[BUGFIX] Avoid INNER JOIN for LEFT JOIN filters

If the first field condition (alphabetically) is a LEFT JOIN filter,
make sure that subsequent fields do not join to it with an INNER
JOIN.

Author: Mateu Aguiló Bosch

src/Plugin/resource/DataProvider/DataProvider.php

@@ -97,6 +97,9 @@ public static function processFilterInput($filter, $public_field) {
       $filter = array('value' => $filter);
     }
     if (!is_array($filter['value'])) {
+      if (!isset($filter['value'])) {
+        throw new BadRequestException(sprintf('Value not present for the "%s" filter. Please check the URL format.', $public_field));
+      }
       $filter['value'] = array($filter['value']);
     }
     // Add the property.

src/Util/EntityFieldQuery.php

@@ -309,13 +309,14 @@ protected function fieldStorageQuery(SelectQuery $select_query) {
     $base_table = $this->metaData['base_table'];
 
     // Add tables for the fields used.
+    $field_base_table = NULL;
     foreach ($this->fields as $key => $field) {
       $tablename = $tablename_function($field);
       $table_alias = _field_sql_storage_tablealias($tablename, $key, $this);
       $table_aliases[$key] = $table_alias;
       $select_query->addMetaData('base_table', $base_table);
       $entity_id_key = $this->metaData['entity_id_key'];
-      if ($key) {
+      if ($field_base_table) {
         if (!isset($query_tables[$table_alias])) {
           $this->addFieldJoin($select_query, $field['field_name'], $tablename, $table_alias, "$table_alias.entity_type = $field_base_table.entity_type AND $table_alias.$id_key = $field_base_table.$id_key");
         }
@@ -332,7 +333,9 @@ protected function fieldStorageQuery(SelectQuery $select_query) {
         if (!isset($this->tags['DANGEROUS_ACCESS_CHECK_OPT_OUT'])) {
           $select_query->addTag('entity_field_access');
         }
-        $field_base_table = $table_alias;
+        if (!$this->containsLeftJoinOperator($this->fields[$key]['field_name'])) {
+          $field_base_table = $table_alias;
+        }
       }
       if ($field['cardinality'] != 1 || $field['translatable']) {
         $select_query->distinct();
@@ -346,13 +349,15 @@ protected function fieldStorageQuery(SelectQuery $select_query) {
     // Add field meta conditions.
     _field_sql_storage_query_field_conditions($this, $select_query, $this->fieldMetaConditions, $table_aliases, '_field_sql_storage_query_columnname');
 
-    // Find out if the query needs the OR.
+    // If there was no field condition that created an INNER JOIN, that means
+    // that additional JOINs need to carry the OR condition. For the base table
+    // we'll use the table for the first field.
     $needs_or = FALSE;
-    foreach ($this->fieldConditions as $field_condition) {
-      if ($field_condition['field']['field_name'] != $this->fields[0]['field_name']) {
-        continue;
-      }
-      $needs_or = in_array($field_condition['operator'], static::$leftJoinOperators);
+    if (!isset($field_base_table)) {
+      $needs_or = TRUE;
+      // Get the table name for the first field.
+      $field_table_name = key($this->fields[0]['storage']['details']['sql'][$this->age]);
+      $field_base_table = _field_sql_storage_tablealias($field_table_name, 0, $this);
     }
 
     if (isset($this->deleted)) {
@@ -454,10 +459,32 @@ public function addCondition(SelectQuery $select_query, $sql_field, $condition,
       return;
     }
     $method = $having ? 'havingCondition' : 'condition';
-    $db_or = db_or()
-      ->condition($sql_field, $condition['value'], $condition['operator'])
-      ->condition($sql_field, NULL, 'IS NULL');
+    $db_or = db_or()->condition($sql_field, $condition['value'], $condition['operator']);
+    if (strtoupper($condition['operator']) != 'IS NULL' && strtoupper($condition['operator']) != 'IS NOT NULL') {
+      $db_or->condition($sql_field, NULL, 'IS NULL');
+    }
     $select_query->$method($db_or);
   }
 
+  /**
+   * Checks if any of the conditions contains a LEFT JOIN operation.
+   *
+   * @param string $field_name
+   *   If provided only this field will be checked.
+   *
+   * @return bool
+   *   TRUE if any of the conditions contain a left join operator.
+   */
+  protected function containsLeftJoinOperator($field_name = NULL) {
+    foreach ($this->fieldConditions as $field_condition) {
+      if ($field_name && $field_condition['field']['field_name'] != $field_name) {
+        continue;
+      }
+      if (in_array($field_condition['operator'], static::$leftJoinOperators)) {
+        return TRUE;
+      }
+    }
+    return FALSE;
+  }
+
 }