[SQLObject] SQLite and :memory:

[Daniel B. <da...@cs...>]

I'm playing with today's svn, and the db connection URIs (used with
connectForURI) for sqlite don't seem to handle the special
memory-resident target, which sqlite calls :memory:.

Normally, if you tell sqlite to use a file named :memory:, it will keep
the database in memory instead of using a file on disk. This worked fine
with the SQLiteConnection(file=':memory:') interface, but the current
URI parsing can't handle it (DBConnection._parseURI).

Some examples:

  URI:       sqlite:/:memory:
  _parseURI: user=None password=None host=None path=/:memory: args={}

  URI:       sqlite://:memory:
  _parseURI: user=None password=None host=:memory: path=/ args={}

  URI:       sqlite:///:memory:
  _parseURI: user=None password=None host=None path=/:memory: args={}

In none of these does the path come out as :memory:. Moreover, the first
and third examples should probably be considered correct, since those
URIs identify the file /:memory: , and not SQLite's pseudo-thing that
indicates the lack of a file.

But in the second URI, the parser interprets an identifer after
schema:// as the host, and expects the path to follow another '/' (which
isn't supplied, in this example).

Since hosts have no other meaning in sqlite URIs, maybe accepting a host
named :memory: would be an acceptable hack?

Here is a (line-broken) `svn diff` of my implementation of this idea. I
also removed the addition of an extra leading '/', which
DBConnection._parseURI already provides:

 danb


Index: sqlobject/sqlite/sqliteconnection.py
===================================================================
--- sqlobject/sqlite/sqliteconnection.py        (revision 126)
+++ sqlobject/sqlite/sqliteconnection.py        (working copy)
@@ -21,10 +21,14 @@
         DBAPI.__init__(self, **kw)
  
     def connectionFromURI(cls, uri):
+        magic_host = ':memory:'
         user, password, host, path, args = cls._parseURI(uri)
-        assert host is None, "SQLite can only be used locally (with a
URI like sqlite:///file or sql:/file, not %r)" % uri
+        assert host in [ None, magic_host ], "SQLite can only be used
locally (with a URI like sqlite:///file or sql:/file, not %r), or with
the magic host '%s' to specify in-memory use." % (uri, magic_host)
         assert user is None and password is None, "You may not provide
usernames or passwords for SQLite databases"
-        return cls(filename='/' + path, **args)
+        if host == magic_host:
+            assert path == '/', "You may not provide a path with the
magic host '%s'" % magic_host
+            path = host
+        return cls(filename=path, **args)
     connectionFromURI = classmethod(connectionFromURI)
  
     def _setAutoCommit(self, conn, auto):


-- 
Daniel Brown
www.utacm.org
www.cs.utexas.edu