From 6776978ce8ff8f6d17cdafeff0451889423e2357 Mon Sep 17 00:00:00 2001
From: Nathan Bossart <nathan@postgresql.org>
Date: Thu, 18 Jun 2026 09:31:27 -0500
Subject: [PATCH] doc: Fix "Prev" link, take 2.

Commit 6678b58d78 fixed a wrong "Prev" link by changing the link
generation code to use [position()=last()] instead of [last()] in
the predicate on the union of reverse axes.  Unfortunately, that
caused documentation builds to take much longer.  To fix, combine
the "preceding" and "ancestor" steps into one "preceding" step and
one "ancestor" step, and revert the predicate back to [last()].
The smaller union evades the libxml2 bug while avoiding the build
time regression.

Reported-by: Tom Lane <tgl@sss.pgh.pa.us>
Tested-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/1132496.1781718007%40sss.pgh.pa.us
Backpatch-through: 14
---
 doc/src/sgml/stylesheet-speedup-xhtml.xsl | 52 +++++++++++------------
 1 file changed, 26 insertions(+), 26 deletions(-)

diff --git a/doc/src/sgml/stylesheet-speedup-xhtml.xsl b/doc/src/sgml/stylesheet-speedup-xhtml.xsl
index a3b3692ba03..0e8e97c7e5c 100644
--- a/doc/src/sgml/stylesheet-speedup-xhtml.xsl
+++ b/doc/src/sgml/stylesheet-speedup-xhtml.xsl
@@ -183,32 +183,32 @@
   </xsl:if>
 
   <xsl:variable name="prev"
-    select="(preceding::book[1]
-             |preceding::preface[1]
-             |preceding::chapter[1]
-             |preceding::appendix[1]
-             |preceding::part[1]
-             |preceding::reference[1]
-             |preceding::refentry[1]
-             |preceding::colophon[1]
-             |preceding::article[1]
-             |preceding::topic[1]
-             |preceding::bibliography[parent::article or parent::book or parent::part][1]
-             |preceding::glossary[parent::article or parent::book or parent::part][1]
-             |preceding::index[$generate.index != 0]
-                               [parent::article or parent::book or parent::part][1]
-             |preceding::setindex[$generate.index != 0][1]
-             |ancestor::set
-             |ancestor::book[1]
-             |ancestor::preface[1]
-             |ancestor::chapter[1]
-             |ancestor::appendix[1]
-             |ancestor::part[1]
-             |ancestor::reference[1]
-             |ancestor::article[1]
-             |ancestor::topic[1]
-             |preceding::sect1[1]
-             |ancestor::sect1[1])[position()=last()]"/>
+    select="(preceding::*[self::book
+                          or self::preface
+                          or self::chapter
+                          or self::appendix
+                          or self::part
+                          or self::reference
+                          or self::refentry
+                          or self::colophon
+                          or self::article
+                          or self::topic
+                          or self::sect1
+                          or self::bibliography[parent::article or parent::book or parent::part]
+                          or self ::glossary[parent::article or parent::book or parent::part]
+                          or self::index[$generate.index != 0]
+                                        [parent::article or parent::book or parent::part]
+                          or self::setindex[$generate.index != 0]][1]
+             |ancestor::*[self::set
+                          or self::book
+                          or self::preface
+                          or self::chapter
+                          or self::appendix
+                          or self::part
+                          or self::reference
+                          or self::article
+                          or self::topic
+                          or self::sect1][1])[last()]"/>
 
   <xsl:variable name="next"
     select="(following::book[1]