I am a Software Engineer from India. I am currently building Daestro. I work in Rust, Javascript and Python. Zola 2025-09-03T00:00:00+00:00 https://vshukla.com/tags/sqlx/atom.xml 2025-09-02T00:00:00+00:00 2025-09-03T00:00:00+00:00 Vivek Shukla https://vshukla.com/tech/2025/postgres-key-value-store-rust-sqlx/

This guide demonstrate how to use Postgres DB for you KV storage needs.

<p>For my smaller application (or personal) or when I’m starting out a new app, I would like to keep the dependencies of my program to minimum. Since I’m going to need a DB anyway, so instead of using Redis and adding one more component to my tech stack, I would like to use <a href="/tags/postgresql/">Postgres</a> as my key value store.</p> <p>Prematurely thinking about scaling your system when you don’t even know if it would be successful enough to actually need all those bells and whistle is sure way to extend the deadline and procrastinate.</p> <h2 id="overview"><a class="zola-anchor" href="#overview" aria-label="Anchor link for: overview">🔗</a>Overview</h2> <p>We are going to create a <code>trait</code> called <code>PgStore</code>, which will implement all the functions to set, get, pop and delete the value.</p> <p>Then you can implement this trait for your own types. Your types must derive serde’s <code>Serialize</code> and <code>Deserialize</code> for this to work.</p> <h2 id="dependencies"><a class="zola-anchor" href="#dependencies" aria-label="Anchor link for: dependencies">🔗</a>Dependencies</h2> <p>You need the following dependencies in your <code>Cargo.toml</code></p> <pre class="giallo z-code"><code data-lang="toml"><span class="giallo-l"><span class="z-variable">chrono</span><span class="z-punctuation z-separator"> =</span><span class="z-variable"> { version</span><span class="z-punctuation z-separator"> =</span><span class="z-string"> &quot;0.4&quot;</span><span class="z-punctuation z-separator">,</span><span class="z-variable"> features</span><span class="z-punctuation z-separator"> =</span><span> [</span><span class="z-string">&quot;serde&quot;</span><span>] }</span></span> <span class="giallo-l"><span class="z-variable">serde</span><span class="z-punctuation z-separator"> =</span><span class="z-variable"> { version</span><span class="z-punctuation z-separator"> =</span><span class="z-string"> &quot;1.0&quot;</span><span class="z-punctuation z-separator">,</span><span class="z-variable"> features</span><span class="z-punctuation z-separator"> =</span><span> [</span><span class="z-string">&quot;derive&quot;</span><span>] }</span></span> <span class="giallo-l"><span class="z-variable">serde_json</span><span class="z-punctuation z-separator"> =</span><span class="z-variable"> { version</span><span class="z-punctuation z-separator"> =</span><span class="z-string"> &quot;1.0&quot;</span><span> }</span></span> <span class="giallo-l"><span class="z-variable">sqlx</span><span class="z-punctuation z-separator"> =</span><span class="z-variable"> { version</span><span class="z-punctuation z-separator"> =</span><span class="z-string"> &quot;0.8&quot;</span><span class="z-punctuation z-separator">,</span><span class="z-variable"> features</span><span class="z-punctuation z-separator"> =</span><span> [</span></span> <span class="giallo-l"><span class="z-string"> &quot;runtime-tokio&quot;</span><span class="z-punctuation z-separator">,</span></span> <span class="giallo-l"><span class="z-string"> &quot;tls-rustls-ring-native-roots&quot;</span><span class="z-punctuation z-separator">,</span></span> <span class="giallo-l"><span class="z-string"> &quot;migrate&quot;</span><span class="z-punctuation z-separator">,</span></span> <span class="giallo-l"><span class="z-string"> &quot;postgres&quot;</span><span class="z-punctuation z-separator">,</span></span> <span class="giallo-l"><span class="z-string"> &quot;macros&quot;</span><span class="z-punctuation z-separator">,</span></span> <span class="giallo-l"><span class="z-string"> &quot;chrono&quot;</span><span class="z-punctuation z-separator">,</span></span> <span class="giallo-l"><span>] }</span></span></code></pre><h2 id="creating-static-pgpool-connection"><a class="zola-anchor" href="#creating-static-pgpool-connection" aria-label="Anchor link for: creating-static-pgpool-connection">🔗</a>Creating static PgPool connection</h2> <p>I don’t like to pass around DB connection across functions or threads or tasks. Instead I like to use tokio’s <code>OnceCell</code> which is a thread safe Cell which can be written to only once, it’s thread safe which means we can use async code in it.</p> <pre class="giallo z-code"><code data-lang="rust"><span class="giallo-l"><span class="z-keyword">use</span><span class="z-entity z-name"> sqlx</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">PgPool</span><span>;</span></span> <span class="giallo-l"><span class="z-keyword">use</span><span class="z-entity z-name"> tokio</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">sync</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">OnceCell</span><span>;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage">static</span><span class="z-constant z-other"> PG_POOL</span><span class="z-keyword z-operator">:</span><span class="z-entity z-name"> OnceCell</span><span>&lt;</span><span class="z-entity z-name">PgPool</span><span>&gt;</span><span class="z-keyword z-operator"> =</span><span class="z-entity z-name"> OnceCell</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">const_new</span><span>();</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-keyword">pub async fn</span><span class="z-entity z-name z-function"> pg_pool</span><span>()</span><span class="z-keyword z-operator"> -&gt; &amp;</span><span>&#39;</span><span class="z-entity z-name">static PgPool</span><span> {</span></span> <span class="giallo-l"><span class="z-constant z-other"> PG_POOL</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">get_or_init</span><span>(</span><span class="z-keyword">async</span><span class="z-keyword z-operator"> ||</span><span> {</span></span> <span class="giallo-l"><span class="z-entity z-name"> PgPool</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">connect</span><span>(</span><span class="z-entity z-name">std</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">env</span><span>(</span><span class="z-string">&quot;DATABASE_URL&quot;</span><span>)</span><span class="z-keyword z-operator">.</span><span class="z-entity z-name z-function">expect</span><span>(</span><span class="z-string">&quot;DATABASE_URL is not set&quot;</span><span>))</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-keyword">await</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">expect</span><span>(</span><span class="z-string">&quot;❌ PgPool connection failed&quot;</span><span>)</span></span> <span class="giallo-l"><span> })</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-keyword">await</span></span> <span class="giallo-l"><span>}</span></span></code></pre> <p>Now we can just use <code>pg_pool().await</code> to fetch the db pool connection wherever we need.</p> <h2 id="db-migration"><a class="zola-anchor" href="#db-migration" aria-label="Anchor link for: db-migration">🔗</a>DB Migration</h2> <p>We are creating a new table <code>kv_store</code> in our Postgres DB. If you notice we are using <code>UNLOGGED</code> keyword to create the table, this tells postgres to not write WAL (write-ahead log) for <code>kv_store</code> table, which improves the performance at the expanse of data durability.</p> <pre class="giallo z-code"><code data-lang="sql"><span class="giallo-l"><span class="z-keyword">CREATE</span><span> UNLOGGED </span><span class="z-keyword">TABLE</span><span class="z-string"> &quot;kv_store&quot;</span><span> (</span></span> <span class="giallo-l"><span class="z-string"> &quot;key&quot;</span><span class="z-storage"> VARCHAR</span><span>(</span><span class="z-constant z-numeric">2048</span><span>)</span><span class="z-storage"> PRIMARY KEY</span><span>,</span></span> <span class="giallo-l"><span class="z-string"> &quot;value&quot;</span><span class="z-storage z-keyword"> TEXT NOT NULL</span><span>,</span></span> <span class="giallo-l"><span class="z-string"> &quot;expires&quot;</span><span class="z-storage z-keyword"> TIMESTAMPTZ NOT NULL</span></span> <span class="giallo-l"><span>);</span></span></code></pre><h2 id="pgstore-trait"><a class="zola-anchor" href="#pgstore-trait" aria-label="Anchor link for: pgstore-trait">🔗</a>PgStore Trait</h2> <p>We are creating <code>PgStore</code> trait which will have methods to store, retrieve and delete the value in the <code>kv_store</code> table.</p> <pre class="giallo z-code"><code data-lang="rust"><span class="giallo-l"><span class="z-keyword">use</span><span class="z-entity z-name"> chrono</span><span class="z-keyword z-operator">::</span><span>{</span><span class="z-entity z-name">DateTime</span><span>,</span><span class="z-entity z-name"> Utc</span><span>};</span></span> <span class="giallo-l"><span class="z-keyword">use</span><span class="z-entity z-name"> serde</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">Serialize</span><span>;</span></span> <span class="giallo-l"><span class="z-keyword">use</span><span class="z-entity z-name"> serde</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">de</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">DeserializeOwned</span><span>;</span></span> <span class="giallo-l"><span class="z-keyword">use</span><span class="z-entity z-name"> std</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">time</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">Duration</span><span>;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span>#[allow(async_fn_in_trait)]</span></span> <span class="giallo-l"><span class="z-keyword z-storage">pub trait</span><span class="z-entity z-name"> PgStore</span><span class="z-keyword z-operator">:</span><span class="z-entity z-name"> Serialize</span><span class="z-keyword z-operator"> +</span><span class="z-entity z-name"> DeserializeOwned</span><span> {</span></span> <span class="giallo-l"><span class="z-storage"> const</span><span class="z-constant z-other"> EXPIRE_IN</span><span class="z-keyword z-operator">:</span><span class="z-entity z-name"> usize</span><span>;</span><span class="z-comment"> // seconds</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-keyword"> fn</span><span class="z-entity z-name z-function"> key_format</span><span class="z-variable">(key</span><span class="z-keyword z-operator">:</span><span class="z-entity z-name"> String</span><span>)</span><span class="z-keyword z-operator"> -&gt;</span><span class="z-entity z-name"> String</span><span>;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-keyword"> fn</span><span class="z-entity z-name z-function"> get_expire_time</span><span>()</span><span class="z-keyword z-operator"> -&gt;</span><span class="z-entity z-name"> DateTime</span><span>&lt;</span><span class="z-entity z-name">Utc</span><span>&gt; {</span></span> <span class="giallo-l"><span class="z-entity z-name"> Utc</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">now</span><span>()</span><span class="z-keyword z-operator"> +</span><span class="z-entity z-name"> Duration</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">from_secs</span><span>(</span><span class="z-variable z-language">Self</span><span class="z-keyword z-operator">::</span><span class="z-constant z-other">EXPIRE_IN</span><span class="z-keyword"> as</span><span class="z-entity z-name"> u64</span><span>)</span></span> <span class="giallo-l"><span> }</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-keyword"> async fn</span><span class="z-entity z-name z-function"> set_ex</span><span>(</span><span class="z-keyword z-operator">&amp;</span><span class="z-variable z-language">self</span><span class="z-variable">, key</span><span class="z-keyword z-operator">:</span><span class="z-entity z-name"> String</span><span>)</span><span class="z-keyword z-operator"> -&gt;</span><span class="z-entity z-name"> Result</span><span>&lt;(),</span><span class="z-entity z-name"> String</span><span>&gt; {</span></span> <span class="giallo-l"><span class="z-storage"> let</span><span class="z-variable"> value</span><span class="z-keyword z-operator"> =</span></span> <span class="giallo-l"><span class="z-entity z-name"> serde_json</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">to_string</span><span>(</span><span class="z-keyword z-operator">&amp;</span><span class="z-variable z-language">self</span><span>)</span><span class="z-keyword z-operator">.</span><span class="z-entity z-name z-function">map_err</span><span>(</span><span class="z-keyword z-operator">|</span><span class="z-variable">_</span><span class="z-keyword z-operator">|</span><span class="z-string"> &quot;Failed to serialize value.&quot;</span><span class="z-keyword z-operator">.</span><span class="z-entity z-name z-function">to_string</span><span>())</span><span class="z-keyword z-operator">?</span><span>;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-entity z-name"> sqlx</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">query!</span><span>(</span></span> <span class="giallo-l"><span class="z-string"> r#&quot;INSERT INTO kv_store (&quot;key&quot;, &quot;value&quot;, expires) VALUES ($1, $2, $3)</span></span> <span class="giallo-l"><span class="z-string"> ON CONFLICT (&quot;key&quot;) DO UPDATE SET &quot;value&quot; = $2, expires = $3&quot;#</span><span>,</span></span> <span class="giallo-l"><span class="z-variable z-language"> Self</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">key_format</span><span class="z-variable">(key),</span></span> <span class="giallo-l"><span class="z-variable"> value,</span></span> <span class="giallo-l"><span class="z-variable z-language"> Self</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">get_expire_time</span><span>(),</span></span> <span class="giallo-l"><span> )</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">execute</span><span>(</span><span class="z-entity z-name">db</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">pg_pool</span><span>()</span><span class="z-keyword z-operator">.</span><span class="z-keyword">await</span><span>)</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-keyword">await</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">map_err</span><span>(</span><span class="z-keyword z-operator">|</span><span class="z-variable">_</span><span class="z-keyword z-operator">|</span><span class="z-string"> &quot;Failed to set value in kv_store&quot;</span><span class="z-keyword z-operator">.</span><span class="z-entity z-name z-function">to_string</span><span>())</span><span class="z-keyword z-operator">?</span><span>;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-entity z-name"> Ok</span><span>(())</span></span> <span class="giallo-l"><span> }</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-comment"> // it will just fetch the value if it exists</span></span> <span class="giallo-l"><span class="z-keyword"> async fn</span><span class="z-entity z-name z-function"> get</span><span class="z-variable">(key</span><span class="z-keyword z-operator">:</span><span class="z-entity z-name"> String</span><span>)</span><span class="z-keyword z-operator"> -&gt;</span><span class="z-entity z-name"> Result</span><span>&lt;</span><span class="z-variable z-language">Self</span><span>,</span><span class="z-entity z-name"> String</span><span>&gt; {</span></span> <span class="giallo-l"><span class="z-storage"> let</span><span class="z-variable"> record</span><span class="z-keyword z-operator"> =</span><span class="z-entity z-name"> sqlx</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">query!</span><span>(</span></span> <span class="giallo-l"><span class="z-string"> r#&quot;SELECT &quot;value&quot; FROM kv_store WHERE &quot;key&quot; = $1&quot;#</span><span>,</span></span> <span class="giallo-l"><span class="z-variable z-language"> Self</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">key_format</span><span class="z-variable">(key)</span></span> <span class="giallo-l"><span> )</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">fetch_one</span><span>(</span><span class="z-entity z-name">db</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">pg_pool</span><span>()</span><span class="z-keyword z-operator">.</span><span class="z-keyword">await</span><span>)</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-keyword">await</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">map_err</span><span>(</span><span class="z-keyword z-operator">|</span><span class="z-variable">_</span><span class="z-keyword z-operator">|</span><span class="z-string"> &quot;Failed to get value from kv_store&quot;</span><span class="z-keyword z-operator">.</span><span class="z-entity z-name z-function">to_string</span><span>())</span><span class="z-keyword z-operator">?</span><span>;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-entity z-name"> serde_json</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">from_str</span><span>(</span><span class="z-keyword z-operator">&amp;</span><span class="z-variable">record</span><span class="z-keyword z-operator">.</span><span>value)</span><span class="z-keyword z-operator">.</span><span class="z-entity z-name z-function">map_err</span><span>(</span><span class="z-keyword z-operator">|</span><span class="z-variable">_</span><span class="z-keyword z-operator">|</span><span class="z-string"> &quot;Failed to deserialize value&quot;</span><span class="z-keyword z-operator">.</span><span class="z-entity z-name z-function">to_string</span><span>())</span></span> <span class="giallo-l"><span> }</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-comment"> // this will fetch the value while extending the expire time</span></span> <span class="giallo-l"><span class="z-keyword"> async fn</span><span class="z-entity z-name z-function"> get_ex</span><span class="z-variable">(key</span><span class="z-keyword z-operator">:</span><span class="z-entity z-name"> String</span><span>)</span><span class="z-keyword z-operator"> -&gt;</span><span class="z-entity z-name"> Result</span><span>&lt;</span><span class="z-variable z-language">Self</span><span>,</span><span class="z-entity z-name"> String</span><span>&gt; {</span></span> <span class="giallo-l"><span class="z-storage"> let</span><span class="z-variable"> record</span><span class="z-keyword z-operator"> =</span><span class="z-entity z-name"> sqlx</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">query!</span><span>(</span></span> <span class="giallo-l"><span class="z-string"> r#&quot;UPDATE kv_store SET expires=$2 WHERE &quot;key&quot;=$1 RETURNING &quot;value&quot;&quot;#</span><span>,</span></span> <span class="giallo-l"><span class="z-variable z-language"> Self</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">key_format</span><span class="z-variable">(key),</span></span> <span class="giallo-l"><span class="z-variable z-language"> Self</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">get_expire_time</span><span>(),</span></span> <span class="giallo-l"><span> )</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">fetch_one</span><span>(</span><span class="z-entity z-name">db</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">pg_pool</span><span>()</span><span class="z-keyword z-operator">.</span><span class="z-keyword">await</span><span>)</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-keyword">await</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">map_err</span><span>(</span><span class="z-keyword z-operator">|</span><span class="z-variable">_</span><span class="z-keyword z-operator">|</span><span class="z-string"> &quot;Failed to get value from kv_store&quot;</span><span class="z-keyword z-operator">.</span><span class="z-entity z-name z-function">to_string</span><span>())</span><span class="z-keyword z-operator">?</span><span>;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-entity z-name"> serde_json</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">from_str</span><span>(</span><span class="z-keyword z-operator">&amp;</span><span class="z-variable">record</span><span class="z-keyword z-operator">.</span><span>value)</span><span class="z-keyword z-operator">.</span><span class="z-entity z-name z-function">map_err</span><span>(</span><span class="z-keyword z-operator">|</span><span class="z-variable">_</span><span class="z-keyword z-operator">|</span><span class="z-string"> &quot;Failed to deserialize value&quot;</span><span class="z-keyword z-operator">.</span><span class="z-entity z-name z-function">to_string</span><span>())</span></span> <span class="giallo-l"><span> }</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-comment"> // it will fetch the value while deleting the key</span></span> <span class="giallo-l"><span class="z-keyword"> async fn</span><span class="z-entity z-name z-function"> get_del</span><span class="z-variable">(key</span><span class="z-keyword z-operator">:</span><span class="z-entity z-name"> String</span><span>)</span><span class="z-keyword z-operator"> -&gt;</span><span class="z-entity z-name"> Result</span><span>&lt;</span><span class="z-variable z-language">Self</span><span>,</span><span class="z-entity z-name"> String</span><span>&gt; {</span></span> <span class="giallo-l"><span class="z-storage"> let</span><span class="z-variable"> record</span><span class="z-keyword z-operator"> =</span><span class="z-entity z-name"> sqlx</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">query!</span><span>(</span></span> <span class="giallo-l"><span class="z-string"> r#&quot;DELETE FROM kv_store WHERE key=$1 RETURNING &quot;value&quot;&quot;#</span><span>,</span></span> <span class="giallo-l"><span class="z-variable z-language"> Self</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">key_format</span><span class="z-variable">(key)</span></span> <span class="giallo-l"><span> )</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">fetch_one</span><span>(</span><span class="z-entity z-name">db</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">pg_pool</span><span>()</span><span class="z-keyword z-operator">.</span><span class="z-keyword">await</span><span>)</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-keyword">await</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">map_err</span><span>(</span><span class="z-keyword z-operator">|</span><span class="z-variable">_</span><span class="z-keyword z-operator">|</span><span class="z-string"> &quot;Failed to get value from kv_store&quot;</span><span class="z-keyword z-operator">.</span><span class="z-entity z-name z-function">to_string</span><span>())</span><span class="z-keyword z-operator">?</span><span>;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-entity z-name"> serde_json</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">from_str</span><span>(</span><span class="z-keyword z-operator">&amp;</span><span class="z-variable">record</span><span class="z-keyword z-operator">.</span><span>value)</span><span class="z-keyword z-operator">.</span><span class="z-entity z-name z-function">map_err</span><span>(</span><span class="z-keyword z-operator">|</span><span class="z-variable">_</span><span class="z-keyword z-operator">|</span><span class="z-string"> &quot;Failed to deserialize value&quot;</span><span class="z-keyword z-operator">.</span><span class="z-entity z-name z-function">to_string</span><span>())</span></span> <span class="giallo-l"><span> }</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-keyword"> async fn</span><span class="z-entity z-name z-function"> del</span><span class="z-variable">(key</span><span class="z-keyword z-operator">:</span><span class="z-entity z-name"> String</span><span>)</span><span class="z-keyword z-operator"> -&gt;</span><span class="z-entity z-name"> Result</span><span>&lt;(),</span><span class="z-entity z-name"> String</span><span>&gt; {</span></span> <span class="giallo-l"><span class="z-entity z-name"> sqlx</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">query!</span><span>(</span></span> <span class="giallo-l"><span class="z-string"> r#&quot;DELETE FROM kv_store WHERE key=$1&quot;#</span><span>,</span></span> <span class="giallo-l"><span class="z-variable z-language"> Self</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">key_format</span><span class="z-variable">(key)</span></span> <span class="giallo-l"><span> )</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">execute</span><span>(</span><span class="z-entity z-name">db</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">pg_pool</span><span>()</span><span class="z-keyword z-operator">.</span><span class="z-keyword">await</span><span>)</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-keyword">await</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">map_err</span><span>(</span><span class="z-keyword z-operator">|</span><span class="z-variable">_</span><span class="z-keyword z-operator">|</span><span class="z-string"> &quot;Failed to delete value&quot;</span><span class="z-keyword z-operator">.</span><span class="z-entity z-name z-function">to_string</span><span>())</span><span class="z-keyword z-operator">?</span><span>;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-entity z-name"> Ok</span><span>(())</span></span> <span class="giallo-l"><span> }</span></span> <span class="giallo-l"><span>}</span></span></code></pre> <p>By defining our trait like <code>PgStore: Serialize + DeserializeOwned</code>, we are telling that whichever type is going to implement <code>PgStore</code> trait it must also have <code>Serialize</code> and <code>DeserializeOwned</code> implemented.</p> <p>Following are the brief explaination of <code>PgStore</code>’s attributes:</p> <p><strong>EXPIRE_IN:</strong> This will be used to set the to be expired in seconds. It must be implemented by the Type you are using it for.</p> <p><strong>key_format:</strong> This function needs to be implemented. It will be used as a way to generate key.</p> <p><strong>set_ex:</strong> This method will store the type against the passed key in DB, overwriting value if it already exists.</p> <p><strong>get:</strong> It will fetch the value for a given key, error will be returned if it does not exist.</p> <p><strong>get_ex:</strong> Fetches the value while resetting the expire time.</p> <p><strong>get_del:</strong> Fetch the value while deleting the key. It’s more like pop.</p> <p><strong>del:</strong> Just deletes the value. Doesn’t return error even if key doesn’t exist.</p> <h2 id="cleaning-up-expired-keys"><a class="zola-anchor" href="#cleaning-up-expired-keys" aria-label="Anchor link for: cleaning-up-expired-keys">🔗</a>Cleaning up expired keys</h2> <p>Then we have a helper function <code>pgstore_cleanup</code> which will cleanup expired keys every 60 seconds. You must spawn to run this function in the background for all the time your program is running.</p> <pre class="giallo z-code"><code data-lang="rust"><span class="giallo-l"><span class="z-keyword">pub async fn</span><span class="z-entity z-name z-function"> pgstore_cleanup</span><span>() {</span></span> <span class="giallo-l"><span class="z-keyword"> loop</span><span> {</span></span> <span class="giallo-l"><span class="z-comment"> // tracing::info!(&quot;🟡 PgStore cleanup is running...&quot;);</span></span> <span class="giallo-l"><span class="z-entity z-name"> sqlx</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">query!</span><span>(</span><span class="z-string">r#&quot;DELETE FROM kv_store WHERE expires &lt; NOW()&quot;#</span><span>)</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">execute</span><span>(</span><span class="z-entity z-name">db</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">pg_pool</span><span>()</span><span class="z-keyword z-operator">.</span><span class="z-keyword">await</span><span>)</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-keyword">await</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">ok</span><span>();</span></span> <span class="giallo-l"><span class="z-entity z-name"> tokio</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">time</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">sleep</span><span>(</span><span class="z-entity z-name">Duration</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">from_secs</span><span>(</span><span class="z-constant z-numeric">60</span><span>))</span><span class="z-keyword z-operator">.</span><span class="z-keyword">await</span><span>;</span></span> <span class="giallo-l"><span> }</span></span> <span class="giallo-l"><span>}</span></span></code></pre><h2 id="usage"><a class="zola-anchor" href="#usage" aria-label="Anchor link for: usage">🔗</a>Usage</h2> <pre class="giallo z-code"><code data-lang="rust"><span class="giallo-l"><span>#[derive(serde</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">Serialize</span><span>, serde</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">Deserialize</span><span>)]</span></span> <span class="giallo-l"><span class="z-keyword z-storage">pub struct</span><span class="z-entity z-name"> Game</span><span> {</span></span> <span class="giallo-l"><span class="z-keyword"> pub</span><span class="z-variable"> id</span><span class="z-keyword z-operator">:</span><span class="z-entity z-name"> usize</span><span>,</span></span> <span class="giallo-l"><span class="z-keyword"> pub</span><span class="z-variable"> name</span><span class="z-keyword z-operator">:</span><span class="z-entity z-name"> String</span><span>,</span></span> <span class="giallo-l"><span class="z-keyword"> pub</span><span class="z-variable"> genre</span><span class="z-keyword z-operator">:</span><span class="z-entity z-name"> String</span><span>,</span></span> <span class="giallo-l"><span>}</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-keyword">impl</span><span class="z-entity z-name"> PgStore</span><span class="z-keyword"> for</span><span class="z-entity z-name"> Game</span><span> {</span></span> <span class="giallo-l"><span class="z-storage"> const</span><span class="z-constant z-other"> EXPIRE_IN</span><span class="z-keyword z-operator">:</span><span class="z-entity z-name"> usize</span><span class="z-keyword z-operator"> =</span><span class="z-constant z-numeric"> 3600</span><span>;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-keyword"> fn</span><span class="z-entity z-name z-function"> key_format</span><span class="z-variable">(key</span><span class="z-keyword z-operator">:</span><span class="z-entity z-name"> String</span><span>)</span><span class="z-keyword z-operator"> -&gt;</span><span class="z-entity z-name"> String</span><span> {</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> format!</span><span>(</span><span class="z-string">&quot;game-{}&quot;</span><span class="z-variable">, key)</span></span> <span class="giallo-l"><span> }</span></span> <span class="giallo-l"><span>}</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span>#[tokio</span><span class="z-keyword z-operator">::</span><span>main]</span></span> <span class="giallo-l"><span class="z-keyword">async fn</span><span class="z-entity z-name z-function"> main</span><span>() {</span></span> <span class="giallo-l"><span class="z-comment"> // make sure to run this to delete expired keys regularly</span></span> <span class="giallo-l"><span class="z-entity z-name"> tokio</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">spawn</span><span>(</span><span class="z-entity z-name z-function">pgstore_cleanup</span><span>());</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage"> let</span><span class="z-variable"> game</span><span class="z-keyword z-operator"> =</span><span class="z-entity z-name"> Game</span><span> {</span></span> <span class="giallo-l"><span class="z-variable"> id</span><span class="z-keyword z-operator">:</span><span class="z-constant z-numeric"> 1</span><span>,</span></span> <span class="giallo-l"><span class="z-variable"> name</span><span class="z-keyword z-operator">:</span><span class="z-string"> &quot;Skyrim&quot;</span><span class="z-keyword z-operator">.</span><span class="z-entity z-name z-function">to_string</span><span>(),</span></span> <span class="giallo-l"><span class="z-variable"> genre</span><span class="z-keyword z-operator">:</span><span class="z-string"> &quot;rpg&quot;</span><span class="z-keyword z-operator">.</span><span class="z-entity z-name z-function">to_string</span><span>(),</span></span> <span class="giallo-l"><span> };</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-comment"> // storing value in kv_store</span></span> <span class="giallo-l"><span class="z-comment"> // it will be store with key: &quot;game-1&quot;</span></span> <span class="giallo-l"><span class="z-storage"> let</span><span class="z-variable"> _</span><span class="z-keyword z-operator"> =</span><span class="z-variable"> game</span><span class="z-keyword z-operator">.</span><span class="z-entity z-name z-function">set_ex</span><span class="z-variable">(game</span><span class="z-keyword z-operator">.</span><span>id</span><span class="z-keyword z-operator">.</span><span class="z-entity z-name z-function">to_string</span><span>())</span><span class="z-keyword z-operator">.</span><span class="z-keyword">await</span><span>;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-comment"> // fetching value</span></span> <span class="giallo-l"><span class="z-keyword z-storage"> if let</span><span class="z-entity z-name"> Ok</span><span class="z-variable">(v)</span><span class="z-keyword z-operator"> =</span><span class="z-entity z-name"> Game</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">get</span><span>(</span><span class="z-constant z-numeric">1</span><span class="z-punctuation z-separator">.</span><span class="z-entity z-name z-function">to_string</span><span>())</span><span class="z-keyword z-operator">.</span><span class="z-keyword">await</span><span> {</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> println!</span><span>(</span><span class="z-string">&quot;fetched game with name: {}&quot;</span><span class="z-variable">, v</span><span class="z-keyword z-operator">.</span><span>name);</span></span> <span class="giallo-l"><span> }</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-comment"> // deleting key</span></span> <span class="giallo-l"><span class="z-storage"> let</span><span class="z-variable"> _</span><span class="z-keyword z-operator"> =</span><span class="z-entity z-name"> Game</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">del</span><span>(</span><span class="z-constant z-numeric">1</span><span class="z-punctuation z-separator">.</span><span class="z-entity z-name z-function">to_string</span><span>())</span><span class="z-keyword z-operator">.</span><span class="z-keyword">await</span><span>;</span></span> <span class="giallo-l"><span>}</span></span></code></pre> <p>Similarly you can do this with your own types, as long as they derive serde’s Serialize and Deserialize.</p> 2025-04-13T00:00:00+00:00 2025-04-13T00:00:00+00:00 Vivek Shukla https://vshukla.com/tech/sqlite-in-rust-with-sqlx/

Guide to use SQLite database in Rust with Sqlx

<p>SQLite is self-contained, file based relational database. If you have a simple use case and want to avoid complex databases then SQLite is one of the best choice.</p> <p>We will use <a rel="noopener external" target="_blank" href="https://github.com/launchbadge/sqlx"><code>sqlx</code> crate</a> to interact with SQLite database.</p> <p>Why Sqlx?</p> <ul> <li>Async support</li> <li>Supports migrations</li> <li>Compile time type safety</li> <li>Supports SQLite, Postgres and MySQL</li> </ul> <h2 id="setup"><a class="zola-anchor" href="#setup" aria-label="Anchor link for: setup">🔗</a>Setup</h2> <pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name">cargo</span><span class="z-string"> init sqlite-demo</span></span></code></pre><h3 id="cargo-toml"><a class="zola-anchor" href="#cargo-toml" aria-label="Anchor link for: cargo-toml">🔗</a>Cargo.toml</h3> <p>Add the following dependencies to your <code>Cargo.toml</code> file. We are using <a rel="noopener external" target="_blank" href="https://github.com/tokio-rs/tokio">tokio runtime</a> and sqlite features of <code>sqlx</code>.</p> <pre class="giallo z-code"><code data-lang="toml"><span class="giallo-l"><span>[</span><span class="z-entity z-name">package</span><span>]</span></span> <span class="giallo-l"><span class="z-variable">name</span><span class="z-punctuation z-separator"> =</span><span class="z-string"> &quot;sqlite-demo&quot;</span></span> <span class="giallo-l"><span class="z-variable">version</span><span class="z-punctuation z-separator"> =</span><span class="z-string"> &quot;0.1.0&quot;</span></span> <span class="giallo-l"><span class="z-variable">edition</span><span class="z-punctuation z-separator"> =</span><span class="z-string"> &quot;2024&quot;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span>[</span><span class="z-entity z-name">dependencies</span><span>]</span></span> <span class="giallo-l"><span class="z-variable">sqlx</span><span class="z-punctuation z-separator"> =</span><span class="z-variable"> { version</span><span class="z-punctuation z-separator"> =</span><span class="z-string"> &quot;0.8&quot;</span><span class="z-punctuation z-separator">,</span><span class="z-variable"> features</span><span class="z-punctuation z-separator"> =</span><span> [</span></span> <span class="giallo-l"><span class="z-string"> &quot;runtime-tokio&quot;</span><span class="z-punctuation z-separator">,</span></span> <span class="giallo-l"><span class="z-string"> &quot;sqlite&quot;</span><span class="z-punctuation z-separator">,</span></span> <span class="giallo-l"><span class="z-string"> &quot;migrate&quot;</span><span class="z-punctuation z-separator">,</span></span> <span class="giallo-l"><span>] }</span></span> <span class="giallo-l"><span class="z-variable">tokio</span><span class="z-punctuation z-separator"> =</span><span class="z-variable"> { version</span><span class="z-punctuation z-separator"> =</span><span class="z-string"> &quot;1.44.2&quot;</span><span class="z-punctuation z-separator">,</span><span class="z-variable"> features</span><span class="z-punctuation z-separator"> =</span><span> [</span><span class="z-string">&quot;full&quot;</span><span>] }</span></span></code></pre><h2 id="connect-to-sqlite-database"><a class="zola-anchor" href="#connect-to-sqlite-database" aria-label="Anchor link for: connect-to-sqlite-database">🔗</a>Connect to SQLite Database</h2> <p>Here we are using <code>SqliteConnectOptions</code> to connect to SQLite database. We are also creating the database file if it doesn’t exist. We are using <code>SqliteJournalMode::Delete</code> to delete the journal file after commit so that we will only have one file in the database directory.</p> <p>Since we want file based database, we are using <code>sqlite://main.db</code> as connection string. For memory based database, we can use <code>sqlite::memory:</code> as connection string.</p> <pre class="giallo z-code"><code data-lang="rust"><span class="giallo-l"><span class="z-keyword">use</span><span class="z-entity z-name"> sqlx</span><span class="z-keyword z-operator">::</span><span>{</span><span class="z-entity z-name">ConnectOptions</span><span>,</span><span class="z-entity z-name"> Connection</span><span>,</span><span class="z-entity z-name"> sqlite</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">SqliteConnectOptions</span><span>};</span></span> <span class="giallo-l"><span class="z-keyword">use</span><span class="z-entity z-name"> std</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">str</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">FromStr</span><span>;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span>#[tokio</span><span class="z-keyword z-operator">::</span><span>main]</span></span> <span class="giallo-l"><span class="z-keyword">async fn</span><span class="z-entity z-name z-function"> main</span><span>() {</span></span> <span class="giallo-l"><span class="z-storage"> let mut</span><span class="z-variable"> conn</span><span class="z-keyword z-operator"> =</span><span class="z-entity z-name"> SqliteConnectOptions</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">from_str</span><span>(</span><span class="z-string">&quot;sqlite://main.db&quot;</span><span>)</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">unwrap</span><span>()</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">create_if_missing</span><span>(</span><span class="z-constant z-language">true</span><span>)</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">journal_mode</span><span>(</span><span class="z-entity z-name">sqlx</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">sqlite</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">SqliteJournalMode</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">Delete</span><span>)</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">connect</span><span>()</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-keyword">await</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">expect</span><span>(</span><span class="z-string">&quot;Failed to connect to database&quot;</span><span>);</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-comment"> // Create the users table if it doesn&#39;t exist</span></span> <span class="giallo-l"><span class="z-entity z-name"> sqlx</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">query</span><span>(</span></span> <span class="giallo-l"><span class="z-string"> &quot;CREATE TABLE IF NOT EXISTS users (</span></span> <span class="giallo-l"><span class="z-string"> id INTEGER PRIMARY KEY AUTOINCREMENT,</span></span> <span class="giallo-l"><span class="z-string"> name TEXT NOT NULL,</span></span> <span class="giallo-l"><span class="z-string"> age INTEGER</span></span> <span class="giallo-l"><span class="z-string"> )&quot;</span><span>,</span></span> <span class="giallo-l"><span> )</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">execute</span><span>(</span><span class="z-keyword z-operator">&amp;</span><span class="z-storage">mut</span><span class="z-variable"> conn)</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-keyword">await</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">unwrap</span><span>();</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage"> let</span><span class="z-variable"> _</span><span class="z-keyword z-operator"> =</span><span class="z-variable"> conn</span><span class="z-keyword z-operator">.</span><span class="z-entity z-name z-function">close</span><span>()</span><span class="z-keyword z-operator">.</span><span class="z-keyword">await</span><span>;</span></span> <span class="giallo-l"><span>}</span></span></code></pre><h2 id="creating-connection-pool"><a class="zola-anchor" href="#creating-connection-pool" aria-label="Anchor link for: creating-connection-pool">🔗</a>Creating Connection Pool</h2> <p>We will use <a rel="noopener external" target="_blank" href="https://docs.rs/sqlx/latest/sqlx/sqlite/type.SqlitePoolOptions.html"><code>SqlitePoolOptions</code></a> to create a connection pool.</p> <p>We will create a helper function <code>db_conn</code> to create a connection pool. This function will return a connection pool that can be used to interact with the database.</p> <pre class="giallo z-code"><code data-lang="rust"><span class="giallo-l"><span class="z-keyword">use</span><span class="z-entity z-name"> sqlx</span><span class="z-keyword z-operator">::</span><span>{</span></span> <span class="giallo-l"><span class="z-entity z-name"> Pool</span><span>,</span><span class="z-entity z-name"> Sqlite</span><span>,</span></span> <span class="giallo-l"><span class="z-entity z-name"> sqlite</span><span class="z-keyword z-operator">::</span><span>{</span><span class="z-entity z-name">SqliteConnectOptions</span><span>,</span><span class="z-entity z-name"> SqlitePoolOptions</span><span>},</span></span> <span class="giallo-l"><span>};</span></span> <span class="giallo-l"><span class="z-keyword">use</span><span class="z-entity z-name"> std</span><span class="z-keyword z-operator">::</span><span>{</span><span class="z-entity z-name">str</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">FromStr</span><span>,</span><span class="z-entity z-name"> time</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">Duration</span><span>};</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span>#[tokio</span><span class="z-keyword z-operator">::</span><span>main]</span></span> <span class="giallo-l"><span class="z-keyword">async fn</span><span class="z-entity z-name z-function"> main</span><span>() {</span></span> <span class="giallo-l"><span class="z-storage"> let</span><span class="z-variable"> conn</span><span class="z-keyword z-operator"> =</span><span class="z-entity z-name z-function"> db_conn</span><span>()</span><span class="z-keyword z-operator">.</span><span class="z-keyword">await</span><span>;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-comment"> // Create the users table if it doesn&#39;t exist</span></span> <span class="giallo-l"><span class="z-entity z-name"> sqlx</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">query</span><span>(</span></span> <span class="giallo-l"><span class="z-string"> &quot;CREATE TABLE IF NOT EXISTS users (</span></span> <span class="giallo-l"><span class="z-string"> id INTEGER PRIMARY KEY AUTOINCREMENT,</span></span> <span class="giallo-l"><span class="z-string"> name TEXT NOT NULL,</span></span> <span class="giallo-l"><span class="z-string"> age INTEGER</span></span> <span class="giallo-l"><span class="z-string"> )&quot;</span><span>,</span></span> <span class="giallo-l"><span> )</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">execute</span><span>(</span><span class="z-keyword z-operator">&amp;</span><span class="z-variable">conn)</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-keyword">await</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">unwrap</span><span>();</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage"> let</span><span class="z-variable"> _</span><span class="z-keyword z-operator"> =</span><span class="z-variable"> conn</span><span class="z-keyword z-operator">.</span><span class="z-entity z-name z-function">close</span><span>()</span><span class="z-keyword z-operator">.</span><span class="z-keyword">await</span><span>;</span></span> <span class="giallo-l"><span>}</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-keyword">async fn</span><span class="z-entity z-name z-function"> db_conn</span><span>()</span><span class="z-keyword z-operator"> -&gt;</span><span class="z-entity z-name"> Pool</span><span>&lt;</span><span class="z-entity z-name">Sqlite</span><span>&gt; {</span></span> <span class="giallo-l"><span class="z-storage"> let</span><span class="z-variable"> db_url</span><span class="z-keyword z-operator"> =</span><span class="z-string"> &quot;sqlite://main.db&quot;</span><span>;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-entity z-name"> SqlitePoolOptions</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">new</span><span>()</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">max_connections</span><span>(</span><span class="z-constant z-numeric">20</span><span>)</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">idle_timeout</span><span>(</span><span class="z-entity z-name">Duration</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">from_secs</span><span>(</span><span class="z-constant z-numeric">60</span><span>))</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">acquire_timeout</span><span>(</span><span class="z-entity z-name">Duration</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">from_secs</span><span>(</span><span class="z-constant z-numeric">5</span><span>))</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">connect_with</span><span>(</span></span> <span class="giallo-l"><span class="z-entity z-name"> SqliteConnectOptions</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">from_str</span><span class="z-variable">(db_url)</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">unwrap</span><span>()</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">create_if_missing</span><span>(</span><span class="z-constant z-language">true</span><span>)</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">journal_mode</span><span>(</span><span class="z-entity z-name">sqlx</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">sqlite</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">SqliteJournalMode</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">Delete</span><span>),</span></span> <span class="giallo-l"><span> )</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-keyword">await</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">unwrap</span><span>()</span></span> <span class="giallo-l"><span>}</span></span></code></pre><h2 id="using-oncecell-to-create-a-connection-pool"><a class="zola-anchor" href="#using-oncecell-to-create-a-connection-pool" aria-label="Anchor link for: using-oncecell-to-create-a-connection-pool">🔗</a>Using OnceCell to create a connection pool</h2> <p>We can use <a rel="noopener external" target="_blank" href="https://docs.rs/tokio/latest/tokio/sync/struct.OnceCell.html"><code>OnceCell</code></a> to create a connection pool. This will ensure that the connection pool is created only once and can be shared across multiple threads. So that we won’t to pass connection pool to every function, we can just use this helper function to get the connection pool and it will re-use the same one.</p> <pre class="giallo z-code"><code data-lang="rust"><span class="giallo-l"><span class="z-keyword">use</span><span class="z-entity z-name"> sqlx</span><span class="z-keyword z-operator">::</span><span>{</span></span> <span class="giallo-l"><span class="z-entity z-name"> Pool</span><span>,</span><span class="z-entity z-name"> Sqlite</span><span>,</span></span> <span class="giallo-l"><span class="z-entity z-name"> sqlite</span><span class="z-keyword z-operator">::</span><span>{</span><span class="z-entity z-name">SqliteConnectOptions</span><span>,</span><span class="z-entity z-name"> SqlitePoolOptions</span><span>},</span></span> <span class="giallo-l"><span>};</span></span> <span class="giallo-l"><span class="z-keyword">use</span><span class="z-entity z-name"> std</span><span class="z-keyword z-operator">::</span><span>{</span><span class="z-entity z-name">str</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">FromStr</span><span>,</span><span class="z-entity z-name"> time</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">Duration</span><span>};</span></span> <span class="giallo-l"><span class="z-keyword">use</span><span class="z-entity z-name"> tokio</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">sync</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">OnceCell</span><span>;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage">static</span><span class="z-constant z-other"> DB_CONN</span><span class="z-keyword z-operator">:</span><span class="z-entity z-name"> OnceCell</span><span>&lt;</span><span class="z-entity z-name">Pool</span><span>&lt;</span><span class="z-entity z-name">Sqlite</span><span>&gt;&gt;</span><span class="z-keyword z-operator"> =</span><span class="z-entity z-name"> OnceCell</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">const_new</span><span>();</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-keyword">async fn</span><span class="z-entity z-name z-function"> db_conn</span><span>()</span><span class="z-keyword z-operator"> -&gt;</span><span class="z-entity z-name"> Pool</span><span>&lt;</span><span class="z-entity z-name">Sqlite</span><span>&gt; {</span></span> <span class="giallo-l"><span class="z-storage"> let</span><span class="z-variable"> db_url</span><span class="z-keyword z-operator"> =</span><span class="z-string"> &quot;sqlite://main.db&quot;</span><span>;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-constant z-other"> DB_CONN</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">get_or_init</span><span>(</span><span class="z-keyword z-operator">||</span><span class="z-keyword"> async</span><span> {</span></span> <span class="giallo-l"><span class="z-entity z-name"> SqlitePoolOptions</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">new</span><span>()</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">max_connections</span><span>(</span><span class="z-constant z-numeric">20</span><span>)</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">idle_timeout</span><span>(</span><span class="z-entity z-name">Duration</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">from_secs</span><span>(</span><span class="z-constant z-numeric">60</span><span>))</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">acquire_timeout</span><span>(</span><span class="z-entity z-name">Duration</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">from_secs</span><span>(</span><span class="z-constant z-numeric">5</span><span>))</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">connect_with</span><span>(</span></span> <span class="giallo-l"><span class="z-entity z-name"> SqliteConnectOptions</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">from_str</span><span class="z-variable">(db_url)</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">unwrap</span><span>()</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">create_if_missing</span><span>(</span><span class="z-constant z-language">true</span><span>)</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">journal_mode</span><span>(</span><span class="z-entity z-name">sqlx</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">sqlite</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">SqliteJournalMode</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">Delete</span><span>),</span></span> <span class="giallo-l"><span> )</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-keyword">await</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">unwrap</span><span>()</span></span> <span class="giallo-l"><span> })</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-keyword">await</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">clone</span><span>()</span></span> <span class="giallo-l"><span>}</span></span></code></pre><h2 id="handling-database-migrations"><a class="zola-anchor" href="#handling-database-migrations" aria-label="Anchor link for: handling-database-migrations">🔗</a>Handling Database Migrations</h2> <p>We will use <a rel="noopener external" target="_blank" href="https://github.com/launchbadge/sqlx/blob/main/sqlx-cli/README.md"><code>sqlx-cli</code></a> to handle migrations.</p> <pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name">cargo</span><span class="z-string"> install sqlx-cli</span></span></code></pre> <p>Create migration file for users table.</p> <pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name">sqlx</span><span class="z-string"> migrate add users</span></span></code></pre> <p>This will create a migration file in <code>migrations</code> directory with empty migration file for users table. Add the following content to the newly created migration file.</p> <pre class="giallo z-code"><code data-lang="sql"><span class="giallo-l"><span class="z-comment">-- Add migration script here</span></span> <span class="giallo-l"><span class="z-keyword">CREATE TABLE</span><span class="z-entity z-name z-function"> IF</span><span class="z-keyword"> NOT EXISTS</span><span> users (</span></span> <span class="giallo-l"><span> id </span><span class="z-storage">INTEGER PRIMARY KEY</span><span> AUTOINCREMENT,</span></span> <span class="giallo-l"><span class="z-keyword z-storage"> name TEXT NOT NULL</span><span>,</span></span> <span class="giallo-l"><span> age </span><span class="z-storage">INTEGER</span></span> <span class="giallo-l"><span>);</span></span></code></pre> <p>Embed the migration file in the executable.</p> <pre class="giallo z-code"><code data-lang="rust"><span class="giallo-l"><span class="z-keyword">use</span><span class="z-entity z-name"> sqlx</span><span class="z-keyword z-operator">::</span><span>{</span></span> <span class="giallo-l"><span class="z-entity z-name"> Pool</span><span>,</span><span class="z-entity z-name"> Sqlite</span><span>,</span></span> <span class="giallo-l"><span class="z-entity z-name"> sqlite</span><span class="z-keyword z-operator">::</span><span>{</span><span class="z-entity z-name">SqliteConnectOptions</span><span>,</span><span class="z-entity z-name"> SqlitePoolOptions</span><span>},</span></span> <span class="giallo-l"><span>};</span></span> <span class="giallo-l"><span class="z-keyword">use</span><span class="z-entity z-name"> std</span><span class="z-keyword z-operator">::</span><span>{</span><span class="z-entity z-name">str</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">FromStr</span><span>,</span><span class="z-entity z-name"> time</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">Duration</span><span>};</span></span> <span class="giallo-l"><span class="z-keyword">use</span><span class="z-entity z-name"> tokio</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">sync</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">OnceCell</span><span>;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span>#[tokio</span><span class="z-keyword z-operator">::</span><span>main]</span></span> <span class="giallo-l"><span class="z-keyword">async fn</span><span class="z-entity z-name z-function"> main</span><span>() {</span></span> <span class="giallo-l"><span class="z-comment"> // this will make sure migrations are added to the executable</span></span> <span class="giallo-l"><span class="z-entity z-name"> sqlx</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">migrate!</span><span>()</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">run</span><span>(</span><span class="z-keyword z-operator">&amp;</span><span class="z-entity z-name z-function">db_conn</span><span>()</span><span class="z-keyword z-operator">.</span><span class="z-keyword">await</span><span>)</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-keyword">await</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">expect</span><span>(</span><span class="z-string">&quot;Migrations went wrong :(&quot;</span><span>);</span></span> <span class="giallo-l"><span>}</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage">static</span><span class="z-constant z-other"> DB_CONN</span><span class="z-keyword z-operator">:</span><span class="z-entity z-name"> OnceCell</span><span>&lt;</span><span class="z-entity z-name">Pool</span><span>&lt;</span><span class="z-entity z-name">Sqlite</span><span>&gt;&gt;</span><span class="z-keyword z-operator"> =</span><span class="z-entity z-name"> OnceCell</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">const_new</span><span>();</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-keyword">async fn</span><span class="z-entity z-name z-function"> db_conn</span><span>()</span><span class="z-keyword z-operator"> -&gt;</span><span class="z-entity z-name"> Pool</span><span>&lt;</span><span class="z-entity z-name">Sqlite</span><span>&gt; {</span></span> <span class="giallo-l"><span class="z-storage"> let</span><span class="z-variable"> db_url</span><span class="z-keyword z-operator"> =</span><span class="z-string"> &quot;sqlite://main.db&quot;</span><span>;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-constant z-other"> DB_CONN</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">get_or_init</span><span>(</span><span class="z-keyword z-operator">||</span><span class="z-keyword"> async</span><span> {</span></span> <span class="giallo-l"><span class="z-entity z-name"> SqlitePoolOptions</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">new</span><span>()</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">max_connections</span><span>(</span><span class="z-constant z-numeric">20</span><span>)</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">idle_timeout</span><span>(</span><span class="z-entity z-name">Duration</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">from_secs</span><span>(</span><span class="z-constant z-numeric">60</span><span>))</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">acquire_timeout</span><span>(</span><span class="z-entity z-name">Duration</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">from_secs</span><span>(</span><span class="z-constant z-numeric">5</span><span>))</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">connect_with</span><span>(</span></span> <span class="giallo-l"><span class="z-entity z-name"> SqliteConnectOptions</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">from_str</span><span class="z-variable">(db_url)</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">unwrap</span><span>()</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">create_if_missing</span><span>(</span><span class="z-constant z-language">true</span><span>)</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">journal_mode</span><span>(</span><span class="z-entity z-name">sqlx</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">sqlite</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">SqliteJournalMode</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">Delete</span><span>),</span></span> <span class="giallo-l"><span> )</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-keyword">await</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">unwrap</span><span>()</span></span> <span class="giallo-l"><span> })</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-keyword">await</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">clone</span><span>()</span></span> <span class="giallo-l"><span>}</span></span></code></pre><h2 id="full-code-with-example-queries"><a class="zola-anchor" href="#full-code-with-example-queries" aria-label="Anchor link for: full-code-with-example-queries">🔗</a>Full Code with Example Queries</h2> <p><strong>main.rs</strong></p> <pre class="giallo z-code"><code data-lang="rust"><span class="giallo-l"><span class="z-keyword">use</span><span class="z-entity z-name"> sqlx</span><span class="z-keyword z-operator">::</span><span>{</span></span> <span class="giallo-l"><span class="z-entity z-name"> Pool</span><span>,</span><span class="z-entity z-name"> Row</span><span>,</span><span class="z-entity z-name"> Sqlite</span><span>,</span></span> <span class="giallo-l"><span class="z-entity z-name"> prelude</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">FromRow</span><span>,</span></span> <span class="giallo-l"><span class="z-entity z-name"> sqlite</span><span class="z-keyword z-operator">::</span><span>{</span><span class="z-entity z-name">SqliteConnectOptions</span><span>,</span><span class="z-entity z-name"> SqlitePoolOptions</span><span>},</span></span> <span class="giallo-l"><span>};</span></span> <span class="giallo-l"><span class="z-keyword">use</span><span class="z-entity z-name"> std</span><span class="z-keyword z-operator">::</span><span>{</span><span class="z-entity z-name">str</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">FromStr</span><span>,</span><span class="z-entity z-name"> time</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">Duration</span><span>};</span></span> <span class="giallo-l"><span class="z-keyword">use</span><span class="z-entity z-name"> tokio</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">sync</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">OnceCell</span><span>;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span>#[tokio</span><span class="z-keyword z-operator">::</span><span>main]</span></span> <span class="giallo-l"><span class="z-keyword">async fn</span><span class="z-entity z-name z-function"> main</span><span>() {</span></span> <span class="giallo-l"><span class="z-entity z-name"> sqlx</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">migrate!</span><span>()</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">run</span><span>(</span><span class="z-keyword z-operator">&amp;</span><span class="z-entity z-name z-function">db_conn</span><span>()</span><span class="z-keyword z-operator">.</span><span class="z-keyword">await</span><span>)</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-keyword">await</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">expect</span><span>(</span><span class="z-string">&quot;❌ Migrations went wrong :(&quot;</span><span>);</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-entity z-name"> sqlx</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">query</span><span>(</span><span class="z-string">&quot;INSERT INTO users (name, age) VALUES (?, ?)&quot;</span><span>)</span><span class="z-comment"> // Use ? for placeholders</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">bind</span><span>(</span><span class="z-string">&quot;Alice&quot;</span><span>)</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">bind</span><span>(</span><span class="z-constant z-numeric">30</span><span>)</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">execute</span><span>(</span><span class="z-keyword z-operator">&amp;</span><span class="z-entity z-name z-function">db_conn</span><span>()</span><span class="z-keyword z-operator">.</span><span class="z-keyword">await</span><span>)</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-keyword">await</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">unwrap</span><span>();</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage"> let</span><span class="z-variable"> query</span><span class="z-keyword z-operator"> =</span><span class="z-entity z-name"> sqlx</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">query</span><span>(</span><span class="z-string">&quot;SELECT count(*) AS count FROM users&quot;</span><span>)</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">fetch_one</span><span>(</span><span class="z-keyword z-operator">&amp;</span><span class="z-entity z-name z-function">db_conn</span><span>()</span><span class="z-keyword z-operator">.</span><span class="z-keyword">await</span><span>)</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-keyword">await</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">unwrap</span><span>();</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-entity z-name z-function"> println!</span><span>(</span><span class="z-string">&quot;Count: {:?}&quot;</span><span class="z-variable">, query</span><span class="z-keyword z-operator">.</span><span class="z-entity z-name z-function">get</span><span class="z-keyword z-operator">::</span><span>&lt;</span><span class="z-entity z-name">i64</span><span>,</span><span class="z-keyword z-operator"> &amp;</span><span class="z-entity z-name">str</span><span>&gt;(</span><span class="z-string">&quot;count&quot;</span><span>));</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage"> let</span><span class="z-variable"> users</span><span class="z-keyword z-operator"> =</span><span class="z-entity z-name"> sqlx</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">query_as</span><span class="z-keyword z-operator">::</span><span class="z-variable">&lt;_,</span><span class="z-entity z-name"> User</span><span>&gt;(</span><span class="z-string">&quot;SELECT id, name, age FROM users&quot;</span><span>)</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">fetch_all</span><span>(</span><span class="z-keyword z-operator">&amp;</span><span class="z-entity z-name z-function">db_conn</span><span>()</span><span class="z-keyword z-operator">.</span><span class="z-keyword">await</span><span>)</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-keyword">await</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">unwrap</span><span>();</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-keyword"> for</span><span class="z-variable"> user</span><span class="z-keyword"> in</span><span class="z-variable"> users {</span></span> <span class="giallo-l"><span class="z-entity z-name z-function"> println!</span><span>(</span><span class="z-string">&quot;Found user: {:?}&quot;</span><span class="z-variable">, user);</span></span> <span class="giallo-l"><span> }</span></span> <span class="giallo-l"><span>}</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage">static</span><span class="z-constant z-other"> DB_CONN</span><span class="z-keyword z-operator">:</span><span class="z-entity z-name"> OnceCell</span><span>&lt;</span><span class="z-entity z-name">Pool</span><span>&lt;</span><span class="z-entity z-name">Sqlite</span><span>&gt;&gt;</span><span class="z-keyword z-operator"> =</span><span class="z-entity z-name"> OnceCell</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">const_new</span><span>();</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-keyword">async fn</span><span class="z-entity z-name z-function"> db_conn</span><span>()</span><span class="z-keyword z-operator"> -&gt;</span><span class="z-entity z-name"> Pool</span><span>&lt;</span><span class="z-entity z-name">Sqlite</span><span>&gt; {</span></span> <span class="giallo-l"><span class="z-storage"> let</span><span class="z-variable"> db_url</span><span class="z-keyword z-operator"> =</span><span class="z-string"> &quot;sqlite://main.db&quot;</span><span>;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-constant z-other"> DB_CONN</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">get_or_init</span><span>(</span><span class="z-keyword z-operator">||</span><span class="z-keyword"> async</span><span> {</span></span> <span class="giallo-l"><span class="z-entity z-name"> SqlitePoolOptions</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">new</span><span>()</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">max_connections</span><span>(</span><span class="z-constant z-numeric">20</span><span>)</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">idle_timeout</span><span>(</span><span class="z-entity z-name">Duration</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">from_secs</span><span>(</span><span class="z-constant z-numeric">60</span><span>))</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">acquire_timeout</span><span>(</span><span class="z-entity z-name">Duration</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">from_secs</span><span>(</span><span class="z-constant z-numeric">5</span><span>))</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">connect_with</span><span>(</span></span> <span class="giallo-l"><span class="z-entity z-name"> SqliteConnectOptions</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">from_str</span><span class="z-variable">(db_url)</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">unwrap</span><span>()</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">create_if_missing</span><span>(</span><span class="z-constant z-language">true</span><span>)</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">journal_mode</span><span>(</span><span class="z-entity z-name">sqlx</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">sqlite</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">SqliteJournalMode</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name">Delete</span><span>),</span></span> <span class="giallo-l"><span> )</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-keyword">await</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">unwrap</span><span>()</span></span> <span class="giallo-l"><span> })</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-keyword">await</span></span> <span class="giallo-l"><span class="z-keyword z-operator"> .</span><span class="z-entity z-name z-function">clone</span><span>()</span></span> <span class="giallo-l"><span>}</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span>#[derive(</span><span class="z-entity z-name">Debug</span><span>,</span><span class="z-entity z-name"> FromRow</span><span>)]</span></span> <span class="giallo-l"><span class="z-storage">struct</span><span class="z-entity z-name"> User</span><span> {</span></span> <span class="giallo-l"><span class="z-variable"> id</span><span class="z-keyword z-operator">:</span><span class="z-entity z-name"> i64</span><span>,</span></span> <span class="giallo-l"><span class="z-variable"> name</span><span class="z-keyword z-operator">:</span><span class="z-entity z-name"> String</span><span>,</span></span> <span class="giallo-l"><span class="z-variable"> age</span><span class="z-keyword z-operator">:</span><span class="z-entity z-name"> Option</span><span>&lt;</span><span class="z-entity z-name">i32</span><span>&gt;,</span></span> <span class="giallo-l"><span>}</span></span></code></pre>