- dbDelete
The dbDelete
function is for deleting
elements, but for the "DB1"
format all it does is remove the
key from the lookup table.
The actual data are still in the database (but inaccessible). If
you reinsert data for the same key, the new data are simply
appended on to the end of the file. Therefore, it's possible to
have multiple copies of data lying around after a while,
potentially making the database file big. The "RDS"
format
does not have this problem.
- dbExists
check to see if a key exists.
- dbFetch
retrieve the value associated with a given key.
- dbMultiFetch
retrieve values associated with multiple keys (a
list of those values is returned).
- dbInsert
insert a key-value pair into the database. If
that key already exists, its associated value is overwritten. For
"RDS"
type databases, there is a safe
option
(defaults to TRUE
) which allows the user to insert objects
somewhat more safely (objects should not be lost in the event of
an interrupt).
- dbList
list all keys in the database.
- dbReorganize
The dbReorganize
function is there for
the purpose of rewriting the database to remove all of the stale
entries. Basically, this function creates a new copy of the
database and then overwrites the old copy. This function has not
been tested extensively and so should be considered
experimental. dbReorganize
is not needed when using
the "RDS"
format.
- dbUnlink
delete an entire database from the disk
- show
print method
- with
allows with
to be used with "filehash"
objects much like it can be used with lists or data frames
- [[,[[<-
elements of a database can be accessed using the [[
operator much like a list or environment, but only character
indices are allowed
- $,$<-
elements of a database can be accessed using the $
operator much like with a list or environment
- lapply
works much like lapply
with lists; a list is
returned.
- names
returns all of the keys in the database
- length
returns the number of elements in the database