default driver and connection

Hi,

[The following comments hold for RSQLite.  I'm pretty sure they hold
for all DBI, but haven't gone and looked to verify the code.]

"Gabor Grothendieck" <ggrothendieck at gmail.com> writes:

Is there a way of finding out if the driver is loaded and if there
are any open connections in RSQLite or other database and what
they are?

The driver is implemented as a singleton so there is no need to worry
about multiple calls to dbDriver("SQLite") or more simply SQLite().
The driver gets loaded on first invocation of SQLite() and subsequent
calls simply return the existing instance.

Even better would be if the code below could work regardless
of whether an SQLite or MySQL connection was open.  I have written pseudocode
in the places where I don't know how to access the functionality.
If all this exists is there an example?  Thanks.

# returns first three rows of iris
# loading any driver and opening any connection if need be
f <- function(m, con, dbname = ":memory:") {
       if (missing(m) {
               m <- if (no.data.base.drivers.loaded)
                       dbDriver("SQLite")
               else loaded.driver
       }
       if (missing(con)) {
               con <- if (no.connections.open)
                       dbConnect(m, dbname)
               active.connection
       }
       dbWriteTable(con, "iris", iris)
       dbGetQuery(con, "select * from iris limit 3")
}

dbListConnections(SQLite()) will tell you about open connections to
the SQLite driver.