diff --git a/doc/src/sgml/xfunc.sgml b/doc/src/sgml/xfunc.sgml
index 5b584a4f144..bf76490cbc0 100644
--- a/doc/src/sgml/xfunc.sgml
+++ b/doc/src/sgml/xfunc.sgml
@@ -2704,6 +2704,142 @@ CREATE FUNCTION concat_text(text, text) RETURNS text
&dfunc;
+
+ Server API and ABI Stability Guidance
+
+
+ This section contains guidance to authors of extensions and other server
+ plugins about API and ABI stability in the
+ PostgreSQL server.
+
+
+
+ General
+
+
+ The PostgreSQL server contains several
+ well-demarcated APIs for server plugins, such as the function manager
+ (fmgr, described in this chapter),
+ SPI (), and various hooks
+ specifically designed for extensions. These interfaces are carefully
+ managed for long-term stability and compatibility. However, the entire
+ set of global functions and variables in the server effectively
+ constitutes the publicly usable API, and most of it was not designed
+ with extensibility and long-term stability in mind.
+
+
+
+ Therefore, while taking advantage of these interfaces is valid, the
+ further one strays from the well-trodden path, the likelier it will be
+ that one might encounter API or ABI compatibility issues at some point.
+ Extension authors are encouraged to provide feedback about their
+ requirements, so that over time, as new use patterns arise, certain
+ interfaces can be considered more stabilized or new, better-designed
+ interfaces can be added.
+
+
+
+
+ API Compatibility
+
+ The API, or application programming interface, is the
+ interface used at compile time.
+
+
+
+ Major Versions
+
+ There is no promise of API compatibility between
+ PostgreSQL major versions. Extension code
+ therefore might require source code changes to work with multiple major
+ versions. These can usually be managed with preprocessor conditions
+ such as #if PG_VERSION_NUM >= 160000.
+ Sophisticated extensions that use interfaces beyond the well-demarcated
+ ones usually require a few such changes for each major server version.
+
+
+
+
+ Minor Versions
+
+ PostgreSQL makes an effort to avoid server
+ API breaks in minor releases. In general, extension code that compiles
+ and works with a minor release should also compile and work with any
+ other minor release of the same major version, past or future.
+
+
+
+ When a change is required, it will be carefully
+ managed, taking the requirements of extensions into account. Such
+ changes will be communicated in the release notes ().
+
+
+
+
+
+ ABI Compatibility
+
+ The ABI, or application binary interface, is the
+ interface used at run time.
+
+
+
+ Major Versions
+
+ Servers of different major versions have intentionally incompatible
+ ABIs. Extensions that use server APIs must therefore be re-compiled for
+ each major release. The inclusion of PG_MODULE_MAGIC
+ (see ) ensures that code compiled for
+ one major version will be rejected by other major versions.
+
+
+
+
+ Minor Versions
+
+ PostgreSQL makes an effort to avoid server
+ ABI breaks in minor releases. In general, an extension compiled against
+ any minor release should work with any other minor release of the same
+ major version, past or future.
+
+
+
+ When a change is required,
+ PostgreSQL will choose the least invasive
+ change possible, for example by squeezing a new field into padding
+ space or appending it to the end of a struct. These sorts of changes
+ should not impact extensions unless they use very unusual code
+ patterns.
+
+
+
+ In rare cases, however, even such non-invasive changes may be
+ impractical or impossible. In such an event, the change will be
+ carefully managed, taking the requirements of extensions into account.
+ Such changes will also be documented in the release notes ().
+
+
+
+ Note, however, that many parts of the server are not designed or
+ maintained as publicly-consumable APIs (and that, in most cases, the
+ actual boundary is also not well-defined). If urgent needs arise,
+ changes in those parts will naturally be made with less consideration
+ for extension code than changes in well-defined and widely used
+ interfaces.
+
+
+
+ Also, in the absence of automated detection of such changes, this is
+ not a guarantee, but historically such breaking changes have been
+ extremely rare.
+
+
+
+
+
+
Composite-Type Arguments