add openai embedding function to nodejs client (#107)

- openai is an optional dependency for lancedb
- added an example to show how to use it

node/src/index.ts

@@ -19,10 +19,14 @@ import {
   Vector
 } from 'apache-arrow'
 import { fromRecordsToBuffer } from './arrow'
+import type { EmbeddingFunction } from './embedding/embedding_function'
 
 // eslint-disable-next-line @typescript-eslint/no-var-requires
 const { databaseNew, databaseTableNames, databaseOpenTable, tableCreate, tableSearch, tableAdd, tableCreateVectorIndex } = require('../native.js')
 
+export type { EmbeddingFunction }
+export { OpenAIEmbeddingFunction } from './embedding/openai'
+
 /**
  * Connect to a LanceDB instance at the given URI
  * @param uri The uri of the database.
@@ -135,14 +139,8 @@ export class Table<T = number[]> {
    * Creates a search query to find the nearest neighbors of the given search term
    * @param query The query search term
    */
-  search (query: T): Query {
-    let queryVector: number[]
-    if (this._embeddings !== undefined) {
-      queryVector = this._embeddings.embed([query])[0]
-    } else {
-      queryVector = query as number[]
-    }
-    return new Query(this._tbl, queryVector)
+  search (query: T): Query<T> {
+    return new Query(this._tbl, query, this._embeddings)
   }
 
   /**
@@ -228,32 +226,35 @@ export type VectorIndexParams = IvfPQIndexConfig
 /**
  * A builder for nearest neighbor queries for LanceDB.
  */
-export class Query {
+export class Query<T = number[]> {
   private readonly _tbl: any
-  private readonly _queryVector: number[]
+  private readonly _query: T
+  private _queryVector?: number[]
   private _limit: number
   private _refineFactor?: number
   private _nprobes: number
   private readonly _columns?: string[]
   private _filter?: string
   private _metricType?: MetricType
+  private readonly _embeddings?: EmbeddingFunction<T>
 
-  constructor (tbl: any, queryVector: number[]) {
+  constructor (tbl: any, query: T, embeddings?: EmbeddingFunction<T>) {
     this._tbl = tbl
-    this._queryVector = queryVector
+    this._query = query
     this._limit = 10
     this._nprobes = 20
     this._refineFactor = undefined
     this._columns = undefined
     this._filter = undefined
     this._metricType = undefined
+    this._embeddings = embeddings
   }
 
   /***
    * Sets the number of results that will be returned
    * @param value number of results
    */
-  limit (value: number): Query {
+  limit (value: number): Query<T> {
     this._limit = value
     return this
   }
@@ -262,7 +263,7 @@ export class Query {
    * Refine the results by reading extra elements and re-ranking them in memory.
    * @param value refine factor to use in this query.
    */
-  refineFactor (value: number): Query {
+  refineFactor (value: number): Query<T> {
     this._refineFactor = value
     return this
   }
@@ -271,7 +272,7 @@ export class Query {
    * The number of probes used. A higher number makes search more accurate but also slower.
    * @param value The number of probes used.
    */
-  nprobes (value: number): Query {
+  nprobes (value: number): Query<T> {
     this._nprobes = value
     return this
   }
@@ -280,7 +281,7 @@ export class Query {
    * A filter statement to be applied to this query.
    * @param value A filter in the same format used by a sql WHERE clause.
    */
-  filter (value: string): Query {
+  filter (value: string): Query<T> {
     this._filter = value
     return this
   }
@@ -289,7 +290,7 @@ export class Query {
    * The MetricType used for this Query.
    * @param value The metric to the. @see MetricType for the different options
    */
-  metricType (value: MetricType): Query {
+  metricType (value: MetricType): Query<T> {
     this._metricType = value
     return this
   }
@@ -298,6 +299,12 @@ export class Query {
    * Execute the query and return the results as an Array of Objects
    */
   async execute<T = Record<string, unknown>> (): Promise<T[]> {
+    if (this._embeddings !== undefined) {
+      this._queryVector = (await this._embeddings.embed([this._query]))[0]
+    } else {
+      this._queryVector = this._query as number[]
+    }
+
     const buffer = await tableSearch.call(this._tbl, this)
     const data = tableFromIPC(buffer)
     return data.toArray().map((entry: Record<string, unknown>) => {
@@ -319,21 +326,6 @@ export enum WriteMode {
   Append = 'append'
 }
 
-/**
- * An embedding function that automatically creates vector representation for a given column.
- */
-export interface EmbeddingFunction<T> {
-  /**
-   * The name of the column that will be used as input for the Embedding Function.
-   */
-  sourceColumn: string
-
-  /**
-   * Creates a vector representation for the given values.
-   */
-  embed: (data: T[]) => number[][]
-}
-
 /**
  * Distance metrics type.
  */