> For the complete documentation index, see [llms.txt](https://docs.postgresql.tw/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.postgresql.tw/client-interfaces/largeobjects/lo-intro.md).

# 33.1. Introduction \#

All large objects are stored in a single system table named [`pg_largeobject`](/internals/catalogs/catalog-pg-largeobject.md). Each large object also has an entry in the system table [`pg_largeobject_metadata`](/internals/catalogs/catalog-pg-largeobject-metadata.md). Large objects can be created, modified, and deleted using a read/write API that is similar to standard operations on files.

PostgreSQL also supports a storage system called [“TOAST”](/internals/storage/storage-toast.md), which automatically stores values larger than a single database page into a secondary storage area per table. This makes the large object facility partially obsolete. One remaining advantage of the large object facility is that it allows values up to 4 TB in size, whereas TOASTed fields can be at most 1 GB. Also, reading and updating portions of a large object can be done efficiently, while most operations on a TOASTed field will read or write the whole value as a unit.

***

原文：[PostgreSQL 18.6 Documentation](https://www.postgresql.org/docs/18/lo-intro.html)（英文原文，待翻譯）


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