xapian: Support combining queries with OR, AND and FILTER operators.

* xapian/xapian.scm: Import (srfi srfi-1).
(query-combine): New function.
(query-and, query-or, query-filter): New public functions.

1 files changed, 32 insertions, 0 deletions

diff --git a/xapian/xapian.scm b/xapian/xapian.scm
index 650c401..f22cfee 100644
--- a/xapian/xapian.scm
+++ b/xapian/xapian.scm
@@ -22,6 +22,7 @@
   #:use-module (rnrs arithmetic bitwise)
   #:use-module (rnrs bytevectors)
   #:use-module (ice-9 match)
+  #:use-module (srfi srfi-1)
   #:use-module (srfi srfi-26)
   #:use-module (htmlprag)
   #:use-module (xapian wrap)
@@ -49,6 +50,9 @@
             index-text!
             increase-termpos!
             parse-query
+            query-and
+            query-or
+            query-filter
             enquire
             enquire-mset
             mset-item-docid
@@ -196,6 +200,34 @@ on the database object."
              (MSetIterator-next head)
              (loop head result))))))
 
+(define (query-combine combine-operator default . queries)
+  (reduce (cut new-Query combine-operator <> <>)
+          default
+          queries))
+
+(define (query-and . queries)
+  "Return a query matching only documents matching all @var{queries}.
+
+In a weighted context, the weight is the sum of the weights for all
+queries."
+  (apply query-combine (Query-OP-AND) (Query-MatchAll) queries))
+
+(define (query-or . queries)
+  "Return a query matching documents which at least one of @var{queries}
+match.
+
+In a weighted context, the weight is the sum of the weights for
+matching queries."
+  (apply query-combine (Query-OP-OR) (Query-MatchNothing) queries))
+
+(define (query-filter . queries)
+  "Return a query matching only documents matching all @var{queries},
+but only take weight from the first of @var{queries}.
+
+In a non-weighted context, @code{query-filter} and @code{query-and}
+are equivalent."
+  (apply query-combine (Query-OP-FILTER) (Query-MatchAll) queries))
+
 (define (get-flag flag-thunk value)
   (if value (flag-thunk) 0))