https://github.com/hackergrrl/hyperdb-index
Build a realtime index over a hyperdb.
https://github.com/hackergrrl/hyperdb-index
Last synced: 6 months ago
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Build a realtime index over a hyperdb.
- Host: GitHub
- URL: https://github.com/hackergrrl/hyperdb-index
- Owner: hackergrrl
- Created: 2017-09-07T21:48:13.000Z (almost 8 years ago)
- Default Branch: master
- Last Pushed: 2018-02-28T00:30:30.000Z (over 7 years ago)
- Last Synced: 2024-12-28T21:45:38.281Z (6 months ago)
- Language: JavaScript
- Homepage:
- Size: 44.9 KB
- Stars: 27
- Watchers: 2
- Forks: 3
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
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README
# hyperdb-index
> Build an incremental index over a [hyperdb][hyperdb].
*If you're planning on using LevelDB for storage, consider the wrapper module
[hyperdb-index-level](https://github.com/noffle/hyperdb-index-level).*
Depends on `[email protected]` or later for the `createHistoryStream` API.
## Usage
Let's build an index that tracks all `node`s in a [spatial point
store](https://github.com/noffle/grid-point-store), for fast bounding box
queries:
```js
var index = require('hyperdb-index')
var hyperdb = require('hyperdb')
var ram = require('random-access-memory')
var GeoStore = require('grid-point-store')
var memdb = require('memdb')
//------------------------------------------------------------------------------
var db = hyperdb(ram, { valueEncoding: 'json' })
var geo = GeoStore(memdb())
var idx = index(db, {
processFn: processFn,
getVersion: getVersion,
setVersion: setVersion
})
var pending = 0
for (var i = 0; i < 5; i++) {
pending++
db.put('/nodes/' + i, { type: 'node', lat: i, lon: -i*2 }, function () {
if (!--pending) query()
})
}
function query () {
idx.ready(function () {
geo.query([[-10, -10], [10, 10]], function (err, nodes) {
console.log('query', nodes)
})
})
}
//------------------------------------------------------------------------------
var now = null
function getVersion (cb) {
cb(null, now)
}
function setVersion (version, cb) {
now = version
cb(null)
}
function processFn (cur, prev, next) {
if (cur.value.type === 'node') {
var v = parseInt(cur.name.split('/')[cur.name.split('/').length - 1])
console.log('process', cur.value)
geo.insert([cur.value.lat, cur.value.lon], v, next)
} else {
next(null)
}
}
```
outputs
```
process { type: 'node', lat: 0, lon: 0 }
process { type: 'node', lat: 4, lon: -8 }
process { type: 'node', lat: 3, lon: -6 }
process { type: 'node', lat: 1, lon: -2 }
process { type: 'node', lat: 2, lon: -4 }
query [ { lat: 4, lon: -8, value: 4 },
{ lat: 3, lon: -6, value: 3 },
{ lat: 2, lon: -4, value: 2 },
{ lat: 1, lon: -2, value: 1 },
{ lat: 0, lon: 0, value: 0 } ]
```
So here `hyperdb-index` is acting like a bridge between the raw point data in
`hyperdb` and the much more efficient point storage module `grid-point-store`.
## API
```js
var index = require('hyperdb-index')
```
### var idx = index(db, opts)
Create a new index. `db` is a [hyperdb][hyperdb] instance.
It is the module consumer's responsibility to store the indexer's version of
what entry it's indexed `db` up to. The module consumer controls this by
implementing the functions `opts.getVersion` and `opts.setVersion` (see
below).
Valid `opts` include:
- `opts.processFn` (required): a function to be called to process a new entry in
`db`. The expected function signature is `function (kv, oldKv, next)`, where
`kv` is of the form `{ key: '...', value: {} }`, `oldKv` is its previous value
(`null` if none), and `next` is a callback to call when processing of that
key-value pair is complete.
- `opts.getVersion` (required): a function that will be called to retrieve the
current version of the [hyperdb][hyperdb]. It has the signature `function
(cb)` and expects a [hyperdb version
buffer](https://github.com/mafintosh/hyperdb/#dbversioncb).
- `opts.setVersion` (required): a function that will be called to store the
current version of the hyperdb. It has the signature `function (version,
cb)`. Call `cb` once you've stored the version object.
- `opts.prefix` (optional): a key prefix to index. If not given, the root key
`'/'` is assumed.
### idx.ready(cb)
Registers the callback `cb` to fire when the indexes have "caught up" to the
latest known change in the hyperdb. The `cb` function fires exactly once. You
may call `idx.ready()` multiple times with different functions.
## Install
With [npm](https://npmjs.org/) installed, run
```
$ npm install hyperdb-index
```
## See Also
- [hyperlog-index](https://github.com/substack/hyperlog-index)
## License
ISC
[hyperdb]: https://github.com/mafintosh/hyperdb