Sophie: python-django-doc-1.8.19-1.2.mga6 noarch

python-django-doc-1.8.19-1.2.mga6.noarch.rpm

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
  "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">


<html xmlns="http://www.w3.org/1999/xhtml" lang="">
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    
    <title>django.db.models.query_utils &#8212; Django 1.8.19 documentation</title>
    
    <link rel="stylesheet" href="../../../../_static/default.css" type="text/css" />
    <link rel="stylesheet" href="../../../../_static/pygments.css" type="text/css" />
    
    <script type="text/javascript">
      var DOCUMENTATION_OPTIONS = {
        URL_ROOT:    '../../../../',
        VERSION:     '1.8.19',
        COLLAPSE_INDEX: false,
        FILE_SUFFIX: '.html',
        HAS_SOURCE:  true
      };
    </script>
    <script type="text/javascript" src="../../../../_static/jquery.js"></script>
    <script type="text/javascript" src="../../../../_static/underscore.js"></script>
    <script type="text/javascript" src="../../../../_static/doctools.js"></script>
    <link rel="index" title="Index" href="../../../../genindex.html" />
    <link rel="search" title="Search" href="../../../../search.html" />
    <link rel="top" title="Django 1.8.19 documentation" href="../../../../contents.html" />
    <link rel="up" title="django" href="../../../django.html" />



 
<script type="text/javascript" src="../../../../templatebuiltins.js"></script>
<script type="text/javascript">
(function($) {
    if (!django_template_builtins) {
       // templatebuiltins.js missing, do nothing.
       return;
    }
    $(document).ready(function() {
        // Hyperlink Django template tags and filters
        var base = "../../../../ref/templates/builtins.html";
        if (base == "#") {
            // Special case for builtins.html itself
            base = "";
        }
        // Tags are keywords, class '.k'
        $("div.highlight\\-html\\+django span.k").each(function(i, elem) {
             var tagname = $(elem).text();
             if ($.inArray(tagname, django_template_builtins.ttags) != -1) {
                 var fragment = tagname.replace(/_/, '-');
                 $(elem).html("<a href='" + base + "#" + fragment + "'>" + tagname + "</a>");
             }
        });
        // Filters are functions, class '.nf'
        $("div.highlight\\-html\\+django span.nf").each(function(i, elem) {
             var filtername = $(elem).text();
             if ($.inArray(filtername, django_template_builtins.tfilters) != -1) {
                 var fragment = filtername.replace(/_/, '-');
                 $(elem).html("<a href='" + base + "#" + fragment + "'>" + filtername + "</a>");
             }
        });
    });
})(jQuery);
</script>


  </head>
  <body role="document">

    <div class="document">
  <div id="custom-doc" class="yui-t6">
    <div id="hd">
      <h1><a href="../../../../index.html">Django 1.8.19 documentation</a></h1>
      <div id="global-nav">
        <a title="Home page" href="../../../../index.html">Home</a>  |
        <a title="Table of contents" href="../../../../contents.html">Table of contents</a>  |
        <a title="Global index" href="../../../../genindex.html">Index</a>  |
        <a title="Module index" href="../../../../py-modindex.html">Modules</a>
      </div>
      <div class="nav">
    <a href="../../../index.html" title="Module code" accesskey="U">up</a></div>
    </div>

    <div id="bd">
      <div id="yui-main">
        <div class="yui-b">
          <div class="yui-g" id="_modules-django-db-models-query_utils">
            
  <h1>Source code for django.db.models.query_utils</h1><div class="highlight"><pre>
<span></span><span class="sd">&quot;&quot;&quot;</span>
<span class="sd">Various data structures used in query construction.</span>

<span class="sd">Factored out from django.db.models.query to avoid making the main module very</span>
<span class="sd">large and/or so that they can be used by other modules without getting into</span>
<span class="sd">circular import difficulties.</span>
<span class="sd">&quot;&quot;&quot;</span>
<span class="kn">from</span> <span class="nn">__future__</span> <span class="k">import</span> <span class="n">unicode_literals</span>

<span class="kn">from</span> <span class="nn">collections</span> <span class="k">import</span> <span class="n">namedtuple</span>

<span class="kn">from</span> <span class="nn">django.core.exceptions</span> <span class="k">import</span> <span class="n">FieldDoesNotExist</span>
<span class="kn">from</span> <span class="nn">django.db.backends</span> <span class="k">import</span> <span class="n">utils</span>
<span class="kn">from</span> <span class="nn">django.db.models.constants</span> <span class="k">import</span> <span class="n">LOOKUP_SEP</span>
<span class="kn">from</span> <span class="nn">django.utils</span> <span class="k">import</span> <span class="n">six</span><span class="p">,</span> <span class="n">tree</span>

<span class="c1"># PathInfo is used when converting lookups (fk__somecol). The contents</span>
<span class="c1"># describe the relation in Model terms (model Options and Fields for both</span>
<span class="c1"># sides of the relation. The join_field is the field backing the relation.</span>
<span class="n">PathInfo</span> <span class="o">=</span> <span class="n">namedtuple</span><span class="p">(</span><span class="s1">&#39;PathInfo&#39;</span><span class="p">,</span> <span class="s1">&#39;from_opts to_opts target_fields join_field m2m direct&#39;</span><span class="p">)</span>


<span class="k">class</span> <span class="nc">InvalidQuery</span><span class="p">(</span><span class="ne">Exception</span><span class="p">):</span>
    <span class="sd">&quot;&quot;&quot;</span>
<span class="sd">    The query passed to raw isn&#39;t a safe query to use with raw.</span>
<span class="sd">    &quot;&quot;&quot;</span>
    <span class="k">pass</span>


<span class="k">class</span> <span class="nc">QueryWrapper</span><span class="p">(</span><span class="nb">object</span><span class="p">):</span>
    <span class="sd">&quot;&quot;&quot;</span>
<span class="sd">    A type that indicates the contents are an SQL fragment and the associate</span>
<span class="sd">    parameters. Can be used to pass opaque data to a where-clause, for example.</span>
<span class="sd">    &quot;&quot;&quot;</span>
    <span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">sql</span><span class="p">,</span> <span class="n">params</span><span class="p">):</span>
        <span class="bp">self</span><span class="o">.</span><span class="n">data</span> <span class="o">=</span> <span class="n">sql</span><span class="p">,</span> <span class="nb">list</span><span class="p">(</span><span class="n">params</span><span class="p">)</span>

    <span class="k">def</span> <span class="nf">as_sql</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">compiler</span><span class="o">=</span><span class="kc">None</span><span class="p">,</span> <span class="n">connection</span><span class="o">=</span><span class="kc">None</span><span class="p">):</span>
        <span class="k">return</span> <span class="bp">self</span><span class="o">.</span><span class="n">data</span>


<div class="viewcode-block" id="Q"><a class="viewcode-back" href="../../../../ref/models/querysets.html#django.db.models.Q">[docs]</a><span class="k">class</span> <span class="nc">Q</span><span class="p">(</span><span class="n">tree</span><span class="o">.</span><span class="n">Node</span><span class="p">):</span>
    <span class="sd">&quot;&quot;&quot;</span>
<span class="sd">    Encapsulates filters as objects that can then be combined logically (using</span>
<span class="sd">    `&amp;` and `|`).</span>
<span class="sd">    &quot;&quot;&quot;</span>
    <span class="c1"># Connection types</span>
    <span class="n">AND</span> <span class="o">=</span> <span class="s1">&#39;AND&#39;</span>
    <span class="n">OR</span> <span class="o">=</span> <span class="s1">&#39;OR&#39;</span>
    <span class="n">default</span> <span class="o">=</span> <span class="n">AND</span>

    <span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="o">*</span><span class="n">args</span><span class="p">,</span> <span class="o">**</span><span class="n">kwargs</span><span class="p">):</span>
        <span class="nb">super</span><span class="p">(</span><span class="n">Q</span><span class="p">,</span> <span class="bp">self</span><span class="p">)</span><span class="o">.</span><span class="n">__init__</span><span class="p">(</span><span class="n">children</span><span class="o">=</span><span class="nb">list</span><span class="p">(</span><span class="n">args</span><span class="p">)</span> <span class="o">+</span> <span class="nb">list</span><span class="p">(</span><span class="n">six</span><span class="o">.</span><span class="n">iteritems</span><span class="p">(</span><span class="n">kwargs</span><span class="p">)))</span>

    <span class="k">def</span> <span class="nf">_combine</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">other</span><span class="p">,</span> <span class="n">conn</span><span class="p">):</span>
        <span class="k">if</span> <span class="ow">not</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">other</span><span class="p">,</span> <span class="n">Q</span><span class="p">):</span>
            <span class="k">raise</span> <span class="ne">TypeError</span><span class="p">(</span><span class="n">other</span><span class="p">)</span>
        <span class="n">obj</span> <span class="o">=</span> <span class="nb">type</span><span class="p">(</span><span class="bp">self</span><span class="p">)()</span>
        <span class="n">obj</span><span class="o">.</span><span class="n">connector</span> <span class="o">=</span> <span class="n">conn</span>
        <span class="n">obj</span><span class="o">.</span><span class="n">add</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">conn</span><span class="p">)</span>
        <span class="n">obj</span><span class="o">.</span><span class="n">add</span><span class="p">(</span><span class="n">other</span><span class="p">,</span> <span class="n">conn</span><span class="p">)</span>
        <span class="k">return</span> <span class="n">obj</span>

    <span class="k">def</span> <span class="nf">__or__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">other</span><span class="p">):</span>
        <span class="k">return</span> <span class="bp">self</span><span class="o">.</span><span class="n">_combine</span><span class="p">(</span><span class="n">other</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">OR</span><span class="p">)</span>

    <span class="k">def</span> <span class="nf">__and__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">other</span><span class="p">):</span>
        <span class="k">return</span> <span class="bp">self</span><span class="o">.</span><span class="n">_combine</span><span class="p">(</span><span class="n">other</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">AND</span><span class="p">)</span>

    <span class="k">def</span> <span class="nf">__invert__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
        <span class="n">obj</span> <span class="o">=</span> <span class="nb">type</span><span class="p">(</span><span class="bp">self</span><span class="p">)()</span>
        <span class="n">obj</span><span class="o">.</span><span class="n">add</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">AND</span><span class="p">)</span>
        <span class="n">obj</span><span class="o">.</span><span class="n">negate</span><span class="p">()</span>
        <span class="k">return</span> <span class="n">obj</span>

    <span class="k">def</span> <span class="nf">clone</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
        <span class="n">clone</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">__class__</span><span class="o">.</span><span class="n">_new_instance</span><span class="p">(</span>
            <span class="n">children</span><span class="o">=</span><span class="p">[],</span> <span class="n">connector</span><span class="o">=</span><span class="bp">self</span><span class="o">.</span><span class="n">connector</span><span class="p">,</span> <span class="n">negated</span><span class="o">=</span><span class="bp">self</span><span class="o">.</span><span class="n">negated</span><span class="p">)</span>
        <span class="k">for</span> <span class="n">child</span> <span class="ow">in</span> <span class="bp">self</span><span class="o">.</span><span class="n">children</span><span class="p">:</span>
            <span class="k">if</span> <span class="nb">hasattr</span><span class="p">(</span><span class="n">child</span><span class="p">,</span> <span class="s1">&#39;clone&#39;</span><span class="p">):</span>
                <span class="n">clone</span><span class="o">.</span><span class="n">children</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">child</span><span class="o">.</span><span class="n">clone</span><span class="p">())</span>
            <span class="k">else</span><span class="p">:</span>
                <span class="n">clone</span><span class="o">.</span><span class="n">children</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">child</span><span class="p">)</span>
        <span class="k">return</span> <span class="n">clone</span>

    <span class="k">def</span> <span class="nf">resolve_expression</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">query</span><span class="o">=</span><span class="kc">None</span><span class="p">,</span> <span class="n">allow_joins</span><span class="o">=</span><span class="kc">True</span><span class="p">,</span> <span class="n">reuse</span><span class="o">=</span><span class="kc">None</span><span class="p">,</span> <span class="n">summarize</span><span class="o">=</span><span class="kc">False</span><span class="p">,</span> <span class="n">for_save</span><span class="o">=</span><span class="kc">False</span><span class="p">):</span>
        <span class="c1"># We must promote any new joins to left outer joins so that when Q is</span>
        <span class="c1"># used as an expression, rows aren&#39;t filtered due to joins.</span>
        <span class="n">clause</span><span class="p">,</span> <span class="n">joins</span> <span class="o">=</span> <span class="n">query</span><span class="o">.</span><span class="n">_add_q</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">reuse</span><span class="p">,</span> <span class="n">allow_joins</span><span class="o">=</span><span class="n">allow_joins</span><span class="p">,</span> <span class="n">split_subq</span><span class="o">=</span><span class="kc">False</span><span class="p">)</span>
        <span class="n">query</span><span class="o">.</span><span class="n">promote_joins</span><span class="p">(</span><span class="n">joins</span><span class="p">)</span>
        <span class="k">return</span> <span class="n">clause</span>

    <span class="nd">@classmethod</span>
    <span class="k">def</span> <span class="nf">_refs_aggregate</span><span class="p">(</span><span class="n">cls</span><span class="p">,</span> <span class="n">obj</span><span class="p">,</span> <span class="n">existing_aggregates</span><span class="p">):</span>
        <span class="k">if</span> <span class="ow">not</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">obj</span><span class="p">,</span> <span class="n">tree</span><span class="o">.</span><span class="n">Node</span><span class="p">):</span>
            <span class="n">aggregate</span><span class="p">,</span> <span class="n">aggregate_lookups</span> <span class="o">=</span> <span class="n">refs_aggregate</span><span class="p">(</span><span class="n">obj</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="o">.</span><span class="n">split</span><span class="p">(</span><span class="n">LOOKUP_SEP</span><span class="p">),</span> <span class="n">existing_aggregates</span><span class="p">)</span>
            <span class="k">if</span> <span class="ow">not</span> <span class="n">aggregate</span> <span class="ow">and</span> <span class="nb">hasattr</span><span class="p">(</span><span class="n">obj</span><span class="p">[</span><span class="mi">1</span><span class="p">],</span> <span class="s1">&#39;refs_aggregate&#39;</span><span class="p">):</span>
                <span class="k">return</span> <span class="n">obj</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="o">.</span><span class="n">refs_aggregate</span><span class="p">(</span><span class="n">existing_aggregates</span><span class="p">)</span>
            <span class="k">return</span> <span class="n">aggregate</span><span class="p">,</span> <span class="n">aggregate_lookups</span>
        <span class="k">for</span> <span class="n">c</span> <span class="ow">in</span> <span class="n">obj</span><span class="o">.</span><span class="n">children</span><span class="p">:</span>
            <span class="n">aggregate</span><span class="p">,</span> <span class="n">aggregate_lookups</span> <span class="o">=</span> <span class="n">cls</span><span class="o">.</span><span class="n">_refs_aggregate</span><span class="p">(</span><span class="n">c</span><span class="p">,</span> <span class="n">existing_aggregates</span><span class="p">)</span>
            <span class="k">if</span> <span class="n">aggregate</span><span class="p">:</span>
                <span class="k">return</span> <span class="n">aggregate</span><span class="p">,</span> <span class="n">aggregate_lookups</span>
        <span class="k">return</span> <span class="kc">False</span><span class="p">,</span> <span class="p">()</span>

    <span class="k">def</span> <span class="nf">refs_aggregate</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">existing_aggregates</span><span class="p">):</span>
        <span class="k">if</span> <span class="ow">not</span> <span class="n">existing_aggregates</span><span class="p">:</span>
            <span class="k">return</span> <span class="kc">False</span>

        <span class="k">return</span> <span class="bp">self</span><span class="o">.</span><span class="n">_refs_aggregate</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">existing_aggregates</span><span class="p">)</span></div>


<span class="k">class</span> <span class="nc">DeferredAttribute</span><span class="p">(</span><span class="nb">object</span><span class="p">):</span>
    <span class="sd">&quot;&quot;&quot;</span>
<span class="sd">    A wrapper for a deferred-loading field. When the value is read from this</span>
<span class="sd">    object the first time, the query is executed.</span>
<span class="sd">    &quot;&quot;&quot;</span>
    <span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">field_name</span><span class="p">,</span> <span class="n">model</span><span class="p">):</span>
        <span class="bp">self</span><span class="o">.</span><span class="n">field_name</span> <span class="o">=</span> <span class="n">field_name</span>

    <span class="k">def</span> <span class="nf">__get__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">instance</span><span class="p">,</span> <span class="n">owner</span><span class="p">):</span>
        <span class="sd">&quot;&quot;&quot;</span>
<span class="sd">        Retrieves and caches the value from the datastore on the first lookup.</span>
<span class="sd">        Returns the cached value.</span>
<span class="sd">        &quot;&quot;&quot;</span>
        <span class="n">non_deferred_model</span> <span class="o">=</span> <span class="n">instance</span><span class="o">.</span><span class="n">_meta</span><span class="o">.</span><span class="n">proxy_for_model</span>
        <span class="n">opts</span> <span class="o">=</span> <span class="n">non_deferred_model</span><span class="o">.</span><span class="n">_meta</span>

        <span class="k">assert</span> <span class="n">instance</span> <span class="ow">is</span> <span class="ow">not</span> <span class="kc">None</span>
        <span class="n">data</span> <span class="o">=</span> <span class="n">instance</span><span class="o">.</span><span class="n">__dict__</span>
        <span class="k">if</span> <span class="n">data</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">field_name</span><span class="p">,</span> <span class="bp">self</span><span class="p">)</span> <span class="ow">is</span> <span class="bp">self</span><span class="p">:</span>
            <span class="c1"># self.field_name is the attname of the field, but only() takes the</span>
            <span class="c1"># actual name, so we need to translate it here.</span>
            <span class="k">try</span><span class="p">:</span>
                <span class="n">f</span> <span class="o">=</span> <span class="n">opts</span><span class="o">.</span><span class="n">get_field</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">field_name</span><span class="p">)</span>
            <span class="k">except</span> <span class="n">FieldDoesNotExist</span><span class="p">:</span>
                <span class="n">f</span> <span class="o">=</span> <span class="p">[</span><span class="n">f</span> <span class="k">for</span> <span class="n">f</span> <span class="ow">in</span> <span class="n">opts</span><span class="o">.</span><span class="n">fields</span> <span class="k">if</span> <span class="n">f</span><span class="o">.</span><span class="n">attname</span> <span class="o">==</span> <span class="bp">self</span><span class="o">.</span><span class="n">field_name</span><span class="p">][</span><span class="mi">0</span><span class="p">]</span>
            <span class="n">name</span> <span class="o">=</span> <span class="n">f</span><span class="o">.</span><span class="n">name</span>
            <span class="c1"># Let&#39;s see if the field is part of the parent chain. If so we</span>
            <span class="c1"># might be able to reuse the already loaded value. Refs #18343.</span>
            <span class="n">val</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">_check_parent_chain</span><span class="p">(</span><span class="n">instance</span><span class="p">,</span> <span class="n">name</span><span class="p">)</span>
            <span class="k">if</span> <span class="n">val</span> <span class="ow">is</span> <span class="kc">None</span><span class="p">:</span>
                <span class="n">instance</span><span class="o">.</span><span class="n">refresh_from_db</span><span class="p">(</span><span class="n">fields</span><span class="o">=</span><span class="p">[</span><span class="bp">self</span><span class="o">.</span><span class="n">field_name</span><span class="p">])</span>
                <span class="n">val</span> <span class="o">=</span> <span class="nb">getattr</span><span class="p">(</span><span class="n">instance</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">field_name</span><span class="p">)</span>
            <span class="n">data</span><span class="p">[</span><span class="bp">self</span><span class="o">.</span><span class="n">field_name</span><span class="p">]</span> <span class="o">=</span> <span class="n">val</span>
        <span class="k">return</span> <span class="n">data</span><span class="p">[</span><span class="bp">self</span><span class="o">.</span><span class="n">field_name</span><span class="p">]</span>

    <span class="k">def</span> <span class="nf">__set__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">instance</span><span class="p">,</span> <span class="n">value</span><span class="p">):</span>
        <span class="sd">&quot;&quot;&quot;</span>
<span class="sd">        Deferred loading attributes can be set normally (which means there will</span>
<span class="sd">        never be a database lookup involved.</span>
<span class="sd">        &quot;&quot;&quot;</span>
        <span class="n">instance</span><span class="o">.</span><span class="n">__dict__</span><span class="p">[</span><span class="bp">self</span><span class="o">.</span><span class="n">field_name</span><span class="p">]</span> <span class="o">=</span> <span class="n">value</span>

    <span class="k">def</span> <span class="nf">_check_parent_chain</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">instance</span><span class="p">,</span> <span class="n">name</span><span class="p">):</span>
        <span class="sd">&quot;&quot;&quot;</span>
<span class="sd">        Check if the field value can be fetched from a parent field already</span>
<span class="sd">        loaded in the instance. This can be done if the to-be fetched</span>
<span class="sd">        field is a primary key field.</span>
<span class="sd">        &quot;&quot;&quot;</span>
        <span class="n">opts</span> <span class="o">=</span> <span class="n">instance</span><span class="o">.</span><span class="n">_meta</span>
        <span class="n">f</span> <span class="o">=</span> <span class="n">opts</span><span class="o">.</span><span class="n">get_field</span><span class="p">(</span><span class="n">name</span><span class="p">)</span>
        <span class="n">link_field</span> <span class="o">=</span> <span class="n">opts</span><span class="o">.</span><span class="n">get_ancestor_link</span><span class="p">(</span><span class="n">f</span><span class="o">.</span><span class="n">model</span><span class="p">)</span>
        <span class="k">if</span> <span class="n">f</span><span class="o">.</span><span class="n">primary_key</span> <span class="ow">and</span> <span class="n">f</span> <span class="o">!=</span> <span class="n">link_field</span><span class="p">:</span>
            <span class="k">return</span> <span class="nb">getattr</span><span class="p">(</span><span class="n">instance</span><span class="p">,</span> <span class="n">link_field</span><span class="o">.</span><span class="n">attname</span><span class="p">)</span>
        <span class="k">return</span> <span class="kc">None</span>


<span class="k">def</span> <span class="nf">select_related_descend</span><span class="p">(</span><span class="n">field</span><span class="p">,</span> <span class="n">restricted</span><span class="p">,</span> <span class="n">requested</span><span class="p">,</span> <span class="n">load_fields</span><span class="p">,</span> <span class="n">reverse</span><span class="o">=</span><span class="kc">False</span><span class="p">):</span>
    <span class="sd">&quot;&quot;&quot;</span>
<span class="sd">    Returns True if this field should be used to descend deeper for</span>
<span class="sd">    select_related() purposes. Used by both the query construction code</span>
<span class="sd">    (sql.query.fill_related_selections()) and the model instance creation code</span>
<span class="sd">    (query.get_klass_info()).</span>

<span class="sd">    Arguments:</span>
<span class="sd">     * field - the field to be checked</span>
<span class="sd">     * restricted - a boolean field, indicating if the field list has been</span>
<span class="sd">       manually restricted using a requested clause)</span>
<span class="sd">     * requested - The select_related() dictionary.</span>
<span class="sd">     * load_fields - the set of fields to be loaded on this model</span>
<span class="sd">     * reverse - boolean, True if we are checking a reverse select related</span>
<span class="sd">    &quot;&quot;&quot;</span>
    <span class="k">if</span> <span class="ow">not</span> <span class="n">field</span><span class="o">.</span><span class="n">rel</span><span class="p">:</span>
        <span class="k">return</span> <span class="kc">False</span>
    <span class="k">if</span> <span class="n">field</span><span class="o">.</span><span class="n">rel</span><span class="o">.</span><span class="n">parent_link</span> <span class="ow">and</span> <span class="ow">not</span> <span class="n">reverse</span><span class="p">:</span>
        <span class="k">return</span> <span class="kc">False</span>
    <span class="k">if</span> <span class="n">restricted</span><span class="p">:</span>
        <span class="k">if</span> <span class="n">reverse</span> <span class="ow">and</span> <span class="n">field</span><span class="o">.</span><span class="n">related_query_name</span><span class="p">()</span> <span class="ow">not</span> <span class="ow">in</span> <span class="n">requested</span><span class="p">:</span>
            <span class="k">return</span> <span class="kc">False</span>
        <span class="k">if</span> <span class="ow">not</span> <span class="n">reverse</span> <span class="ow">and</span> <span class="n">field</span><span class="o">.</span><span class="n">name</span> <span class="ow">not</span> <span class="ow">in</span> <span class="n">requested</span><span class="p">:</span>
            <span class="k">return</span> <span class="kc">False</span>
    <span class="k">if</span> <span class="ow">not</span> <span class="n">restricted</span> <span class="ow">and</span> <span class="n">field</span><span class="o">.</span><span class="n">null</span><span class="p">:</span>
        <span class="k">return</span> <span class="kc">False</span>
    <span class="k">if</span> <span class="n">load_fields</span><span class="p">:</span>
        <span class="k">if</span> <span class="n">field</span><span class="o">.</span><span class="n">attname</span> <span class="ow">not</span> <span class="ow">in</span> <span class="n">load_fields</span><span class="p">:</span>
            <span class="k">if</span> <span class="n">restricted</span> <span class="ow">and</span> <span class="n">field</span><span class="o">.</span><span class="n">name</span> <span class="ow">in</span> <span class="n">requested</span><span class="p">:</span>
                <span class="k">raise</span> <span class="n">InvalidQuery</span><span class="p">(</span><span class="s2">&quot;Field </span><span class="si">%s</span><span class="s2">.</span><span class="si">%s</span><span class="s2"> cannot be both deferred&quot;</span>
                                   <span class="s2">&quot; and traversed using select_related&quot;</span>
                                   <span class="s2">&quot; at the same time.&quot;</span> <span class="o">%</span>
                                   <span class="p">(</span><span class="n">field</span><span class="o">.</span><span class="n">model</span><span class="o">.</span><span class="n">_meta</span><span class="o">.</span><span class="n">object_name</span><span class="p">,</span> <span class="n">field</span><span class="o">.</span><span class="n">name</span><span class="p">))</span>
            <span class="k">return</span> <span class="kc">False</span>
    <span class="k">return</span> <span class="kc">True</span>


<span class="c1"># This function is needed because data descriptors must be defined on a class</span>
<span class="c1"># object, not an instance, to have any effect.</span>

<span class="k">def</span> <span class="nf">deferred_class_factory</span><span class="p">(</span><span class="n">model</span><span class="p">,</span> <span class="n">attrs</span><span class="p">):</span>
    <span class="sd">&quot;&quot;&quot;</span>
<span class="sd">    Returns a class object that is a copy of &quot;model&quot; with the specified &quot;attrs&quot;</span>
<span class="sd">    being replaced with DeferredAttribute objects. The &quot;pk_value&quot; ties the</span>
<span class="sd">    deferred attributes to a particular instance of the model.</span>
<span class="sd">    &quot;&quot;&quot;</span>
    <span class="k">if</span> <span class="ow">not</span> <span class="n">attrs</span><span class="p">:</span>
        <span class="k">return</span> <span class="n">model</span>
    <span class="n">opts</span> <span class="o">=</span> <span class="n">model</span><span class="o">.</span><span class="n">_meta</span>
    <span class="c1"># Never create deferred models based on deferred model</span>
    <span class="k">if</span> <span class="n">model</span><span class="o">.</span><span class="n">_deferred</span><span class="p">:</span>
        <span class="c1"># Deferred models are proxies for the non-deferred model. We never</span>
        <span class="c1"># create chains of defers =&gt; proxy_for_model is the non-deferred</span>
        <span class="c1"># model.</span>
        <span class="n">model</span> <span class="o">=</span> <span class="n">opts</span><span class="o">.</span><span class="n">proxy_for_model</span>
    <span class="c1"># The app registry wants a unique name for each model, otherwise the new</span>
    <span class="c1"># class won&#39;t be created (we get an exception). Therefore, we generate</span>
    <span class="c1"># the name using the passed in attrs. It&#39;s OK to reuse an existing class</span>
    <span class="c1"># object if the attrs are identical.</span>
    <span class="n">name</span> <span class="o">=</span> <span class="s2">&quot;</span><span class="si">%s</span><span class="s2">_Deferred_</span><span class="si">%s</span><span class="s2">&quot;</span> <span class="o">%</span> <span class="p">(</span><span class="n">model</span><span class="o">.</span><span class="n">__name__</span><span class="p">,</span> <span class="s1">&#39;_&#39;</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="nb">sorted</span><span class="p">(</span><span class="nb">list</span><span class="p">(</span><span class="n">attrs</span><span class="p">))))</span>
    <span class="n">name</span> <span class="o">=</span> <span class="n">utils</span><span class="o">.</span><span class="n">truncate_name</span><span class="p">(</span><span class="n">name</span><span class="p">,</span> <span class="mi">80</span><span class="p">,</span> <span class="mi">32</span><span class="p">)</span>

    <span class="k">try</span><span class="p">:</span>
        <span class="k">return</span> <span class="n">opts</span><span class="o">.</span><span class="n">apps</span><span class="o">.</span><span class="n">get_model</span><span class="p">(</span><span class="n">model</span><span class="o">.</span><span class="n">_meta</span><span class="o">.</span><span class="n">app_label</span><span class="p">,</span> <span class="n">name</span><span class="p">)</span>

    <span class="k">except</span> <span class="ne">LookupError</span><span class="p">:</span>

        <span class="k">class</span> <span class="nc">Meta</span><span class="p">:</span>
            <span class="n">proxy</span> <span class="o">=</span> <span class="kc">True</span>
            <span class="n">apps</span> <span class="o">=</span> <span class="n">opts</span><span class="o">.</span><span class="n">apps</span>
            <span class="n">app_label</span> <span class="o">=</span> <span class="n">opts</span><span class="o">.</span><span class="n">app_label</span>

        <span class="n">overrides</span> <span class="o">=</span> <span class="p">{</span><span class="n">attr</span><span class="p">:</span> <span class="n">DeferredAttribute</span><span class="p">(</span><span class="n">attr</span><span class="p">,</span> <span class="n">model</span><span class="p">)</span> <span class="k">for</span> <span class="n">attr</span> <span class="ow">in</span> <span class="n">attrs</span><span class="p">}</span>
        <span class="n">overrides</span><span class="p">[</span><span class="s2">&quot;Meta&quot;</span><span class="p">]</span> <span class="o">=</span> <span class="n">Meta</span>
        <span class="n">overrides</span><span class="p">[</span><span class="s2">&quot;__module__&quot;</span><span class="p">]</span> <span class="o">=</span> <span class="n">model</span><span class="o">.</span><span class="n">__module__</span>
        <span class="n">overrides</span><span class="p">[</span><span class="s2">&quot;_deferred&quot;</span><span class="p">]</span> <span class="o">=</span> <span class="kc">True</span>
        <span class="k">return</span> <span class="nb">type</span><span class="p">(</span><span class="nb">str</span><span class="p">(</span><span class="n">name</span><span class="p">),</span> <span class="p">(</span><span class="n">model</span><span class="p">,),</span> <span class="n">overrides</span><span class="p">)</span>


<span class="c1"># The above function is also used to unpickle model instances with deferred</span>
<span class="c1"># fields.</span>
<span class="n">deferred_class_factory</span><span class="o">.</span><span class="n">__safe_for_unpickling__</span> <span class="o">=</span> <span class="kc">True</span>


<span class="k">def</span> <span class="nf">refs_aggregate</span><span class="p">(</span><span class="n">lookup_parts</span><span class="p">,</span> <span class="n">aggregates</span><span class="p">):</span>
    <span class="sd">&quot;&quot;&quot;</span>
<span class="sd">    A little helper method to check if the lookup_parts contains references</span>
<span class="sd">    to the given aggregates set. Because the LOOKUP_SEP is contained in the</span>
<span class="sd">    default annotation names we must check each prefix of the lookup_parts</span>
<span class="sd">    for a match.</span>
<span class="sd">    &quot;&quot;&quot;</span>
    <span class="k">for</span> <span class="n">n</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="nb">len</span><span class="p">(</span><span class="n">lookup_parts</span><span class="p">)</span> <span class="o">+</span> <span class="mi">1</span><span class="p">):</span>
        <span class="n">level_n_lookup</span> <span class="o">=</span> <span class="n">LOOKUP_SEP</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="n">lookup_parts</span><span class="p">[</span><span class="mi">0</span><span class="p">:</span><span class="n">n</span><span class="p">])</span>
        <span class="k">if</span> <span class="n">level_n_lookup</span> <span class="ow">in</span> <span class="n">aggregates</span> <span class="ow">and</span> <span class="n">aggregates</span><span class="p">[</span><span class="n">level_n_lookup</span><span class="p">]</span><span class="o">.</span><span class="n">contains_aggregate</span><span class="p">:</span>
            <span class="k">return</span> <span class="n">aggregates</span><span class="p">[</span><span class="n">level_n_lookup</span><span class="p">],</span> <span class="n">lookup_parts</span><span class="p">[</span><span class="n">n</span><span class="p">:]</span>
    <span class="k">return</span> <span class="kc">False</span><span class="p">,</span> <span class="p">()</span>


<span class="k">def</span> <span class="nf">refs_expression</span><span class="p">(</span><span class="n">lookup_parts</span><span class="p">,</span> <span class="n">annotations</span><span class="p">):</span>
    <span class="sd">&quot;&quot;&quot;</span>
<span class="sd">    A helper method to check if the lookup_parts contains references</span>
<span class="sd">    to the given annotations set. Because the LOOKUP_SEP is contained in the</span>
<span class="sd">    default annotation names we must check each prefix of the lookup_parts</span>
<span class="sd">    for a match.</span>
<span class="sd">    &quot;&quot;&quot;</span>
    <span class="k">for</span> <span class="n">n</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="nb">len</span><span class="p">(</span><span class="n">lookup_parts</span><span class="p">)</span> <span class="o">+</span> <span class="mi">1</span><span class="p">):</span>
        <span class="n">level_n_lookup</span> <span class="o">=</span> <span class="n">LOOKUP_SEP</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="n">lookup_parts</span><span class="p">[</span><span class="mi">0</span><span class="p">:</span><span class="n">n</span><span class="p">])</span>
        <span class="k">if</span> <span class="n">level_n_lookup</span> <span class="ow">in</span> <span class="n">annotations</span> <span class="ow">and</span> <span class="n">annotations</span><span class="p">[</span><span class="n">level_n_lookup</span><span class="p">]:</span>
            <span class="k">return</span> <span class="n">annotations</span><span class="p">[</span><span class="n">level_n_lookup</span><span class="p">],</span> <span class="n">lookup_parts</span><span class="p">[</span><span class="n">n</span><span class="p">:]</span>
    <span class="k">return</span> <span class="kc">False</span><span class="p">,</span> <span class="p">()</span>
</pre></div>

          </div>
        </div>
      </div>
      
        
          <div class="yui-b" id="sidebar">
            
      <div class="sphinxsidebar" role="navigation" aria-label="main navigation">
        <div class="sphinxsidebarwrapper">
  <h3>Browse</h3>
  <ul>
    
    
  </ul>
  <h3>You are here:</h3>
  <ul>
      <li>
        <a href="../../../../index.html">Django 1.8.19 documentation</a>
        
          <ul><li><a href="../../../index.html">Module code</a>
        
          <ul><li><a href="../../../django.html">django</a>
        
        <ul><li>django.db.models.query_utils</li></ul>
        </li></ul></li></ul>
      </li>
  </ul>

<div id="searchbox" style="display: none" role="search">
  <h3>Quick search</h3>
    <form class="search" action="../../../../search.html" method="get">
      <div><input type="text" name="q" /></div>
      <div><input type="submit" value="Go" /></div>
      <input type="hidden" name="check_keywords" value="yes" />
      <input type="hidden" name="area" value="default" />
    </form>
</div>
<script type="text/javascript">$('#searchbox').show(0);</script>
        </div>
      </div>
              <h3>Last update:</h3>
              <p class="topless">Feb 12, 2019</p>
          </div>
        
      
    </div>

    <div id="ft">
      <div class="nav">
    <a href="../../../index.html" title="Module code" accesskey="U">up</a></div>
    </div>
  </div>

      <div class="clearer"></div>
    </div>
  </body>
</html>