More info needed in hook_views_data docs/sample body

Looks pretty solid for me.

+++ b/core/modules/views/views.api.php
@@ -185,6 +188,28 @@ function hook_views_data() {
+    // 'extra' is an array of extra WHERE conditions for the join.

Should we replace the 'extra' here with 'additional'?

+++ b/core/modules/views/views.api.php
@@ -221,6 +224,28 @@ function hook_views_data() {
+  // You can also do a more complex join. For instance, since this table
+  // has a language code field, you might want to join to node-based views
+  // via the node_field_data table, rather than the base node table, and you
+  // might want to join on both the nid field and the langcode field. To do
+  // this:
+  $data['example_table']['table']['join']['node'] = array(
+    // 'node' above is the base we're joining to in Views. 'left_table'
+    // is the table we're actually joining to, in order to get to 'node'. It
+    // has to be something that Views knows how to join to 'node'.
+    'left_table' => 'node_field_data',
+    'left_field' => 'nid',
+    'field' => 'nid',
+    // 'extra' is an array of additional conditions on the join.
+    'extra' => array(
+      // This syntax matches additional fields in the two tables.
+      array('left_field' => 'langcode', 'field' => 'langcode'),
+      // This syntax adds a condition on our table. 'operator' defaults to
+      // '=' for non-array values, or 'IN' for array values.
+      array('field' => 'numeric_field', 'value' => 0, 'numeric' => TRUE, 'operator' => '>'),
+    ),
+  );

+1 for the general part. What about adding an example how the resulting SQL query would look like then?

And... well this example doesn't work any more, because the base table for joining to nodes is now node_field_data, not node. So I made up a fictitious example instead.

Great observation!

IMHO this is a good step forward, so let's get it in.

Committed/pushed to 8.1.x and cherry-picked to 8.0.x. Thanks!