Subject: Re: [bug#32297] [PATCH] make postgresql find its plugins

From: Julien Lepiller <[email-masked]>
Date: Fri, 14 Sep 2018 22:49:36 +0200

Le Fri, 14 Sep 2018 22:14:07 +0200,
Julien Lepiller <[email-masked]> a écrit :

> Le Fri, 14 Sep 2018 22:03:53 +0200,
> Julien Lepiller <[email-masked]> a écrit :
> 
> > Le Fri, 14 Sep 2018 17:29:19 +0200,
> > Gábor Boskovits <[email-masked]> a écrit :
> >   
> > > This looks good to me.
> > > 
> > > The extensions field is a good idea.
> > > 
> > > I also believe that after adding an extensions field it would be
> > > easier to document this.    
> > 
> > Here is a new series of 2 patches: the first one is unchanged (only
> > rebased to master) and the second one introduces the extensions
> > field and documents it. I added an example in the documentation.
> >   
> > > 
> > > Do you think that it might be possible to list these extension
> > > packages somehow, or even stop them being directly installable,
> > > noting to use the extensions field in your service definition?
> > > Would that make sense?    
> > 
> > Extension packages still have to be visible for users to list them
> > in the new field, so it seems hard to hide them at the same time :)
> > I agree it would make sense to be able to list all such extensions,
> > and so is listing extensions to other packages. Maybe we can think
> > of a generic mechanism for that?  
> 
> Whoops, that last patch wasn't complete :)

I must be really tired, I spotted more mistakes after trying to run
guix system on a config with postgis.
From dd1f67a5682eb126f118d7aedd0842d855e38b19 Mon Sep 17 00:00:00 2001
From: Julien Lepiller <[email-masked]>
Date: Fri, 14 Sep 2018 21:44:08 +0200
Subject: [PATCH 2/2] gnu: postgresql: Add extensions.

* gnu/services/databases.scm (postgresql-configuration): Add extensions.
(postgresql-shepherd-service): New key #:extensions.
* doc/guix.texi (Database Services): Document it.
---
 doc/guix.texi              | 34 +++++++++++++++++++++++++++++++-
 gnu/services/databases.scm | 40 +++++++++++++++++++++++++++++++-------
 2 files changed, 66 insertions(+), 8 deletions(-)

diff --git a/doc/guix.texi b/doc/guix.texi
index cccf166d0..ecd486112 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -13718,13 +13718,45 @@ The @code{(gnu services databases)} module provides the following services.
 
 @deffn {Scheme Procedure} postgresql-service [#:postgresql postgresql] @
        [#:config-file] [#:data-directory ``/var/lib/postgresql/data''] @
-       [#:port 5432] [#:locale ``en_US.utf8'']
+       [#:port 5432] [#:locale ``en_US.utf8''] [#:extensions '()]
 Return a service that runs @var{postgresql}, the PostgreSQL database
 server.
 
 The PostgreSQL daemon loads its runtime configuration from @var{config-file},
 creates a database cluster with @var{locale} as the default
 locale, stored in @var{data-directory}.  It then listens on @var{port}.
+
+@cindex postgresql extensions
+Additional extensions are loaded from packages listed in @var{extensions}.
+Extensions are available at runtime.  For instance, to create a geographic
+database using the @code{postgis} extension, a user can configure the
+postgresql-service as in this example:
+
+@cindex postgis
+@example
+(use-package-modules databases geo)
+
+(operating-system
+  ...
+  ;; postgresql is required to run `psql' but postgis is not required for
+  ;; proper operation.
+  (packages (cons* postgresql %base-packages))
+  (services
+    (cons*
+      (postgresql-service #:extensions (list postgis))
+      %base-services)))
+@end example
+
+Then the extension becomes visible and you can initialise an empty geographic
+database in this way:
+
+@example
+psql -U postgres
+> create database postgistest;
+> \connect postgistest;
+> create extension postgis;
+> create extension postgis_topology;
+@end example
 @end deffn
 
 @deffn {Scheme Procedure} mysql-service [#:config (mysql-configuration)]
diff --git a/gnu/services/databases.scm b/gnu/services/databases.scm
index aff78a056..59cd36c3f 100644
--- a/gnu/services/databases.scm
+++ b/gnu/services/databases.scm
@@ -4,6 +4,7 @@
 ;;; Copyright © 2016 Leo Famulari <[email-masked]>
 ;;; Copyright © 2017 Christopher Baines <[email-masked]>
 ;;; Copyright © 2018 Clément Lassieur <[email-masked]>
+;;; Copyright © 2018 Julien Lepiller <[email-masked]>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -26,7 +27,10 @@
   #:use-module (gnu system shadow)
   #:use-module (gnu packages admin)
   #:use-module (gnu packages databases)
+  #:use-module (guix build-system trivial)
+  #:use-module (guix build union)
   #:use-module (guix modules)
+  #:use-module (guix packages)
   #:use-module (guix records)
   #:use-module (guix gexp)
   #:use-module (srfi srfi-1)
@@ -150,7 +154,9 @@ host	all	all	::1/128 	trust"))
   (config-file    postgresql-configuration-file
                   (default (postgresql-config-file)))
   (data-directory postgresql-configuration-data-directory
-                  (default "/var/lib/postgresql/data")))
+                  (default "/var/lib/postgresql/data"))
+  (extensions     postgresql-configuration-extensions
+                  (default '())))
 
 (define %postgresql-accounts
   (list (user-group (name "postgres") (system? #t))
@@ -162,15 +168,33 @@ host	all	all	::1/128 	trust"))
          (home-directory "/var/empty")
          (shell (file-append shadow "/sbin/nologin")))))
 
+(define (final-postgresql postgresql extensions)
+  (if (null? extensions)
+    postgresql
+    (package
+      (inherit postgresql)
+      (source #f)
+      (build-system trivial-build-system)
+      (arguments
+       `(#:modules ((guix build utils) (guix build union))
+         #:builder
+         (begin
+           (use-modules (guix build utils) (guix build union) (srfi srfi-26))
+           (union-build (assoc-ref %outputs "out") (map (lambda (input) (cdr input)) %build-inputs))
+           #t)))
+      (inputs
+       `(("postgresql" ,postgresql)
+         ,@(map (lambda (extension) (list "extension" extension)) extensions))))))
+
 (define postgresql-activation
   (match-lambda
-    (($ <postgresql-configuration> postgresql port locale config-file data-directory)
+    (($ <postgresql-configuration> postgresql port locale config-file data-directory extensions)
      #~(begin
          (use-modules (guix build utils)
                       (ice-9 match))
 
          (let ((user (getpwnam "postgres"))
-               (initdb (string-append #$postgresql "/bin/initdb"))
+               (initdb (string-append #$(final-postgresql postgresql extensions) "/bin/initdb"))
                (initdb-args
                 (append
                  (if #$locale
@@ -202,7 +226,7 @@ host	all	all	::1/128 	trust"))
 
 (define postgresql-shepherd-service
   (match-lambda
-    (($ <postgresql-configuration> postgresql port locale config-file data-directory)
+    (($ <postgresql-configuration> postgresql port locale config-file data-directory extensions)
      (let* ((pg_ctl-wrapper
              ;; Wrapper script that switches to the 'postgres' user before
              ;; launching daemon.
@@ -214,7 +238,7 @@ host	all	all	::1/128 	trust"))
                   (match (command-line)
                     ((_ mode)
                      (let ((user (getpwnam "postgres"))
-                           (pg_ctl #$(file-append postgresql "/bin/pg_ctl"))
+                           (pg_ctl #$(file-append (final-postgresql postgresql extensions) "/bin/pg_ctl"))
                            (options (format #f "--config-file=~a -p ~d"
                                             #$config-file #$port)))
                        (setgid (passwd:gid user))
@@ -253,7 +277,8 @@ host	all	all	::1/128 	trust"))
                              (port 5432)
                              (locale "en_US.utf8")
                              (config-file (postgresql-config-file))
-                             (data-directory "/var/lib/postgresql/data"))
+                             (data-directory "/var/lib/postgresql/data")
+                             (extensions '()))
   "Return a service that runs @var{postgresql}, the PostgreSQL database server.
 
 The PostgreSQL daemon loads its runtime configuration from @var{config-file}
@@ -264,7 +289,8 @@ and stores the database cluster in @var{data-directory}."
             (port port)
             (locale locale)
             (config-file config-file)
-            (data-directory data-directory))))
+            (data-directory data-directory)
+            (extensions extensions))))
 
 
 ;;;
-- 
2.18.0