feat: triple store support for @cap-js/sqlite

lib/knowledge-graph/SQLiteService.js

@@ -0,0 +1,42 @@
+import SQLiteService from '@cap-js/sqlite'
+import TripleStore from './triplestore.js'
+import cds from '@sap/cds'
+
+export default class SQLiteServiceKG extends SQLiteService {
+  init() {
+    this._tripleStore ??= new TripleStore()
+    return super.init()
+  }
+
+  get factory() {
+    const factory = super.factory
+    factory._create = factory.create
+    factory.create = async (tenant) => {
+      const dbc = await factory._create(tenant)
+      dbc.function('sparql_table', { deterministic: true }, (query) => this._tripleStore.query(query, 'accept: json').RESPONSE)
+      return dbc
+    }
+    return factory
+  }
+
+  onPlainSQL(req, next) {
+    const { query } = req
+    if (/^\s*CALL SPARQL_EXECUTE/i.test(query)) {
+      const [_, sparql, headers] = /SPARQL_EXECUTE\s*\(\s*'((?:[^']|'')*)'\s*,\s*'((?:[^']|'')*)'\s*,\s*\?\s*,\s*\?\s*\)/.exec(query)
+      return this._tripleStore.query(sparql, headers)
+    }
+    return super.onPlainSQL(req, next)
+  }
+
+  static CQN2SQL = class CQN2SQLKG extends SQLiteService.CQN2SQL {
+    static Functions = {
+      ...SQLiteService.CQN2SQL.Functions,
+      sparql_table: (query, headers) => {
+        const split = query.val.split('?').slice(1).map(m => m.trim().split(/\s+/))
+        const last = split.findIndex(s => s.length > 1)
+        const cols = split.slice(0, last + 1).map(c => c[0])
+        return `(SELECT ${cols.map(c => `value->>'$.${c}.value' as "${c}"`)} FROM json_each(sparql_table(${query})->'$.results.bindings'))`
+      }
+    }
+  }
+} 

lib/knowledge-graph/triplestore.js

@@ -0,0 +1,52 @@
+let oxigraph
+try {
+  oxigraph = await import('oxigraph')
+} catch (err) {
+  if (err.code !== 'ERR_MODULE_NOT_FOUND') throw err
+}
+
+import { pipeline } from 'node:stream/promises'
+import { text } from 'node:stream/consumers'
+import { createReadStream } from 'node:fs'
+import { createGunzip } from 'node:zlib'
+
+import cds from '@sap/cds'
+const { path } = cds.utils
+
+export default class TripleStore extends (oxigraph?.Store || (class Store { })) {
+
+  async load(file, graph) {
+    this._ready()
+
+    const graphNode = graph == null
+      ? oxigraph.defaultGraph()
+      : oxigraph.namedNode(graph)
+
+    const steps = [createReadStream(file)]
+    let ext = path.extname(file)
+    if (ext.endsWith('.gz')) {
+      steps.push(createGunzip())
+      ext = path.extname(file.slice(0, -3))
+    }
+    steps.push(text)
+    return super.load(await pipeline(...steps), { format: ext.slice(1), to_graph_name: graphNode })
+  }
+
+  query(query, headers) {
+    this._ready()
+
+    const accept = (headers?.split('\r\n')
+      .find(header => /accept:/i.test(header)) ?? 'accept:application/sparql-results+json')
+      .replace(/accept:/i, '').trim() // strip HTTP header formatting
+
+    // oxigraph does not support LOAD queries
+    if (/^\w*LOAD/i.test(query)) {
+      const [_, file, graph] = /LOAD <([^>]*)> INTO GRAPH <([^>]*)>/.exec(query)
+      return this.load(file, graph)
+    }
+    const RESPONSE = super.query(query, { use_default_graph_as_union: true, results_format: accept })
+    return { RESPONSE }
+  }
+
+  _ready() { if (!oxigraph) throw new Error(`Cannot find 'oxigraph'. Make sure to install it with 'npm i oxigraph'`) }
+}

package.json

@@ -25,7 +25,13 @@
     "@cap-js/cds-types": "^0.16.0"
   },
   "peerDependencies": {
-    "@sap/cds": ">=9"
+    "@sap/cds": ">=9",
+    "oxigraph": "^0.5.9"
+  },
+  "peerDependenciesMeta": {
+    "oxigraph": {
+      "optional": true
+    }
   },
   "engines": {
     "node": ">=20.0.0"
@@ -49,6 +55,12 @@
           "vcap": {
             "label": "aicore"
           }
+        },
+        "sql": {
+          "[development]": {
+            "kind":"sqlite",
+            "impl": "@cap-js/ai/lib/knowledge-graph/SQLiteService.js"
+          }
         }
       }
     }

tests/bookshop/db/data/cap.ttl

@@ -0,0 +1,17 @@
+@prefix cap: <https://cap.cloud.sap/> .
+
+# CAP sample turtle file
+
+cap:Service cap:label "Service" .
+cap:DatabaseService a cap:Service .
+cap:DatabaseService cap:label "Database Service" .
+cap:SQLiteService a cap:DatabaseService .
+cap:SQLiteService cap:name "SQLite Service" .
+cap:SQLiteService cap:label "SQLite Service" .
+cap:HANAService cap:implementedBy cap:cap-js-sqlite .
+cap:HANAService a cap:DatabaseService .
+cap:HANAService cap:name "HANA Service" .
+cap:HANAService cap:label "HANA Service" .
+cap:HANAService cap:implementedBy cap:cap-js-hana .
+cap:cap-js-hana cap:label "@cap-js/hana" .
+cap:cap-js-sqlite cap:label "@cap-js/sqlite" .

tests/bookshop/test/knowledge-graph.test.js

@@ -0,0 +1,39 @@
+import TripleStore from '../../../lib/knowledge-graph/triplestore.js'
+import cds from '@sap/cds'
+
+describe('Knowledge Graph', () => {
+  const { expect } = cds.test()
+
+  beforeEach(() => { cds.db._tripleStore = new TripleStore() })
+
+  describe('sparql', () => {
+    const file = '/db/data/cap.ttl'
+    const graph = 'https://cap.cloud.sap/example'
+
+    test('LOAD .ttl', async () => {
+      await cds.run(`CALL SPARQL_EXECUTE('LOAD <${cds.root}${file}> INTO GRAPH <${graph}>','', ?, ?)`)
+      const { results: { bindings: { 0: { count } } } } = JSON.parse(cds.db._tripleStore.query('SELECT (COUNT(?p) AS ?count) WHERE { ?s ?p ?o . }').RESPONSE)
+      expect(count).property('value').equal('13')
+    })
+
+    test('LOAD .ttl.gz', async () => {
+      await cds.run(`CALL SPARQL_EXECUTE('LOAD <${cds.root}${file}.gz> INTO GRAPH <${graph}>','', ?, ?)`)
+      const { results: { bindings: { 0: { count } } } } = JSON.parse(cds.db._tripleStore.query('SELECT (COUNT(?p) AS ?count) WHERE { ?s ?p ?o . }').RESPONSE)
+      expect(count).property('value').equal('13')
+    })
+
+    test('SELECT', async () => {
+      const query = { SELECT: { from: cds.ql.func('sparql_table', 'SELECT ?subject ?predicate ?object WHERE { ?subject ?predicate ?object .}') } }
+
+      const empty = await cds.run(query)
+      expect(empty).property('length').eq(0)
+
+      const res = await cds.run(`CALL SPARQL_EXECUTE('LOAD <${cds.root}${file}.gz> INTO GRAPH <${graph}>','', ?, ?)`)
+      const loaded = await cds.run(query)
+      expect(loaded).property('length').eq(13)
+      expect(loaded).property('0').property('subject')
+      expect(loaded).property('0').property('predicate')
+      expect(loaded).property('0').property('object')
+    })
+  })
+})