Sorting Order in Django Haystack SOLR

Question

I am trying to sort by a date field in Haystack Solr on Django. It has a lot of NULL values. I want the not null values to be sorted and come on top. The -order_by('field') is not doing this. It is bringing the null values between the non-null values. I want the sorting to happen purely on this field irrespective of the scores.

---

EDIT

The field in schema.xml

 <field name="sort_date" type="date" indexed="true" stored="true"
 multiValued="false" />

 <field name="sort_date_exact" type="date" indexed="true" stored="true"
 multiValued="false" />

---

EDIT

The whole schema.xml without the fields

 <?xml version="1.0" ?>
<!--
 Licensed to the Apache Software Foundation (ASF) under one or more
 contributor license agreements.  See the NOTICE file distributed with
 this work for additional information regarding copyright ownership.
 The ASF licenses this file to You under the Apache License, Version 2.0
 (the "License"); you may not use this file except in compliance with
 the License.  You may obtain a copy of the License at

 http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
  -->

<schema name="default" version="1.4">
  <types>
<fieldtype name="string"  class="solr.StrField" sortMissingLast="true" omitNorms="true"/>
<fieldType name="boolean" class="solr.BoolField" sortMissingLast="true" omitNorms="true"/>
<fieldtype name="binary" class="solr.BinaryField"/>

<!-- Numeric field types that manipulate the value into
     a string value that isn't human-readable in its internal form,
     but with a lexicographic ordering the same as the numeric ordering,
     so that range queries work correctly. -->
<fieldType name="int" class="solr.TrieIntField" precisionStep="0" omitNorms="true"       sortMissingLast="true" positionIncrementGap="0"/>
<fieldType name="float" class="solr.TrieFloatField" precisionStep="0" omitNorms="true" sortMissingLast="true" positionIncrementGap="0"/>
<fieldType name="long" class="solr.TrieLongField" precisionStep="0" omitNorms="true" sortMissingLast="true" positionIncrementGap="0"/>
<fieldType name="double" class="solr.TrieDoubleField" precisionStep="0" omitNorms="true" sortMissingLast="true" positionIncrementGap="0"/>

<fieldType name="tint" class="solr.TrieIntField" precisionStep="8" omitNorms="true" positionIncrementGap="0"/>
<fieldType name="tfloat" class="solr.TrieFloatField" precisionStep="8" omitNorms="true" positionIncrementGap="0"/>
<fieldType name="tlong" class="solr.TrieLongField" precisionStep="8" omitNorms="true" positionIncrementGap="0"/>
<fieldType name="tdouble" class="solr.TrieDoubleField" precisionStep="8" omitNorms="true" positionIncrementGap="0"/>

<fieldType name="date" class="solr.TrieDateField" omitNorms="true" precisionStep="0" positionIncrementGap="0"/>
<!-- A Trie based date field for faster date range queries and date faceting. -->
<fieldType name="tdate" class="solr.TrieDateField" omitNorms="true" precisionStep="6" positionIncrementGap="0"/>

<fieldType name="point" class="solr.PointType" dimension="2" subFieldSuffix="_d"/>
<fieldType name="location" class="solr.LatLonType" subFieldSuffix="_coordinate"/>
<fieldtype name="geohash" class="solr.GeoHashField"/>

<fieldType name="text_general" class="solr.TextField" positionIncrementGap="100">
  <analyzer type="index">
    <tokenizer class="solr.StandardTokenizerFactory"/>
    <filter class="solr.StopFilterFactory" ignoreCase="true" words="lang/stopwords_en.txt" enablePositionIncrements="true" />
    <!-- in this example, we will only use synonyms at query time
    <filter class="solr.SynonymFilterFactory" synonyms="index_synonyms.txt" ignoreCase="true" expand="false"/>
    -->
    <filter class="solr.LowerCaseFilterFactory"/>
  </analyzer>
  <analyzer type="query">
    <tokenizer class="solr.StandardTokenizerFactory"/>
    <filter class="solr.StopFilterFactory" ignoreCase="true" words="lang/stopwords_en.txt" enablePositionIncrements="true" />
    <filter class="solr.SynonymFilterFactory" synonyms="synonyms.txt" ignoreCase="true" expand="true"/>
    <filter class="solr.LowerCaseFilterFactory"/>
  </analyzer>
</fieldType>

<fieldType name="text_en" class="solr.TextField" positionIncrementGap="100">
  <analyzer type="index">
    <tokenizer class="solr.StandardTokenizerFactory"/>
    <filter class="solr.StopFilterFactory"
            ignoreCase="true"
            words="lang/stopwords_en.txt"
            enablePositionIncrements="true"
            />
    <filter class="solr.LowerCaseFilterFactory"/>
    <filter class="solr.EnglishPossessiveFilterFactory"/>
    <filter class="solr.KeywordMarkerFilterFactory" protected="protwords.txt"/>
    <!-- Optionally you may want to use this less aggressive stemmer instead of PorterStemFilterFactory:
      <filter class="solr.EnglishMinimalStemFilterFactory"/>
    -->
    <filter class="solr.PorterStemFilterFactory"/>
  </analyzer>
  <analyzer type="query">
    <tokenizer class="solr.StandardTokenizerFactory"/>
    <filter class="solr.SynonymFilterFactory" synonyms="synonyms.txt" ignoreCase="true" expand="true"/>
    <filter class="solr.StopFilterFactory"
            ignoreCase="true"
            words="lang/stopwords_en.txt"
            enablePositionIncrements="true"
            />
    <filter class="solr.LowerCaseFilterFactory"/>
    <filter class="solr.EnglishPossessiveFilterFactory"/>
    <filter class="solr.KeywordMarkerFilterFactory" protected="protwords.txt"/>
    <!-- Optionally you may want to use this less aggressive stemmer instead of PorterStemFilterFactory:
      <filter class="solr.EnglishMinimalStemFilterFactory"/>
    -->
    <filter class="solr.PorterStemFilterFactory"/>
  </analyzer>
</fieldType>

<fieldType name="text_ws" class="solr.TextField" positionIncrementGap="100">
  <analyzer>
    <tokenizer class="solr.WhitespaceTokenizerFactory"/>
  </analyzer>
</fieldType>

<fieldType name="ngram" class="solr.TextField" >
  <analyzer type="index">
    <tokenizer class="solr.KeywordTokenizerFactory"/>
    <filter class="solr.LowerCaseFilterFactory"/>
    <filter class="solr.NGramFilterFactory" minGramSize="3" maxGramSize="15" />
  </analyzer>
  <analyzer type="query">
    <tokenizer class="solr.KeywordTokenizerFactory"/>
    <filter class="solr.LowerCaseFilterFactory"/>
  </analyzer>
</fieldType>

<fieldType name="edge_ngram" class="solr.TextField" positionIncrementGap="1">
  <analyzer type="index">
    <tokenizer class="solr.WhitespaceTokenizerFactory" />
    <filter class="solr.LowerCaseFilterFactory" />
    <filter class="solr.WordDelimiterFilterFactory" generateWordParts="1" generateNumberParts="1" catenateWords="0" catenateNumbers="0" catenateAll="0" splitOnCaseChange="1"/>
    <filter class="solr.EdgeNGramFilterFactory" minGramSize="2" maxGramSize="15" side="front" />
  </analyzer>
  <analyzer type="query">
    <tokenizer class="solr.WhitespaceTokenizerFactory" />
    <filter class="solr.LowerCaseFilterFactory" />
    <filter class="solr.WordDelimiterFilterFactory" generateWordParts="1" generateNumberParts="1" catenateWords="0" catenateNumbers="0" catenateAll="0" splitOnCaseChange="1"/>
  </analyzer>
</fieldType>
  </types>

  <fields>
<!-- general -->
<field name="id" type="string" indexed="true" stored="true" multiValued="false" required="true"/>
<field name="django_ct" type="string" indexed="true" stored="true" multiValued="false"/>
<field name="django_id" type="string" indexed="true" stored="true" multiValued="false"/>

<dynamicField name="*_i"  type="int"    indexed="true"  stored="true"/>
<dynamicField name="*_s"  type="string"  indexed="true"  stored="true"/>
<dynamicField name="*_l"  type="long"   indexed="true"  stored="true"/>
<dynamicField name="*_t"  type="text_en"    indexed="true"  stored="true"/>
<dynamicField name="*_b"  type="boolean" indexed="true"  stored="true"/>
<dynamicField name="*_f"  type="float"  indexed="true"  stored="true"/>
<dynamicField name="*_d"  type="double" indexed="true"  stored="true"/>
<dynamicField name="*_dt" type="date" indexed="true" stored="true"/>
<dynamicField name="*_p" type="location" indexed="true" stored="true"/>
<dynamicField name="*_coordinate"  type="tdouble" indexed="true"  stored="false"/>


<field name="_version_" type="long" indexed="true" stored="true" multiValued="false"/>

 </fields>

<!-- field to use to determine and enforce document uniqueness. -->
<uniqueKey>id</uniqueKey>

<!-- field for the QueryParser to use when an explicit fieldname is absent -->
<defaultSearchField>text</defaultSearchField>

 <!-- SolrQueryParser configuration: defaultOperator="AND|OR" -->
 <solrQueryParser defaultOperator="AND"/>
   </schema>

Answer 1

Add sortMissingLast="true" to the field that shall have the behaviour. After that ordering ascending or descending by that field will put the null values last. As far as I know this change will require you to re-index, before it takes effect.

<field name="sort_date" type="date" indexed="true" stored="true"
 multiValued="false" sortMissingLast="true" />

<field name="sort_date_exact" type="date" indexed="true" stored="true"
 multiValued="false" sortMissingLast="true" />

There have been some issues prior to Solr 3.5, which you can read up in the related question Sorting dates using Solr is messing up some dates. As I do not know which version you use, this could be of interest.