--- title: All Your GUCs in a Row: local_preload_libraries | daily.dev description: A deep dive into local_preload_libraries, a PostgreSQL GUC that lets non-superuser roles load shared libraries into their own backend sessions, restricted to... canonical: https://daily.dev/posts/all-your-gucs-in-a-row-local-preload-libraries-hi1uo8fjf twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: All Your GUCs in a Row: local_preload_libraries | daily.dev og:description: A deep dive into local_preload_libraries, a PostgreSQL GUC that lets non-superuser roles load shared libraries into their own backend sessions, restricted to... og:url: https://daily.dev/posts/all-your-gucs-in-a-row-local-preload-libraries-hi1uo8fjf og:image: https://api.daily.dev/og/posts/Hi1uo8fjF.png og:image:alt: All Your GUCs in a Row: local_preload_libraries og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # All Your GUCs in a Row: local_preload_libraries **[Planet PostgreSQL](https://daily.dev/sources/planet-postgresql)** · 4 min read · 0 upvotes · 0 comments ## Summary A deep dive into local_preload_libraries, a PostgreSQL GUC that lets non-superuser roles load shared libraries into their own backend sessions, restricted to the $libdir/plugins directory. Covers its mechanics, the history dating back to Postgres 8.2 (originally for the EDB PL/pgSQL debugger), how it differs from session_preload_libraries and shared_preload_libraries, failure modes when a typo'd library name locks out logins, and a practical example using auto_explain with GRANT SET ON PARAMETER (available since Postgres 15) to let developers self-enable plan logging per session. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### What is local_preload_libraries in PostgreSQL and how does it differ from session_preload_libraries? local_preload_libraries lets any role, not just superusers, load a shared library into its own backend session at connection time, but only from the fixed $libdir/plugins directory. session_preload_libraries is superuser-only but can load from anywhere in $libdir. Both are read once at backend startup; a later SET updates SHOW output but loads nothing. _Teams tuning postgres access controls can track GUC behavior details like this via daily.dev._ ### Why does setting local_preload_libraries with ALTER ROLE fail to actually load the library after I run SET again mid-session? The preload library list is only read once, during backend startup, right after role and database settings from pg_db_role_setting are applied. Running SET local_preload_libraries mid-session succeeds and updates what SHOW reports, but it is purely decorative since nothing gets loaded until the next new connection. _Developers debugging postgres session quirks can revisit explanations like this on daily.dev._ ### How can I let a developer enable auto_explain for a single psql session without granting superuser access in PostgreSQL? Symlink auto_explain.so into $libdir/plugins, then run GRANT SET ON PARAMETER auto_explain.log_min_duration, auto_explain.log_analyze TO developers (this GRANT SET syntax requires PostgreSQL 15 or later). The developer can then set local_preload_libraries via PGOPTIONS on their own connection to turn on plan logging for just that session. _Database admins scripting fine-grained postgres permissions can save practical recipes like this on daily.dev._ ## Similar posts on daily.dev - [All Your GUCs in a Row: dynamic\_library\_path](https://daily.dev/posts/all-your-gucs-in-a-row-dynamic-library-path-brjzn5wkf) · Planet PostgreSQL · 1 upvotes · 0 comments - [All Your GUCs in a Row: plan\_cache\_mode](https://daily.dev/posts/all-your-gucs-in-a-row-plan-cache-mode-grfcl9ncg) · Planet PostgreSQL · 0 upvotes · 0 comments - [All Your GUCs in a Row: extension\_control\_path](https://daily.dev/posts/all-your-gucs-in-a-row-extension-control-path-nnvvjerix) · Planet PostgreSQL · 0 upvotes · 1 comments - [All Your GUCs in a Row: port](https://daily.dev/posts/all-your-gucs-in-a-row-port-uoacyypyd) · Planet PostgreSQL · 0 upvotes · 0 comments --- Tags: [#security](https://daily.dev/tags/security), [#postgresql](https://daily.dev/tags/postgresql) [View this post on daily.dev](https://daily.dev/posts/all-your-gucs-in-a-row-local-preload-libraries-hi1uo8fjf) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"All Your GUCs in a Row: local_preload_libraries","url":"https://daily.dev/posts/all-your-gucs-in-a-row-local-preload-libraries-hi1uo8fjf","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/all-your-gucs-in-a-row-local-preload-libraries-hi1uo8fjf"},"datePublished":"2026-08-22T01:04:29.746Z","dateModified":"2026-08-22T01:04:50.061Z","description":"A deep dive into local_preload_libraries, a PostgreSQL GUC that lets non-superuser roles load shared libraries into their own backend sessions, restricted to...","image":"https://media.daily.dev/image/upload/s--ZrL_HSsR--/f_auto/v1722860399/public/Placeholder%2006","thumbnailUrl":"https://media.daily.dev/image/upload/s--ZrL_HSsR--/f_auto/v1722860399/public/Placeholder%2006","isAccessibleForFree":true,"articleSection":"Planet PostgreSQL","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"Planet PostgreSQL","logo":"https://media.daily.dev/image/upload/logos/placeholder.jpg","url":"https://daily.dev/sources/planet-postgresql"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/all-your-gucs-in-a-row-local-preload-libraries-hi1uo8fjf","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"security,postgresql","timeRequired":"PT4M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"Planet PostgreSQL","item":"https://daily.dev/sources/planet-postgresql"},{"@type":"ListItem","position":3,"name":"All Your GUCs in a Row: local_preload_libraries"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/all-your-gucs-in-a-row-local-preload-libraries-hi1uo8fjf#faq","mainEntity":[{"@type":"Question","name":"What is local_preload_libraries in PostgreSQL and how does it differ from session_preload_libraries?","acceptedAnswer":{"@type":"Answer","text":"local_preload_libraries lets any role, not just superusers, load a shared library into its own backend session at connection time, but only from the fixed $libdir/plugins directory. session_preload_libraries is superuser-only but can load from anywhere in $libdir. 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