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diff --git a/doc/src/sgml/html/protocol-logical-replication.html b/doc/src/sgml/html/protocol-logical-replication.html new file mode 100644 index 0000000..971707b --- /dev/null +++ b/doc/src/sgml/html/protocol-logical-replication.html @@ -0,0 +1,84 @@ +<?xml version="1.0" encoding="UTF-8" standalone="no"?> +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>55.5. Logical Streaming Replication Protocol</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="protocol-replication.html" title="55.4. Streaming Replication Protocol" /><link rel="next" href="protocol-message-types.html" title="55.6. Message Data Types" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">55.5. Logical Streaming Replication Protocol</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="protocol-replication.html" title="55.4. Streaming Replication Protocol">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="protocol.html" title="Chapter 55. Frontend/Backend Protocol">Up</a></td><th width="60%" align="center">Chapter 55. Frontend/Backend Protocol</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 15.4 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="protocol-message-types.html" title="55.6. Message Data Types">Next</a></td></tr></table><hr /></div><div class="sect1" id="PROTOCOL-LOGICAL-REPLICATION"><div class="titlepage"><div><div><h2 class="title" style="clear: both">55.5. Logical Streaming Replication Protocol</h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="sect2"><a href="protocol-logical-replication.html#PROTOCOL-LOGICAL-REPLICATION-PARAMS">55.5.1. Logical Streaming Replication Parameters</a></span></dt><dt><span class="sect2"><a href="protocol-logical-replication.html#PROTOCOL-LOGICAL-MESSAGES">55.5.2. Logical Replication Protocol Messages</a></span></dt><dt><span class="sect2"><a href="protocol-logical-replication.html#PROTOCOL-LOGICAL-MESSAGES-FLOW">55.5.3. Logical Replication Protocol Message Flow</a></span></dt></dl></div><p> + This section describes the logical replication protocol, which is the message + flow started by the <code class="literal">START_REPLICATION</code> + <code class="literal">SLOT</code> <em class="replaceable"><code>slot_name</code></em> + <code class="literal">LOGICAL</code> replication command. + </p><p> + The logical streaming replication protocol builds on the primitives of + the physical streaming replication protocol. + </p><div class="sect2" id="PROTOCOL-LOGICAL-REPLICATION-PARAMS"><div class="titlepage"><div><div><h3 class="title">55.5.1. Logical Streaming Replication Parameters</h3></div></div></div><p> + The logical replication <code class="literal">START_REPLICATION</code> command + accepts following parameters: + + </p><div class="variablelist"><dl class="variablelist"><dt><span class="term"> + proto_version + </span></dt><dd><p> + Protocol version. Currently versions <code class="literal">1</code>, <code class="literal">2</code>, + and <code class="literal">3</code> are supported. + </p><p> + Version <code class="literal">2</code> is supported only for server version 14 + and above, and it allows streaming of large in-progress transactions. + </p><p> + Version <code class="literal">3</code> is supported only for server version 15 + and above, and it allows streaming of two-phase commits. + </p></dd><dt><span class="term"> + publication_names + </span></dt><dd><p> + Comma separated list of publication names for which to subscribe + (receive changes). The individual publication names are treated + as standard objects names and can be quoted the same as needed. + </p></dd></dl></div><p> + + </p></div><div class="sect2" id="PROTOCOL-LOGICAL-MESSAGES"><div class="titlepage"><div><div><h3 class="title">55.5.2. Logical Replication Protocol Messages</h3></div></div></div><p> + The individual protocol messages are discussed in the following + subsections. Individual messages are described in + <a class="xref" href="protocol-logicalrep-message-formats.html" title="55.9. Logical Replication Message Formats">Section 55.9</a>. + </p><p> + All top-level protocol messages begin with a message type byte. + While represented in code as a character, this is a signed byte with no + associated encoding. + </p><p> + Since the streaming replication protocol supplies a message length there + is no need for top-level protocol messages to embed a length in their + header. + </p></div><div class="sect2" id="PROTOCOL-LOGICAL-MESSAGES-FLOW"><div class="titlepage"><div><div><h3 class="title">55.5.3. Logical Replication Protocol Message Flow</h3></div></div></div><p> + With the exception of the <code class="literal">START_REPLICATION</code> command and + the replay progress messages, all information flows only from the backend + to the frontend. + </p><p> + The logical replication protocol sends individual transactions one by one. + This means that all messages between a pair of Begin and Commit messages + belong to the same transaction. Similarly, all messages between a pair of + Begin Prepare and Prepare messages belong to the same transaction. + It also sends changes of large in-progress transactions between a pair of + Stream Start and Stream Stop messages. The last stream of such a transaction + contains a Stream Commit or Stream Abort message. + </p><p> + Every sent transaction contains zero or more DML messages (Insert, + Update, Delete). In case of a cascaded setup it can also contain Origin + messages. The origin message indicates that the transaction originated on + different replication node. Since a replication node in the scope of logical + replication protocol can be pretty much anything, the only identifier + is the origin name. It's downstream's responsibility to handle this as + needed (if needed). The Origin message is always sent before any DML + messages in the transaction. + </p><p> + Every DML message contains a relation OID, identifying the publisher's + relation that was acted on. Before the first DML message for a given + relation OID, a Relation message will be sent, describing the schema of + that relation. Subsequently, a new Relation message will be sent if + the relation's definition has changed since the last Relation message + was sent for it. (The protocol assumes that the client is capable of + remembering this metadata for as many relations as needed.) + </p><p> + Relation messages identify column types by their OIDs. In the case + of a built-in type, it is assumed that the client can look up that + type OID locally, so no additional data is needed. For a non-built-in + type OID, a Type message will be sent before the Relation message, + to provide the type name associated with that OID. Thus, a client that + needs to specifically identify the types of relation columns should + cache the contents of Type messages, and first consult that cache to + see if the type OID is defined there. If not, look up the type OID + locally. + </p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="protocol-replication.html" title="55.4. Streaming Replication Protocol">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="protocol.html" title="Chapter 55. Frontend/Backend Protocol">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="protocol-message-types.html" title="55.6. Message Data Types">Next</a></td></tr><tr><td width="40%" align="left" valign="top">55.4. Streaming Replication Protocol </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 15.4 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 55.6. Message Data Types</td></tr></table></div></body></html>
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