docs: collect refreshed mongo-ops wiki site (API-correct overhaul, v0.1.5)
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<span class="md-ellipsis">
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02 components
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Core Components
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</span>
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<li class="md-nav__item">
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<a href="#whats-new" class="md-nav__link">
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<span class="md-ellipsis">
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📦 What’s New?
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📦 What's New?
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</span>
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</a>
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</li>
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<li class="md-nav__item">
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<a href="#quick-example" class="md-nav__link">
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<a href="#example" class="md-nav__link">
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<span class="md-ellipsis">
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🚀 Quick Example
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🚀 Example
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</span>
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</a>
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</li>
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<li class="md-nav__item">
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<a href="#tips" class="md-nav__link">
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<span class="md-ellipsis">
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💡 Tips
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</span>
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</a>
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</li>
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<li class="md-nav__item">
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<a href="#related" class="md-nav__link">
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<span class="md-ellipsis">
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Related
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</span>
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</a>
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<h1 id="use-case-8-document-population">Use Case 8: Document Population</h1>
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<p><strong>Scenario:</strong><br />
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An API needs to return a single, denormalised JSON payload that includes related documents (e.g., a <code>User</code> with an embedded <code>Profile</code>, or an <code>Order</code> with its <code>LineItem</code>s) without the caller having to issue multiple requests.</p>
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<p><strong>Scenario:</strong> An API returns a <code>User</code> with its related <code>Profile</code> embedded in one JSON payload — no second round-trip from the client, no joins.</p>
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<hr />
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<h2 id="whats-new">📦 What’s New?</h2>
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<h2 id="whats-new">📦 What's New?</h2>
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<table>
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<thead>
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<tr>
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@@ -1031,99 +1048,109 @@ An API needs to return a single, denormalised JSON payload that includes related
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</thead>
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<tbody>
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<tr>
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<td><strong><code>PopulateRule</code></strong></td>
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<td>Declarative rule that tells the engine how to populate a field.<br>Key attributes:<br>• <code>field_name</code> – Target attribute on the source model.<br>• <code>collection_name</code> – Collection that stores the referenced documents.<br>• <code>ref_field</code> – Name of the reference field (normally an <code>ObjectId</code>).<br>• Optional <code>nested_rules</code> for deep population, <code>max_depth</code> to bound recursion, and <code>filter</code> / <code>projection</code> for fine‑grained queries.</td>
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<td><code>PopulateRule</code></td>
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<td>Declares <em>which field</em> to resolve. <code>field_name</code> holds the <code>ObjectId</code> (or <code>list[ObjectId]</code>) <strong>and is the same field the resolved document replaces in place</strong>. <code>collection_name</code> says where the referenced documents live.</td>
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</tr>
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<tr>
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<td><strong><code>PopulationEngine</code></strong></td>
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<td>Core engine that resolves a list of <code>PopulateRule</code>s recursively. It:<br>• Detects circular references and raises <code>CircularReferenceError</code>.<br>• Honors per‑rule <code>max_depth</code> and a global <code>global_max_depth</code> (default 10).<br>• Supports MongoDB filters and projections for each populated relation.</td>
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<td><code>PopulationEngine</code></td>
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<td>Holds repositories by collection name and resolves rules recursively, detecting cycles (<code>CircularReferenceError</code>).</td>
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</tr>
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<tr>
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<td><strong><code>PopulatingRepository</code></strong></td>
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<td>Extends <code>BaseRepository</code> with automatic population support. Stores a reference to a <code>PopulationEngine</code> and a list of <code>PopulateRule</code>s, exposing two helpers:<br>• <code>_populate(document)</code> – Returns the same document with the requested relations populated.<br>• <code>_depopulate(document)</code> – Strips populated fields (useful before serialisation).</td>
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</tr>
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<tr>
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<td><strong>Cache‑aware population</strong> (optional) – The engine works with any <code>CacheBackend</code>. When used together with <code>CachedBaseRepository</code>, populated documents benefit from caching in the same way as regular CRUD results.</td>
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<td></td>
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<td><code>PopulatingRepository[T]</code></td>
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<td><code>get_by_id</code>/<code>get_many</code> populate on read; <code>create</code>/<code>update</code> depopulate on write; <code>patch</code> rejects FK fields.</td>
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</tr>
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</tbody>
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</table>
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<blockquote>
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<p>⚠️ <code>PopulateRule</code> does <strong>not</strong> have a separate "ref field" vs "target field" — the ref field is the populated field. <code>filter</code>/<code>projection</code> on <code>PopulateRule</code> are declared but not yet applied by the engine.</p>
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</blockquote>
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<hr />
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<h2 id="quick-example">🚀 Quick Example</h2>
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<div class="language-python highlight"><span class="filename">Python</span><pre><span></span><code><a id="__codelineno-0-1" name="__codelineno-0-1" href="#__codelineno-0-1"></a><span class="kn">from</span><span class="w"> </span><span class="nn">bson</span><span class="w"> </span><span class="kn">import</span> <span class="n">ObjectId</span>
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<a id="__codelineno-0-2" name="__codelineno-0-2" href="#__codelineno-0-2"></a><span class="kn">from</span><span class="w"> </span><span class="nn">mongo_ops</span><span class="w"> </span><span class="kn">import</span> <span class="n">BaseDocument</span><span class="p">,</span> <span class="n">PopulatingRepository</span><span class="p">,</span> <span class="n">ModelRegistry</span>
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<a id="__codelineno-0-3" name="__codelineno-0-3" href="#__codelineno-0-3"></a><span class="kn">from</span><span class="w"> </span><span class="nn">mongo_ops.populate</span><span class="w"> </span><span class="kn">import</span> <span class="n">PopulateRule</span><span class="p">,</span> <span class="n">PopulationEngine</span>
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<a id="__codelineno-0-4" name="__codelineno-0-4" href="#__codelineno-0-4"></a><span class="kn">from</span><span class="w"> </span><span class="nn">mongo_ops.cache</span><span class="w"> </span><span class="kn">import</span> <span class="n">InMemoryCacheBackend</span>
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<a id="__codelineno-0-5" name="__codelineno-0-5" href="#__codelineno-0-5"></a>
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<a id="__codelineno-0-6" name="__codelineno-0-6" href="#__codelineno-0-6"></a><span class="c1"># ----------------------------------------------------------------------</span>
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<a id="__codelineno-0-7" name="__codelineno-0-7" href="#__codelineno-0-7"></a><span class="c1"># 1️⃣ Define the data models</span>
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<a id="__codelineno-0-8" name="__codelineno-0-8" href="#__codelineno-0-8"></a><span class="c1"># ----------------------------------------------------------------------</span>
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<h2 id="example">🚀 Example</h2>
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<div class="language-python highlight"><span class="filename">Python</span><pre><span></span><code><a id="__codelineno-0-1" name="__codelineno-0-1" href="#__codelineno-0-1"></a><span class="kn">from</span><span class="w"> </span><span class="nn">contextlib</span><span class="w"> </span><span class="kn">import</span> <span class="n">asynccontextmanager</span>
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<a id="__codelineno-0-2" name="__codelineno-0-2" href="#__codelineno-0-2"></a>
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<a id="__codelineno-0-3" name="__codelineno-0-3" href="#__codelineno-0-3"></a><span class="kn">from</span><span class="w"> </span><span class="nn">fastapi</span><span class="w"> </span><span class="kn">import</span> <span class="n">FastAPI</span><span class="p">,</span> <span class="n">HTTPException</span>
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<a id="__codelineno-0-4" name="__codelineno-0-4" href="#__codelineno-0-4"></a><span class="kn">from</span><span class="w"> </span><span class="nn">mongo_ops</span><span class="w"> </span><span class="kn">import</span> <span class="n">BaseDocument</span><span class="p">,</span> <span class="n">MongoConnectionManager</span><span class="p">,</span> <span class="n">ModelRegistry</span><span class="p">,</span> <span class="n">PopulatingRepository</span>
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<a id="__codelineno-0-5" name="__codelineno-0-5" href="#__codelineno-0-5"></a><span class="kn">from</span><span class="w"> </span><span class="nn">mongo_ops.populate</span><span class="w"> </span><span class="kn">import</span> <span class="n">PopulateRule</span><span class="p">,</span> <span class="n">PopulationEngine</span>
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<a id="__codelineno-0-6" name="__codelineno-0-6" href="#__codelineno-0-6"></a>
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<a id="__codelineno-0-7" name="__codelineno-0-7" href="#__codelineno-0-7"></a>
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<a id="__codelineno-0-8" name="__codelineno-0-8" href="#__codelineno-0-8"></a><span class="c1"># 1. Models — `profile` holds an ObjectId in the DB and becomes a Profile on read.</span>
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<a id="__codelineno-0-9" name="__codelineno-0-9" href="#__codelineno-0-9"></a><span class="k">class</span><span class="w"> </span><span class="nc">Profile</span><span class="p">(</span><span class="n">BaseDocument</span><span class="p">):</span>
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<a id="__codelineno-0-10" name="__codelineno-0-10" href="#__codelineno-0-10"></a> <span class="n">avatar_url</span><span class="p">:</span> <span class="nb">str</span> <span class="o">=</span> <span class="s2">""</span>
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<a id="__codelineno-0-11" name="__codelineno-0-11" href="#__codelineno-0-11"></a> <span class="n">bio</span><span class="p">:</span> <span class="nb">str</span> <span class="o">=</span> <span class="s2">""</span>
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<a id="__codelineno-0-12" name="__codelineno-0-12" href="#__codelineno-0-12"></a>
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<a id="__codelineno-0-13" name="__codelineno-0-13" href="#__codelineno-0-13"></a><span class="k">class</span><span class="w"> </span><span class="nc">User</span><span class="p">(</span><span class="n">BaseDocument</span><span class="p">):</span>
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<a id="__codelineno-0-14" name="__codelineno-0-14" href="#__codelineno-0-14"></a> <span class="n">username</span><span class="p">:</span> <span class="nb">str</span> <span class="o">=</span> <span class="s2">""</span>
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<a id="__codelineno-0-15" name="__codelineno-0-15" href="#__codelineno-0-15"></a> <span class="n">email</span><span class="p">:</span> <span class="nb">str</span> <span class="o">=</span> <span class="s2">""</span>
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<a id="__codelineno-0-16" name="__codelineno-0-16" href="#__codelineno-0-16"></a> <span class="n">profile_id</span><span class="p">:</span> <span class="n">ObjectId</span> <span class="o">=</span> <span class="kc">None</span> <span class="c1"># Reference to Profile</span>
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<a id="__codelineno-0-17" name="__codelineno-0-17" href="#__codelineno-0-17"></a> <span class="n">profile</span><span class="p">:</span> <span class="n">Profile</span> <span class="o">|</span> <span class="kc">None</span> <span class="o">=</span> <span class="kc">None</span> <span class="c1"># Populated field (filled by engine)</span>
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<a id="__codelineno-0-13" name="__codelineno-0-13" href="#__codelineno-0-13"></a>
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<a id="__codelineno-0-14" name="__codelineno-0-14" href="#__codelineno-0-14"></a><span class="k">class</span><span class="w"> </span><span class="nc">User</span><span class="p">(</span><span class="n">BaseDocument</span><span class="p">):</span>
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<a id="__codelineno-0-15" name="__codelineno-0-15" href="#__codelineno-0-15"></a> <span class="n">username</span><span class="p">:</span> <span class="nb">str</span> <span class="o">=</span> <span class="s2">""</span>
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<a id="__codelineno-0-16" name="__codelineno-0-16" href="#__codelineno-0-16"></a> <span class="n">email</span><span class="p">:</span> <span class="nb">str</span> <span class="o">=</span> <span class="s2">""</span>
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<a id="__codelineno-0-17" name="__codelineno-0-17" href="#__codelineno-0-17"></a> <span class="n">profile</span><span class="p">:</span> <span class="n">Profile</span> <span class="o">|</span> <span class="kc">None</span> <span class="o">=</span> <span class="kc">None</span> <span class="c1"># ObjectId in MongoDB, Profile in memory</span>
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<a id="__codelineno-0-18" name="__codelineno-0-18" href="#__codelineno-0-18"></a>
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<a id="__codelineno-0-19" name="__codelineno-0-19" href="#__codelineno-0-19"></a><span class="c1"># ----------------------------------------------------------------------</span>
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<a id="__codelineno-0-20" name="__codelineno-0-20" href="#__codelineno-0-20"></a><span class="c1"># 2️⃣ (Optional) Set up a cache; helpful for deep graphs</span>
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<a id="__codelineno-0-21" name="__codelineno-0-21" href="#__codelineno-0-21"></a><span class="c1"># ----------------------------------------------------------------------</span>
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<a id="__codelineno-0-22" name="__codelineno-0-22" href="#__codelineno-0-22"></a><span class="n">cache</span> <span class="o">=</span> <span class="n">InMemoryCacheBackend</span><span class="p">(</span><span class="n">max_entries</span><span class="o">=</span><span class="mi">10_000</span><span class="p">,</span> <span class="n">default_ttl</span><span class="o">=</span><span class="mi">300</span><span class="p">)</span>
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<a id="__codelineno-0-23" name="__codelineno-0-23" href="#__codelineno-0-23"></a><span class="n">ModelRegistry</span><span class="o">.</span><span class="n">set_cache_backend</span><span class="p">(</span><span class="n">cache</span><span class="p">)</span>
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<a id="__codelineno-0-24" name="__codelineno-0-24" href="#__codelineno-0-24"></a>
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<a id="__codelineno-0-25" name="__codelineno-0-25" href="#__codelineno-0-25"></a><span class="c1"># ----------------------------------------------------------------------</span>
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<a id="__codelineno-0-26" name="__codelineno-0-26" href="#__codelineno-0-26"></a><span class="c1"># 3️⃣ Create a PopulationEngine – repositories will be registered later</span>
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<a id="__codelineno-0-27" name="__codelineno-0-27" href="#__codelineno-0-27"></a><span class="c1"># ----------------------------------------------------------------------</span>
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<a id="__codelineno-0-28" name="__codelineno-0-28" href="#__codelineno-0-28"></a><span class="n">engine</span> <span class="o">=</span> <span class="n">PopulationEngine</span><span class="p">({})</span>
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<a id="__codelineno-0-29" name="__codelineno-0-29" href="#__codelineno-0-29"></a>
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<a id="__codelineno-0-30" name="__codelineno-0-30" href="#__codelineno-0-30"></a><span class="c1"># ----------------------------------------------------------------------</span>
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<a id="__codelineno-0-31" name="__codelineno-0-31" href="#__codelineno-0-31"></a><span class="c1"># 4️⃣ Declare how the `profile` field should be populated</span>
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<a id="__codelineno-0-32" name="__codelineno-0-32" href="#__codelineno-0-32"></a><span class="c1"># ----------------------------------------------------------------------</span>
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<a id="__codelineno-0-33" name="__codelineno-0-33" href="#__codelineno-0-33"></a><span class="n">profile_rule</span> <span class="o">=</span> <span class="n">PopulateRule</span><span class="p">(</span>
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<a id="__codelineno-0-34" name="__codelineno-0-34" href="#__codelineno-0-34"></a> <span class="n">field_name</span><span class="o">=</span><span class="s2">"profile"</span><span class="p">,</span>
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<a id="__codelineno-0-35" name="__codelineno-0-35" href="#__codelineno-0-35"></a> <span class="n">collection_name</span><span class="o">=</span><span class="s2">"profiles"</span><span class="p">,</span>
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<a id="__codelineno-0-36" name="__codelineno-0-36" href="#__codelineno-0-36"></a> <span class="n">ref_field</span><span class="o">=</span><span class="s2">"profile_id"</span><span class="p">,</span>
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<a id="__codelineno-0-37" name="__codelineno-0-37" href="#__codelineno-0-37"></a> <span class="c1"># No further nesting in this simple example</span>
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<a id="__codelineno-0-38" name="__codelineno-0-38" href="#__codelineno-0-38"></a><span class="p">)</span>
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<a id="__codelineno-0-39" name="__codelineno-0-39" href="#__codelineno-0-39"></a>
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<a id="__codelineno-0-40" name="__codelineno-0-40" href="#__codelineno-0-40"></a><span class="c1"># ----------------------------------------------------------------------</span>
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<a id="__codelineno-0-41" name="__codelineno-0-41" href="#__codelineno-0-41"></a><span class="c1"># 5️⃣ Repository that uses the engine + rule</span>
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<a id="__codelineno-0-42" name="__codelineno-0-42" href="#__codelineno-0-42"></a><span class="c1"># ----------------------------------------------------------------------</span>
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<a id="__codelineno-0-43" name="__codelineno-0-43" href="#__codelineno-0-43"></a><span class="k">class</span><span class="w"> </span><span class="nc">UserRepository</span><span class="p">(</span><span class="n">PopulatingRepository</span><span class="p">[</span><span class="n">User</span><span class="p">]):</span>
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<a id="__codelineno-0-44" name="__codelineno-0-44" href="#__codelineno-0-44"></a> <span class="k">def</span><span class="w"> </span><span class="fm">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
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<a id="__codelineno-0-45" name="__codelineno-0-45" href="#__codelineno-0-45"></a> <span class="nb">super</span><span class="p">()</span><span class="o">.</span><span class="fm">__init__</span><span class="p">(</span>
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<a id="__codelineno-0-46" name="__codelineno-0-46" href="#__codelineno-0-46"></a> <span class="n">collection_name</span><span class="o">=</span><span class="s2">"users"</span><span class="p">,</span>
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<a id="__codelineno-0-47" name="__codelineno-0-47" href="#__codelineno-0-47"></a> <span class="n">model</span><span class="o">=</span><span class="n">User</span><span class="p">,</span>
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<a id="__codelineno-0-48" name="__codelineno-0-48" href="#__codelineno-0-48"></a> <span class="n">population_engine</span><span class="o">=</span><span class="n">engine</span><span class="p">,</span>
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<a id="__codelineno-0-49" name="__codelineno-0-49" href="#__codelineno-0-49"></a> <span class="n">populate_rules</span><span class="o">=</span><span class="p">[</span><span class="n">profile_rule</span><span class="p">],</span>
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<a id="__codelineno-0-50" name="__codelineno-0-50" href="#__codelineno-0-50"></a> <span class="p">)</span>
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<a id="__codelineno-0-19" name="__codelineno-0-19" href="#__codelineno-0-19"></a>
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<a id="__codelineno-0-20" name="__codelineno-0-20" href="#__codelineno-0-20"></a><span class="c1"># 2. Engine + rule — repositories are registered later (after connect()).</span>
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<a id="__codelineno-0-21" name="__codelineno-0-21" href="#__codelineno-0-21"></a><span class="n">engine</span> <span class="o">=</span> <span class="n">PopulationEngine</span><span class="p">({})</span>
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<a id="__codelineno-0-22" name="__codelineno-0-22" href="#__codelineno-0-22"></a><span class="n">profile_rule</span> <span class="o">=</span> <span class="n">PopulateRule</span><span class="p">(</span>
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<a id="__codelineno-0-23" name="__codelineno-0-23" href="#__codelineno-0-23"></a> <span class="n">field_name</span><span class="o">=</span><span class="s2">"profile"</span><span class="p">,</span>
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||||
<a id="__codelineno-0-24" name="__codelineno-0-24" href="#__codelineno-0-24"></a> <span class="n">collection_name</span><span class="o">=</span><span class="s2">"profiles"</span><span class="p">,</span>
|
||||
<a id="__codelineno-0-25" name="__codelineno-0-25" href="#__codelineno-0-25"></a><span class="p">)</span>
|
||||
<a id="__codelineno-0-26" name="__codelineno-0-26" href="#__codelineno-0-26"></a>
|
||||
<a id="__codelineno-0-27" name="__codelineno-0-27" href="#__codelineno-0-27"></a>
|
||||
<a id="__codelineno-0-28" name="__codelineno-0-28" href="#__codelineno-0-28"></a><span class="c1"># 3. The repository the app uses.</span>
|
||||
<a id="__codelineno-0-29" name="__codelineno-0-29" href="#__codelineno-0-29"></a><span class="k">class</span><span class="w"> </span><span class="nc">UserRepository</span><span class="p">(</span><span class="n">PopulatingRepository</span><span class="p">[</span><span class="n">User</span><span class="p">]):</span>
|
||||
<a id="__codelineno-0-30" name="__codelineno-0-30" href="#__codelineno-0-30"></a> <span class="k">def</span><span class="w"> </span><span class="fm">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
|
||||
<a id="__codelineno-0-31" name="__codelineno-0-31" href="#__codelineno-0-31"></a> <span class="nb">super</span><span class="p">()</span><span class="o">.</span><span class="fm">__init__</span><span class="p">(</span>
|
||||
<a id="__codelineno-0-32" name="__codelineno-0-32" href="#__codelineno-0-32"></a> <span class="n">collection_name</span><span class="o">=</span><span class="s2">"users"</span><span class="p">,</span>
|
||||
<a id="__codelineno-0-33" name="__codelineno-0-33" href="#__codelineno-0-33"></a> <span class="n">model</span><span class="o">=</span><span class="n">User</span><span class="p">,</span>
|
||||
<a id="__codelineno-0-34" name="__codelineno-0-34" href="#__codelineno-0-34"></a> <span class="n">population_engine</span><span class="o">=</span><span class="n">engine</span><span class="p">,</span>
|
||||
<a id="__codelineno-0-35" name="__codelineno-0-35" href="#__codelineno-0-35"></a> <span class="n">populate_rules</span><span class="o">=</span><span class="p">[</span><span class="n">profile_rule</span><span class="p">],</span>
|
||||
<a id="__codelineno-0-36" name="__codelineno-0-36" href="#__codelineno-0-36"></a> <span class="p">)</span>
|
||||
<a id="__codelineno-0-37" name="__codelineno-0-37" href="#__codelineno-0-37"></a>
|
||||
<a id="__codelineno-0-38" name="__codelineno-0-38" href="#__codelineno-0-38"></a>
|
||||
<a id="__codelineno-0-39" name="__codelineno-0-39" href="#__codelineno-0-39"></a><span class="nd">@asynccontextmanager</span>
|
||||
<a id="__codelineno-0-40" name="__codelineno-0-40" href="#__codelineno-0-40"></a><span class="k">async</span> <span class="k">def</span><span class="w"> </span><span class="nf">lifespan</span><span class="p">(</span><span class="n">_app</span><span class="p">:</span> <span class="n">FastAPI</span><span class="p">):</span>
|
||||
<a id="__codelineno-0-41" name="__codelineno-0-41" href="#__codelineno-0-41"></a> <span class="k">async</span> <span class="k">with</span> <span class="n">MongoConnectionManager</span><span class="o">.</span><span class="n">lifespan</span><span class="p">(</span>
|
||||
<a id="__codelineno-0-42" name="__codelineno-0-42" href="#__codelineno-0-42"></a> <span class="n">uri</span><span class="o">=</span><span class="s2">"mongodb://localhost:27017"</span><span class="p">,</span> <span class="n">db_name</span><span class="o">=</span><span class="s2">"mydb"</span>
|
||||
<a id="__codelineno-0-43" name="__codelineno-0-43" href="#__codelineno-0-43"></a> <span class="p">):</span>
|
||||
<a id="__codelineno-0-44" name="__codelineno-0-44" href="#__codelineno-0-44"></a> <span class="c1"># Tells the engine which repository resolves "profiles" refs.</span>
|
||||
<a id="__codelineno-0-45" name="__codelineno-0-45" href="#__codelineno-0-45"></a> <span class="n">engine</span><span class="o">.</span><span class="n">register_repo</span><span class="p">(</span><span class="s2">"profiles"</span><span class="p">,</span> <span class="n">PopulatingRepository</span><span class="p">[</span><span class="n">Profile</span><span class="p">](</span><span class="s2">"profiles"</span><span class="p">,</span> <span class="n">Profile</span><span class="p">))</span>
|
||||
<a id="__codelineno-0-46" name="__codelineno-0-46" href="#__codelineno-0-46"></a> <span class="k">await</span> <span class="n">ModelRegistry</span><span class="o">.</span><span class="n">initialize_all</span><span class="p">()</span>
|
||||
<a id="__codelineno-0-47" name="__codelineno-0-47" href="#__codelineno-0-47"></a> <span class="k">yield</span>
|
||||
<a id="__codelineno-0-48" name="__codelineno-0-48" href="#__codelineno-0-48"></a>
|
||||
<a id="__codelineno-0-49" name="__codelineno-0-49" href="#__codelineno-0-49"></a>
|
||||
<a id="__codelineno-0-50" name="__codelineno-0-50" href="#__codelineno-0-50"></a><span class="n">app</span> <span class="o">=</span> <span class="n">FastAPI</span><span class="p">(</span><span class="n">lifespan</span><span class="o">=</span><span class="n">lifespan</span><span class="p">)</span>
|
||||
<a id="__codelineno-0-51" name="__codelineno-0-51" href="#__codelineno-0-51"></a>
|
||||
<a id="__codelineno-0-52" name="__codelineno-0-52" href="#__codelineno-0-52"></a><span class="c1"># ----------------------------------------------------------------------</span>
|
||||
<a id="__codelineno-0-53" name="__codelineno-0-53" href="#__codelineno-0-53"></a><span class="c1"># 6️⃣ Register the repository with the engine so it can resolve refs</span>
|
||||
<a id="__codelineno-0-54" name="__codelineno-0-54" href="#__codelineno-0-54"></a><span class="c1"># ----------------------------------------------------------------------</span>
|
||||
<a id="__codelineno-0-55" name="__codelineno-0-55" href="#__codelineno-0-55"></a><span class="n">engine</span><span class="o">.</span><span class="n">register_repo</span><span class="p">(</span><span class="s2">"profiles"</span><span class="p">,</span> <span class="n">PopulatingRepository</span><span class="p">[</span><span class="n">Profile</span><span class="p">](</span><span class="s2">"profiles"</span><span class="p">,</span> <span class="n">Profile</span><span class="p">))</span>
|
||||
<a id="__codelineno-0-56" name="__codelineno-0-56" href="#__codelineno-0-56"></a><span class="n">engine</span><span class="o">.</span><span class="n">register_repo</span><span class="p">(</span><span class="s2">"users"</span><span class="p">,</span> <span class="n">UserRepository</span><span class="p">())</span>
|
||||
<a id="__codelineno-0-57" name="__codelineno-0-57" href="#__codelineno-0-57"></a>
|
||||
<a id="__codelineno-0-58" name="__codelineno-0-58" href="#__codelineno-0-58"></a><span class="c1"># ----------------------------------------------------------------------</span>
|
||||
<a id="__codelineno-0-59" name="__codelineno-0-59" href="#__codelineno-0-59"></a><span class="c1"># 7️⃣ FastAPI lifespan – initialise DB, indexes, and the cache</span>
|
||||
<a id="__codelineno-0-60" name="__codelineno-0-60" href="#__codelineno-0-60"></a><span class="c1"># ----------------------------------------------------------------------</span>
|
||||
<a id="__codelineno-0-61" name="__codelineno-0-61" href="#__codelineno-0-61"></a><span class="kn">from</span><span class="w"> </span><span class="nn">mongo_ops</span><span class="w"> </span><span class="kn">import</span> <span class="n">MongoConnectionManager</span>
|
||||
<a id="__codelineno-0-62" name="__codelineno-0-62" href="#__codelineno-0-62"></a><span class="kn">from</span><span class="w"> </span><span class="nn">contextlib</span><span class="w"> </span><span class="kn">import</span> <span class="n">asynccontextmanager</span>
|
||||
<a id="__codelineno-0-52" name="__codelineno-0-52" href="#__codelineno-0-52"></a>
|
||||
<a id="__codelineno-0-53" name="__codelineno-0-53" href="#__codelineno-0-53"></a><span class="c1"># 4. Writing — pass the model; the repository depopulates to an ObjectId.</span>
|
||||
<a id="__codelineno-0-54" name="__codelineno-0-54" href="#__codelineno-0-54"></a><span class="nd">@app</span><span class="o">.</span><span class="n">post</span><span class="p">(</span><span class="s2">"/users/"</span><span class="p">,</span> <span class="n">response_model</span><span class="o">=</span><span class="n">User</span><span class="p">)</span>
|
||||
<a id="__codelineno-0-55" name="__codelineno-0-55" href="#__codelineno-0-55"></a><span class="k">async</span> <span class="k">def</span><span class="w"> </span><span class="nf">create_user</span><span class="p">():</span>
|
||||
<a id="__codelineno-0-56" name="__codelineno-0-56" href="#__codelineno-0-56"></a> <span class="n">user</span> <span class="o">=</span> <span class="n">User</span><span class="p">(</span>
|
||||
<a id="__codelineno-0-57" name="__codelineno-0-57" href="#__codelineno-0-57"></a> <span class="n">username</span><span class="o">=</span><span class="s2">"alice"</span><span class="p">,</span>
|
||||
<a id="__codelineno-0-58" name="__codelineno-0-58" href="#__codelineno-0-58"></a> <span class="n">email</span><span class="o">=</span><span class="s2">"alice@example.com"</span><span class="p">,</span>
|
||||
<a id="__codelineno-0-59" name="__codelineno-0-59" href="#__codelineno-0-59"></a> <span class="n">profile</span><span class="o">=</span><span class="n">Profile</span><span class="p">(</span><span class="n">avatar_url</span><span class="o">=</span><span class="s2">"alice.png"</span><span class="p">,</span> <span class="n">bio</span><span class="o">=</span><span class="s2">"hi"</span><span class="p">),</span>
|
||||
<a id="__codelineno-0-60" name="__codelineno-0-60" href="#__codelineno-0-60"></a> <span class="p">)</span>
|
||||
<a id="__codelineno-0-61" name="__codelineno-0-61" href="#__codelineno-0-61"></a> <span class="k">return</span> <span class="k">await</span> <span class="n">UserRepository</span><span class="p">()</span><span class="o">.</span><span class="n">create</span><span class="p">(</span><span class="n">user</span><span class="p">)</span>
|
||||
<a id="__codelineno-0-62" name="__codelineno-0-62" href="#__codelineno-0-62"></a> <span class="c1"># ^ stored as {"profile": <ObjectId>}, returned with profile populated</span>
|
||||
<a id="__codelineno-0-63" name="__codelineno-0-63" href="#__codelineno-0-63"></a>
|
||||
<a id="__codelineno-0-64" name="__codelineno-0-64" href="#__codelineno-0-64"></a><span class="nd">@asynccontextmanager</span>
|
||||
<a id="__codelineno-0-65" name="__codelineno-0-65" href="#__codelineno-0-65"></a><span class="k">async</span> <span class="k">def</span><span class="w"> </span><span class="nf">lifespan</span><span class="p">(</span><span class="n">app</span><span class="p">):</span>
|
||||
<a id="__codelineno-0-66" name="__codelineno-0-66" href="#__codelineno-0-66"></a> <span class="k">async</span> <span class="k">with</span> <span class="n">MongoConnectionManager</span><span class="o">.</span><span class="n">lifespan</span><span class="p">(</span>
|
||||
<a id="__codelineno-0-67" name="__codelineno-0-67" href="#__codelineno-0-67"></a> <span class="n">uri</span><span class="o">=</span><span class="s2">"mongodb://localhost:27017"</span><span class="p">,</span>
|
||||
<a id="__codelineno-0-68" name="__codelineno-0-68" href="#__codelineno-0-68"></a> <span class="n">db_name</span><span class="o">=</span><span class="s2">"mydb"</span>
|
||||
<a id="__codelineno-0-69" name="__codelineno-0-69" href="#__codelineno-0-69"></a> <span class="p">):</span>
|
||||
<a id="__codelineno-0-70" name="__codelineno-0-70" href="#__codelineno-0-70"></a> <span class="k">await</span> <span class="n">ModelRegistry</span><span class="o">.</span><span class="n">initialize_all</span><span class="p">()</span>
|
||||
<a id="__codelineno-0-71" name="__codelineno-0-71" href="#__codelineno-0-71"></a> <span class="c1"># If you set up a cache backend (see step 2), initialize it here</span>
|
||||
<a id="__codelineno-0-72" name="__codelineno-0-72" href="#__codelineno-0-72"></a> <span class="k">await</span> <span class="n">ModelRegistry</span><span class="o">.</span><span class="n">initialize_cache</span><span class="p">()</span>
|
||||
<a id="__codelineno-0-73" name="__codelineno-0-73" href="#__codelineno-0-73"></a> <span class="k">yield</span>
|
||||
<a id="__codelineno-0-64" name="__codelineno-0-64" href="#__codelineno-0-64"></a>
|
||||
<a id="__codelineno-0-65" name="__codelineno-0-65" href="#__codelineno-0-65"></a><span class="c1"># 5. Reading — get_by_id resolves the reference on the way back.</span>
|
||||
<a id="__codelineno-0-66" name="__codelineno-0-66" href="#__codelineno-0-66"></a><span class="nd">@app</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="s2">"/users/</span><span class="si">{user_id}</span><span class="s2">"</span><span class="p">,</span> <span class="n">response_model</span><span class="o">=</span><span class="n">User</span><span class="p">)</span>
|
||||
<a id="__codelineno-0-67" name="__codelineno-0-67" href="#__codelineno-0-67"></a><span class="k">async</span> <span class="k">def</span><span class="w"> </span><span class="nf">get_user</span><span class="p">(</span><span class="n">user_id</span><span class="p">:</span> <span class="nb">str</span><span class="p">):</span>
|
||||
<a id="__codelineno-0-68" name="__codelineno-0-68" href="#__codelineno-0-68"></a> <span class="n">user</span> <span class="o">=</span> <span class="k">await</span> <span class="n">UserRepository</span><span class="p">()</span><span class="o">.</span><span class="n">get_by_id</span><span class="p">(</span><span class="n">user_id</span><span class="p">)</span>
|
||||
<a id="__codelineno-0-69" name="__codelineno-0-69" href="#__codelineno-0-69"></a> <span class="k">if</span> <span class="ow">not</span> <span class="n">user</span><span class="p">:</span>
|
||||
<a id="__codelineno-0-70" name="__codelineno-0-70" href="#__codelineno-0-70"></a> <span class="k">raise</span> <span class="n">HTTPException</span><span class="p">(</span><span class="n">status_code</span><span class="o">=</span><span class="mi">404</span><span class="p">,</span> <span class="n">detail</span><span class="o">=</span><span class="s2">"User not found"</span><span class="p">)</span>
|
||||
<a id="__codelineno-0-71" name="__codelineno-0-71" href="#__codelineno-0-71"></a> <span class="k">return</span> <span class="n">user</span> <span class="c1"># user.profile is a Profile instance</span>
|
||||
</code></pre></div>
|
||||
<hr />
|
||||
<h2 id="tips">💡 Tips</h2>
|
||||
<ul>
|
||||
<li><code>Patch</code>ing an FK field raises <code>ValueError</code> — switch FK changes to <code>update(user_id, model)</code> instead. See <a href="../05_soft_deletes/">use case 05</a> for the reasoning with soft deletes.</li>
|
||||
<li>Missing references resolve to <code>None</code>, not an error.</li>
|
||||
<li>A field holding an embedded dict (instead of an <code>ObjectId</code>) raises a <code>ValueError</code> ("run repair script") — migrate embedded docs to a separate collection first.</li>
|
||||
<li>If <code>create</code>/<code>update</code> receives a field that is <em>already</em> an <code>ObjectId</code> under a populate rule, <code>_depopulate</code> raises <code>ValueError("...was populate skipped?")</code> — populate-then-depopulate pairs must be balanced.</li>
|
||||
</ul>
|
||||
<hr />
|
||||
<h2 id="related">Related</h2>
|
||||
<ul>
|
||||
<li><a href="../09_advanced_population/">09 – Advanced population</a> · <a href="../10_cache_and_population/">10 – Cache + population</a> · <a href="../14_testing_guide/">14 – Testing guide</a></li>
|
||||
</ul>
|
||||
|
||||
|
||||
|
||||
|
||||
Reference in New Issue
Block a user