Leveldb-addon
Leveldb addon for Node.js, supports synchronous and asynchronous invocation, and supports event emitter
FEATURES
- Support synchronization method call Leveldb, code logic more clear
- Also supports asynchronous method call Leveldb to make running more efficient
- Asynchronous calls use Promise to make the code clearer
INSTALLATION
npm install l-db --saveAPI
-
Properties
-
Ldb.prototype.location Reflects the string of the database path
-
Ldb.prototype.isOpen Reflects the boolearn of the database is available
-
Ldb.prototype.stateCode Reflects the number of the databease status , whenever a database change changes
Methods
- Ldb.prototype.open(location, [options])
- Ldb.prototype.close()
- Ldb.prototype.put( key, value ) or Ldb.prototype.put( json ) return Boolean when execution succeeds return true
- Ldb.prototype.del( key ) or Ldb.prototype.del( keys ) return Boolean when execution succeeds return true
- Ldb.prototype.get( key ) or Ldb.prototype.get( keys ) return [values]
- Ldb.prototype.forEach( callback, [iteratorOptions] )
- Ldb.prototype.asyncPut() return Promise object
- Ldb.prototype.asyncDel() return Promise object
- Ldb.prototype.asyncGet() return Promise object
- Ldb.prototype.asyncForEach( callback, [iteratorOptions] )
- Ldb.prototype.getIterator([iteratorOptions]) return Ldb.Iterator
- Ldb.prototype.addListener( type, callback, once )
- Ldb.prototype.removeListener( type, callback )
- Ldb.prototype.match(prefix, offset)
-
-
Ldb.open(location, options) return Ldb instance
-
- start
- end
- prefix
- reverse
- snapshot: default true
-
- Iterator.read() If the iterator is valid to return itself, the invalid returns undefined
- Iterator.key
- Iterator.value
- Iterator.isEnd
- iterator.break() release iterator
new Ldb([options])
const Ldb = require('l-db');
let options = {
// base settings
"location" : './test.db',
"writeSync" : false,
"readFillCache" : true,
// Levedb default settings
"createIfMissing" : true,
"errorIfExists" : false,
"compression" : true,
"writeBufferSize" : 4194304,
"blockSize" : 4096,
"maxOpenFiles" : 1000,
"blockRestartInterval" :16,
"maxFileSize" : 2097152,
"block_cache" : 8388608,
"filterPolicy" : 10,
// EventListener
"onReady" : ()=>{},
"onCreate" : ()=>{},
"onChanged" : ()=> {},
"onError" : ()=>{},
"onClosed" : ()=>{}
};
let ldb = new Ldb(options);For information about setting items, see the Leveldb documentation
Ldb.prototype.open(location, [options])
ldb.open('./test.db', {});Ldb.prototype.close()
ldb.close();Ldb.prototype.put( key, value ) or Ldb.prototype.put( json )
if (ldb.put("abc", 123)) {
console.log('ok');
}
ldb.put({
"abc": null, // delete abc
"def": 456,
"ghi": [7, 8, 9]
});Ldb.prototype.del( key ) or Ldb.prototype.del( keys )
ldb.del("abc");
ldb.del(["abc", "def"]);Ldb.prototype.get( key ) or Ldb.prototype.get( keys )
let value = ldb.get("abc");
let value_json = ldb.get(["abc", "def", "ghi"]);Ldb.prototype.forEach( callback, [iteratorOptions] )
ldb.put({"a1": 1, "a2": 2, "b1": 3, "b2": 4, "c1": 5, "c2" : 6, "d.1": 7, "d.2": 8});
ldb.forEach((iter)=>{
if(!/b/.test(iter.key)){
iter.break();
}else{
console.log(iter.key, iter.value);
}
});
let callback = (iter) => {console.log(iter.key, ":", iter.value);}
ldb.forEach(callback, {start: "b"});
// print: b1:3, b2:4, c1:5, c2:6, d.1:7, d.2:8
ldb.forEach(callback, {start: "b", end:"c"});
// print: b1:3, b2:4
ldb.forEach(callback, {start: "c", end:"b", reverse:true});
// print: c1:5, c2:6
ldb.forEach(callback, {prefix: "d."});
// print: d.1:7, d.2:8
Ldb.prototype.asyncPut()
ldb.asyncPut("abc", 123).then(()=>{
...
}).catch((error)=>{
console.log(error);
});(async ()=>{
await ldb.asyncPut("abc", 1234);
})()Ldb.prototype.asyncDel()
ldb.asyncDel("abc").then(()=>{
...
});(async ()=>{
await ldb.asyncDel("abc")
})()Ldb.prototype.asyncGet()
ldb.asyncGet("abc", 123).then((value)=>{
console.log(value)
});(async ()=>{
let value = await ldb.asyncGet("abc");
})()Ldb.prototype.asyncForEach( callback, [iterator_options] )
ldb.forEach((iter)=>{
console.log(iter.key, iter.value);
});Ldb.prototype.getIterator([iterator_options])
let iter = ldb.getIterator({start: "b"});
while(iter.read()){
console.log(iter.key, iter.value);
}Ldb.prototype.addListener( type, callback, once )
- type :
-
readyTrigger event after database open -
createTriggers an event when the database is created -
changedTriggers an event when the put or del operation is executed -
errorTriggers an event when an error occurs -
closedTrigger event after database shutdown
-
ldb.addEventListener("changed", (info)=>{
console.log( info.from, info.key );
// print: put "abc"
});
ldb.put("abc", 123);Ldb.prototype.removeListener( type, callback )
ldb.removeEventListener("ready", func);Ldb.open(location, options)
let ldb = Ldb.open("./test.db")Ldb.destroy(location)
Ldb.destroy("./test.db")Ldb.repair(location)
Ldb.repair("./test.db")Iterator Options
let options = {
"start":"a",
"end": "b",
"prefix": "c",
"reverse": true,
"limit":
}
