gnu: Use Xapian index for package search.

* gnu/packages.scm (search-package-index): New function.
* guix/ui.scm (display-package-search-results): New function.
* guix/scripts/package.scm (process-query): Search using the Xapian package
index if current profile is available. Else, search using regexps.

1 files changed, 21 insertions, 1 deletions

diff --git a/gnu/packages.scm b/gnu/packages.scm
index c8e221de68..3cbd7c63e3 100644
--- a/gnu/packages.scm
+++ b/gnu/packages.scm
@@ -67,7 +67,8 @@
             specifications->manifest
 
             generate-package-cache
-            generate-package-search-index))
+            generate-package-search-index
+            search-package-index))
 
 ;;; Commentary:
 ;;;
@@ -466,6 +467,25 @@ reducing the memory footprint."
 
   db-path)
 
+(define (search-package-index profile query-string)
+  "Search Xapian index in PROFILE for packages matching the Xapian query
+QUERY-STRING.  Return a list of search result texts each corresponding to one
+matching package."
+  (call-with-database (string-append profile %package-search-index)
+    (lambda (db)
+      (let ((query (parse-query query-string #:stemmer (make-stem "en"))))
+        (mset-fold (lambda (item result)
+                     (let ((search-result-text
+                            (call-with-output-string
+                              (cut format <> "~a~%relevance: ~a~%~%"
+                                   (document-data (mset-item-document item))
+                                   ;; Round score to one decimal place.
+                                   (/ (round (* 10 (mset-item-weight item))) 10)))))
+                       (append result (list search-result-text))))
+                   '()
+                   (enquire-mset (enquire db query)
+                                 #:maximum-items (database-document-count db)))))))
+
 
 (define %sigint-prompt
   ;; The prompt to jump to upon SIGINT.