Object LevelDB

LevelDB database objects

Used to create and manage dictionary objects, the creation method:

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var db = require("db");
var test = new db.openLevelDB("test.db");

Inheritance relationship

Member function

has

Check whether there is data with the specified key value in the database

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Boolean LevelDB.has(Buffer key) async;

Call parameters:

• key: Buffer, Specify the key value to be checked

Return result:

• Boolean, Return whether the key value exists

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get

Query the value of the specified key

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Buffer LevelDB.get(Buffer key) async;

Call parameters:

• key: Buffer, Specify the key value to be queried

Return result:

• Buffer, Returns the value corresponding to the key value, if it does not exist, returns null

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mget

Query a set of specified key values

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NArray LevelDB.mget(Array keys);

Call parameters:

• keys: Array, specify the key value array to be queried

Return result:

• NArray, Returns an array containing key values

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set

Set a key value data, insert new data if the key value does not exist

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LevelDB.set(Buffer key,
    Buffer value) async;

Call parameters:

• key: Buffer, Specify the key value to be set
• value: Buffer, Specify the data to be set

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mset

Set a set of key-value data, insert new data if the key-value does not exist

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LevelDB.mset(Object map);

Call parameters:

• map: Object, specify the key-value data dictionary to be set

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mremove

Delete a set of specified key values

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LevelDB.mremove(Array keys);

Call parameters:

• keys: Array, specify the key value array to be deleted

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remove

Delete all values ​​of the specified key value

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LevelDB.remove(Buffer key) async;

Call parameters:

• key: Buffer, Specify the key value to be deleted

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forEach

Enumerate all key-value pairs in the database

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LevelDB.forEach(Function func);

Call parameters:

• func: Function, enumeration callback function

The callback function has two parameters, (value, key)

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var db = require("db");
var test = new db.openLevelDB("test.db");

test.forEach(function(value, key) {
    ...
});

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between

Enumerate the key-value pairs between from and to in the database

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LevelDB.between(Buffer from,
    Buffer to,
    Function func);

Call parameters:

• from: Buffer, The minimum key value of the enumeration, this key value is included in the enumeration
• to: Buffer, The maximum key value of the enumeration, this key value is not included in the enumeration
• func: Function, enumeration callback function

The callback function has two parameters, (value, key)

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var db = require("db");
var test = new db.openLevelDB("test.db");

test.between("aaa", "bbb", function(value, key) {
    ...
});

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begin

Start a transaction on the current database

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LevelDB LevelDB.begin();

Return result:

• LevelDB, Return an open transaction object

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commit

Commit the current transaction

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LevelDB.commit();

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close

Close the current database connection or transaction

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LevelDB.close() async;

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toString

Returns the string representation of the object, generally returns "[Native Object]", the object can be re-implemented according to its own characteristics

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String LevelDB.toString();

Return result:

• String, Returns the string representation of the object

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toJSON

Returns the JSON format representation of the object, generally returns a collection of readable attributes defined by the object

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Value LevelDB.toJSON(String key = "");

Call parameters:

• key: String, unused

Return result:

• Value, Returns a value containing JSON serializable