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DBMS Connections which disconnect themselves.

Source: R/db.R
with_db_connection.Rd

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

Usage

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)
})

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)