[R] Closing unreferenced result sets in dbi / RSQLite

[Andreas Borg]

Hello R-help members,

I have one problem with the database interface dbi (more specifically, I 
work with RSQLite). Consider the following example, which writes a test 
table to a temporary SQLite database and sends a query to read from it:

library(RSQLite)
df <- as.data.frame(matrix(runif(4), nrow=2, ncol=2))
drv <- dbDriver("SQLite")
con <- dbConnect(drv)
dbWriteTable(con, "df", df)
dbSendQuery(con, "select * from df")


In the last line I "forgot" to assign the DBIResult object returned by 
dbSendQuery() to a variable, which happens from time to time when I work 
interactively. The following attempt to correct the mistake:

res <- dbSendQuery(con, "select * from df")

fails because the orphaned result set from the preceeding call is still 
active. Consequently, I have to close the connection to keep on working, 
which is especially annoying when working with a temporary data base 
where everything is discarded on disconnection. Is there any way to 
create a new reference to the pending result set or to close result sets 
which are not bound to a variable?

Thanks for any suggestion,

Andreas


-- 
Andreas Borg
Medizinische Informatik

UNIVERSITÄTSMEDIZIN
der Johannes Gutenberg-Universität
Institut für Medizinische Biometrie, Epidemiologie und Informatik
Obere Zahlbacher Straße 69, 55131 Mainz
www.imbei.uni-mainz.de

Telefon +49 (0) 6131 175062
E-Mail: borg at imbei.uni-mainz.de

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