Does R provide anything cleaner than tryCatch() to safely make SQL queries?

Question

I am making SQL queries, using tryCatch() to prevent R from silently using up all the slots for database connections. It looks like this:

sql <- "SELECT * FROM addresses WHERE zipcode=10202"
con <- dbConnect(PostgreSQL(), user='user', password='pswd',
                 dbname='contacts',host='dbserv')
tryCatch( {
    rs <- dbSendQuery(con, statement=sql)                              
    fp <- fetch(rs,n=-1) # Fetch all
    dbClearResult(rs)
    fp},
  finally=dbDisconnect(con))
fp

Does R provide anything cleaner for the purpose? I'm thinking of how readLines() works with a string argument to make sure no file connection is left open.

Answer 1

You might try on.exit, something like the following:

    foo <- function() {

      con <- dbConnect(
        PostgreSQL(),
        user=config$db.user,
        password=config$db.password,
        dbname=config$db.name,
        host=config$db.host
      )

      on.exit({
        dbDisconnect(con)
      })

      ## ... do something w/ connection

    }

When the function foo is about to return (or exit due to an exception), the expression passed to on.exit will be evaluated.