docs: explicitly state how to change DuckDB configuration options (#587)

* docs: explicitly state how to change DuckDB configuration options

* Tweak

---------

Co-authored-by: Kirill Müller <[email protected]>

Author: maelle

R/exec.R

@@ -3,10 +3,15 @@
 #' The \pkg{duckplyr} package relies on a DBI connection
 #' to an in-memory database.
 #' The `db_exec()` function allows running SQL statements
-#' with this connection to, e.g., set up credentials
+#' with side effects on this connection.
+#' It can be used to execute statements that start with
+#' `PRAGMA`, `SET`, or `ATTACH`
+#' to, e.g., set up credentials, change configuration options,
 #' or attach other databases.
 #' See <https://duckdb.org/docs/configuration/overview.html>
-#' for more information on the configuration options.
+#' for more information on the configuration options,
+#' and <https://duckdb.org/docs/sql/statements/attach.html>
+#' for attaching databases.
 #'
 #' @seealso [read_sql_duckdb()]
 #'

man/db_exec.Rd

@@ -269,7 +269,7 @@ At the time of writing, direct JSON export is not supported.
 
 Computations carried out by DuckDB allocate RAM in the context of the R process.
 This memory separate from the memory used by R objects, and is managed by DuckDB.
-Limit the memory used by DuckDB by setting a pragma:
+Limit the memory used by DuckDB by setting a pragma with `db_exec()`:
 
 ```{r}
 read_sql_duckdb("SELECT current_setting('memory_limit') AS memlimit")