level-update v0.1.0
level-update
A levelup plugin that can be used implements conditional updates.
The name of this module may change if I think of something better.
Example
level-update' intercepts database mutations (
put, del, batch),
retrives the current value for that key, and passed the old value,
and the new value to a user supplied
merge` function.
The merge function can be used a number of ways - if it throws an error, the put/del/batch will callback an error.
If it returns a string
or Buffer
, then that value will be saved instead.
And if it returns something else, then the new value will be saved as normal.
var Update = require('level-update')
Update(db, function merge (oldValue, newValue) {
})
db.put('key', 'VALUE', function (err) {
//this will be intercepted
})
If oldValue
is null, the operation is a create.
If newValue
is null, the operation is a delete.
Otherwise, the operation is an update.
Use as validation / Authentication.
check that new value is correct, or throw error.
Use for versioning
check that new value comes after old, or merge concurrent updates.
License
MIT