feat: add support for REDUCED

engines/config-query-sparql-incremental/config/query-operation/actors.json

@@ -12,6 +12,7 @@
     "ccqs:config/query-operation/actors/query/minus.json",
     "ccqs:config/query-operation/actors/query/nop.json",
     "icqsi:config/query-operation/actors/query/slice.json",
+    "icqsi:config/query-operation/actors/query/reduced.json",
     "ccqs:config/query-operation/actors/query/leftjoin.json",
     "ccqs:config/query-operation/actors/query/values.json",
     "ccqs:config/query-operation/actors/query/bgp.json",

engines/config-query-sparql-incremental/config/query-operation/actors/query/reduced.json

@@ -0,0 +1,17 @@
+{
+  "@context": [
+    "https://linkedsoftwaredependencies.org/bundles/npm/@comunica/runner/^4.0.0/components/context.jsonld",
+
+    "https://linkedsoftwaredependencies.org/bundles/npm/@incremunica/actor-query-operation-reduced-hash/^1.0.0/components/context.jsonld"
+  ],
+  "@id": "urn:comunica:default:Runner",
+  "@type": "Runner",
+  "actors": [
+    {
+      "@id": "urn:comunica:default:query-operation/actors#reduced",
+      "@type": "ActorQueryOperationReducedHash",
+      "mediatorQueryOperation": { "@id": "urn:comunica:default:query-operation/mediators#main" },
+      "mediatorHashBindings": { "@id": "urn:comunica:default:hash-bindings/mediators#main" }
+    }
+  ]
+}

engines/query-sparql-incremental/package.json

@@ -269,6 +269,7 @@
     "@incremunica/actor-merge-bindings-context-is-addition": "^1.3.0",
     "@incremunica/actor-query-operation-distinct-hash": "^1.3.0",
     "@incremunica/actor-query-operation-group": "^1.3.0",
+    "@incremunica/actor-query-operation-reduced-hash": "^1.3.0",
     "@incremunica/actor-query-operation-slice": "^1.3.0",
     "@incremunica/actor-query-source-identify-hypermedia-none": "^1.3.0",
     "@incremunica/actor-query-source-identify-stream": "^1.3.0",

packages/actor-query-operation-reduced-hash/README.md

@@ -0,0 +1,38 @@
+# Incremunica Reduced Hash Query Operation Actor
+
+[![npm version](https://badge.fury.io/js/%40incremunica%2Factor-query-operation-reduced-hash.svg)](https://www.npmjs.com/package/@incremunica/actor-query-operation-reduced-hash)
+
+A [Query Operation](https://github.com/comunica/comunica/tree/master/packages/bus-query-operation) actor that handles [SPARQL `REDUCED`](https://www.w3.org/TR/sparql11-query/#sparqlReduced) operations
+by maintaining a hash-based cache of a fixed size.
+
+## Install
+
+```bash
+$ yarn add @incremunica/actor-query-operation-reduced-hash
+```
+
+## Configure
+
+After installing, this package can be added to your engine's configuration as follows:
+```text
+{
+  "@context": [
+    ...
+    "https://linkedsoftwaredependencies.org/bundles/npm/@incremunica/actor-query-operation-reduced-hash/^1.0.0/components/context.jsonld"
+  ],
+  "actors": [
+    ...
+    {
+      "@id": "urn:comunica:default:query-operation/actors#reduced",
+      "@type": "ActorQueryOperationReducedHash",
+      "mediatorQueryOperation": { "@id": "urn:comunica:default:query-operation/mediators#main" },
+      "mediatorHashBindings": { "@id": "urn:comunica:default:hash-bindings/mediators#main" }
+    }
+  ]
+}
+```
+
+### Config Parameters
+
+* `mediatorQueryOperation`: A mediator over the [Query Operation bus](https://github.com/comunica/comunica/tree/master/packages/bus-query-operation).
+* `mediatorHashBindings`: A mediator over the [Hash Bindings bus](https://github.com/comunica/comunica/tree/master/packages/bus-hash-bindings).

packages/actor-query-operation-reduced-hash/lib/ActorQueryOperationReducedHash.ts

@@ -0,0 +1,88 @@
+import type { MediatorHashBindings } from '@comunica/bus-hash-bindings';
+import type { IActorQueryOperationTypedMediatedArgs } from '@comunica/bus-query-operation';
+import { ActorQueryOperationTypedMediated } from '@comunica/bus-query-operation';
+import type { IActorTest, TestResult } from '@comunica/core';
+import { passTestVoid } from '@comunica/core';
+import type {
+  BindingsStream,
+  IActionContext,
+  IQueryOperationResult,
+  IQueryOperationResultBindings,
+} from '@comunica/types';
+import type { Bindings } from '@comunica/utils-bindings-factory';
+import { getSafeBindings } from '@comunica/utils-query-operation';
+import { KeysBindings } from '@incremunica/context-entries';
+import type * as RDF from '@rdfjs/types';
+import type { AsyncIterator } from 'asynciterator';
+import type { Algebra } from 'sparqlalgebrajs';
+
+/**
+ * An Incremunica Reduced Hash Query Operation Actor.
+ */
+export class ActorQueryOperationReducedHash extends ActorQueryOperationTypedMediated<Algebra.Reduced> {
+  public readonly mediatorHashBindings: MediatorHashBindings;
+
+  public constructor(args: IActorQueryOperationReducedHashArgs) {
+    super(args, 'reduced');
+  }
+
+  public async testOperation(_operation: Algebra.Reduced, _context: IActionContext): Promise<TestResult<IActorTest>> {
+    return passTestVoid();
+  }
+
+  public async runOperation(operation: Algebra.Reduced, context: IActionContext): Promise<IQueryOperationResult> {
+    const output: IQueryOperationResultBindings = getSafeBindings(
+      await this.mediatorQueryOperation.mediate({ operation: operation.input, context }),
+    );
+    const variables = (await output.metadata()).variables.map(v => v.variable);
+    const bindingsStream: BindingsStream =
+      <BindingsStream><any>(<AsyncIterator<Bindings>><any>output.bindingsStream)
+        .filter(await this.newHashFilter(context, variables));
+    return {
+      type: 'bindings',
+      bindingsStream,
+      metadata: output.metadata,
+    };
+  }
+
+  /**
+   * Create a new distinct filter function.
+   * This will maintain an internal hash datastructure so that every bindings object only returns true once.
+   * @param context The action context.
+   * @param variables The variables to take into account while hashing.
+   * @return {(bindings: Bindings) => boolean} A distinct filter for bindings.
+   */
+  public async newHashFilter(
+    context: IActionContext,
+    variables: RDF.Variable[],
+  ): Promise<(bindings: Bindings) => boolean> {
+    const { hashFunction } = await this.mediatorHashBindings.mediate({ context });
+    const hashes: Map<number, number> = new Map<number, number>();
+    return (bindings: Bindings) => {
+      const hash = hashFunction(bindings, variables);
+      const hasMapValue = hashes.get(hash);
+      const isAddition = bindings.getContextEntry(KeysBindings.isAddition) ?? true;
+      if (isAddition) {
+        if (hasMapValue) {
+          hashes.set(hash, hasMapValue + 1);
+          return false;
+        }
+        hashes.set(hash, 1);
+        return true;
+      }
+      if (!hasMapValue) {
+        return false;
+      }
+      if (hasMapValue === 1) {
+        hashes.delete(hash);
+        return true;
+      }
+      hashes.set(hash, hasMapValue - 1);
+      return false;
+    };
+  }
+}
+
+export interface IActorQueryOperationReducedHashArgs extends IActorQueryOperationTypedMediatedArgs {
+  mediatorHashBindings: MediatorHashBindings;
+}

packages/actor-query-operation-reduced-hash/lib/index.ts

@@ -0,0 +1 @@
+export * from './ActorQueryOperationReducedHash';

packages/actor-query-operation-reduced-hash/package.json

@@ -0,0 +1,50 @@
+{
+  "name": "@incremunica/actor-query-operation-reduced-hash",
+  "version": "1.3.0",
+  "description": "A reduced-hash query-operation actor",
+  "lsd:module": true,
+  "license": "MIT",
+  "homepage": "https://maartyman.github.io/incremunica/",
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/comunica/comunica.git",
+    "directory": "packages/actor-query-operation-reduced-hash"
+  },
+  "bugs": {
+    "url": "https://github.com/comunica/comunica/issues"
+  },
+  "keywords": [
+    "incremunica",
+    "actor",
+    "query-operation",
+    "reduced-hash"
+  ],
+  "sideEffects": false,
+  "main": "lib/index.js",
+  "typings": "lib/index",
+  "publishConfig": {
+    "access": "public"
+  },
+  "files": [
+    "components",
+    "lib/**/*.d.ts",
+    "lib/**/*.js",
+    "lib/**/*.js.map"
+  ],
+  "scripts": {
+    "build": "yarn run build:ts && yarn run build:components",
+    "build:ts": "node \"../../node_modules/typescript/bin/tsc\"",
+    "build:components": "componentsjs-generator"
+  },
+  "dependencies": {
+    "@comunica/bus-hash-bindings": "^4.0.2",
+    "@comunica/bus-query-operation": "^4.0.2",
+    "@comunica/core": "^4.0.2",
+    "@comunica/types": "^4.0.2",
+    "@comunica/utils-bindings-factory": "^4.0.2",
+    "@comunica/utils-query-operation": "^4.0.2",
+    "@incremunica/context-entries": "^1.3.0",
+    "@rdfjs/types": "*",
+    "sparqlalgebrajs": "^4.3.8"
+  }
+}