store: database: Stop finalizing prepared statements.

Especially since we're asking for these to be cached.

Management of prepared statements isn't trivial, since you don't want to keep
them forever as this can lead to poor query performance, but I don't think
that finalizing them immediately is the right solution.

Change-Id: I61706b4d09d771835bb8f074b8f6a6ee871f5e2d

* guix/store/database.scm (sqlite-step-and-reset): New procedure.
(last-insert-row, path-id, update-or-insert, add-references): Don't finalize
prepared statements.

Change-Id: I2a2c6deb43935d67df9e43000a5105343d72b3e6

guix/store/database.scm

@@ -167,16 +167,19 @@ If FILE doesn't exist, create it and initialize it as a new database.  Pass
     ((_ file db exp ...)
      (call-with-database file (lambda (db) exp ...)))))
 
+(define (sqlite-step-and-reset statement)
+  (let ((val (sqlite-step statement)))
+    (sqlite-reset statement)
+    val))
+
 (define (last-insert-row-id db)
   ;; XXX: (sqlite3) currently lacks bindings for 'sqlite3_last_insert_rowid'.
   ;; Work around that.
-  (let* ((stmt   (sqlite-prepare db "SELECT last_insert_rowid();"
-                                 #:cache? #t))
-         (result (sqlite-fold cons '() stmt)))
-    (sqlite-finalize stmt)
-    (match result
-      ((#(id)) id)
-      (_ #f))))
+  (let ((stmt (sqlite-prepare db
+                              "SELECT last_insert_rowid();"
+                              #:cache? #t)))
+    (vector-ref (sqlite-step-and-reset stmt)
+                0)))
 
 (define* (path-id db path)
   "If PATH exists in the 'ValidPaths' table, return its numerical
@@ -187,11 +190,9 @@ identifier.  Otherwise, return #f."
 SELECT id FROM ValidPaths WHERE path = :path"
                #:cache? #t)))
     (sqlite-bind-arguments stmt #:path path)
-    (let ((result (sqlite-fold cons '() stmt)))
-      (sqlite-finalize stmt)
-      (match result
-        ((#(id) . _) id)
-        (_ #f)))))
+    (match (sqlite-step-and-reset stmt)
+      (#(id) id)
+      (#f #f))))
 
 (define-inlinable (assert-integer proc in-range? key number)
   (unless (integer? number)
@@ -225,9 +226,8 @@ WHERE id = :id"
           (sqlite-bind-arguments stmt #:id id
                                  #:deriver deriver
                                  #:hash hash #:size nar-size #:time time)
-          (sqlite-fold cons '() stmt)
-          (sqlite-finalize stmt)
-          (last-insert-row-id db))
+          (sqlite-step-and-reset stmt)
+          id)
         (let ((stmt (sqlite-prepare
                      db
                      "
@@ -237,8 +237,7 @@ VALUES (:path, :hash, :time, :deriver, :size)"
           (sqlite-bind-arguments stmt
                                  #:path path #:deriver deriver
                                  #:hash hash #:size nar-size #:time time)
-          (sqlite-fold cons '() stmt)             ;execute it
-          (sqlite-finalize stmt)
+          (sqlite-step-and-reset stmt)
           (last-insert-row-id db)))))
 
 (define (add-references db referrer references)
@@ -251,13 +250,10 @@ INSERT OR REPLACE INTO Refs (referrer, reference)
 VALUES (:referrer, :reference)"
                #:cache? #t)))
     (for-each (lambda (reference)
-                (sqlite-reset stmt)
                 (sqlite-bind-arguments stmt #:referrer referrer
                                        #:reference reference)
-                (sqlite-fold cons '() stmt)       ;execute it
-                (last-insert-row-id db))
-              references)
-    (sqlite-finalize stmt)))
+                (sqlite-step-and-reset stmt))
+              references)))
 
 (define (timestamp)
   "Return a timestamp, either the current time of SOURCE_DATE_EPOCH."