Merge pull request #245 from shiftcode/#243-projection-expression

#243 projection expression

src/dynamo/expression/request-expression-builder.ts

@@ -151,18 +151,18 @@ export function doAddCondition<T, R extends ConditionalParamsHost>(
 /**
  * @hidden
  */
-export function addPartitionKeyCondition<R extends StandardRequest<any, any, any>>(
+export function addPartitionKeyCondition<R extends StandardRequest<any, any, any, any>>(
   keyName: keyof any,
   keyValue: any,
   request: R,
 ): R
-export function addPartitionKeyCondition<T, R extends StandardRequest<T, any, any>>(
+export function addPartitionKeyCondition<T, R extends StandardRequest<T, any, any, any>>(
   keyName: keyof T,
   keyValue: any,
   request: R,
   metadata: Metadata<T>,
 ): R
-export function addPartitionKeyCondition<T, R extends StandardRequest<T, any, any>>(
+export function addPartitionKeyCondition<T, R extends StandardRequest<T, any, any, any>>(
   keyName: keyof T,
   keyValue: any,
   request: R,

src/dynamo/request/base.request.spec.ts

@@ -4,7 +4,7 @@ import { ModelConstructor } from '../../model/model-constructor'
 import { BaseRequest } from './base.request'
 
 describe('base request', () => {
-  class TestRequest<T> extends BaseRequest<T, any, BaseRequest<T, any, any>> {
+  class TestRequest<T> extends BaseRequest<T, T, any, BaseRequest<T, T, any, any>> {
     constructor(modelClazz: ModelConstructor<T>) {
       super(<any>null, modelClazz)
     }

src/dynamo/request/base.request.ts

@@ -15,6 +15,7 @@ import { getTableName } from '../get-table-name.function'
  */
 export abstract class BaseRequest<
   T,
+  T2,
   I extends
     | DynamoDB.DeleteItemInput
     | DynamoDB.GetItemInput
@@ -26,7 +27,7 @@ export abstract class BaseRequest<
     | DynamoDB.BatchWriteItemInput
     | DynamoDB.TransactGetItemsInput
     | DynamoDB.TransactWriteItemsInput,
-  R extends BaseRequest<T, I, any>
+  R extends BaseRequest<T, T2, I, any>
 > {
   readonly dynamoDBWrapper: DynamoDbWrapper
 
@@ -86,5 +87,5 @@ export abstract class BaseRequest<
   /**
    * execute request and return the parsed item(s) or void if none were requested.
    */
-  abstract exec(): Promise<T | T[] | void | null>
+  abstract exec(): Promise<T2 | T2[] | void | null>
 }

src/dynamo/request/batchgetsingletable/batch-get-single-table.request.spec.ts

@@ -60,13 +60,25 @@ describe('batch get', () => {
       })
     })
 
-    it('ConsistentRead', () => {
+    it('consistent read', () => {
       const request = new BatchGetSingleTableRequest<any>(<any>null, SimpleWithPartitionKeyModel, [{ id: 'myId' }])
       request.consistentRead()
       expect(request.params.RequestItems).toBeDefined()
       expect(request.params.RequestItems[getTableName(SimpleWithPartitionKeyModel)]).toBeDefined()
       expect(request.params.RequestItems[getTableName(SimpleWithPartitionKeyModel)].ConsistentRead).toBeTruthy()
     })
+
+    it('projection expression', () => {
+      const request = new BatchGetSingleTableRequest<any>(<any>null, SimpleWithPartitionKeyModel, [{ id: 'myId' }])
+      request.projectionExpression('age')
+      expect(request.params.RequestItems).toBeDefined()
+      const params = request.params.RequestItems[getTableName(SimpleWithPartitionKeyModel)]
+      expect(params).toBeDefined()
+      expect(params.ProjectionExpression).toBe('#age')
+      expect(params.ExpressionAttributeNames).toEqual({
+        '#age': 'age',
+      })
+    })
   })
 
   describe('should return appropriate value', () => {

src/dynamo/request/batchgetsingletable/batch-get-single-table.request.ts

@@ -12,15 +12,17 @@ import { batchGetItemsFetchAll } from '../../batchget/batch-get-utils'
 import { BATCH_GET_DEFAULT_TIME_SLOT, BATCH_GET_MAX_REQUEST_ITEM_COUNT } from '../../batchget/batch-get.const'
 import { DynamoDbWrapper } from '../../dynamo-db-wrapper'
 import { BaseRequest } from '../base.request'
+import { addProjectionExpressionParam } from '../helper/add-projection-expression-param.function'
 import { BatchGetSingleTableResponse } from './batch-get-single-table.response'
 
 /**
  * Request class for BatchGetItem operation which supports a single model class only.
  */
-export class BatchGetSingleTableRequest<T> extends BaseRequest<
+export class BatchGetSingleTableRequest<T, T2 = T> extends BaseRequest<
   T,
+  T2,
   DynamoDB.BatchGetItemInput,
-  BatchGetSingleTableRequest<T>
+  BatchGetSingleTableRequest<T, T2>
 > {
   private readonly logger: Logger
 
@@ -39,11 +41,23 @@ export class BatchGetSingleTableRequest<T> extends BaseRequest<
     }
   }
 
-  consistentRead(value: boolean = true): BatchGetSingleTableRequest<T> {
+  /**
+   * Determines the read consistency model: If set to true, then the operation uses strongly consistent reads; otherwise, the operation uses eventually consistent reads.
+   */
+  consistentRead(value: boolean = true): this {
     this.params.RequestItems[this.tableName].ConsistentRead = value
     return this
   }
 
+  /**
+   * Specifies the list of model attributes to be returned from the table instead of returning the entire document
+   * @param attributesToGet List of model attributes to be returned
+   */
+  projectionExpression(...attributesToGet: Array<keyof T | string>): BatchGetSingleTableRequest<T, Partial<T>> {
+    addProjectionExpressionParam(attributesToGet, this.params.RequestItems[this.tableName], this.metadata)
+    return this
+  }
+
   /**
    * fetch all entries and return the raw response (without parsing the attributes to js objects)
    * @param backoffTimer when unprocessed keys are returned the next value of backoffTimer is used to determine how many time slots to wait before doing the next request
@@ -64,7 +78,7 @@ export class BatchGetSingleTableRequest<T> extends BaseRequest<
   execFullResponse(
     backoffTimer = randomExponentialBackoffTimer,
     throttleTimeSlot = BATCH_GET_DEFAULT_TIME_SLOT,
-  ): Promise<BatchGetSingleTableResponse<T>> {
+  ): Promise<BatchGetSingleTableResponse<T2>> {
     return this.fetch(backoffTimer, throttleTimeSlot)
       .then(this.mapResponse)
       .then(promiseTap(response => this.logger.debug('mapped items', response.Items)))
@@ -75,18 +89,18 @@ export class BatchGetSingleTableRequest<T> extends BaseRequest<
    * @param backoffTimer when unprocessed keys are returned the next value of backoffTimer is used to determine how many time slots to wait before doing the next request
    * @param throttleTimeSlot the duration of a time slot in ms
    */
-  exec(backoffTimer = randomExponentialBackoffTimer, throttleTimeSlot = BATCH_GET_DEFAULT_TIME_SLOT): Promise<T[]> {
+  exec(backoffTimer = randomExponentialBackoffTimer, throttleTimeSlot = BATCH_GET_DEFAULT_TIME_SLOT): Promise<T2[]> {
     return this.fetch(backoffTimer, throttleTimeSlot)
       .then(this.mapResponse)
       .then(r => r.Items)
       .then(promiseTap(items => this.logger.debug('mapped items', items)))
   }
 
   private mapResponse = (response: DynamoDB.BatchGetItemOutput) => {
-    let items: T[] = []
+    let items: T2[] = []
     if (response.Responses && Object.keys(response.Responses).length && response.Responses[this.tableName]) {
-      const mapped: T[] = response.Responses[this.tableName].map(attributeMap =>
-        fromDb(<Attributes<T>>attributeMap, this.modelClazz),
+      const mapped: T2[] = response.Responses[this.tableName].map(attributeMap =>
+        fromDb(<Attributes<T2>>attributeMap, <any>this.modelClazz),
       )
       items = mapped
     }

src/dynamo/request/batchgetsingletable/batch-get-single-table.response.ts

@@ -8,7 +8,7 @@ import * as DynamoDB from 'aws-sdk/clients/dynamodb'
  */
 export interface BatchGetSingleTableResponse<T> {
   /**
-   * A map of table name to a list of items. Each object in Responses consists of a table name, along with a map of attribute data consisting of the data type and attribute value.
+   * A map of table name to a list of items. Each object in Responses consists of a table name, along with a map of attribute data consisting of the data type and attribute value, as specified by ProjectionExpression.
    */
   Items: T[]
   /**

src/dynamo/request/batchwritesingletable/batch-write-single-table.request.ts

@@ -14,10 +14,11 @@ import { BaseRequest } from '../base.request'
 /**
  * Request class for BatchWriteItem operation which supports a single model class only.
  */
-export class BatchWriteSingleTableRequest<T> extends BaseRequest<
+export class BatchWriteSingleTableRequest<T, T2 = T> extends BaseRequest<
   T,
+  T2,
   DynamoDB.BatchWriteItemInput,
-  BatchWriteSingleTableRequest<T>
+  BatchWriteSingleTableRequest<T, T2>
 > {
   private readonly logger: Logger
   private toKey = createToKeyFn(this.modelClazz)
@@ -33,19 +34,20 @@ export class BatchWriteSingleTableRequest<T> extends BaseRequest<
   /**
    * return item collection metrics.
    */
-  returnItemCollectionMetrics(value: DynamoDB.ReturnItemCollectionMetrics) {
+  returnItemCollectionMetrics(value: DynamoDB.ReturnItemCollectionMetrics): this {
     this.params.ReturnItemCollectionMetrics = value
+    return this
   }
 
-  delete(items: Array<Partial<T>>): BatchWriteSingleTableRequest<T> {
+  delete(items: Array<Partial<T>>): this {
     if (this.params.RequestItems[this.tableName].length + items.length > BATCH_WRITE_MAX_REQUEST_ITEM_COUNT) {
       throw new Error(`batch write takes at max ${BATCH_WRITE_MAX_REQUEST_ITEM_COUNT} items`)
     }
     this.params.RequestItems[this.tableName].push(...items.map(this.createDeleteRequest))
     return this
   }
 
-  put(items: T[]): BatchWriteSingleTableRequest<T> {
+  put(items: T[]): this {
     if (this.params.RequestItems[this.tableName].length + items.length > BATCH_WRITE_MAX_REQUEST_ITEM_COUNT) {
       throw new Error(`batch write takes at max ${BATCH_WRITE_MAX_REQUEST_ITEM_COUNT} items`)
     }