sqliteSupport {RSQLite}R Documentation

Support Functions

Description

These functions are the workhorses behind the RSQLite package, but users need not invoke these directly.

Usage

   ## SQLiteDriver-related
   sqliteInitDriver(max.con=16, fetch.default.rec = 500, force.reload=FALSE,
                    shared.cache=FALSE)
   sqliteDriverInfo(obj, what, ...)
   sqliteDescribeDriver(obj, verbose = FALSE, ...)
   sqliteCloseDriver(drv, ...)

   ## SQLiteConnection-related
   sqliteNewConnection(drv, dbname, loadable.extensions=TRUE, cache_size=NULL,
                       synchronous=0, flags = NULL, vfs = NULL)
   sqliteConnectionInfo(obj, what, ...)
   sqliteDescribeConnection(obj, verbose = FALSE, ...)
   sqliteCloseConnection(con, ...)

   ## SQLiteResult-related
   sqliteExecStatement(con, statement, bind.data=NULL)
   sqliteTransactionStatement(con, statement)
   sqliteFetch(res, n=0, ...)
   sqliteQuickSQL(con, statement, bind.data=NULL, ...)
   sqliteResultInfo(obj, what, ...)
   sqliteDescribeResult(obj, verbose = FALSE, ...)
   sqliteCloseResult(res, ...)

   ## data mappings and convenience functions
   sqliteDataType(obj, ...)
   sqliteReadTable(con, name, row.names = "row_names", check.names = TRUE, ...)
   sqliteImportFile(con, name, value, field.types, overwrite=FALSE,
      append=FALSE, header, row.names, nrows=50, sep=",", eol="\n",
      skip = 0, ...)
   sqliteWriteTable(con, name, value, row.names = TRUE,
                    overwrite = FALSE, append = FALSE,
                    field.types = NULL, ...)
   sqliteTableFields(con, name, ...)

Arguments

max.con

positive integer specifying maximum number of open connections. The default is 10. Note that since SQLite is embedded in R/S-Plus connections are simple, very efficient direct C calls.

fetch.default.rec

default number of rows to fetch (move to R/S-Plus). This default is used in sqliteFetch. The default is 500.

force.reload

logical indicating whether to re-initialize the driver. This may be useful if you want to change the defaults (e.g., fetch.default.rec). Note that the driver is a singleton (subsequent inits just returned the previously initialized driver, thus this argument).

obj

any of the SQLite DBI objects (e.g., SQLiteConnection, SQLiteResult).

what

character vector of metadata to extract, e.g., "version", "statement", "isSelect".

verbose

logical controlling how much information to display. Defaults to FALSE.

drv

an SQLiteDriver object as produced by sqliteInit.

con

an SQLiteConnection object as produced by sqliteNewConnection.

res

an SQLiteResult object as produced by by sqliteExecStatement.

dbname

character string with the SQLite database file name (SQLite, like Microsoft's Access, stores an entire database in one file).

loadable.extensions

logical describing whether loadable extensions will be enabled for this connection. The default is FALSE.

flags

An integer that will be interpretted as a collection of flags by the SQLite API. If NULL, the flags will default to SQLITE_RWC which will open the file in read/write mode and create the file if it does not exist. You can use SQLITE_RW to open in read/write mode and SQLITE_RO to open in read only mode. In both cases, an error is raised if the database file does not already exist. See http://sqlite.org/c3ref/open.html for more details.

shared.cache

logical describing whether shared-cache mode should be enabled on the SQLite driver. The default is FALSE.

bind.data

a data frame which will be used to bind variables in the statement.

cache_size

positive integer to pass to the PRAGMA cache_size; this changes the maximum number of disk pages that SQLite will hold in memory (SQLite's default is 2000 pages).

synchronous

values the PRAGMA synchronous flag, possible values are 0, 1, or 2 or the corresponding strings "OFF", "NORMAL", or "FULL". The RSQLite package uses a default of 0 (OFF), although SQLite's default is 2 (FULL) as of version 3.2.8. Users have reported significant speed ups using sychronous="OFF", and the SQLite documentation itself implies considerably improved performance at the very modest risk of database corruption in the unlikely case of the operating system (not the R application) crashing.

vfs

The name of the SQLite virtual filesystem module to use. If NULL, the default module will be used. Module availability depends on your operating as summarized by the following table:

module

OSX

Unix (not OSX)

Windows

"unix-none"

Y

Y

N

"unix-dotfile"

Y

Y

N

"unix-flock"

Y

N

N

"unix-afp"

Y

N

N

"unix-posix"

Y

N

N

See http://www.sqlite.org/compile.html for details.

force

logical indicating whether to close a connection that has open result sets. The default is FALSE.

statement

character string holding SQL statements.

n

number of rows to fetch from the given result set. A value of -1 indicates to retrieve all the rows. The default of 0 specifies to extract whatever the fetch.default.rec was specified during driver initialization sqliteInit.

name

character vector of names (table names, fields, keywords).

value

a data.frame.

field.types

a list specifying the mapping from R/S-Plus fields in the data.frame value to SQL data types. The default is sapply(value,SQLDataType), see SQLiteSQLType.

row.names

a logical specifying whether to prepend the value data.frame row names or not. The default is TRUE.

check.names

a logical specifying whether to convert DBMS field names into legal S names. Default is TRUE.

overwrite

logical indicating whether to replace the table name with the contents of the data.frame value. The defauls is FALSE.

append

logical indicating whether to append value to the existing table name.

header

logical, does the input file have a header line? Default is the same heuristic used by read.table, i.e., TRUE if the first line has one fewer column that the second line.

nrows

number of lines to rows to import using read.table from the input file to create the proper table definition. Default is 50.

sep

field separator character.

eol

end-of-line separator.

skip

number of lines to skip before reading data in the input file.

...

placeholder for future use.

Value

sqliteInitDriver returns an SQLiteDriver object.

sqliteDriverInfo returns a list of name-value metadata pairs.

sqliteDescribeDriver returns NULL (displays the object's metadata).

sqliteCloseDriver returns a logical indicating whether the operation succeeded or not.

sqliteNewConnection returns an SQLiteConnection object.

sqliteConnectionInforeturns a list of name-value metadata pairs.

sqliteDescribeConnection returns NULL (displays the object's metadata).

sqliteCloseConnection returns a logical indicating whether the operation succeeded or not.

sqliteExecStatement returns an SQLiteResult object.

sqliteFetch returns a data.frame.

sqliteQuickSQL returns either a data.frame if the statement is a select-like or NULL otherwise.

sqliteDescribeResult returns NULL (displays the object's metadata).

sqliteCloseResult returns a logical indicating whether the operation succeeded or not.

sqliteReadTable returns a data.frame with the contents of the DBMS table.

sqliteWriteTable returns a logical indicating whether the operation succeeded or not.

sqliteImportFile returns a logical indicating whether the operation succeeded or not.

sqliteTableFields returns a character vector with the table name field names.

sqliteDataType retuns a character string with the closest SQL data type. Note that SQLite is typeless, so this is mostly for creating table that are compatible across RDBMS.

sqliteResultInfo returns a list of name-value metadata pairs.

Constants

.SQLitePkgName (currently "RSQLite"), .SQLitePkgVersion (the R package version), .SQLitePkgRCS (the RCS revision), .SQLitecle.NA.string (character that SQLite uses to denote NULL on input), .conflicts.OK.

The following constants can be used as the value of the flags argument to sqliteNewConnection to control the mode of the databse connection:

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

[Package RSQLite version 0.10.0 Index]