level-sublevel

level-sublevel

Separate sections of levelup, with hooks!

This module allows you to create seperate sections of a levelup database, kinda like tables in an sql database, but evented, and ranged, for real-time changing data.

Stability

Unstable: Expect patches and features, possible api changes.

This is module is working well, but may change in the future as it's use is futher explored.

Example

var LevelUp = require('levelup')
var Sublevel = require('level-sublevel')

var db = Sublevel(LevelUp('/tmp/sublevel-example'))
var sub = db.sublevel('stuff')

//put a key into the main levelup
db.put(key, value, function () {
  
})

//put a key into the sub-section!
sub.put(key2, value, function () {

})

Sublevel prefixes each subsection so that it will not collide with the outer db when saving or reading!

Hooks

Hooks are specially built into Sublevel so that you can do all sorts of clever stuff, like generating views or logs when records are inserted!

Records added via hooks will be atomically with the triggering change.

Hooks Example

Whenever a record is inserted, save an index to it by the time it was inserted.

var sub = db.sublevel('SEQ')

db.pre(function (ch, add) {
  add({
    key: ''+Date.now(), 
    value: ch.key, 
    type: 'put',
    prefix: sub //NOTE pass the destination db to add
               //and the value will end up in that subsection!
  })
})

db.put('key', 'VALUE', function (err) {

  //read all the records inserted by the hook!

  sub.createReadStream()
    .on('data', console.log)

})

Notice that sub is the second argument to add, which tells the hook to save the new record in the sub section.

Batches

In sublevel batches also support a prefix: subdb property, if set, this row will be inserted into that database section, instead of the current section.

var sub1 = db.sublevel('SUB_1')
var sub2 = db.sublevel('SUM_2')

sub.batch([
  {key: 'key', value: 'Value', type: 'put'},
  {key: 'key', value: 'Value', type: 'put', prefix: sub2},
], function (err) {...})

License

MIT