https://example.org/en/tags/sql/Recent content in Sql on My New Hugo ProjectHugo -- gohugo.ioen© 2026 Blog AuthorSat, 15 Aug 2026 09:00:00 +0800https://example.org/en/db/sql-tuning/Sat, 15 Aug 2026 09:00:00 +0800https://example.org/en/db/sql-tuning/<h2 class="relative group">Finding slow queries <div id="finding-slow-queries" class="anchor"></div> <span class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none"> <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#finding-slow-queries" aria-label="Anchor">#</a> </span> </h2> <ul> <li>Enable the slow-query log: <code>log_min_duration_statement</code></li> <li>Analyze plans with <code>EXPLAIN ANALYZE</code></li> <li>Watch <code>pg_stat_statements</code> for the most frequent SQL</li> </ul> <h2 class="relative group">Common performance killers <div id="common-performance-killers" class="anchor"></div> <span class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none"> <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#common-performance-killers" aria-label="Anchor">#</a> </span> </h2> <ul> <li><strong>Full table scans</strong>: missing indexes or conditions that can&rsquo;t use them</li> <li><strong>Implicit type casts</strong>: functions on indexed columns disable the index</li> <li><strong>N+1 queries</strong>: querying row-by-row inside a loop</li> <li><strong>Large-offset pagination</strong>: <code>OFFSET 1000000</code> gets slower as you page</li> </ul> <h2 class="relative group">Fixes <div id="fixes" class="anchor"></div> <span class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none"> <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#fixes" aria-label="Anchor">#</a> </span> </h2> <ul> <li>Rewrite SQL: drive big tables with small result sets (join order)</li> <li>Use indexes wisely: covering and composite indexes</li> <li>Denormalize judiciously: precomputed summary tables</li> </ul> <h2 class="relative group">Summary <div id="summary" class="anchor"></div> <span class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none"> <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#summary" aria-label="Anchor">#</a> </span> </h2> <p>SQL tuning is about <strong>understanding the execution plan</strong>. Locate the bottleneck first, then fix it — don&rsquo;t blindly add indexes.</p>