osm-p2p-db


> p2p database for open street map data

Table of Contents

- Install
- Usage
- API
- var osm = osmdb(opts)
- osm.create(doc, opts={}, cb)
- osm.put(id, doc, opts={}, cb)
- osm.del(id, opts={}, cb)
- osm.batch(rows, opts={}, cb)
- osm.get(id, opts={}, cb)
- osm.getByVersion(version, opts={}, cb)
- osm.query(q, opts, cb)
- osm.getReferrers(id, cb)
- osm.ready(cb)
- osm.close(cb)
- var rstream = osm.queryStream(q, opts)
- var rstream = osm.getChanges(changeset, cb)
- osm.on('error', function (err) {})
- osm.kv
- osm.log
- Browser
- Replication
- Architecture
- Contribute
- License

Install

``
npm install osm-p2p-db
`

Usage

` js
var hyperlog = require('hyperlog')

var level = require('level')
var db = {
log: level('/tmp/osm-p2p/log'),
index: level('/tmp/osm-p2p/index')
}
var fdstore = require('fd-chunk-store')
var storefile = '/tmp/osm-p2p/kdb'

var osmdb = require('osm-p2p-db')
var osm = osmdb({
log: hyperlog(db.log, { valueEncoding: 'json' }),
db: db.index,
store: fdstore(4096, storefile)
})

if (process.argv[2] === 'create') {
var value = JSON.parse(process.argv[3])
osm.create(value, function (err, key, node) {
if (err) console.error(err)
else console.log(key)
})
} else if (process.argv[2] === 'query') {
var q = process.argv.slice(3).map(csplit)
osm.query(q, function (err, pts) {
if (err) console.error(err)
else pts.forEach(function (pt) {
console.log(pt)
})
})
}

function csplit (x) { return x.split(',').map(Number) }
`

Now we can create a few nodes and search with a bounding box query:

`
$ mkdir /tmp/osm-p2p
$ node db.js create '{"type":"node","lat":64.6,"lon":-147.8}'
11892499690884077339
$ node db.js create '{"type":"node","lat":64.3,"lon":-148.2}'
1982521011513780909
$ node db.js create '{"type":"node","lat":64.5,"lon":-147.3}'
14062704270722785878
$ node db.js query 64.1,64.6 -148,-147
{ type: 'node',
lat: 64.5,
lon: -147.3,
id: '14062704270722785878',
version: 'e635d07b9fc0a9d048cdd5d9e97a44a19ba3a0b2a51830d1e3e0fadcb80935fc' }
`

We can make a way document that refers to a list of node documents:

`
$ node db.js create '{"type":"way","refs":
["11892499690884077339","1982521011513780909","14062704270722785878"]}'
14666931246975765366
`

When we query, any ways that have one or more nodes within the bounding box
will turn up in the results:

`
$ node db.js query 64.1,64.6 -148,-147
{ type: 'node',
lat: 64.5,
lon: -147.3,
id: '14062704270722785878',
version: 'e635d07b9fc0a9d048cdd5d9e97a44a19ba3a0b2a51830d1e3e0fadcb80935fc' }
{ type: 'way',
refs: [ '11892499690884077339', '1982521011513780909', '14062704270722785878' ],
id: '14666931246975765366',
version: 'f4fc0045e298ca4f9373fab78dee4f0561b4056dcd7975eb92f21d0a05e0eede' }
`

Terminology

- document: a map element, such a a node or way.
- document id, osm id: an identifier of a document at its latest known
version.
- version, version id: an identifier of a document *at a specific point in
time*.

API

` js
var osmdb = require('osm-p2p-db')
`

$3

Create a new osm instance with:

* opts.log - a [hyperlog][1] with a valueEncoding of json
* opts.db - a [levelup][2] instance to store index data
* opts.store - an [abstract-chunk-store][3] instance

You may optionally pass in a [hyperkv][4] instance as opts.kv, but otherwise
one will be created from the opts.log and opts.db.

You may safely delete the index database whenever you like. The index data is
automatically regenerated. This is very useful if there are breaking changes to
the index code or if the data becomes corrupted. The hyperlog contains the
source of truth.

[1]: https://npmjs.com/package/hyperlog
[2]: https://npmjs.com/package/levelup
[3]: https://npmjs.com/package/abstract-chunk-store

$3

Store a new document from doc. cb(err, id, node) fires with the generated
OSM id and the node from the underlying hyperlog.

Elements are node, way, and relation. Each element should have a type
property that contains the element type as a string.

* Nodes should have doc.lat and doc.lon coordinates.
* Ways should have an array of OSM keys as doc.refs.
* Relations should have an array member objects as doc.members.
Each member object has a member.type of the document pointed at by
member.ref and optionally a [member.role][7].

Another type of document is a changeset.
Each element should have a changeset property that refers to the id of a
changeset document.

It is recommended to use tags.comment to store free-form text describing the
changeset.

[7]: http://wiki.openstreetmap.org/wiki/Relation#Roles

$3

Replace a document at id with doc.

If the document didn't exist previously, it will be created.

The options opts are passed to the underlying [hyperkv][4] instance.

By default, hyperkv will merge the most recent known forks into a single fork.
To add modifications to a fork without merging the changes into other forks,
set opts.links to an array of only the single key you want to update.

[4]: https://npmjs.com/package/hyperkv

$3

Delete a document at id.

The options opts are passed to the underlying [hyperkv][4] instance.

cb(err, node) fires with the underlying node in the hyperlog.

$3

Atomically insert an array of documents rows.

Each row in rows should have:

* row.type - 'put' or 'del'
* row.key or row.id - the id of the document (generated if not specified)
* row.links - array of links to ancestor keys
* row.value - for puts, the value to store

$3

Get a document as cb(err, docs) by its OSM id.

docs is an object mapping hyperlog hashes to current document values. If a
document has been deleted, it will only have the properties { id: ,
version: , deleted: true}.

$3

Fetch a specific OSM element by its version string. Returns null if not found,
otherwise the single element.

$3

Query for all nodes, ways, and relations in the query given by the array q.
Queries are arrays of [[minLat,maxLat],[minLon,maxLon]] specifying a bounding
box.

cb(err, res) fires with an array of results res. Each result is the document
augmented with an id property and a version property that is the hash key
from the underlying hyperlog. If a document has been deleted, it will only have
the properties { id: , version: , deleted: true}.

Optionally:

* opts.order - set to 'type' to order by type: node, way, relation

$3

Fetch a list of all OSM ways and relations that refer to the element with ID
id. For a node, this can be ways or relations. For a way or relation, this can
only be relations.

Objects of the following form are returned:

`js
{
id: '...',
version: '...'
}
`

$3

Runs the callback cb once all of osm's internal indexes are caught up to the latest data. cb is called exactly once.

$3

Closes the Level and chunk-store backends associated with the database. cb is
called upon completion.

$3

Return a readable object stream rstream of query results contained in the
query q. Queries are arrays of [[minLat,maxLat],[minLon,maxLon]] specifying
a bounding box.

Each object in the stream is a document augmented with an id property and a
version property that is the hash key from the underlying hyperlog.

Optionally:

* opts.order - set to 'type' to order by type: node, way, relation

$3

Get the list of document version ids in a changeset by a changeset id
changeset.

If a callback is provided, the version ids are returned as cb(err, versions).
Without callback, the versions are provided by the returned readable object
stream rstream.

$3

Handle errors from the underlying indexes with the 'error' event.

$3

You can get at the [hyperkv][4] instance directly to perform more operations
using osm.kv.

For example, you can use osm.kv.createReadStream() to list all the id/value
pairs in the database.

$3

The [hyperlog][1] instance is available as the opts.log property if you need
to get at it directly later.

Browser

To use this module in the browser, use [level-browserify][5] to provide the
opts.db instance and [idb-chunk-store][6] as the opts.store. Each of these
is backed by IndexedDB, a native browser storage interface.

[5]: https://npmjs.com/package/level-browserify
[6]: https://www.npmjs.com/package/idb-chunk-store

Replication

If you have two hyperlogs log0 and log1, pipe them together and back again
to replicate:

`
var r0 = log0.replicate()
var r1 = log1.replicate()
r0.pipe(r1).pipe(r0)
`

Insert additional streams as necessary for network transports if the logs live
in different processes or machines.

If both logs have made edits to the same IDs, multiple records will appear for
the same ID in the results. To merge these "conflicts" back into a single value,
use osm.put(id, doc, cb)` to store the desired document value.

Architecture

Read about the internal architecture.

Contribute

If you would like to support our work, or if you have ideas about how to use and
adapt osm-p2p for your own project, then please dive in. Open an
issue with a bug report or
feature request, or send us a pull
request with a bug-fix or new
feature.

We need help right now adding tests and fixing edge-cases with
osm-p2p-server and increasing
compatibility with other OSM tools such as
JOSM.

License

BSD (c) 2016, Digital Democracy.