Skip to content
⚡️💻⚡️ R client for the Lightning Memory-Mapped Database
Branch: master
Clone or download
Fetching latest commit…
Cannot retrieve the latest commit at this time.
Permalink
Type Name Latest commit message Commit time
Failed to load latest commit information.
R
inst
man-roxygen
man
scripts
src
tests
vignettes
vignettes_src
.Rbuildignore
.gitignore
.travis.yml
DESCRIPTION
LICENSE
Makefile
NAMESPACE
NEWS.md
README.Rmd
README.md
appveyor.yml
cleanup

README.md

thor

Project Status: Active – The project has reached a stable, usable state and is being actively developed. Linux Build Status Windows Build status codecov.io

An R interface to LMDB. 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.

Documentation

The package comes with a vignette that describes the main features of the package and of LMDB - see here for a version online. The package also has reference documentation for all methods. It may be useful to refer to the LMDB documentation along side the reference documentation for some details (but hopefully not too much).

Usage

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$put("hello", "world")
## NULL
env$exists("hello")
## [1] TRUE
env$get("hello") # world
## [1] "world"
env$del("hello")
## [1] TRUE

LMDB is transactional, and thor 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 yet
txn$commit()
env$get("key") # new transactions see the value

There is a cursor interface for advanced features (see the vignette). Both keys and values can be strings or binary value, the latter working well with serialize. For efficient use from R, thor extends the LMDB interface to implement bulk reads, writes and deletes (mget, mput and mdel).

Performance

lldb 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 lldb 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.

Installation

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)

License

MIT + file LICENSE © Rich FitzJohn. The package contains included code from lmdb which it itself under the "OpenLDAP Public License" - see inst/LICENSE.lmdb for details

You can’t perform that action at this time.