use WAL mode if available; don't delete media in check

anki/collection.py

@@ -124,6 +124,7 @@ crt=?, mod=?, scm=?, dty=?, usn=?, ls=?, conf=?""",
                 self.save()
             else:
                 self.rollback()
+            self.db.execute("pragma journal_mode = delete")
             self.db.close()
             self.db = None
             self.media.close()

anki/media.py

@@ -122,7 +122,7 @@ If the same name exists, compare checksums."""
     # Rebuilding DB
     ##########################################################################
 
-    def check(self, delete=False, local=None):
+    def check(self, local=None):
         "Return (missingFiles, unusedFiles)."
         mdir = self.dir()
         # generate card q/a and look through all references
@@ -150,11 +150,6 @@ If the same name exists, compare checksums."""
                 unused.append(file)
             else:
                 del normrefs[nfile]
-        # optionally delete
-        if delete:
-            for f in unused:
-                path = os.path.join(mdir, f)
-                os.unlink(path)
         nohave = normrefs.keys()
         return (nohave, unused)
 

anki/storage.py

@@ -27,6 +27,7 @@ def Collection(path, queue=True, lock=True, server=False):
         ver = _upgradeSchema(db)
     db.execute("pragma temp_store = memory")
     db.execute("pragma cache_size = 10000")
+    db.execute("pragma journal_mode = wal")
     # add db to col and do any remaining upgrades
     col = _Collection(db, server)
     if ver < SCHEMA_VERSION: