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diff --git a/doc/src/sgml/html/custom-rmgr.html b/doc/src/sgml/html/custom-rmgr.html new file mode 100644 index 0000000..78f328b --- /dev/null +++ b/doc/src/sgml/html/custom-rmgr.html @@ -0,0 +1,81 @@ +<?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>Chapter 66. Custom WAL Resource Managers</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="generic-wal.html" title="Chapter 65. Generic WAL Records" /><link rel="next" href="btree.html" title="Chapter 67. B-Tree Indexes" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">Chapter 66. Custom WAL Resource Managers</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="generic-wal.html" title="Chapter 65. Generic WAL Records">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="internals.html" title="Part VII. Internals">Up</a></td><th width="60%" align="center">Part VII. Internals</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="btree.html" title="Chapter 67. B-Tree Indexes">Next</a></td></tr></table><hr /></div><div class="chapter" id="CUSTOM-RMGR"><div class="titlepage"><div><div><h2 class="title">Chapter 66. Custom WAL Resource Managers</h2></div></div></div><p> + This chapter explains the interface between the core + <span class="productname">PostgreSQL</span> system and custom WAL resource + managers, which enable extensions to integrate directly with the <a class="link" href="wal.html" title="Chapter 30. Reliability and the Write-Ahead Log"><acronym class="acronym">WAL</acronym></a>. + </p><p> + An extension, especially a <a class="link" href="tableam.html" title="Chapter 63. Table Access Method Interface Definition">Table Access + Method</a> or <a class="link" href="indexam.html" title="Chapter 64. Index Access Method Interface Definition">Index Access Method</a>, may + need to use WAL for recovery, replication, and/or <a class="link" href="logicaldecoding.html" title="Chapter 49. Logical Decoding">Logical Decoding</a>. Custom resource managers + are a more flexible alternative to <a class="link" href="generic-wal.html" title="Chapter 65. Generic WAL Records">Generic + WAL</a> (which does not support logical decoding), but more complex for + an extension to implement. + </p><p> + To create a new custom WAL resource manager, first define an + <code class="structname">RmgrData</code> structure with implementations for the + resource manager methods. Refer to + <code class="filename">src/backend/access/transam/README</code> and + <code class="filename">src/include/access/xlog_internal.h</code> in the + <span class="productname">PostgreSQL</span> source. +</p><pre class="programlisting"> +/* + * Method table for resource managers. + * + * This struct must be kept in sync with the PG_RMGR definition in + * rmgr.c. + * + * rm_identify must return a name for the record based on xl_info (without + * reference to the rmid). For example, XLOG_BTREE_VACUUM would be named + * "VACUUM". rm_desc can then be called to obtain additional detail for the + * record, if available (e.g. the last block). + * + * rm_mask takes as input a page modified by the resource manager and masks + * out bits that shouldn't be flagged by wal_consistency_checking. + * + * RmgrTable[] is indexed by RmgrId values (see rmgrlist.h). If rm_name is + * NULL, the corresponding RmgrTable entry is considered invalid. + */ +typedef struct RmgrData +{ + const char *rm_name; + void (*rm_redo) (XLogReaderState *record); + void (*rm_desc) (StringInfo buf, XLogReaderState *record); + const char *(*rm_identify) (uint8 info); + void (*rm_startup) (void); + void (*rm_cleanup) (void); + void (*rm_mask) (char *pagedata, BlockNumber blkno); + void (*rm_decode) (struct LogicalDecodingContext *ctx, + struct XLogRecordBuffer *buf); +} RmgrData; +</pre><p> + </p><p> + Then, register your new resource + manager. + +</p><pre class="programlisting"> +/* + * Register a new custom WAL resource manager. + * + * Resource manager IDs must be globally unique across all extensions. Refer + * to https://wiki.postgresql.org/wiki/CustomWALResourceManagers to reserve a + * unique RmgrId for your extension, to avoid conflicts with other extension + * developers. During development, use RM_EXPERIMENTAL_ID to avoid needlessly + * reserving a new ID. + */ +extern void RegisterCustomRmgr(RmgrId rmid, RmgrData *rmgr); +</pre><p> + <code class="function">RegisterCustomRmgr</code> must be called from the + extension module's <a class="link" href="xfunc-c.html#XFUNC-C-DYNLOAD" title="38.10.1. Dynamic Loading">_PG_init</a> function. + While developing a new extension, use <code class="literal">RM_EXPERIMENTAL_ID</code> + for <em class="parameter"><code>rmid</code></em>. When you are ready to release the extension + to users, reserve a new resource manager ID at the <a class="ulink" href="https://wiki.postgresql.org/wiki/CustomWALResourceManagers" target="_top">Custom WAL + Resource Manager</a> page. + </p><p> + Place the extension module implementing the custom resource manager in <a class="xref" href="runtime-config-client.html#GUC-SHARED-PRELOAD-LIBRARIES">shared_preload_libraries</a> so that it will be loaded early + during <span class="productname">PostgreSQL</span> startup. + </p><div class="note"><h3 class="title">Note</h3><p> + The extension must remain in shared_preload_libraries as long as any + custom WAL records may exist in the system. Otherwise + <span class="productname">PostgreSQL</span> will not be able to apply or decode + the custom WAL records, which may prevent the server from starting. + </p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="generic-wal.html" title="Chapter 65. Generic WAL Records">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="internals.html" title="Part VII. Internals">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="btree.html" title="Chapter 67. B-Tree Indexes">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 65. Generic WAL Records </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"> Chapter 67. B-Tree Indexes</td></tr></table></div></body></html>
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