- Notifications
You must be signed in to change notification settings - Fork2
⚡💻⚡ R client for the Lightning Memory-Mapped Database
License
richfitz/thor
Folders and files
| Name | Name | Last commit message | Last commit date | |
|---|---|---|---|---|
Repository files navigation
An R interface toLMDB. LMDB is an embedded transactional key-value store and this package provides R mappings to it. It wraps the entire LMDB interface, except for support for duplicated keys.
The package comes with a vignette that describes the main features of the package and of LMDB - seehere for a version online. The package also has reference documentation for all methods. It may be useful to refer to theLMDB documentation along side the reference documentation for some details (but hopefully not too much).
Everything starts by creating an environment (which lives at a point in the file system), and then using methods of the environment object to interact with the database
env<-thor::mdb_env(tempfile())env
## <mdb_env>## Informational:## path()## flags()## info()## stat()## maxkeysize()## maxreaders()## Transactions:## begin(db = NULL, write = FALSE, sync = NULL, metasync = ...## with_transaction(fun, db = NULL, write = FALSE)## Databases:## open_database(key = NULL, reversekey = FALSE, create = TRUE)## drop_database(db, delete = TRUE)## Management:## sync(force = FALSE)## copy(path, compact = FALSE)## close()## destroy()## reader_list()## reader_check()## Helpers:## get(key, missing_is_error = TRUE, as_raw = NULL, db = NULL)## put(key, value, overwrite = TRUE, append = FALSE, db = NULL)## del(key, db = NULL)## exists(key, db = NULL)## list(starts_with = NULL, as_raw = FALSE, size = NULL, db ...## mget(key, as_raw = NULL, db = NULL)## mput(key, value, overwrite = TRUE, append = FALSE, db = ...## mdel(key, db = NULL)env$put("hello","world")
## NULLenv$exists("hello")
## [1] TRUEenv$get("hello")# world
## [1] "world"env$del("hello")
## [1] TRUELMDB istransactional, andthor exposes this like so:
txn<-env$begin(write=TRUE)txn
## <mdb_txn>## Informational:## id()## stat()## Finish:## commit()## abort(cache = TRUE)## Cursors:## cursor()## Data:## get(key, missing_is_error = TRUE, as_proxy = FALSE, as_r ...## put(key, value, overwrite = TRUE, append = FALSE)## del(key)## exists(key)## list(starts_with = NULL, as_raw = FALSE, size = NULL)## mget(key, as_proxy = FALSE, as_raw = NULL)## mput(key, value, overwrite = TRUE, append = FALSE)## mdel(key)## replace(key, value, as_raw = NULL)## pop(key, as_raw = NULL)## Compare:## cmp(a, b)Only one write transaction is active at a given point in time. There can be an unlimited number of read transactions.
txn$put("key", "value")env$get("key", missing_is_error = FALSE) # NULL - not committed yettxn$commit()env$get("key") # new transactions see the valueThere is a cursor interface for advanced features (see the vignette). Both keys and values can be strings or binary value, the latter working well withserialize. For efficient use from R,thor extends the LMDB interface to implement bulk reads, writes and deletes (mget,mput andmdel).
lmdb is an extremely fast database, but this package may be much less fast than the underlying library. In order to make the interface safe to use from R, there is quite a bit of error checking, and the length of time involved in calling methods in R6 objects is orders of magnitude slower than performing an action on an lmdb database (this is not R6's fault and primarily caused by the cost of S3 method lookup for$ on an object with a class attribute). The vectorised functions will help here (e.g.,mget,mput), so prefer these where practical if speed is a concern.
Install from CRAN with
install.packages("thor")If you want to try the development version from github, you can install with
devtools::install_github("richfitz/thor",upgrade=FALSE)
MIT + file LICENSE ©Rich FitzJohn. The package contains included code from lmdb which it itself under the "OpenLDAP Public License" - seeinst/LICENSE.lmdb for details
About
⚡💻⚡ R client for the Lightning Memory-Mapped Database
Resources
License
Uh oh!
There was an error while loading.Please reload this page.
Stars
Watchers
Forks
Packages0
Uh oh!
There was an error while loading.Please reload this page.
Contributors2
Uh oh!
There was an error while loading.Please reload this page.