Improve scanning performance by a factor of approximately 8.

Schema fix.

ChangeLog

+2003-04-20  Per Cederqvist  <ceder@ceder.dyndns.org>
+
+	Schema fix.
+	* createdb.sql (file): The filename, size, mtime, dir_id should be
+	sufficient as a unique key.
+
+	Improve scanning performance by a factor of approximately 8.
+	* scanner.py (scan): Performance fix: don't do a select per file
+	we examine.  Insert all of the files into a temporary table
+	instead, and do a left join to find out which of them that are
+	new.
+	(insert_tmp_files): New function.
+
 2003-04-19  Per Cederqvist  <ceder@ceder.dyndns.org>
 
 	Optimize the database.