class GroupwiseMax

Relationship handler that allows a groupwise maximum of the linked in table. For a definition, see: http://dev.mysql.com/doc/refman/5.0/en/example-maximum-column-group-row.... In lay terms, instead of joining to get all matching records in the linked table, we get only one record, a 'representative record' picked according to a given criteria.

Example: Suppose we have a term view that gives us the terms: Horse, Cat, Aardvark. We wish to show for each term the most recent node of that term. What we want is some kind of relationship from term to node. But a regular relationship will give us all the nodes for each term, giving the view multiple rows per term. What we want is just one representative node per term, the node that is the 'best' in some way: eg, the most recent, the most commented on, the first in alphabetical order.

This handler gives us that kind of relationship from term to node. The method of choosing the 'best' implemented with a sort that the user selects in the relationship settings.

So if we want our term view to show the most commented node for each term, add the relationship and in its options, pick the 'Comment count' sort.

Relationship definition

'outer field': The outer field to substitute into the correlated subquery. This must be the full field name, not the alias. Eg: 'term_data.tid'.
'argument table', 'argument field': These options define a views argument that the subquery must add to itself to filter by the main view. Example: the main view shows terms, this handler is being used to get to the nodes base table. Your argument must be 'term_node', 'tid', as this is the argument that should be added to a node view to filter on terms.

A note on performance: This relationship uses a correlated subquery, which is expensive. Subsequent versions of this handler could also implement the alternative way of doing this, with a join -- though this looks like it could be pretty messy to implement. This is also an expensive method, so providing both methods and allowing the user to choose which one works fastest for their data might be the best way. If your use of this relationship handler is likely to result in large data sets, you might want to consider storing statistics in a separate table, in the same way as node_comment_statistics.

Plugin annotation


@Plugin(
  id = "groupwise_max"
)

Hierarchy

class \Drupal\Component\Plugin\PluginBase implements PluginInspectionInterface
- class \Drupal\views\Plugin\views\PluginBase
  - class \Drupal\views\Plugin\views\HandlerBase
    class \Drupal\views\Plugin\views\relationship\RelationshipPluginBase
    class \Drupal\views\Plugin\views\relationship\GroupwiseMax

Expanded class hierarchy of GroupwiseMax

File

drupal/core/modules/views/lib/Drupal/views/Plugin/views/relationship/GroupwiseMax.php, line 66: Definition of Drupal\views\Plugin\views\relationship\GroupwiseMax.

Namespace

Drupal\views\Plugin\views\relationship

View source

class GroupwiseMax extends RelationshipPluginBase {

  /**
   * Defines default values for options.
   */
  protected function defineOptions() {
    $options = parent::defineOptions();
    $options['subquery_sort'] = array(
      'default' => NULL,
    );

    // Descending more useful.
    $options['subquery_order'] = array(
      'default' => 'DESC',
    );
    $options['subquery_regenerate'] = array(
      'default' => FALSE,
      'bool' => TRUE,
    );
    $options['subquery_view'] = array(
      'default' => FALSE,
    );
    $options['subquery_namespace'] = array(
      'default' => FALSE,
    );
    return $options;
  }

  /**
   * Extends the relationship's basic options, allowing the user to pick
   * a sort and an order for it.
   */
  public function buildOptionsForm(&$form, &$form_state) {
    parent::buildOptionsForm($form, $form_state);

    // Get the sorts that apply to our base.
    $sorts = views_fetch_fields($this->definition['base'], 'sort');
    foreach ($sorts as $sort_id => $sort) {
      $sort_options[$sort_id] = "{$sort['group']}: {$sort['title']}";
    }
    $base_table_data = views_fetch_data($this->definition['base']);
    $form['subquery_sort'] = array(
      '#type' => 'select',
      '#title' => t('Representative sort criteria'),
      // Provide the base field as sane default sort option.
      '#default_value' => !empty($this->options['subquery_sort']) ? $this->options['subquery_sort'] : $this->definition['base'] . '.' . $base_table_data['table']['base']['field'],
      '#options' => $sort_options,
      '#description' => t("The sort criteria is applied to the data brought in by the relationship to determine how a representative item is obtained for each row. For example, to show the most recent node for each user, pick 'Content: Updated date'."),
    );
    $form['subquery_order'] = array(
      '#type' => 'radios',
      '#title' => t('Representative sort order'),
      '#description' => t("The ordering to use for the sort criteria selected above."),
      '#options' => array(
        'ASC' => t('Ascending'),
        'DESC' => t('Descending'),
      ),
      '#default_value' => $this->options['subquery_order'],
    );
    $form['subquery_namespace'] = array(
      '#type' => 'textfield',
      '#title' => t('Subquery namespace'),
      '#description' => t('Advanced. Enter a namespace for the subquery used by this relationship.'),
      '#default_value' => $this->options['subquery_namespace'],
    );

    // WIP: This stuff doens't work yet: namespacing issues.
    // A list of suitable views to pick one as the subview.
    $views = array(
      '' => '<none>',
    );
    $all_views = views_get_all_views();
    foreach ($all_views as $view) {

      // Only get views that are suitable:
      // - base must the base that our relationship joins towards
      // - must have fields.
      if ($view->base_table == $this->definition['base'] && !empty($view->display['default']['display_options']['fields'])) {

        // TODO: check the field is the correct sort?
        // or let users hang themselves at this stage and check later?
        if ($view->type == 'Default') {
          $views[t('Default Views')][$view->storage
            ->get('name')] = $view->storage
            ->get('name');
        }
        else {
          $views[t('Existing Views')][$view->storage
            ->get('name')] = $view->storage
            ->get('name');
        }
      }
    }
    $form['subquery_view'] = array(
      '#type' => 'select',
      '#title' => t('Representative view'),
      '#default_value' => $this->options['subquery_view'],
      '#options' => $views,
      '#description' => t('Advanced. Use another view to generate the relationship subquery. This allows you to use filtering and more than one sort. If you pick a view here, the sort options above are ignored. Your view must have the ID of its base as its only field, and should have some kind of sorting.'),
    );
    $form['subquery_regenerate'] = array(
      '#type' => 'checkbox',
      '#title' => t('Generate subquery each time view is run.'),
      '#default_value' => $this->options['subquery_regenerate'],
      '#description' => t('Will re-generate the subquery for this relationship every time the view is run, instead of only when these options are saved. Use for testing if you are making changes elsewhere. WARNING: seriously impairs performance.'),
    );
  }

  /**
   * Helper function to create a pseudo view.
   *
   * We use this to obtain our subquery SQL.
   */
  function get_temporary_view() {
    $view = entity_create('view', array(
      'base_table' => $this->definition['base'],
    ));
    $view
      ->addDisplay('default');
    return $view
      ->get('executable');
  }

  /**
   * When the form is submitted, take sure to clear the subquery string cache.
   */
  public function submitOptionsForm(&$form, &$form_state) {
    $cid = 'views_relationship_groupwise_max:' . $this->view->storage
      ->get('name') . ':' . $this->view->current_display . ':' . $this->options['id'];
    cache('views_results')
      ->delete($cid);
  }

  /**
   * Generate a subquery given the user options, as set in the options.
   * These are passed in rather than picked up from the object because we
   * generate the subquery when the options are saved, rather than when the view
   * is run. This saves considerable time.
   *
   * @param $options
   *   An array of options:
   *    - subquery_sort: the id of a views sort.
   *    - subquery_order: either ASC or DESC.
   * @return
   *    The subquery SQL string, ready for use in the main query.
   */
  function left_query($options) {

    // Either load another view, or create one on the fly.
    if ($options['subquery_view']) {
      $temp_view = views_get_view($options['subquery_view']);

      // Remove all fields from default display
      unset($temp_view->display['default']['display_options']['fields']);
    }
    else {

      // Create a new view object on the fly, which we use to generate a query
      // object and then get the SQL we need for the subquery.
      $temp_view = $this
        ->get_temporary_view();

      // Add the sort from the options to the default display.
      // This is broken, in that the sort order field also gets added as a
      // select field. See http://drupal.org/node/844910.
      // We work around this further down.
      $sort = $options['subquery_sort'];
      list($sort_table, $sort_field) = explode('.', $sort);
      $sort_options = array(
        'order' => $options['subquery_order'],
      );
      $temp_view
        ->addItem('default', 'sort', $sort_table, $sort_field, $sort_options);
    }

    // Get the namespace string.
    $temp_view->namespace = !empty($options['subquery_namespace']) ? '_' . $options['subquery_namespace'] : '_INNER';
    $this->subquery_namespace = !empty($options['subquery_namespace']) ? '_' . $options['subquery_namespace'] : 'INNER';

    // The value we add here does nothing, but doing this adds the right tables
    // and puts in a WHERE clause with a placeholder we can grab later.
    $temp_view->args[] = '**CORRELATED**';

    // Add the base table ID field.
    $views_data = views_fetch_data($this->definition['base']);
    $base_field = $views_data['table']['base']['field'];
    $temp_view
      ->addItem('default', 'field', $this->definition['base'], $this->definition['field']);
    $relationship_id = NULL;

    // Add the used relationship for the subjoin, if defined.
    if (isset($this->definition['relationship'])) {
      list($relationship_table, $relationship_field) = explode(':', $this->definition['relationship']);
      $relationship_id = $temp_view
        ->addItem('default', 'relationship', $relationship_table, $relationship_field);
    }
    $temp_item_options = array(
      'relationship' => $relationship_id,
    );

    // Add the correct argument for our relationship's base
    // ie the 'how to get back to base' argument.
    // The relationship definition tells us which one to use.
    $temp_view
      ->addItem('default', 'argument', $this->definition['argument table'], $this->definition['argument field'], $temp_item_options);

    // Build the view. The creates the query object and produces the query
    // string but does not run any queries.
    $temp_view
      ->build();

    // Now take the SelectQuery object the View has built and massage it
    // somewhat so we can get the SQL query from it.
    $subquery = $temp_view->build_info['query'];

    // Workaround until http://drupal.org/node/844910 is fixed:
    // Remove all fields from the SELECT except the base id.
    $fields =& $subquery
      ->getFields();
    foreach (array_keys($fields) as $field_name) {

      // The base id for this subquery is stored in our definition.
      if ($field_name != $this->definition['field']) {
        unset($fields[$field_name]);
      }
    }

    // Make every alias in the subquery safe within the outer query by
    // appending a namespace to it, '_inner' by default.
    $tables =& $subquery
      ->getTables();
    foreach (array_keys($tables) as $table_name) {
      $tables[$table_name]['alias'] .= $this->subquery_namespace;

      // Namespace the join on every table.
      if (isset($tables[$table_name]['condition'])) {
        $tables[$table_name]['condition'] = $this
          ->condition_namespace($tables[$table_name]['condition']);
      }
    }

    // Namespace fields.
    foreach (array_keys($fields) as $field_name) {
      $fields[$field_name]['table'] .= $this->subquery_namespace;
      $fields[$field_name]['alias'] .= $this->subquery_namespace;
    }

    // Namespace conditions.
    $where =& $subquery
      ->conditions();
    $this
      ->alter_subquery_condition($subquery, $where);

    // Not sure why, but our sort order clause doesn't have a table.
    // TODO: the call to add_item() above to add the sort handler is probably
    // wrong -- needs attention from someone who understands it.
    // In the meantime, this works, but with a leap of faith...
    $orders =& $subquery
      ->getOrderBy();
    foreach ($orders as $order_key => $order) {

      // But if we're using a whole view, we don't know what we have!
      if ($options['subquery_view']) {
        list($sort_table, $sort_field) = explode('.', $order_key);
      }
      $orders[$sort_table . $this->subquery_namespace . '.' . $sort_field] = $order;
      unset($orders[$order_key]);
    }

    // The query we get doesn't include the LIMIT, so add it here.
    $subquery
      ->range(0, 1);

    // Extract the SQL the temporary view built.
    $subquery_sql = $subquery
      ->__toString();

    // Replace the placeholder with the outer, correlated field.
    // Eg, change the placeholder ':users_uid' into the outer field 'users.uid'.
    // We have to work directly with the SQL, because putting a name of a field
    // into a SelectQuery that it does not recognize (because it's outer) just
    // makes it treat it as a string.
    $outer_placeholder = ':' . str_replace('.', '_', $this->definition['outer field']);
    $subquery_sql = str_replace($outer_placeholder, $this->definition['outer field'], $subquery_sql);
    return $subquery_sql;
  }

  /**
   * Recursive helper to add a namespace to conditions.
   *
   * Similar to _views_query_tag_alter_condition().
   *
   * (Though why is the condition we get in a simple query 3 levels deep???)
   */
  function alter_subquery_condition(AlterableInterface $query, &$conditions) {
    foreach ($conditions as $condition_id => &$condition) {

      // Skip the #conjunction element.
      if (is_numeric($condition_id)) {
        if (is_string($condition['field'])) {
          $condition['field'] = $this
            ->condition_namespace($condition['field']);
        }
        elseif (is_object($condition['field'])) {
          $sub_conditions =& $condition['field']
            ->conditions();
          $this
            ->alter_subquery_condition($query, $sub_conditions);
        }
      }
    }
  }

  /**
   * Helper function to namespace query pieces.
   *
   * Turns 'foo.bar' into 'foo_NAMESPACE.bar'.
   */
  function condition_namespace($string) {
    return str_replace('.', $this->subquery_namespace . '.', $string);
  }

  /**
   * Called to implement a relationship in a query.
   * This is mostly a copy of our parent's query() except for this bit with
   * the join class.
   */
  public function query() {

    // Figure out what base table this relationship brings to the party.
    $table_data = views_fetch_data($this->definition['base']);
    $base_field = empty($this->definition['base field']) ? $table_data['table']['base']['field'] : $this->definition['base field'];
    $this
      ->ensureMyTable();
    $def = $this->definition;
    $def['table'] = $this->definition['base'];
    $def['field'] = $base_field;
    $def['left_table'] = $this->tableAlias;
    $def['left_field'] = $this->field;
    $def['adjusted'] = TRUE;
    if (!empty($this->options['required'])) {
      $def['type'] = 'INNER';
    }
    if ($this->options['subquery_regenerate']) {

      // For testing only, regenerate the subquery each time.
      $def['left_query'] = $this
        ->left_query($this->options);
    }
    else {

      // Get the stored subquery SQL string.
      $cid = 'views_relationship_groupwise_max:' . $this->view->storage
        ->get('name') . ':' . $this->view->current_display . ':' . $this->options['id'];
      $cache = cache('views_results')
        ->get($cid);
      if (isset($cache->data)) {
        $def['left_query'] = $cache->data;
      }
      else {
        $def['left_query'] = $this
          ->left_query($this->options);
        cache('views_results')
          ->set($cid, $def['left_query']);
      }
    }
    if (!empty($def['join_id'])) {
      $id = $def['join_id'];
    }
    else {
      $id = 'subquery';
    }
    $join = drupal_container()
      ->get('plugin.manager.views.join')
      ->createInstance($id, $def);

    // use a short alias for this:
    $alias = $def['table'] . '_' . $this->table;
    $this->alias = $this->query
      ->add_relationship($alias, $join, $this->definition['base'], $this->relationship);
  }

}

Members

Name	Modifiers	Type	Description	Overrides
GroupwiseMax::alter_subquery_condition		function	Recursive helper to add a namespace to conditions.
GroupwiseMax::buildOptionsForm	public	function	Extends the relationship's basic options, allowing the user to pick a sort and an order for it. Overrides RelationshipPluginBase::buildOptionsForm
GroupwiseMax::condition_namespace		function	Helper function to namespace query pieces.
GroupwiseMax::defineOptions	protected	function	Defines default values for options. Overrides RelationshipPluginBase::defineOptions
GroupwiseMax::get_temporary_view		function	Helper function to create a pseudo view.
GroupwiseMax::left_query		function	Generate a subquery given the user options, as set in the options. These are passed in rather than picked up from the object because we generate the subquery when the options are saved, rather than when the view is run. This saves considerable time.
GroupwiseMax::query	public	function	Called to implement a relationship in a query. This is mostly a copy of our parent's query() except for this bit with the join class. Overrides RelationshipPluginBase::query
GroupwiseMax::submitOptionsForm	public	function	When the form is submitted, take sure to clear the subquery string cache. Overrides HandlerBase::submitOptionsForm
HandlerBase::$actualField	public	property	When a field has been moved this property is set.
HandlerBase::$actualTable	public	property	When a table has been moved this property is set.
HandlerBase::$field	public	property	With field you can override the realField if the real field is not set.
HandlerBase::$query	public	property	Where the $query object will reside:	1
HandlerBase::$realField	public	property	The actual field in the database table, maybe different on other kind of query plugins/special handlers.
HandlerBase::$relationship	public	property	The relationship used for this field.
HandlerBase::$table	public	property	The table this handler is attached to.
HandlerBase::$tableAlias	public	property	The alias of the table of this handler which is used in the query.
HandlerBase::acceptExposedInput	public	function	Take input from exposed handlers and assign to this handler, if necessary.	1
HandlerBase::access	public	function	Check whether current user has access to this handler.	6
HandlerBase::adminLabel	public	function	Return a string representing this handler's name in the UI.	9
HandlerBase::adminSummary	public	function	Provide text for the administrative summary	4
HandlerBase::breakPhrase	public static	function	Breaks x,y,z and x+y+z into an array. Numeric only.
HandlerBase::breakPhraseString	public static	function	Breaks x,y,z and x+y+z into an array. Works for strings.
HandlerBase::broken	public	function	Determine if the handler is considered 'broken', meaning it's a a placeholder used when a handler can't be found.	6
HandlerBase::buildExposedForm	public	function	Render our chunk of the exposed handler form when selecting	1
HandlerBase::buildExposeForm	public	function	Form for exposed handler options.	2
HandlerBase::buildExtraOptionsForm	public	function	Provide a form for setting options.	1
HandlerBase::buildGroupByForm	public	function	Provide a form for aggregation settings.	1
HandlerBase::canExpose	public	function	Determine if a handler can be exposed.	2
HandlerBase::caseTransform	protected	function	Transform a string by a certain method.
HandlerBase::defaultExposeOptions	public	function	Set new exposed option defaults when exposed setting is flipped on.	2
HandlerBase::defineExtraOptions	public	function	Provide defaults for the handler.
HandlerBase::ensureMyTable	public	function	Ensure the main table for this handler is in the query. This is used a lot.	8
HandlerBase::exposedInfo	public	function	Get information about the exposed form for the form renderer.	1
HandlerBase::getEntityType	public	function	Determines the entity type used by this handler.
HandlerBase::getField	public	function	Shortcut to get a handler's raw field value.
HandlerBase::getJoin	public	function	Get the join object that should be used for this handler.
HandlerBase::getSQLDateField	public	function	Creates cross-database SQL dates.
HandlerBase::getSQLFormat	public	function	Creates cross-database SQL date formatting.
HandlerBase::getTableJoin	public static	function	Fetches a handler to join one table to a primary table from the data cache.
HandlerBase::getTimezone	public static	function	Figure out what timezone we're in; needed for some date manipulations.
HandlerBase::hasExtraOptions	public	function	If a handler has 'extra options' it will get a little settings widget and another form called extra_options.	1
HandlerBase::isAGroup	public	function	Returns TRUE if the exposed filter works like a grouped filter.	1
HandlerBase::isExposed	public	function	Determine if this item is 'exposed', meaning it provides form elements to let users modify the view.
HandlerBase::multipleExposedInput	public	function	Define if the exposed input has to be submitted multiple times. This is TRUE when exposed filters grouped are using checkboxes as widgets.	1
HandlerBase::placeholder	protected	function	Provides a unique placeholders for handlers.
HandlerBase::postExecute	public	function	Run after the view is executed, before the result is cached.
HandlerBase::preQuery	public	function	Run before the view is built.	1
HandlerBase::sanitizeValue	protected	function	Sanitize the value for output.
HandlerBase::setRelationship	public	function	Called just prior to query(), this lets a handler set up any relationship it needs.
HandlerBase::showExposeButton	public	function	Shortcut to display the expose/hide button.	2
HandlerBase::showExposeForm	public	function	Shortcut to display the exposed options form.
HandlerBase::storeExposedInput	public	function	If set to remember exposed input in the session, store it there.	1
HandlerBase::submitExposed	public	function	Submit the exposed handler form
HandlerBase::submitExposeForm	public	function	Perform any necessary changes to the form exposes prior to storage. There is no need for this function to actually store the data.
HandlerBase::submitExtraOptionsForm	public	function	Perform any necessary changes to the form values prior to storage. There is no need for this function to actually store the data.
HandlerBase::submitGroupByForm	public	function	Perform any necessary changes to the form values prior to storage. There is no need for this function to actually store the data.	1
HandlerBase::validate	public	function	Validates the handler against the complete View. Overrides PluginBase::validate	1
HandlerBase::validateExposed	public	function	Validate the exposed handler form	4
HandlerBase::validateExposeForm	public	function	Validate the options form.	1
HandlerBase::validateExtraOptionsForm	public	function	Validate the options form.
HandlerBase::validateOptionsForm	public	function	Validate the options form. Overrides PluginBase::validateOptionsForm	4
HandlerBase::__construct	public	function	Constructs a Handler object. Overrides PluginBase::__construct
PluginBase::$configuration	protected	property	Configuration information passed into the plugin.	1
PluginBase::$definition	public	property	Plugins's definition
PluginBase::$discovery	protected	property	The discovery object.
PluginBase::$displayHandler	public	property	The display object this plugin is for.
PluginBase::$options	public	property	Options for this plugin will be held here.
PluginBase::$plugin_id	protected	property	The plugin_id.
PluginBase::$usesOptions	protected	property	Denotes whether the plugin has an additional options form.	8
PluginBase::$view	public	property	The top object of a view.	1
PluginBase::additionalThemeFunctions	public	function	Provide a list of additional theme functions for the theme information page
PluginBase::destroy	public	function	Clears a plugin.	2
PluginBase::getAvailableGlobalTokens	public	function	Returns an array of available token replacements.
PluginBase::getDefinition	public	function	Implements Drupal\Component\Plugin\PluginInterface::getDefinition(). Overrides PluginInspectionInterface::getDefinition
PluginBase::getPluginId	public	function	Implements Drupal\Component\Plugin\PluginInterface::getPluginId(). Overrides PluginInspectionInterface::getPluginId
PluginBase::globalTokenForm	public	function	Adds elements for available core tokens to a form.
PluginBase::globalTokenReplace	public	function	Returns a string with any core tokens replaced.
PluginBase::pluginTitle	public	function	Return the human readable name of the display.
PluginBase::setOptionDefaults	protected	function
PluginBase::summaryTitle	public	function	Returns the summary of the settings in the display.	6
PluginBase::themeFunctions	public	function	Provide a full list of possible theme templates used by this style.	1
PluginBase::unpackOptions	public	function	Unpack options over our existing defaults, drilling down into arrays so that defaults don't get totally blown away.
PluginBase::usesOptions	public	function	Returns the usesOptions property.	8
RelationshipPluginBase::init	public	function	Init handler to let relationships live on tables other than the table they operate on. Overrides HandlerBase::init	2
RelationshipPluginBase::label		function	Get this field's label.
RelationshipPluginBase::usesGroupBy	public	function	You can't groupby a relationship. Overrides HandlerBase::usesGroupBy

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