https://waylonwalker.com/tags/orm/atom.xml 2024-01-12T02:18:35Z All posts with the tag "orm" Waylon Walker markata-go https://waylonwalker.com/thought-195/ 2024-01-12T02:18:35Z 2024-01-12T02:18:35Z

!https://sqlmodel.tiangolo.com/tutorial/limit-and-offset/

<div class="embed-card embed-card-external"> <a class="embed-card-link has-avatar has-avatar-before" href="https://sqlmodel.tiangolo.com/tutorial/limit-and-offset/" rel="noopener noreferrer" target="_blank" style="--favicon-url: url(&#39;/assets/markata/link-avatars/sqlmodel.tiangolo.com.png&#39;);" data-favicon="/assets/markata/link-avatars/sqlmodel.tiangolo.com.png"> <div class="embed-card-content"> <div class="embed-card-title">Read a Range of Data - LIMIT and OFFSET - SQLModel</div> <div class="embed-card-description">SQLModel, SQL databases in Python, designed for simplicity, compatibility, and robustness.</div> <div class="embed-card-meta">sqlmodel.tiangolo.com</div> </div> </a> </div> <p>Today I was running some sqlmodel queries through the sqlalchemy orm. Admittedly I’ve not done enough orm queries before, and I’ve done quite a bit of raw sql. I was trying to get objects from two separate models that had relationships setup.</p> <pre class="chroma"><code><span class="line"><span class="cl"><span class="n">session</span><span class="o">.</span><span class="n">query</span><span class="p">(</span><span class="n">User</span><span class="p">,</span> <span class="n">Images</span><span class="p">)</span><span class="o">.</span><span class="n">where</span><span class="p">(</span><span class="n">User</span><span class="o">.</span><span class="n">id</span> <span class="o">==</span> <span class="mi">3</span><span class="p">)</span><span class="o">.</span><span class="n">all</span><span class="p">()</span> </span></span></code></pre><p>It is incredibly slow, and gives me the following warning.</p> <pre class="chroma"><code><span class="line"><span class="cl"><span class="n">SELECT</span> <span class="n">statement</span> <span class="n">has</span> <span class="n">a</span> <span class="n">cartesian</span> <span class="n">product</span> <span class="n">between</span> <span class="n">FROM</span> <span class="n">element</span><span class="p">(</span><span class="n">s</span><span class="p">)</span> </span></span></code></pre><p>What I learned from the SQLModel docs is that you should give it a join to correct this and go much faster.</p> <pre class="chroma"><code><span class="line"><span class="cl"><span class="n">session</span><span class="o">.</span><span class="n">query</span><span class="p">(</span><span class="n">User</span><span class="p">,</span> <span class="n">Images</span><span class="p">)</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="n">Images</span><span class="p">)</span><span class="o">.</span><span class="n">where</span><span class="p">(</span><span class="n">User</span><span class="o">.</span><span class="n">id</span> <span class="o">==</span> <span class="mi">3</span><span class="p">)</span><span class="o">.</span><span class="n">all</span><span class="p">()</span> </span></span></code></pre> Waylon Walker hello@waylonwalker.com https://waylonwalker.com