doc: Speed up XSLT builds

The upstream XSLT stylesheets use some very general XPath expressions in
some places that end up being very slow.  We can optimize them with
knowledge about the DocBook document structure and our particular use
thereof.  For example, when counting preceding chapters to get a number
for the current chapter, we only need to count preceding sibling
nodes (more or less) instead of searching through the entire node tree
for chapter elements.

This change attacks the slowest pieces as identified by xsltproc
--profile.  This makes the HTML build roughly 10 times faster, resulting
in the new total build time being about the same as the old DSSSL-based
build.  Some of the non-HTML build targets (especially FO) will also
benefit a bit, but they have not been specifically analyzed.

With this, also remove the pg.fast parameter, which was previously a
hack to get the build to a manageable speed.

Alexander Lakhin <a.lakhin@postgrespro.ru>, with some additional
tweaking by me

doc/src/sgml/stylesheet-common.xsl

@@ -7,11 +7,10 @@
   all output formats (HTML, HTML Help, XSL-FO, etc.).
   -->
 
+<xsl:include href="stylesheet-speedup-common.xsl" />
 
 <!-- Parameters -->
 
-<xsl:param name="pg.fast" select="'0'"/>
-
 <!--
 <xsl:param name="draft.mode">
   <xsl:choose>
@@ -31,9 +30,8 @@
 <xsl:param name="callout.graphics" select="'0'"></xsl:param>
 <xsl:param name="toc.section.depth">2</xsl:param>
 <xsl:param name="linenumbering.extension" select="'0'"></xsl:param>
-<xsl:param name="generate.index" select="1 - $pg.fast"></xsl:param>
-<xsl:param name="section.autolabel" select="1 - $pg.fast"></xsl:param>
-<xsl:param name="section.label.includes.component.label" select="1 - $pg.fast"></xsl:param>
+<xsl:param name="section.autolabel" select="1"></xsl:param>
+<xsl:param name="section.label.includes.component.label" select="1"></xsl:param>
 <xsl:param name="refentry.xref.manvolnum" select="0"/>
 <xsl:param name="formal.procedures" select="0"></xsl:param>
 <xsl:param name="punct.honorific" select="''"></xsl:param>

doc/src/sgml/stylesheet-speedup-common.xsl

+<?xml version="1.0" encoding="utf-8"?>
+<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
+                version='1.0'>
+
+<!-- Performance-optimized versions of some upstream templates from common/
+     directory -->
+
+<!-- from common/labels.xsl -->
+
+<xsl:template match="chapter" mode="label.markup">
+  <xsl:choose>
+    <xsl:when test="@label">
+      <xsl:value-of select="@label"/>
+    </xsl:when>
+    <xsl:when test="string($chapter.autolabel) != 0">
+      <xsl:if test="$component.label.includes.part.label != 0 and
+                      ancestor::part">
+        <xsl:variable name="part.label">
+          <xsl:apply-templates select="ancestor::part"
+                               mode="label.markup"/>
+        </xsl:variable>
+        <xsl:if test="$part.label != ''">
+          <xsl:value-of select="$part.label"/>
+          <xsl:apply-templates select="ancestor::part"
+                               mode="intralabel.punctuation">
+            <xsl:with-param name="object" select="."/>
+          </xsl:apply-templates>
+        </xsl:if>
+      </xsl:if>
+      <xsl:variable name="format">
+        <xsl:call-template name="autolabel.format">
+          <xsl:with-param name="format" select="$chapter.autolabel"/>
+        </xsl:call-template>
+      </xsl:variable>
+      <xsl:choose>
+        <xsl:when test="$label.from.part != 0 and ancestor::part">
+          <xsl:number from="part" count="chapter" format="{$format}" level="any"/>
+        </xsl:when>
+        <xsl:otherwise>
+          <!-- Optimization for pgsql-docs: When counting to get label for
+               this chapter, preceding chapters can only be our siblings or
+               children of a preceding part, so only count those instead of
+               scanning the entire node tree. -->
+          <!-- <xsl:number from="book" count="chapter" format="{$format}" level="any"/> -->
+          <xsl:number value="count(../preceding-sibling::part/chapter) + count(preceding-sibling::chapter) + 1" format="{$format}"/>
+        </xsl:otherwise>
+      </xsl:choose>
+    </xsl:when>
+  </xsl:choose>
+</xsl:template>
+
+<xsl:template match="appendix" mode="label.markup">
+  <xsl:choose>
+    <xsl:when test="@label">
+      <xsl:value-of select="@label"/>
+    </xsl:when>
+    <xsl:when test="string($appendix.autolabel) != 0">
+      <xsl:if test="$component.label.includes.part.label != 0 and
+                      ancestor::part">
+        <xsl:variable name="part.label">
+          <xsl:apply-templates select="ancestor::part"
+                               mode="label.markup"/>
+        </xsl:variable>
+        <xsl:if test="$part.label != ''">
+          <xsl:value-of select="$part.label"/>
+          <xsl:apply-templates select="ancestor::part"
+                               mode="intralabel.punctuation">
+            <xsl:with-param name="object" select="."/>
+          </xsl:apply-templates>
+        </xsl:if>
+      </xsl:if>
+      <xsl:variable name="format">
+        <xsl:call-template name="autolabel.format">
+          <xsl:with-param name="format" select="$appendix.autolabel"/>
+        </xsl:call-template>
+      </xsl:variable>
+      <xsl:choose>
+        <xsl:when test="$label.from.part != 0 and ancestor::part">
+          <xsl:number from="part" count="appendix" format="{$format}" level="any"/>
+        </xsl:when>
+        <xsl:otherwise>
+          <!-- Optimization for pgsql-docs: When counting to get label for
+               this appendix, preceding appendixes can only be our siblings or
+               children of a preceding part, so only count those instead of
+               scanning the entire node tree. -->
+          <!-- <xsl:number from="book|article" count="appendix" format="{$format}" level="any"/> -->
+          <xsl:number value="count(../preceding-sibling::part/appendix) + count(preceding-sibling::appendix) + 1" format="{$format}"/>
+        </xsl:otherwise>
+      </xsl:choose>
+    </xsl:when>
+  </xsl:choose>
+</xsl:template>
+
+</xsl:stylesheet>

doc/src/sgml/stylesheet.xsl

@@ -6,6 +6,7 @@
 
 <xsl:import href="http://docbook.sourceforge.net/release/xsl/current/xhtml/chunk.xsl"/>
 <xsl:include href="stylesheet-common.xsl" />
+<xsl:include href="stylesheet-speedup-xhtml.xsl" />
 
 
 <!-- Parameters -->