Connections to Database Management Systems which automatically disconnect. In particular connections which are created with DBI::dbConnect() and closed with DBI::dbDisconnect().

with_db_connection(con, code)

local_db_connection(con, .local_envir = parent.frame())

Arguments

con

For with_db_connection() a named list with the connection(s) to create. For local_db_connection() the code to create a single connection, which is then returned.

code

[any] Code to execute in the temporary environment

.local_envir

[environment] The environment to use for scoping.

Value

[any] The results of the evaluation of the code argument.

See also

withr for examples

Examples

db <- tempfile() with_db_connection( list(con = DBI::dbConnect(RSQLite::SQLite(), db)), { DBI::dbWriteTable(con, "mtcars", mtcars) })
#> Loading required namespace: DBI
head_db_table <- function(...) { con <- local_db_connection(DBI::dbConnect(RSQLite::SQLite(), db)) head(DBI::dbReadTable(con, "mtcars"), ...) } head_db_table()
#> mpg cyl disp hp drat wt qsec vs am gear carb #> 1 21.0 6 160 110 3.90 2.620 16.46 0 1 4 4 #> 2 21.0 6 160 110 3.90 2.875 17.02 0 1 4 4 #> 3 22.8 4 108 93 3.85 2.320 18.61 1 1 4 1 #> 4 21.4 6 258 110 3.08 3.215 19.44 1 0 3 1 #> 5 18.7 8 360 175 3.15 3.440 17.02 0 0 3 2 #> 6 18.1 6 225 105 2.76 3.460 20.22 1 0 3 1
unlink(db)