pysolr update document with error
<p><strong>update:</strong> Pysolr Version: 3.2.0</p>

<p><strong>This seems a bug in solr. when update nothing in an operation, it will delete this doc.</strong></p>

<p>Former I used code in <a href="https://stackoverflow.com/questions/24415659/how-to-make-atomic-updates-to-solr-using-pysolr">using pysolr in atomic update</a>, but I made error in following case.</p>

<p>Now a document schema maybe like this:</p>

<pre><code>doc = {
   'id':    ...,
   'title': ...,
   'body':  ...,
}
</code></pre>

<p>I have indexed a batch of docs and now I want to update every doc with a new field anchor_text. Here is my code:</p>

<pre><code>solr = pysolr.Solr(url_solr)
doc_update = {
   'id': ...,
   'anchor_text': [a,b,c,...]
}
solr.add([doc_update], fieldUpdates={
    'anchor_text': 'set'
})
</code></pre>

<p>But I found some of original docs were <strong>removed</strong> only with <strong>id</strong> field left.
Something like this after update:</p>

<pre><code>doc = {
  'id':...
}
</code></pre>

<p>Especially, for those whose anchor_text field are empty lists, the original docs are removed. While others are not.(Probably I guess because I only see several cases).</p>

<p>I've looked at the source code but found nothing valuable. What's going on here?</p>

<p>What are the correct way to use pysolr in update document?</p>