README.md

A erlang key/vlaue storage-engine based on LMDB.

API

every key-value must be in a named sub-db

• open/1 : equivalent to lmdb:open(DirName, 10485760)
• close/1: closes the lmdb database
• ls/1: list all sub-db
• put/3: inserts/update Key with value Val into the sub-db
• get/2: retrieves the value stored with Key in the sub-db
• range/3: retrives the key-value pairs in the range [From...) in the sub-db
• range/4: retrives the key-value pairs between the range [From,To] in the sub-db
• del/2: Removes the key-value pair with key from the sub-db
• count/2: Count the key-value number for the sub-db
• drop/2: deletes all key-value pairs in the sub-db.

the 1st argument is always a reference as handle for lmdb database; the 2nd argument is a {Subdb, Key} tuple, or a single SubDB string/bitstring;

when put the FIRST data item in a sub-db, the key type determine the sub-db's key type;

• if key is a integer, it means a integer-key sub-db;
• if key is a string, it means a binary-key sub-db;

Usage

$ make app shell

%% open or create a lmdb database
1> D = elmdb:open("./testdb").

%% insert the key <<"a">> with value <<"1">> into sub-db "layer1"
2> elmdb:put(D, {"layer1", <<"a">>}, <<"1">>).

%% insert the integer key 789 with value <<"789">> into sub-db "layer2"
3> elmdb:put(D, {"layer2", 789}, <<"789">>).

%% retrieve the value for key <<"a">> in sub-db "layer1"
4> elmdb:get(D, {"layer1", <<"a">>}).

%% retrieve the value by id=789, from sub-db "layer2"
5> elmdb:get(D, {"layer2", 789}).

%% list all sub-db
6> elmdb:ls(D).

%% count the data-item number of sub-db "layer1"
7> elmdb:count(D, "layer1")

%% delete key <<"a">> from sub-db "layer1"
8> elmdb:del(D, {"layer1", <<"a">>}).

%% drop sub-db "layer2"
9> elmdb:drop(D, "layer2").

%% close lmdb explicitly, not necessary because of garbage-collection
10> lmdb:close(D).