Load entire database into an environment
dbLoad(db, ...)# S4 method for filehash
dbLoad(db, env = parent.frame(2), keys = NULL, ...)
dbLazyLoad(db, ...)
# S4 method for filehash
dbLazyLoad(db, env = parent.frame(2), keys = NULL, ...)
db2env(db)
dbLoad, dbLazyLoad: a character vector is returned (invisibly) containing the keys associated with the values loaded into the environment.
db2env: environment containing database keys
filehash database object
arguments passed to other methods
environment into which objects should be loaded
specific keys to be loaded (if NULL then all keys are loaded)
dbLoad(filehash): Method for filehash databases
dbLazyLoad(filehash): Method for filehash databases
dbLazyLoad(): Lazy load a filehash database
db2env(): Load active bindings into an environment and return the environment
dbLoad loads objects in the database directly into the
environment specified, like load does except with active bindings.
dbLoad takes a second argument env, which is an
environment, and the default for env is parent.frame().
The use of makeActiveBinding in db2env and
dbLoad allows for potentially large databases to, at least
conceptually, be used in R, as long as you don't need simultaneous access to
all of the elements in the database.
dbLazyLoad loads objects in the database directly into the
environment specified, like load does except with promises.
dbLazyLoad takes a second argument env, which is an
environment, and the default for env is parent.frame().
With dbLazyLoad database objects are "lazy-loaded" into
the environment. Promises to load the objects are created in the environment
specified by env. Upon first access, those objects are copied into
the environment and will from then on reside in memory. Changes to the
database will not be reflected in the object residing in the environment
after first access. Conversely, changes to the object in the environment
will not be reflected in the database. This type of loading is useful for
read-only databases.
db2env loads the entire database db into an
environment via calls to makeActiveBinding. Therefore, the data
themselves are not stored in the environment, but a function pointing to
the data in the database is stored. When an element of the environment is
accessed, the function is called to retrieve the data from the database.
If the data in the database is changed, the changes will be reflected in the
environment.
dbLoad, dbLazyLoad