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<span class="day">16</span>
<span class="rest">Nov 2015</span>
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<h1 class="title">Retrieve and Rank and Python</h1>
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<h2 id="introduction">Introduction</h2>
<p>Retrieve and Rank (R&amp;R), if you hadnt already heard about it, is IBM Watsons new web service component for information retrieval and question answering. My colleague Chris Madison has summarised how it works in a high level way <a href="http://cmadison.me/2015/10/23/introducing-ibms-retrieve-and-rank-service/">here</a>.</p>
<p>R&amp;R is based on the Apache SOLR search engine with a machine learning result ranking plugin that learns what answers are most relevant given an input query and presents them in the learnt “relevance” order.</p>
<p>Some of my partners have found that getting documents in and out of retrieve and rank is a little bit cumbersome using CURL and json files from the command-line. Here I want to demonstrate a much easier way of managing your SOLR documents with <a href="https://github.com/edsu/solrpy">solrpy</a>  a wrapper around Apache SOLR in Python. Since R&amp;R and SOLR are API compatible (until you start using and training the custom ranker) it is perfectly fine to use solrpy in R&amp;R with a few special tweaks.</p>
<h2 id="getting-started">Getting Started</h2>
<p>**You will need</p>
<p>** An R&amp;R instance with a cluster and collection already configured. Im using a schema which has three fields fields  id, title and text.</p>
<p>Firstly youll want to install the library -normally you could do this with pip. Unfortunately I had to make a small change to get the library to work with retrieve and rank so youll need to install it from my github repo:</p>
<pre>$ git clone git@github.com:ravenscroftj/solrpy.git
$ python setup.py install</pre>
<p>The next step is to run python and initialise your connection. The URL you should use to initialise your SOLR connection has the following structure:</p>
<pre>https://gateway.watsonplatform.net/retrieve-and-rank/api/v1/solr_clusters/&lt;CLUSTER_ID&gt;/solr/&lt;COLLECTION_NAME&gt;</pre>
<p>You will also need the credentials from your bluemix service which should look something like this:</p>
<pre>{
"credentials": {
"url": "https://gateway.watsonplatform.net/retrieve-and-rank/api",
"username": "&lt;USERNAME&gt;",
"password": "&lt;PASSWORD&gt;"
}
}</pre>
<p>In python you should try running the following (I am using the interactive python shell <a href="https://en.wikipedia.org/wiki/IDLE_(Python)">IDLE</a> for this example)</p>
<pre>&gt;&gt;&gt; import solr
>&gt;&gt; s = solr.Solr("https://gateway.watsonplatform.net/retrieve-and-rank/api/v1/solr_clusters/&lt;CLUSTER_ID&gt;/solr/&lt;COLLECTION_NAME&gt;", http_user="&lt;USERNAME&gt;", http_pass="&lt;PASSWORD&gt;")
>&gt;&gt; s.search("hello world")
<em><strong>&lt;solr.core.Response object at 0x7ff77f91d7d0&gt;</strong></em></pre>
<p>If this worked then you will see something like _**&lt;solr.core.Response object at 0x7ff77f91d7d0&gt; **_as output here. If you get an error response try checking that you have substituted in valid values for &lt;CLUSTER_ID&gt;, &lt;COLLECTION_NAME&gt;, <USERNAME> and <PASSWORD>.</p>
<p>From this point onwards things get very easy. solrpy has simple functions for creating, removing and searching items in the SOLR index.</p>
<p>To add a document you can use the code below:</p>
<pre>&gt;&gt;&gt; s.add({"title" : "test", "text" : "this is a test", "id" : 1})
<strong>'&lt;?xml version="1.0" encoding="UTF-8"?&gt;\n&lt;response&gt;\n&lt;lst name="responseHeader"&gt;&lt;int name="status"&gt;0&lt;/int&gt;&lt;int name="QTime"&gt;167&lt;/int&gt;&lt;/lst&gt;\n&lt;/response&gt;\n'</strong>
>&gt;&gt; s.commit()
<strong>'&lt;?xml version="1.0" encoding="UTF-8"?&gt;\n&lt;response&gt;\n&lt;lst name="responseHeader"&gt;&lt;int name="status"&gt;0&lt;/int&gt;&lt;int name="QTime"&gt;68&lt;/int&gt;&lt;/lst&gt;\n&lt;/response&gt;\n'</strong></pre>
<p>The XML output shows that the initial add and then commit operations were both successful.</p>
<h2 id="content-management">Content Management</h2>
<p>You can also add a number of documents this is specifically useful if you have a large number of python objects to insert into SOLR:</p>
<pre>&gt;&gt;&gt; s.add_many( [ { "title" : x['title'], "text" : x['text'], "id" : i } for i,x in enumerate(my_list_of_items) ] )
<strong>'&lt;?xml version="1.0" encoding="UTF-8"?&gt;\n&lt;response&gt;\n&lt;lst name="responseHeader"&gt;&lt;int name="status"&gt;0&lt;/int&gt;&lt;int name="QTime"&gt;20&lt;/int&gt;&lt;/lst&gt;\n&lt;/response&gt;\n'</strong></pre>
<p>Of course you can also delete items via their ID from python too:</p>
<pre>&gt;&gt;&gt; s.delete(id=1)
<strong>'&lt;?xml version="1.0" encoding="UTF-8"?&gt;\n&lt;response&gt;\n&lt;lst name="responseHeader"&gt;&lt;int name="status"&gt;0&lt;/int&gt;&lt;int name="QTime"&gt;43&lt;/int&gt;&lt;/lst&gt;\n&lt;/response&gt;\n'</strong></pre>
<h2 id="querying-solr-unranked-results">Querying SOLR (unranked results)</h2>
<p>And you can use SOLR queries too (but importantly note that this does not use the retrieve and rank rankers this only gives you access to the SOLR rankers.)</p>
<pre>&gt;&gt;&gt; r = s.select("test")
>&gt;&gt; r.numFound
<strong>1L
</strong>&gt;&gt;&gt; r.results
<strong>[{u'_version_': 1518020997236654080L, u'text': [u'this is a test'], u'score': 0.0, u'id': u'1', u'title': [u'test']}]</strong>
</pre>
<h2 id="querying-rankers">Querying Rankers</h2>
<p>Provided you have <a href="http://www.ibm.com/smarterplanet/us/en/ibmwatson/developercloud/doc/retrieve-rank/get_start.shtml#create-train">successfully trained a ranker </a> and have the ranker ID handy, you can also query your ranker directly from Python using solrpy too.</p>
<pre>&gt;&gt;&gt; import solr
>&gt;&gt; s = solr.Solr("https://gateway.watsonplatform.net/retrieve-and-rank/api/v1/solr_clusters/&lt;CLUSTER_ID&gt;/solr/&lt;COLLECTION_NAME&gt;", http_user="&lt;USERNAME&gt;", http_pass="&lt;PASSWORD&gt;")
>&gt;&gt; fcselect = solr.SearchHandler(s, "/fcselect")
>&gt;&gt; r = fcselect("my query text", ranker_id="&lt;RANKER-ID&gt;")</pre>
<p>in this case **r **is the same type as in the above non-ranker example, you can access the results via <strong>r.results.</strong></p>
<h2 id="more-information">More information</h2>
<p>For more information on how to use solrpy, visit their documentation page <a href="http://pythonhosted.org/solrpy/">here</a></p>
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<div class="tags">
<ul class="flat">
<li><a href="/tags/api">api</a></li>
<li><a href="/tags/cloud">cloud</a></li>
<li><a href="/tags/custom">custom</a></li>
<li><a href="/tags/developer">developer</a></li>
<li><a href="/tags/ecosystem">ecosystem</a></li>
<li><a href="/tags/fcselect">fcselect</a></li>
<li><a href="/tags/ibm">ibm</a></li>
<li><a href="/tags/python">python</a></li>
<li><a href="/tags/query">query</a></li>
<li><a href="/tags/rank">rank</a></li>
<li><a href="/tags/ranker">ranker</a></li>
<li><a href="/tags/retrieve">retrieve</a></li>
<li><a href="/tags/services">services</a></li>
<li><a href="/tags/solr">solr</a></li>
<li><a href="/tags/train">train</a></li>
<li><a href="/tags/watson">watson</a></li>
<li><a href="/tags/wdc">wdc</a></li>
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