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Chapter 49. Logical Decoding

Table of Contents

49.2. Logical Decoding Concepts : 49.2.1. Logical Decoding

[49.2.2. Replication Slots](logicaldecoding-explanation.md#LOGICALDECODING-REPLICATION-SLOTS)

[49.2.3. Output Plugins](logicaldecoding-explanation.md#id-1.8.14.8.4)

[49.2.4. Exported Snapshots](logicaldecoding-explanation.md#id-1.8.14.8.5)

49.3. Streaming Replication Protocol Interface

49.4. Logical Decoding SQL Interface

49.5. System Catalogs Related to Logical Decoding

49.6. Logical Decoding Output Plugins : 49.6.1. Initialization Function

[49.6.2. Capabilities](logicaldecoding-output-plugin.md#LOGICALDECODING-CAPABILITIES)

[49.6.3. Output Modes](logicaldecoding-output-plugin.md#LOGICALDECODING-OUTPUT-MODE)

[49.6.4. Output Plugin Callbacks](logicaldecoding-output-plugin.md#LOGICALDECODING-OUTPUT-PLUGIN-CALLBACKS)

[49.6.5. Functions for Producing Output](logicaldecoding-output-plugin.md#LOGICALDECODING-OUTPUT-PLUGIN-OUTPUT)

49.7. Logical Decoding Output Writers

49.8. Synchronous Replication Support for 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).

Changes can be consumed either using the streaming replication protocol (see Section 53.4 and Section 49.3), or by calling functions via SQL (see Section 49.4). It is also possible to write additional methods of consuming the output of a replication slot without modifying core code (see Section 49.7).