adbcdrivermanager (version 0.22.0)

with_adbc: Cleanup helpers

Description

Managing the lifecycle of databases, connections, and statements can be complex and error-prone. The R objects that wrap the underlying ADBC pointers will perform cleanup in the correct order if you rely on garbage collection (i.e., do nothing and let the objects go out of scope); however it is good practice to explicitly clean up these objects. These helpers are designed to make explicit and predictable cleanup easy to accomplish.

Usage

with_adbc(x, code)
local_adbc(x, .local_envir = parent.frame())

Value

• with_adbc() returns the result of code

• local_adbc() returns the input, invisibly.

Arguments

x

An ADBC database, ADBC connection, ADBC statement, or nanoarrow_array_stream returned from calls to an ADBC function.

code

Code to execute before cleaning up the input.

.local_envir

The execution environment whose scope should be tied to the input.

Details

Note that you can use adbc_connection_join() and adbc_statement_join() to tie the lifecycle of the parent object to that of the child object. These functions mark any previous references to the parent object as released so you can still use local and with helpers to manage the parent object before it is joined. Use stream_join_parent = TRUE in adbc_statement_execute_query() to tie the lifecycle of a statement to the output stream.

Examples

# Using with_adbc():
with_adbc(db <- adbc_database_init(adbc_driver_void()), {
  with_adbc(con <- adbc_connection_init(db), {
    with_adbc(stmt <- adbc_statement_init(con), {
      # adbc_statement_set_sql_query(stmt, "SELECT * FROM foofy")
      # adbc_statement_execute_query(stmt)
      "some result"
    })
  })
})

# Using local_adbc_*() (works best within a function, test, or local())
local({
  db <- local_adbc(adbc_database_init(adbc_driver_void()))
  con <- local_adbc(adbc_connection_init(db))
  stmt <- local_adbc(adbc_statement_init(con))
  # adbc_statement_set_sql_query(stmt, "SELECT * FROM foofy")
  # adbc_statement_execute_query(stmt)
  "some result"
})