foreign keys' => [
Chris@0:       'node_revision' => [
Chris@0:         'table' => 'node_field_revision',
Chris@0:         'columns' => ['vid' => 'vid'],
Chris@0:       ],
Chris@0:       'node_author' => [
Chris@0:         'table' => 'users',
Chris@0:         'columns' => ['uid' => 'uid'],
Chris@0:       ],
Chris@0:     ],
Chris@0:     'primary key' => ['nid'],
Chris@0:   ];
Chris@0:   return $schema;
Chris@0: }
Chris@0: 
Chris@0: /**
Chris@0:  * @} End of "addtogroup hooks".
Chris@0:  */