Polymorphic Associations in Postgres
The article discusses polymorphic associations in PostgreSQL and their impact on ORM frameworks. It highlights the challenges of optimizing outer joins and introduces techniques to improve execution efficiency. The author explains the structure of polymorphic references and their prevalence in real-world data models.
- ▪Polymorphic associations allow references to multiple target entity types in a database.
- ▪The article explores the inefficiencies of outer joins in PostgreSQL and suggests optimizations.
- ▪Polymorphic reference resolution is a common pattern in various ORM frameworks like Rails and Django.
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| Original publisher | Hacker News (Newest) |
| Canonical URL | https://danolivo.substack.com/p/on-polymorphic-associations-in-postgres |
| Publication time | Tue, 26 May 2026 04:23:05 +0000 |
| Retrieval time | 2026-05-26T04:37:43.007Z |
| Last seen | 2026-05-26T04:37:43.007Z |
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Opening excerpt (first ~120 words) tap to expand
On Polymorphic Associations in Postgresor one more time on ORM-systems complexity Andrei LepikhovMay 24, 20261ShareOUTER JOIN is a typical plague of ORM-based PostgreSQL configurations: the planner is still relatively poor at optimising it. At the same time, ORM frameworks — and 1C as a prominent example — often generate outer joins from standard templates, which opens the door to targeted optimisations. In this article, I dig into one such template — polymorphic reference resolution: what the pattern is, where it comes from (Rails, Django, Hibernate, Salesforce — not just 1C), how widespread it is, and why its structural properties make it possible to significantly speed up execution.Just for the introductionThink of the homepage of a typical online store — say, Amazon.
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