add prefixes to keys on put, and decode them on get

Author: Benjamin Forster

index.js

@@ -6,6 +6,7 @@ const events = require('events')
 const SparqlIterator = require('sparql-iterator')
 
 const utils = require('./lib/utils')
+const prefixes = require('./lib/prefixes')
 const Variable = require('./lib/Variable')
 const HyperdbReadTransform = require('./lib/HyperdbReadTransform')
 const JoinStream = require('./lib/JoinStream')
@@ -37,6 +38,24 @@ inherits(Graph, events.EventEmitter)
 
 Graph.prototype.v = (name) => new Variable(name)
 
+Graph.prototype.prefixes = function (callback) {
+  // should cache this somehow
+  const prefixStream = this.db.createReadStream(prefixes.PREFIX_KEY)
+  utils.collect(prefixStream, (err, data) => {
+    if (err) return callback(err)
+    var names = data.reduce((p, nodes) => {
+      var data = prefixes.fromNodes(nodes)
+      p[data.prefix] = data.uri
+      return p
+    }, {})
+    callback(null, names)
+  })
+}
+
+Graph.prototype.addPrefix = function (prefix, uri, cb) {
+  this.db.put(prefixes.toKey(prefix), uri, cb)
+}
+
 Graph.prototype.getStream = function (triple, opts) {
   const stream = this.db.createReadStream(utils.createQuery(triple))
   return stream.pipe(new HyperdbReadTransform(this.db, opts))

lib/utils.js

@@ -1,4 +1,5 @@
 const Variable = require('./Variable')
+const prefixes = require('./prefixes')
 
 const defs = {
   spo: ['subject', 'predicate', 'object'],
@@ -22,15 +23,6 @@ function collect (stream, cb) {
   stream.once('end', cb.bind(null, null, res))
 }
 
-function namespaceBlankVariables (triple) {
-  Object.keys(triple).forEach((key) => {
-    if (triple[key].startsWith && triple[key].startsWith('_:')) {
-      triple[key] = triple[key].replace(/^_:/, 'hg:')
-    }
-  })
-  return triple
-}
-
 function filterTriple (triple) {
   const filtered = {}
   defs.spo.forEach((key) => {
@@ -43,13 +35,13 @@ function filterTriple (triple) {
 
 function escapeKeyValue (value) {
   if (typeof value === 'string' || value instanceof String) {
-    return value.replace(/(\/)/g, '%2F')
+    return prefixes.toPrefixed(value, prefixes.DEFAULT_PREFIXES).replace(/(\/)/g, '%2F')
   }
   return value
 }
 
 function unescapeKeyValue (value) {
-  return value.replace(/%2F/g, '/')
+  return prefixes.fromPrefixed(value.replace(/%2F/g, '/'), prefixes.DEFAULT_PREFIXES)
 }
 
 function decodeKey (key) {
@@ -86,13 +78,12 @@ function encodeKeys (triple) {
 }
 
 function generateBatch (triple, action) {
-  const namespacedTriple = namespaceBlankVariables(triple)
   if (!action) action = 'put'
   var data = null
   if (action === 'put') {
     data = JSON.stringify(extraDataMask(triple))
   }
-  return encodeKeys(namespacedTriple).map(key => ({
+  return encodeKeys(triple).map(key => ({
     type: 'put', // no delete in hyperdb so just putting nulls
     key: key,
     value: data

test/fixture/foaf.js

@@ -38,4 +38,4 @@ module.exports = [{
   subject: 'davide',
   predicate: 'age',
   object: 70
-}];
+}]

test/sparql.spec.js

@@ -45,7 +45,7 @@ describe('hypergraph.queryStream', () => {
     it('performs CONSTRUCT query type with UNION operator', (done) => {
       console.time('query')
       var expected = [
-        { subject: 'hg:b0_b',
+        { subject: 'hg://b0_b',
           predicate: 'http://www.w3.org/2001/vcard-rdf/3.0#N',
           object: '_:b0' },
         { subject: '_:b0',
@@ -54,7 +54,7 @@ describe('hypergraph.queryStream', () => {
         { subject: '_:b0',
           predicate: 'http://www.w3.org/2001/vcard-rdf/3.0#familyName',
           object: '"Hacker"' },
-        { subject: 'hg:b0_a',
+        { subject: 'hg://b0_a',
           predicate: 'http://www.w3.org/2001/vcard-rdf/3.0#N',
           object: '_:b1' },
         { subject: '_:b1',

test/utils.spec.js

@@ -2,42 +2,44 @@
 const expect = require('chai').expect
 const utils = require('../lib/utils')
 
-describe('encodeKey', () => {
-  it('generates a unique index key for a triple (spo)', () => {
-    var key = utils.encodeKey('spo', { subject: 'a-subject', object: 'a-object', predicate: 'a-predicate' })
-    expect(key).to.eql('spo/a-subject/a-predicate/a-object')
-  })
-  it('generates a unique index key for a triple (spo)', () => {
-    var key = utils.encodeKey('sop', { subject: 'a-subject', object: 'a-object', predicate: 'a-predicate' })
-    expect(key).to.eql('sop/a-subject/a-object/a-predicate')
-  })
-  it('generates a unique index key for a triple (osp)', () => {
-    var key = utils.encodeKey('osp', { subject: 'a-subject', object: 'a-object', predicate: 'a-predicate' })
-    expect(key).to.eql('osp/a-object/a-subject/a-predicate')
-  })
+describe('util functions', () => {
+  describe('encodeKey', () => {
+    it('generates a unique index key for a triple (spo)', () => {
+      var key = utils.encodeKey('spo', { subject: 'a-subject', object: 'a-object', predicate: 'a-predicate' })
+      expect(key).to.eql('spo/a-subject/a-predicate/a-object')
+    })
+    it('generates a unique index key for a triple (spo)', () => {
+      var key = utils.encodeKey('sop', { subject: 'a-subject', object: 'a-object', predicate: 'a-predicate' })
+      expect(key).to.eql('sop/a-subject/a-object/a-predicate')
+    })
+    it('generates a unique index key for a triple (osp)', () => {
+      var key = utils.encodeKey('osp', { subject: 'a-subject', object: 'a-object', predicate: 'a-predicate' })
+      expect(key).to.eql('osp/a-object/a-subject/a-predicate')
+    })
 
-  it('escapes forward slashes in the triple', () => {
-    var key = utils.encodeKey('spo', { subject: 'a/subject' })
-    expect(key).to.eql('spo/a%2Fsubject/')
+    it('escapes forward slashes in the triple', () => {
+      var key = utils.encodeKey('spo', { subject: 'a/subject' })
+      expect(key).to.eql('spo/a%2Fsubject/')
+    })
   })
-})
 
-describe('decodeKey', () => {
-  it('generates a triple from a index key (spo)', () => {
-    var triple = utils.decodeKey('spo/a-subject/a-predicate/a-object')
-    expect(triple).to.eql({ subject: 'a-subject', object: 'a-object', predicate: 'a-predicate' })
-  })
-  it('generates a triple from a index key (spo)', () => {
-    var triple = utils.decodeKey('sop/a-subject/a-object/a-predicate')
-    expect(triple).to.eql({ subject: 'a-subject', object: 'a-object', predicate: 'a-predicate' })
-  })
-  it('generates a triple from a index key (osp)', () => {
-    var triple = utils.decodeKey('osp/a-object/a-subject/a-predicate')
-    expect(triple).to.eql({ subject: 'a-subject', object: 'a-object', predicate: 'a-predicate' })
-  })
+  describe('decodeKey', () => {
+    it('generates a triple from a index key (spo)', () => {
+      var triple = utils.decodeKey('spo/a-subject/a-predicate/a-object')
+      expect(triple).to.eql({ subject: 'a-subject', object: 'a-object', predicate: 'a-predicate' })
+    })
+    it('generates a triple from a index key (spo)', () => {
+      var triple = utils.decodeKey('sop/a-subject/a-object/a-predicate')
+      expect(triple).to.eql({ subject: 'a-subject', object: 'a-object', predicate: 'a-predicate' })
+    })
+    it('generates a triple from a index key (osp)', () => {
+      var triple = utils.decodeKey('osp/a-object/a-subject/a-predicate')
+      expect(triple).to.eql({ subject: 'a-subject', object: 'a-object', predicate: 'a-predicate' })
+    })
 
-  it('unescapes escaped /‘s from index key (spo)', () => {
-    var triple = utils.decodeKey('spo/a%2Fsubject/a%2Fpredicate/a%2Fobject')
-    expect(triple).to.eql({ subject: 'a/subject', object: 'a/object', predicate: 'a/predicate' })
+    it('unescapes escaped /‘s from index key (spo)', () => {
+      var triple = utils.decodeKey('spo/a%2Fsubject/a%2Fpredicate/a%2Fobject')
+      expect(triple).to.eql({ subject: 'a/subject', object: 'a/object', predicate: 'a/predicate' })
+    })
   })
 })