From 16f38896815d91a9cf163814bc5ad0819f7faaaf Mon Sep 17 00:00:00 2001
From: Arun Isaac
Date: Sun, 16 Feb 2020 09:19:48 +0530
Subject: examples: Add comments.

* examples/index.scm, examples/search.scm: Add comments.
---
 examples/index.scm | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

(limited to 'examples/index.scm')

diff --git a/examples/index.scm b/examples/index.scm
index 396df7c..292334e 100644
--- a/examples/index.scm
+++ b/examples/index.scm
@@ -22,25 +22,46 @@
              (xapian xapian))
 
 (define (index datapath dbpath)
+  ;; Open database for writing. call-with-writable-database
+  ;; automatically closes the database once we're done.
   (call-with-writable-database dbpath
     (lambda (db)
       (for-each
        (lambda (record)
          (match record
            ((description title identifier)
-            (let* ((idterm (string-append "Q" identifier))
+            (let* (;; Make a document and tell the term generator to
+                   ;; use it. The data of the document is stored for
+                   ;; display purposes. Storing data is optional and
+                   ;; can be skipped to cut down on database size. The
+                   ;; unique idterm ensures each document ends up in
+                   ;; the database only once no matter how many times
+                   ;; we run the database.
+                   (idterm (string-append "Q" identifier))
                    (doc (make-document #:data (call-with-output-string (cut write record <>))
                                        #:terms `((,idterm . 0))))
                    (term-generator (make-term-generator #:stem (make-stem "en")
                                                         #:document doc)))
+              ;; Index title and description with a suitable
+              ;; prefix. This is used to allow for searching separate
+              ;; fields as in title:sunwatch, description:leather,
+              ;; etc.
               (index-text! term-generator title #:prefix "S")
               (index-text! term-generator description #:prefix "XD")
+
+              ;; Index title and description without prefixes for
+              ;; general search.
               (index-text! term-generator title)
               (increase-termpos! term-generator)
               (index-text! term-generator description)
+
+              ;; Add the document to the database. The unique idterm
+              ;; ensures each object ends up in the database only once
+              ;; no matter how many times we run the indexer.
               (replace-document! db idterm doc)))))
        (call-with-input-file datapath read)))))
 
+;; Handle command line arguments
 (match (command-line)
   ((_ datapath dbpath)
    (index datapath dbpath))
-- 
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