SQLite: Connect to an SQLite database

Description

Together, SQLite() and dbConnect() allow you to connect to a SQLite database file. See DBI::dbSendQuery() for how to issue queries and receive results.

Usage

SQLite(...)
# S4 method for SQLiteDriver
dbConnect(drv, dbname = "", ...,
  loadable.extensions = TRUE, cache_size = NULL, synchronous = "off",
  flags = SQLITE_RWC, vfs = NULL)
# S4 method for SQLiteConnection
dbConnect(drv, ...)
# S4 method for SQLiteConnection
dbDisconnect(conn, ...)

Arguments

...

In previous versions, SQLite() took arguments. These have now all been moved to dbConnect(), and any arguments here will be ignored with a warning.

drv, conn

An objected generated by SQLite(), or an existing '>SQLiteConnection. If an connection, the connection will be cloned.

dbname

The path to the database file. SQLite keeps each database instance in one single file. The name of the database is the file name, thus database names should be legal file names in the running platform. There are two exceptions:

"" will create a temporary on-disk database. The file will be deleted when the connection is closed.
":memory:" or "file::memory:" will create a temporary in-memory database.

loadable.extensions

When TRUE (default) SQLite3 loadable extensions are enabled. Setting this value to FALSE prevents extensions from being loaded.

cache_size

Advanced option. A positive integer to change the maximum number of disk pages that SQLite holds in memory (SQLite's default is 2000 pages). See http://www.sqlite.org/pragma.html#pragma_cache_size for details.

synchronous

Advanced options. Possible values for synchronous are "off" (the default), "normal", or "full". Users have reported significant speed ups using sychronous = "off", and the SQLite documentation itself implies considerable improved performance at the very modest risk of database corruption in the unlikely case of the operating system (not the R application) crashing. See http://www.sqlite.org/pragma.html#pragma_synchronous for details.

flags

SQLITE_RWC: open the database in read/write mode and create the database file if it does not already exist; SQLITE_RW: open the database in read/write mode. Raise an error if the file does not already exist; SQLITE_RO: open the database in read only mode. Raise an error if the file does not already exist

vfs

Select the SQLite3 OS interface. See http://www.sqlite.org/vfs.html for details. Allowed values are "unix-posix", "unix-unix-afp", "unix-unix-flock", "unix-dotfile", and "unix-none".

Value

SQLite() returns an object of class '>SQLiteDriver.

dbConnect() returns an object of class '>SQLiteConnection.

Details

Connections are automatically cleaned-up after they're deleted and reclaimed by the GC. You can use DBI::dbDisconnect() to terminate the connection early, but it will not actually close until all open result sets have been closed (and you'll get a warning message to this effect).

Examples

Run this code

# NOT RUN {
library(DBI)
# Initialize a temporary in memory database and copy a data.frame into it
con <- dbConnect(RSQLite::SQLite(), ":memory:")
data(USArrests)
dbWriteTable(con, "USArrests", USArrests)
dbListTables(con)

# Fetch all query results into a data frame:
dbGetQuery(con, "SELECT * FROM USArrests")

# Or do it in batches
rs <- dbSendQuery(con, "SELECT * FROM USArrests")
d1 <- dbFetch(rs, n = 10)      # extract data in chunks of 10 rows
dbHasCompleted(rs)
d2 <- dbFetch(rs, n = -1)      # extract all remaining data
dbHasCompleted(rs)
dbClearResult(rs)

# clean up
dbDisconnect(con)
# }