added projection api for nodejs (#140)

node/src/index.ts

@@ -233,7 +233,7 @@ export class Query<T = number[]> {
   private _limit: number
   private _refineFactor?: number
   private _nprobes: number
-  private readonly _columns?: string[]
+  private _select?: string[]
   private _filter?: string
   private _metricType?: MetricType
   private readonly _embeddings?: EmbeddingFunction<T>
@@ -244,7 +244,7 @@ export class Query<T = number[]> {
     this._limit = 10
     this._nprobes = 20
     this._refineFactor = undefined
-    this._columns = undefined
+    this._select = undefined
     this._filter = undefined
     this._metricType = undefined
     this._embeddings = embeddings
@@ -286,6 +286,15 @@ export class Query<T = number[]> {
     return this
   }
 
+  /** Return only the specified columns.
+   *
+   * @param value Only select the specified columns. If not specified, all columns will be returned.
+   */
+  select (value: string[]): Query<T> {
+    this._select = value
+    return this
+  }
+
   /**
    * The MetricType used for this Query.
    * @param value The metric to the. @see MetricType for the different options

node/src/test/test.ts

@@ -72,6 +72,22 @@ describe('LanceDB client', function () {
       assert.equal(results.length, 1)
       assert.equal(results[0].id, 2)
     })
+
+    it('select only a subset of columns', async function () {
+      const uri = await createTestDB()
+      const con = await lancedb.connect(uri)
+      const table = await con.openTable('vectors')
+      const results = await table.search([0.1, 0.1]).select(['is_active']).execute()
+      assert.equal(results.length, 2)
+      // vector and score are always returned
+      assert.isDefined(results[0].vector)
+      assert.isDefined(results[0].score)
+      assert.isDefined(results[0].is_active)
+
+      assert.isUndefined(results[0].id)
+      assert.isUndefined(results[0].name)
+      assert.isUndefined(results[0].price)
+    })
   })
 
   describe('when creating a new dataset', function () {
@@ -181,11 +197,13 @@ describe('Query object', function () {
       .limit(1)
       .metricType(MetricType.Cosine)
       .refineFactor(100)
+      .select(['a', 'b'])
       .nprobes(20) as Record<string, any>
     assert.equal(query._limit, 1)
     assert.equal(query._metricType, MetricType.Cosine)
     assert.equal(query._refineFactor, 100)
     assert.equal(query._nprobes, 20)
+    assert.deepEqual(query._select, ['a', 'b'])
   })
 })