> 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/11/server-programming/48.-logical-decoding.md). # 49. Logical Decoding PostgreSQL provides infrastructure to stream the modifications performed via SQL to external consumers. This functionality can be used for a variety of purposes, including replication solutions and auditing. Changes are sent out in streams identified by logical replication slots. The format in which those changes are streamed is determined by the output plugin used. An example plugin is provided in the PostgreSQL distribution. Additional plugins can be written to extend the choice of available formats without modifying any core code. Every output plugin has access to each individual new row produced by `INSERT` and the new row version created by `UPDATE`. Availability of old row versions for `UPDATE` and `DELETE` depends on the configured replica identity (see [`REPLICA IDENTITY`](https://www.postgresql.org/docs/10/static/sql-altertable.html#SQL-CREATETABLE-REPLICA-IDENTITY)). Changes can be consumed either using the streaming replication protocol (see [Section 52.4](https://www.postgresql.org/docs/10/static/protocol-replication.html) and [Section 48.3](https://www.postgresql.org/docs/10/static/logicaldecoding-walsender.html)), or by calling functions via SQL (see [Section 48.4](https://www.postgresql.org/docs/10/static/logicaldecoding-sql.html)). It is also possible to write additional methods of consuming the output of a replication slot without modifying core code (see [Section 48.7](https://www.postgresql.org/docs/10/static/logicaldecoding-writer.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 by asking a question. Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters: ``` GET https://docs.postgresql.tw/11/server-programming/48.-logical-decoding.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case. 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.