> For the complete documentation index, see [llms.txt](https://docs.subsalt.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.subsalt.io/configuration/creating-synthetic-databases/system-catalogs.md). # System catalogs The system catalogs are the place where users can access schema metadata, such as information about tables and columns, and other bookkeeping information. Subsalt supports two standard system catalogs: `pg_catalog` and `information_schema`. All catalog tables are read-only, and can be queried with standard SQL statements. ### pg\_catalog `pg_catalog` is [Postgres' system catalog](https://www.postgresql.org/docs/current/catalogs.html) and contains information about tables, namespaces, data types, and many other entities. Subsalt supports the full schema for all tables for compatibility reasons, though some values don't apply to generative databases and aren't populated. ### information\_schema `information_schema` is the ANSI SQL standard system catalog and contains information about entities common to all relational databases (tables, columns, etc). Subsalt supports the [set of tables supported by Postgres](https://www.postgresql.org/docs/current/information-schema.html). --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://docs.subsalt.io/configuration/creating-synthetic-databases/system-catalogs.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.