From 2e552ad3afd3d892a9e160afcd565517695a69d4 Mon Sep 17 00:00:00 2001 From: Gregory Burd Date: Sun, 19 May 2013 00:27:44 -0400 Subject: [PATCH] Updated a bit. --- README.md | 67 ++++++++++++++++++++++++++++++++++++------------------- 1 file changed, 44 insertions(+), 23 deletions(-) diff --git a/README.md b/README.md index 1437b51..fdbeb41 100644 --- a/README.md +++ b/README.md @@ -1,16 +1,25 @@ -EMDB ==== EMDB is a NIF library for the [Memory-Mapped Database](http://highlandsun.com/hyc/mdb/) database, aka. MDB. The main purpose of this package is to provide a **very fast** Riak [backend](http://wiki.basho.com/Storage-Backends.html). +EMDB +==== -But this module could also be used as a general key-value store to replace: +EMDB is a NIF library for the [Memory-Mapped Database](http://highlandsun.com/hyc/mdb/) database, aka. MDB. -* [DETS](http://www.erlang.org/doc/man/dets.html) -* TokyoCabinet: [TCERL](http://code.google.com/p/tcerl/) -* [QDBM](http://fallabs.com/qdbm/) -* [Bitcask](https://github.com/basho/bitcask) -* [eLevelDB](https://github.com/basho/eleveldb) -* [BerkleyDB](http://www.oracle.com/technetwork/products/berkeleydb/overview/index.html) -* ... Requirements ------------ -* Erlang R14B04+ * GCC 4.2+ or MS VisualStudio 2010+ Build ----- $ make API --- - The following functions were implemented: +The main purpose of this package is to provide an Erlang API for this excellent BTREE implementation. Secondly to build an alternative Riak/KV [backend](http://wiki.basho.com/Storage-Backends.html) and Riak's AAE feature based on this. Finally it'd be nice to build an ETS-compatible API (ala "lets" for LevelDB) to ease adoption in other places where DETS is just not up to the task. + +Requirements +------------ +* Erlang R14B04+ +* GCC 4.2+ or MS VisualStudio 2010+ + +Build +----- + +$ make + + +API +--- + +The following functions were implemented: * `open/1`: equivalent to `emdb:open(DirName, 10485760)`. * `open/2`: equivalent to `emdb:open(DirName, 10485760, 0)`. @@ -22,13 +31,14 @@ But this module could also be used as a general key-value store to replace: * `put/2`: inserts Key with value Val into the database. Assumes that the key is not present, 'key_exit' is returned otherwise. * `get/1`: retrieves the value stored with Key in the database. * `del/1`: Removes the key-value with key Key from database. -* `update/2`: inserts Key with value Val into the database if the key is not present, otherwise updates Key to value Val. +* `update/2` or `upd/2`: inserts Key with value Val into the database if the key is not present, otherwise updates Key to value Val. * `drop/1`: deletes all key-value pairs in the database. Usage ----- +``` $ make $ ./start.sh %% create a new database @@ -82,32 +92,32 @@ $ ./start.sh ... 17> q(). - +``` #### Note: -The code below creates a new database with **80GB** MapSize, **avoid fsync** -after each commit (for max speed) and use the experimental **MDB_FIXEDMAP**. +The code below creates a new database with **80GB** MapSize, **avoids fsync** after each commit (for an "ACI" but not "D" database we trade durability for speed) and uses the experimental **MDB_FIXEDMAP**. +``` {ok, Handle} = emdb:open("/tmp/emdb2", 85899345920, ?MDB_NOSYNC bor ?MDB_FIXEDMAP). +``` Performance ----------- -For maximum speed, this library use only binaries for both keys and values. - -See the impressive [microbench](http://highlandsun.com/hyc/mdb/microbench/) against: +See the [microbench](http://highlandsun.com/hyc/mdb/microbench/) against: * Google's LevelDB (which is slower and can stall unlike Basho's fork of LevelDB) * SQLite3 * Kyoto TreeDB * BerkeleyDB 5.x -MDB performs better on 64-bit arch. +MDB performs mmap's the database, so unless your dataset is < 2^32 bytes you'll +need to run on a 64-bit arch system. Supported Operating Systems -------------- -Should work on 32/64-bit architectures: +Should work on: * Linux * OSX @@ -124,13 +134,24 @@ TODO * basho_bench driver * EQC, PULSE testing * Key expirey -* Atomic group commit (for 2i) - -Volunteers are always welcome! +* renaming + * emdb -> lmdb + * emdb.c -> lmdb_nif.c +* improve stats +* txn API +* cursor API +* config +* use async_nif affinity +* riak_kv backend + * use dups + * 2i +* aae alternative Status ------ +Work in progress, not production quality and not supported by Basho Technologies. + LICENSE -------