How do I get comments to be indexed?
Apachesolr Comments


  By default the apachesolr module index comments attached to the node.
  So you can not search comments directly. This module separates
  comments from the nodes and allows you to search them directly.


UPDATE:

For search api apply this patch 

diff --git a/modules/callbacks.inc b/modules/callbacks.inc
index dca9e1d..e12be6a 100644
--- a/modules/callbacks.inc
+++ b/modules/callbacks.inc
@@ -80,6 +80,12 @@ function entity_metadata_comment_get_node_properties($node, array $options, $nam

     case 'comment_count_new':
       return comment_num_new($node-&gt;nid);
+
+    case 'comments':
+      $select = db_select('comment', 'c')
+        -&gt;fields('c', array('cid'))
+        -&gt;condition('c.nid', $node-&gt;nid);
+      return array_keys($select-&gt;execute()-&gt;fetchAllKeyed(0, 0));
   }
 }

diff --git a/modules/comment.info.inc b/modules/comment.info.inc
index 4321b4c..a9d7fe9 100644
--- a/modules/comment.info.inc
+++ b/modules/comment.info.inc
@@ -136,6 +136,13 @@ function entity_metadata_comment_entity_property_info_alter(&amp;$info) {
     'setter permission' =&gt; 'administer comments',
     'type' =&gt; 'integer',
   );
+  $properties['comments'] = array(
+    'label' =&gt; t("Comments"),
+    'type' =&gt; 'list&lt;comment&gt;',
+    'description' =&gt; t("The node comments."),
+    'getter callback' =&gt; 'entity_metadata_comment_get_node_properties',
+    'computed' =&gt; TRUE,
+  );
   $properties['comment_count'] = array(
     'label' =&gt; t("Comment count"),
     'description' =&gt; t("The number of comments posted on a node."),


Taken from the source https://drupal.org/node/1414688#comment-7037540 and also worth looking at this http://blog.merge.nl/shorts/search-api-indexing-nodes-including-comments