RBerkeley-package: R Interface to Embedded Oracle Berkeley DB

In hrbrmstr/RBerkeley: Oracle 'Berkeley DB' Interface for R

Description

Package provides a low and high level interface to the C API of the Oracle Berkeley DB embedded database product.

Details

Initial implementation will be to provide direct access to the low-level API calls in their entirety.

The project will eventually include a higher-level interface to make using the DB from R easier.

A large part of the API had been coded, though a much smaller subset is currently documented with respect to differences of design or necessity between RBerkleley and the C-API.

Primary difference with respect to design include the automatic serialization of objects via serialize. This can be bypassed by providing a RAW type vector to the get and put operations.

From a API perspective, some functions related to threads are not yet implemented, as they are not an absolute priority. Additionally functions that require C level callback function pointers have also been intentionally skipped until a later time.

All functions that appear in the RBerkeley documentation with an asterisk next to them are currently not available in the API.

Author(s)

Jeffrey A. Ryan

References

Oracle Berkey DB
http://www.oracle.com/technetwork/database/database-technologies/berkeleydb/overview/index.html

See Also

Databases, Environments, Cursors, Mutexes

Examples

## Not run: 
db_version()

dbh <- db_create()

# set some flags and open new db
db_get_flags(dbh)
db_set_flags(dbh,mkFlags(DB_DUP))
db_open(dbh,flags=mkFlags(DB_CREATE))
db_get_flags(dbh)

db_get_dbname(dbh)

# look for non-existant key
db_get(dbh, key="mykey")

# add a key=>value
db_put(dbh, key=charToRaw("myKey"), data="myValue")
x <- matrix(1:10)
db_put(dbh, key="myKey2", data=x)
db_put(dbh, key="myKey3", data="newValue")
db_put(dbh, key="myKey4", data="myValue")
db_key_range(dbh, key="myKey2")

# add a few hundred keys/values
system.time(
for(i in 1:1000)
{
  db_put(dbh, key=i, data=x)
}
)

# get value by key
db_get(dbh, key="myKey2")
db_set_priority(dbh, priority=mkFlags(DB_PRIORITY_VERY_LOW))

xr <- db_get(dbh, key="myKey2")

xr
unserialize(xr)

# cursors
dbc <- db_cursor(dbh)
dbc2 <- dbcursor_dup(dbc)
dbc2

dbcursor_get_priority(dbc)
dbcursor_set_priority(dbc, flags=mkFlags(DB_PRIORITY_LOW))
dbcursor_get_priority(dbc)
dbcursor_get(dbc, key=NULL, data=NULL, flags=0L, n=1L)

# using mkFlags for bitwise OR operations on DB constants
mkFlags(DB_SET);

dbcursor_get(dbc2, key="myKey2", data=NULL, flags=mkFlags(DB_SET), n=1L)
dbcursor_put(dbc2, key="mynewKey", data="MyNewValue", flags=mkFlags(DB_KEYFIRST))
dbcursor_get(dbc2, key="myKey2", data=NULL, flags=mkFlags(DB_PREV), n=1L)
dbcursor_get(dbc2, key="myKey2", data=NULL, flags=mkFlags(DB_FIRST), n=1L)
dbcursor_get(dbc, key=NULL, data=NULL, flags=0L, n=2L) # get 2 records
dbcursor_close(dbc)
dbcursor_close(dbc2)

dbc <- db_cursor(dbh)
dbcursor_get(dbc, key=NULL, data=NULL, flags=0L, n=-1L)
db_stat_print(dbh)
db_stat_print(dbh, flags=mkFlags(DB_FAST_STAT))
dbcursor_close(dbc)

db_exists(dbh, NULL, "myKey2", 0L)
db_get(dbh,key="myKey")

# flush to disk
db_sync(dbh)

db_get_type(dbh)

# close db
db_close(dbh)

# remove (need new handle)
dbh <- db_create()
db_remove(dbh, "access.db", NULL)

## End(Not run)

hrbrmstr/RBerkeley documentation built on May 17, 2019, 4:54 p.m.