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<?php
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/**
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* @file
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* Relationship for groupwise maximum handler.
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*/
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/**
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* Relationship handler that allows a groupwise maximum of the linked in table.
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* For a definition, see:
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* http://dev.mysql.com/doc/refman/5.0/en/example-maximum-column-group-row.html
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* In lay terms, instead of joining to get all matching records in the linked
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* table, we get only one record, a 'representative record' picked according
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* to a given criteria.
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*
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* Example:
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* Suppose we have a term view that gives us the terms: Horse, Cat, Aardvark.
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* We wish to show for each term the most recent node of that term.
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* What we want is some kind of relationship from term to node.
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* But a regular relationship will give us all the nodes for each term,
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* giving the view multiple rows per term. What we want is just one
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* representative node per term, the node that is the 'best' in some way:
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* eg, the most recent, the most commented on, the first in alphabetical order.
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*
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* This handler gives us that kind of relationship from term to node.
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* The method of choosing the 'best' implemented with a sort
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* that the user selects in the relationship settings.
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*
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* So if we want our term view to show the most commented node for each term,
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* add the relationship and in its options, pick the 'Comment count' sort.
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*
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* Relationship definition
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* - 'outer field': The outer field to substitute into the correlated subquery.
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* This must be the full field name, not the alias.
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* Eg: 'term_data.tid'.
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* - 'argument table',
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* 'argument field': These options define a views argument that the subquery
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* must add to itself to filter by the main view.
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* Example: the main view shows terms, this handler is being used to get to
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* the nodes base table. Your argument must be 'term_node', 'tid', as this
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* is the argument that should be added to a node view to filter on terms.
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*
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* A note on performance:
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* This relationship uses a correlated subquery, which is expensive.
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* Subsequent versions of this handler could also implement the alternative way
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* of doing this, with a join -- though this looks like it could be pretty messy
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* to implement. This is also an expensive method, so providing both methods and
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* allowing the user to choose which one works fastest for their data might be
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* the best way.
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* If your use of this relationship handler is likely to result in large
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* data sets, you might want to consider storing statistics in a separate table,
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* in the same way as node_comment_statistics.
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*
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* @ingroup views_relationship_handlers
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*/
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class views_handler_relationship_groupwise_max extends views_handler_relationship {
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/**
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* Defines default values for options.
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*/
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function option_definition() {
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$options = parent::option_definition();
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$options['subquery_sort'] = array('default' => NULL);
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// Descending more useful.
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$options['subquery_order'] = array('default' => 'DESC');
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$options['subquery_regenerate'] = array('default' => FALSE, 'bool' => TRUE);
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$options['subquery_view'] = array('default' => FALSE);
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$options['subquery_namespace'] = array('default' => FALSE);
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return $options;
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}
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/**
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* Extends the relationship's basic options, allowing the user to pick
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* a sort and an order for it.
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*/
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function options_form(&$form, &$form_state) {
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parent::options_form($form, $form_state);
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// Get the sorts that apply to our base.
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$sorts = views_fetch_fields($this->definition['base'], 'sort');
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foreach ($sorts as $sort_id => $sort) {
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$sort_options[$sort_id] = "$sort[group]: $sort[title]";
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}
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$base_table_data = views_fetch_data($this->definition['base']);
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$form['subquery_sort'] = array(
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'#type' => 'select',
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'#title' => t('Representative sort criteria'),
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// Provide the base field as sane default sort option.
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'#default_value' => !empty($this->options['subquery_sort']) ? $this->options['subquery_sort'] : $this->definition['base'] . '.' . $base_table_data['table']['base']['field'],
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'#options' => $sort_options,
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'#description' => theme('advanced_help_topic', array('module' => 'views', 'topic' => 'relationship-representative')) .
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t("The sort criteria is applied to the data brought in by the relationship to determine how a representative item is obtained for each row. For example, to show the most recent node for each user, pick 'Content: Updated date'."),
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);
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$form['subquery_order'] = array(
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'#type' => 'radios',
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'#title' => t('Representative sort order'),
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'#description' => t("The ordering to use for the sort criteria selected above."),
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'#options' => array('ASC' => t('Ascending'), 'DESC' => t('Descending')),
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'#default_value' => $this->options['subquery_order'],
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);
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$form['subquery_namespace'] = array(
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'#type' => 'textfield',
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'#title' => t('Subquery namespace'),
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'#description' => t('Advanced. Enter a namespace for the subquery used by this relationship.'),
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'#default_value' => $this->options['subquery_namespace'],
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);
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// WIP: This stuff doens't work yet: namespacing issues.
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// A list of suitable views to pick one as the subview.
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$views = array('' => '<none>');
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$all_views = views_get_all_views();
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foreach ($all_views as $view) {
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// Only get views that are suitable:
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// - base must the base that our relationship joins towards
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// - must have fields.
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if ($view->base_table == $this->definition['base'] && !empty($view->display['default']->display_options['fields'])) {
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// TODO: check the field is the correct sort?
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// or let users hang themselves at this stage and check later?
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if ($view->type == 'Default') {
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$views[t('Default Views')][$view->name] = $view->name;
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}
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else {
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$views[t('Existing Views')][$view->name] = $view->name;
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}
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}
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}
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$form['subquery_view'] = array(
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'#type' => 'select',
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'#title' => t('Representative view'),
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'#default_value' => $this->options['subquery_view'],
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'#options' => $views,
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'#description' => t('Advanced. Use another view to generate the relationship subquery. This allows you to use filtering and more than one sort. If you pick a view here, the sort options above are ignored. Your view must have the ID of its base as its only field, and should have some kind of sorting.'),
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);
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$form['subquery_regenerate'] = array(
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'#type' => 'checkbox',
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'#title' => t('Generate subquery each time view is run.'),
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'#default_value' => $this->options['subquery_regenerate'],
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'#description' => t('Will re-generate the subquery for this relationship every time the view is run, instead of only when these options are saved. Use for testing if you are making changes elsewhere. WARNING: seriously impairs performance.'),
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);
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}
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/**
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* Helper function to create a pseudo view.
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*
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* We use this to obtain our subquery SQL.
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*/
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function get_temporary_view() {
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views_include('view');
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$view = new view();
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$view->vid = 'new'; // @todo: what's this?
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$view->base_table = $this->definition['base'];
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$view->add_display('default');
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return $view;
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}
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/**
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* When the form is submitted, take sure to clear the subquery string cache.
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*/
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function options_form_submit(&$form, &$form_state) {
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$cid = 'views_relationship_groupwise_max:' . $this->view->name . ':' . $this->view->current_display . ':' . $this->options['id'];
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cache_clear_all($cid, 'cache_views_data');
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}
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/**
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* Generate a subquery given the user options, as set in the options.
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* These are passed in rather than picked up from the object because we
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* generate the subquery when the options are saved, rather than when the view
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* is run. This saves considerable time.
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*
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* @param $options
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* An array of options:
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* - subquery_sort: the id of a views sort.
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* - subquery_order: either ASC or DESC.
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* @return
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* The subquery SQL string, ready for use in the main query.
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*/
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function left_query($options) {
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// Either load another view, or create one on the fly.
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if ($options['subquery_view']) {
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$temp_view = views_get_view($options['subquery_view']);
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// Remove all fields from default display
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unset($temp_view->display['default']->display_options['fields']);
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}
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else {
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// Create a new view object on the fly, which we use to generate a query
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// object and then get the SQL we need for the subquery.
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$temp_view = $this->get_temporary_view();
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// Add the sort from the options to the default display.
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// This is broken, in that the sort order field also gets added as a
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// select field. See http://drupal.org/node/844910.
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// We work around this further down.
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$sort = $options['subquery_sort'];
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list($sort_table, $sort_field) = explode('.', $sort);
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$sort_options = array('order' => $options['subquery_order']);
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$temp_view->add_item('default', 'sort', $sort_table, $sort_field, $sort_options);
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}
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// Get the namespace string.
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$temp_view->namespace = (!empty($options['subquery_namespace'])) ? '_'. $options['subquery_namespace'] : '_INNER';
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$this->subquery_namespace = (!empty($options['subquery_namespace'])) ? '_'. $options['subquery_namespace'] : 'INNER';
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// The value we add here does nothing, but doing this adds the right tables
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// and puts in a WHERE clause with a placeholder we can grab later.
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$temp_view->args[] = '**CORRELATED**';
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// Add the base table ID field.
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$views_data = views_fetch_data($this->definition['base']);
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$base_field = $views_data['table']['base']['field'];
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$temp_view->add_item('default', 'field', $this->definition['base'], $this->definition['field']);
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// Add the correct argument for our relationship's base
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// ie the 'how to get back to base' argument.
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// The relationship definition tells us which one to use.
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$temp_view->add_item(
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'default',
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'argument',
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$this->definition['argument table'], // eg 'term_node',
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$this->definition['argument field'] // eg 'tid'
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);
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// Build the view. The creates the query object and produces the query
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// string but does not run any queries.
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$temp_view->build();
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// Now take the SelectQuery object the View has built and massage it
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// somewhat so we can get the SQL query from it.
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$subquery = $temp_view->build_info['query'];
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// Workaround until http://drupal.org/node/844910 is fixed:
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// Remove all fields from the SELECT except the base id.
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$fields =& $subquery->getFields();
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foreach (array_keys($fields) as $field_name) {
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// The base id for this subquery is stored in our definition.
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if ($field_name != $this->definition['field']) {
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unset($fields[$field_name]);
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}
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}
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// Make every alias in the subquery safe within the outer query by
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// appending a namespace to it, '_inner' by default.
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$tables =& $subquery->getTables();
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foreach (array_keys($tables) as $table_name) {
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$tables[$table_name]['alias'] .= $this->subquery_namespace;
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// Namespace the join on every table.
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if (isset($tables[$table_name]['condition'])) {
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$tables[$table_name]['condition'] = $this->condition_namespace($tables[$table_name]['condition']);
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}
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}
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// Namespace fields.
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foreach (array_keys($fields) as $field_name) {
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$fields[$field_name]['table'] .= $this->subquery_namespace;
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$fields[$field_name]['alias'] .= $this->subquery_namespace;
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}
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// Namespace conditions.
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$where =& $subquery->conditions();
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$this->alter_subquery_condition($subquery, $where);
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// Not sure why, but our sort order clause doesn't have a table.
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// TODO: the call to add_item() above to add the sort handler is probably
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// wrong -- needs attention from someone who understands it.
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// In the meantime, this works, but with a leap of faith...
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$orders =& $subquery->getOrderBy();
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foreach ($orders as $order_key => $order) {
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// But if we're using a whole view, we don't know what we have!
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if ($options['subquery_view']) {
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list($sort_table, $sort_field) = explode('.', $order_key);
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}
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$orders[$sort_table . $this->subquery_namespace . '.' . $sort_field] = $order;
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unset($orders[$order_key]);
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}
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// The query we get doesn't include the LIMIT, so add it here.
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$subquery->range(0, 1);
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// Extract the SQL the temporary view built.
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$subquery_sql = $subquery->__toString();
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// Replace the placeholder with the outer, correlated field.
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// Eg, change the placeholder ':users_uid' into the outer field 'users.uid'.
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// We have to work directly with the SQL, because putting a name of a field
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// into a SelectQuery that it does not recognize (because it's outer) just
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// makes it treat it as a string.
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$outer_placeholder = ':' . str_replace('.', '_', $this->definition['outer field']);
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$subquery_sql = str_replace($outer_placeholder, $this->definition['outer field'], $subquery_sql);
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return $subquery_sql;
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}
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/**
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* Recursive helper to add a namespace to conditions.
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*
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* Similar to _views_query_tag_alter_condition().
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*
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* (Though why is the condition we get in a simple query 3 levels deep???)
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*/
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function alter_subquery_condition(QueryAlterableInterface $query, &$conditions) {
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foreach ($conditions as $condition_id => &$condition) {
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// Skip the #conjunction element.
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if (is_numeric($condition_id)) {
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if (is_string($condition['field'])) {
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$condition['field'] = $this->condition_namespace($condition['field']);
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}
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elseif (is_object($condition['field'])) {
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$sub_conditions =& $condition['field']->conditions();
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$this->alter_subquery_condition($query, $sub_conditions);
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}
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}
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}
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}
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/**
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* Helper function to namespace query pieces.
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*
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* Turns 'foo.bar' into 'foo_NAMESPACE.bar'.
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*/
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function condition_namespace($string) {
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return str_replace('.', $this->subquery_namespace . '.', $string);
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}
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/**
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* Called to implement a relationship in a query.
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* This is mostly a copy of our parent's query() except for this bit with
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* the join class.
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*/
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function query() {
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// Figure out what base table this relationship brings to the party.
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$table_data = views_fetch_data($this->definition['base']);
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$base_field = empty($this->definition['base field']) ? $table_data['table']['base']['field'] : $this->definition['base field'];
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$this->ensure_my_table();
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$def = $this->definition;
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$def['table'] = $this->definition['base'];
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$def['field'] = $base_field;
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$def['left_table'] = $this->table_alias;
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$def['left_field'] = $this->field;
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if (!empty($this->options['required'])) {
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$def['type'] = 'INNER';
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}
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if ($this->options['subquery_regenerate']) {
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// For testing only, regenerate the subquery each time.
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$def['left_query'] = $this->left_query($this->options);
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}
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else {
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// Get the stored subquery SQL string.
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$cid = 'views_relationship_groupwise_max:' . $this->view->name . ':' . $this->view->current_display . ':' . $this->options['id'];
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$cache = cache_get($cid, 'cache_views_data');
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if (isset($cache->data)) {
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$def['left_query'] = $cache->data;
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}
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else {
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$def['left_query'] = $this->left_query($this->options);
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cache_set($cid, $def['left_query'], 'cache_views_data');
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}
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}
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if (!empty($def['join_handler']) && class_exists($def['join_handler'])) {
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$join = new $def['join_handler'];
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}
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else {
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$join = new views_join_subquery();
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}
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$join->definition = $def;
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$join->construct();
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$join->adjusted = TRUE;
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// use a short alias for this:
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$alias = $def['table'] . '_' . $this->table;
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$this->alias = $this->query->add_relationship($alias, $join, $this->definition['base'], $this->relationship);
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}
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}
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