Added handler to facilitate joins using linking tables (ie: Feature => analysisfeature => Analysis) using a single join description in hook_voiews_data

base/tripal_analysis/views/analysis.views.inc

@@ -51,25 +51,17 @@ function retrieve_analysis_views_data() {
   }
 
   // Define relationships between this table and others
-  $data['analysis']['table']['join'] = array(
-    'analysisfeature' => array(
-      'left_field' => 'analysis_id',
-      'field' => 'analysis_id',
-    ),
-    'feature' => array(
-      'left_table' => 'analysisfeature',
-      'left_field' => 'analysis_id',
+  $data['analysis']['table']['join']['feature'] = array(
+    'linking' => array(
+      'table' => 'analysisfeature',
+      'left_field' => 'feature_id',
       'field' => 'analysis_id',
     ),
+    'left_field' => 'feature_id',
+    'field' => 'analysis_id',
+    'handler' => 'views_handler_join_chado_through_linking'
   );
 
-  // Describe the joins with the analysis_feature table
-  $data['analysisfeature']['table']['join'] = array(
-    'feature' => array(
-      'left_field' => 'feature_id',
-      'field' => 'feature_id',
-    ),
-  );
 	
 	// Table Field Definitions----------------------
 	// Field: analysis_id (primary key)

base/tripal_core/tripal_core.views.inc

@@ -1,5 +1,8 @@
 <?php
 
+include('views/handlers/views_handler_join_chado_through_linking.inc');
+//include('views/handlers/views_handler_join_chado_one2many.inc');
+
 /**
  * @defgroup views Views Integration
  * @{
@@ -81,6 +84,9 @@ function tripal_core_views_handlers() {
      'views_handler_field_chado_rel_by_type' => array(
       'parent' => 'views_handler_field_prerender_list',
      ),
+     'views_handler_join_chado_one2many' => array(
+      'parent' => 'views_join'
+     ),
    ),
  );
 }

base/tripal_core/views/handlers/views_handler_join_chado_through_linking.inc

@@ -0,0 +1,112 @@
+<?php
+
+/**
+ * Handler to allow joins between records via a linking table
+ *
+ * Example Usage:
+ *   To join the analysis table to the feature table through the analysisfeature table,
+ *   (ie: get analysis fields to show up in a feature view)
+ *   Use the following code in the analysis hook_views_data:
+ *   @code
+        $data['analysis']['table']['join']['feature'] = array(
+          'linking' => array(
+            'table' => 'analysisfeature',
+            'left_field' => 'feature_id',
+            'field' => 'analysis_id',
+          ),
+          'left_field' => 'feature_id',
+          'field' => 'analysis_id',
+          'handler' => 'views_handler_join_chado_through_linking'
+        ); 
+ *   @endcode
+ *
+ * NOTE: If the right table is in the drupal schema rather then the chado schema 
+ *  (ie: node, chado_feature) then add the following to the above join description:
+ *  @code
+    'table_is_drupal' => TRUE
+ *  @endcode
+ *  This will ensure the drupal table is surrounded by { } and as such any database
+ *  prefixes are added correctly. If the left table is in the drupal schema it should already
+ *  be defined by a previous join (or the From clause).
+ */
+class views_handler_join_chado_through_linking extends views_join {
+
+  // PHP 4 doesn't call constructors of the base class automatically from a
+  // constructor of a derived class. It is your responsibility to propagate
+  // the call to constructors upstream where appropriate.
+  function construct($table = NULL, $left_table = NULL, $left_field = NULL, $field = NULL, $extra = array(), $type = 'LEFT', $added = NULL) {
+    parent::construct($table, $left_table, $left_field, $field, $extra, $type);
+  }
+  
+  /**
+   * Creates SQL for both joins table => linking_table and linking_table => left_table
+   * NOTE: Uses fields in definition as passed in from hook_views_data join definition
+   */
+  function join($table, &$query) {
+    $output = '';
+    $joins = array();
+
+    $joins[] = $this->create_single_join(
+      $query,
+      array(
+        'table' => $this->definition['linking']['table'],
+        'field' => $this->definition['linking']['left_field'],
+        'is_drupal' => FALSE,
+      ),
+      array(
+        'table' => $this->definition['left_table'],
+        'field' => $this->definition['left_field'],
+      ),
+      'LEFT'
+    );
+    
+    $joins[] = $this->create_single_join(
+      $query,
+      array(
+        'table' => $this->definition['table'],
+        'field' => $this->definition['field'],
+        'is_drupal' => $this->definition['table_is_drupal'],
+      ),
+      array(
+        'table' => $this->definition['linking']['table'],
+        'field' => $this->definition['linking']['field'],
+      ),
+      'LEFT'
+    );
+    
+    $output .= implode("\n",$joins);
+    return $output;
+  }
+  
+  /**
+   * Creates SQL for a single join based on parameters
+   */
+  function create_single_join (&$query, $right_spec, $left_spec, $join_type) {
+    
+    if ($right_spec['table']) {
+      $right = $query->get_table_info($right_spec['table']);
+      if (!$right['alias']) { $right['alias'] = $right_spec['table']; }
+      $right_field = "$right[alias].$right_spec[field]";
+
+      if ($right_spec['is_drupal']) {
+        $right_table = '{'.$right_spec['table'].'}';
+      } else {
+        $right_table = $right_spec['table'];
+      }
+    }   
+
+    if ($left_spec['table']) {
+      $left = $query->get_table_info($left_spec['table']);
+      if (!$left['alias']) { $left['alias'] = $left_spec['table']; }
+      $left_field = "$left[alias].$left_spec[field]";
+    } else {
+      // This can be used if left_field is a formula or something. It should be used only *very* rarely.
+      $left_field = $this->left_spec['field'];
+    }
+    
+    $output = " $join_type JOIN $right_table $right[alias] ON $left_field = $right_field";
+     
+    return $output;
+  }
+ 
+}