services: postgresql: Use Guile datatypes.

* gnu/services/databases.scm (postgresql-config-file-compiler): Support Guile
datatypes in the "extra-config" field.
* gnu/tests/databases.scm (%postgresql-os): Test it.
* doc/guix.texi (Database Services): Document it.

doc/guix.texi

@@ -19410,12 +19410,12 @@ local	all	all			trust
 host	all	all	127.0.0.1/32 	md5
 host	all	all	::1/128 	md5"))
             (extra-config
-             '(("session_preload_libraries"     "'auto_explain'")
-               ("random_page_cost"              "2")
-               ("auto_explain.log_min_duration" "'100ms'")
-               ("work_mem"                      "'500MB'")
-               ("logging_collector"             "on")
-               ("log_directory"                 "'/var/log/postgresql'")))))))
+             '(("session_preload_libraries"     "auto_explain")
+               ("random_page_cost"              2)
+               ("auto_explain.log_min_duration" "100 ms")
+               ("work_mem"                      "500 MB")
+               ("logging_collector"             #t)
+               ("log_directory"                 "/var/log/postgresql")))))))
 @end lisp
 
 @table @asis
@@ -19435,6 +19435,12 @@ List of additional keys and values to include in the PostgreSQL config
 file.  Each entry in the list should be a list where the first element
 is the key, and the remaining elements are the values.
 
+The values can be numbers, booleans or strings and will be mapped to
+PostgreSQL parameters types @code{Boolean}, @code{String},
+@code{Numeric}, @code{Numeric with Unit} and @code{Enumerated} described
+@uref{https://www.postgresql.org/docs/current/config-setting.html,
+here}.
+
 @end table
 @end deftp
 

gnu/services/databases.scm

@@ -115,22 +115,28 @@ host	all	all	::1/128 	md5"))
   (match file
     (($ <postgresql-config-file> log-destination hba-file
                                  ident-file extra-config)
-     (define (single-quote string)
-       (if string
-           (list "'" string "'")
-           '()))
+     ;; See: https://www.postgresql.org/docs/current/config-setting.html.
+    (define (format-value value)
+      (cond
+       ((boolean? value)
+        (list (if value "on" "off")))
+       ((number? value)
+        (list (number->string value)))
+       (else
+        (list "'" value "'"))))
 
-     (define contents
-       (append-map
-        (match-lambda
-          ((key) '())
-          ((key . #f) '())
-          ((key values ...) `(,key " = " ,@values "\n")))
+    (define contents
+      (append-map
+       (match-lambda
+         ((key) '())
+         ((key . #f) '())
+         ((key values ...)
+          `(,key " = " ,@(append-map format-value values) "\n")))
 
-        `(("log_destination" ,@(single-quote log-destination))
-          ("hba_file" ,@(single-quote hba-file))
-          ("ident_file" ,@(single-quote ident-file))
-          ,@extra-config)))
+       `(("log_destination" ,log-destination)
+         ("hba_file" ,hba-file)
+         ("ident_file" ,ident-file)
+         ,@extra-config)))
 
      (gexp->derivation
       "postgresql.conf"

gnu/tests/databases.scm

@@ -218,7 +218,15 @@
   (simple-operating-system
    (service postgresql-service-type
             (postgresql-configuration
-             (postgresql postgresql-10)))))
+             (postgresql postgresql-10)
+             (config-file
+              (postgresql-config-file
+               (extra-config
+                '(("session_preload_libraries" "auto_explain")
+                  ("random_page_cost" 2)
+                  ("auto_explain.log_min_duration" "100 ms")
+                  ("work_mem" "500 MB")
+                  ("debug_print_plan" #t)))))))))
 
 (define (run-postgresql-test)
   "Run tests in %POSTGRESQL-OS."