Documentation
PostgreSQL has four primary documentation formats:
Plain text, for pre-installation information
HTML, for on-line browsing and reference
PDF, for printing
man pages, for quick reference.
Additionally, a number of plain-text README files can be found throughout the PostgreSQL source tree, documenting various implementation issues.
HTML documentation and man pages are part of a standard distribution and are installed by default. PDF format documentation is available separately for download.
10.153. DocBook
The documentation sources are written in DocBook, which is a markup language defined in XML. In what follows, the terms DocBook and XML are both used, but technically they are not interchangeable.
DocBook allows an author to specify the structure and content of a technical document without worrying about presentation details. A document style defines how that content is rendered into one of several final forms. DocBook is maintained by the OASIS group. The official DocBook site has good introductory and reference documentation and a complete O’Reilly book for your online reading pleasure. The NewbieDoc Docbook Guide is very helpful for beginners. The FreeBSD Documentation Project also uses DocBook and has some good information, including a number of style guidelines that might be worth considering.
10.154. Tool Sets
The following tools are used to process the documentation. Some might be optional, as noted.
This is the definition of DocBook itself. We currently use version 4.5; you cannot use later or earlier versions. You need the XML variant of the DocBook DTD, not the SGML variant.
These contain the processing instructions for converting the DocBook sources to other formats, such as HTML.
The minimum required version is currently 1.77.0, but it is recommended to use the latest available version for best results.
This library and the xmllint tool it contains are used for processing XML. Many developers will already have Libxml2 installed, because it is also used when building the PostgreSQL code. Note, however, that xmllint might need to be installed from a separate subpackage.
xsltproc is an XSLT processor, that is, a program to convert XML to other formats using XSLT stylesheets.
This is a program for converting, among other things, XML to PDF.
We have documented experience with several installation methods for the various tools that are needed to process the documentation. These will be described below. There might be some other packaged distributions for these tools. Please report package status to the documentation mailing list, and we will include that information here.
You can get away with not installing DocBook XML and the DocBook XSLT stylesheets locally, because the required files will be downloaded from the Internet and cached locally. This may in fact be the preferred solution if your operating system packages provide only an old version of these files, or if no packages are available at all. If you want to prevent any attempt to access the Internet while building the documentation, you need to pass the –nonet option to xmllint and xsltproc; see below for an example.
10.154.1. Installation on Fedora, RHEL, and Derivatives
To install the required packages, use:
yum install docbook-dtds docbook-style-xsl fop libxslt
10.154.2. Installation on FreeBSD
To install the required packages with pkg, use:
pkg install docbook-xml docbook-xsl fop libxslt
When building the documentation from the doc directory you’ll need to use gmake, because the makefile provided is not suitable for FreeBSD’s make.
10.154.3. Debian Packages
There is a full set of packages of the documentation tools available for Debian GNU/Linux. To install, simply use:
apt-get install docbook-xml docbook-xsl fop libxml2-utils xsltproc
10.154.4. macOS
On macOS, you can build the HTML and man documentation without installing anything extra. If you want to build PDFs or want to install a local copy of DocBook, you can get those from your preferred package manager.
If you use MacPorts, the following will get you set up:
sudo port install docbook-xml-4.5 docbook-xsl fop
If you use Homebrew, use this:
brew install docbook docbook-xsl fop
10.154.5. Detection by configure
Before you can build the documentation you need to run the configure script, as you would when building the PostgreSQL programs themselves. Check the output near the end of the run; it should look something like this:
checking for xmllint... xmllint
checking for xsltproc... xsltproc
checking for fop... fop
checking for dbtoepub... dbtoepub
If xmllint or xsltproc is not
found, you will not be able to build any of the documentation. fop is only needed to build the documentation in PDF format. dbtoepub is only needed to build the documentation in EPUB format.
If necessary, you can tell configure where to find these programs, for example
./configure ... XMLLINT=/opt/local/bin/xmllint ...
Also, if you want to ensure that xmllint
and xsltproc will not perform any network access, you can do something like
./configure ... XMLLINT="xmllint --nonet" XSLTPROC="xsltproc --nonet" ...
10.155. Building the Documentation
Once you have everything set up, change to the directory doc/src/sgml and run one of the commands described in the following subsections to build the documentation. (Remember to use GNU make.)
10.155.1. HTML
To build the HTML version of the documentation:
doc/src/sgml$ make html
This is also the default target. The output appears in the
subdirectory html.
To produce HTML documentation with the stylesheet used on postgresql.org instead of the default simple style use:
doc/src/sgml$ make STYLE=website html
If the STYLE=website option is used, the generated HTML files include references to stylesheets hosted on postgresql.org and require network access to view.
10.155.2. Manpages
We use the DocBook XSL stylesheets to convert DocBook refentry pages to *roff output suitable for man pages. To create the man pages, use the command:
doc/src/sgml$ make man
10.155.3. PDF
To produce a PDF rendition of the documentation using FOP, you can use one of the following commands, depending on the preferred paper format:
For A4 format:
doc/src/sgml$ make postgres-A4.pdf
For U.S. letter format:
doc/src/sgml$ make postgres-US.pdf
Because the PostgreSQL documentation is fairly big, FOP will require a significant amount of memory. Because of that, on some systems, the build will fail with a memory-related error message. This can usually be fixed by configuring Java heap settings in the configuration file ~/.foprc, for example:
# FOP binary distribution
FOP_OPTS='-Xmx1500m'
# Debian
JAVA_ARGS='-Xmx1500m'
# Red Hat
ADDITIONAL_FLAGS='-Xmx1500m'
There is a minimum amount of memory that is required, and to some extent
more memory appears to make things a bit faster. On systems with very little memory (less than 1 GB), the build will either be very slow due to swapping or will not work at all.
Other XSL-FO processors can also be used manually, but the automated build process only supports FOP.
10.155.4. Plain Text Files
The installation instructions are also distributed as plain text, in case they are needed in a situation where better reading tools are not available. The INSTALL file corresponds to installation, with some minor changes to account for the different context. To recreate the file, change to the directory doc/src/sgml and enter make INSTALL. Building text output requires Pandoc version 1.13 or newer as an additional build tool.
In the past, the release notes and regression testing instructions were also distributed as plain text, but this practice has been discontinued.
10.155.5. Syntax Check
Building the documentation can take very long. But there is a method to just check the correct syntax of the documentation files, which only takes a few seconds:
doc/src/sgml$ make check
10.157. Style Guide
10.157.1. Reference Pages
Reference pages should follow a standard layout. This allows users to find the desired information more quickly, and it also encourages writers to document all relevant aspects of a command. Consistency is not only desired among PostgreSQL reference pages, but also with reference pages provided by the operating system and other packages. Hence the following guidelines have been developed. They are for the most part consistent with similar guidelines established by various operating systems.
Reference pages that describe executable commands should contain the following sections, in this order. Sections that do not apply can be omitted. Additional top-level sections should only be used in special circumstances; often that information belongs in the Usage section.
This section is generated automatically. It contains the command name and a half-sentence summary of its functionality.
This section contains the syntax diagram of the command. The synopsis should normally not list each command-line option; that is done below. Instead, list the major components of the command line, such as where input and output files go.
Several paragraphs explaining what the command does.
A list describing each command-line option. If there are a lot of options, subsections can be used.
If the program uses 0 for success and non-zero for failure, then you do not need to document it. If there is a meaning behind the different non-zero exit codes, list them here.
Describe any sublanguage or run-time interface of the program. If the program is not interactive, this section can usually be omitted. Otherwise, this section is a catch-all for describing run-time features. Use subsections if appropriate.
List all environment variables that the program might use. Try to be complete; even seemingly trivial variables like SHELL might be of interest to the user.
List any files that the program might access implicitly. That is, do not list input and output files that were specified on the command line, but list configuration files, etc.
Explain any unusual output that the program might create. Refrain from listing every possible error message. This is a lot of work and has little use in practice. But if, say, the error messages have a standard format that the user can parse, this would be the place to explain it.
Anything that doesn’t fit elsewhere, but in particular bugs, implementation flaws, security considerations, compatibility issues.
Examples
If there were some major milestones in the history of the program, they might be listed here. Usually, this section can be omitted.
Author (only used in the contrib section)
Cross-references, listed in the following order: other PostgreSQL command reference pages, PostgreSQL SQL command reference pages, citation of PostgreSQL manuals, other reference pages (e.g., operating system, other packages), other documentation. Items in the same group are listed alphabetically.
Reference pages describing SQL commands should contain the following sections: Name, Synopsis, Description, Parameters, Outputs, Notes, Examples, Compatibility, History, See Also. The Parameters section is like the Options section, but there is more freedom about which clauses of the command can be listed. The Outputs section is only needed if the command returns something other than a default command-completion tag. The Compatibility section should explain to what extent this command conforms to the SQL standard(s), or to which other database system it is compatible. The See Also section of SQL commands should list SQL commands before cross-references to programs.