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queryIterator.ts
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queryIterator.ts
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/// <reference lib="esnext.asynciterable" />
import { ClientContext } from "./ClientContext";
import { getPathFromLink, ResourceType, StatusCodes, SubStatusCodes } from "./common";
import {
CosmosHeaders,
DefaultQueryExecutionContext,
ExecutionContext,
FetchFunctionCallback,
getInitialHeader,
mergeHeaders,
PipelinedQueryExecutionContext,
SqlQuerySpec
} from "./queryExecutionContext";
import { Response } from "./request";
import { ErrorResponse, PartitionedQueryExecutionInfo } from "./request/ErrorResponse";
import { FeedOptions } from "./request/FeedOptions";
import { FeedResponse } from "./request/FeedResponse";
/**
* Represents a QueryIterator Object, an implmenetation of feed or query response that enables
* traversal and iterating over the response
* in the Azure Cosmos DB database service.
*/
export class QueryIterator<T> {
private fetchAllTempResources: T[]; // TODO
private fetchAllLastResHeaders: CosmosHeaders;
private queryExecutionContext: ExecutionContext;
private queryPlanPromise: Promise<Response<PartitionedQueryExecutionInfo>>;
/**
* @hidden
*/
constructor(
private clientContext: ClientContext,
private query: SqlQuerySpec | string,
private options: FeedOptions,
private fetchFunctions: FetchFunctionCallback | FetchFunctionCallback[],
private resourceLink?: string,
private resourceType?: ResourceType
) {
this.query = query;
this.fetchFunctions = fetchFunctions;
this.options = options;
this.resourceLink = resourceLink;
this.fetchAllLastResHeaders = getInitialHeader();
this.reset();
}
/**
* Gets an async iterator that will yield results until completion.
*
* NOTE: AsyncIterators are a very new feature and you might need to
* use polyfils/etc. in order to use them in your code.
*
* If you're using TypeScript, you can use the following polyfill as long
* as you target ES6 or higher and are running on Node 6 or higher.
*
* ```typescript
* if (!Symbol || !Symbol.asyncIterator) {
* (Symbol as any).asyncIterator = Symbol.for("Symbol.asyncIterator");
* }
* ```
*
* @example Iterate over all databases
* ```typescript
* for await(const {result: db} in client.databases.readAll().getAsyncIterator()) {
* console.log(`Got ${db.id} from AsyncIterator`);
* }
* ```
*/
public async *getAsyncIterator(): AsyncIterable<FeedResponse<T>> {
this.reset();
this.queryPlanPromise = this.fetchQueryPlan();
while (this.queryExecutionContext.hasMoreResults()) {
let response: Response<any>;
try {
response = await this.queryExecutionContext.fetchMore();
} catch (error) {
if (this.needsQueryPlan(error)) {
await this.createPipelinedExecutionContext();
response = await this.queryExecutionContext.fetchMore();
} else {
throw error;
}
}
const feedResponse = new FeedResponse<T>(
response.result,
response.headers,
this.queryExecutionContext.hasMoreResults()
);
if (response.result !== undefined) {
yield feedResponse;
}
}
}
/**
* Determine if there are still remaining resources to processs based on the value of the continuation token or the\
* elements remaining on the current batch in the QueryIterator.
* @returns {Boolean} true if there is other elements to process in the QueryIterator.
*/
public hasMoreResults(): boolean {
return this.queryExecutionContext.hasMoreResults();
}
/**
* Fetch all pages for the query and return a single FeedResponse.
*/
public async fetchAll(): Promise<FeedResponse<T>> {
this.reset();
this.fetchAllTempResources = [];
return this.toArrayImplementation();
}
/**
* Retrieve the next batch from the feed.
*
* This may or may not fetch more pages from the backend depending on your settings
* and the type of query. Aggregate queries will generally fetch all backend pages
* before returning the first batch of responses.
*/
public async fetchNext(): Promise<FeedResponse<T>> {
this.queryPlanPromise = this.fetchQueryPlan();
let response: Response<any>;
try {
response = await this.queryExecutionContext.fetchMore();
} catch (error) {
if (this.needsQueryPlan(error)) {
await this.createPipelinedExecutionContext();
response = await this.queryExecutionContext.fetchMore();
} else {
throw error;
}
}
return new FeedResponse<T>(response.result, response.headers, this.queryExecutionContext.hasMoreResults());
}
/**
* Reset the QueryIterator to the beginning and clear all the resources inside it
*/
public reset() {
this.queryPlanPromise = undefined;
this.queryExecutionContext = new DefaultQueryExecutionContext(this.options, this.fetchFunctions);
}
private async toArrayImplementation(): Promise<FeedResponse<T>> {
this.queryPlanPromise = this.fetchQueryPlan();
while (this.queryExecutionContext.hasMoreResults()) {
let response: Response<any>;
try {
response = await this.queryExecutionContext.nextItem();
} catch (error) {
if (this.needsQueryPlan(error)) {
await this.createPipelinedExecutionContext();
response = await this.queryExecutionContext.nextItem();
} else {
throw error;
}
}
const { result, headers } = response;
// concatenate the results and fetch more
mergeHeaders(this.fetchAllLastResHeaders, headers);
if (result !== undefined) {
this.fetchAllTempResources.push(result);
}
}
return new FeedResponse(
this.fetchAllTempResources,
this.fetchAllLastResHeaders,
this.queryExecutionContext.hasMoreResults()
);
}
private async createPipelinedExecutionContext() {
const queryPlanResponse = await this.queryPlanPromise;
// We always coerce queryPlanPromise to resolved. So if it errored, we need to manually inspect the resolved value
if (queryPlanResponse instanceof Error) {
throw queryPlanResponse;
}
const queryPlan = queryPlanResponse.result;
const queryInfo = queryPlan.queryInfo;
if (queryInfo.aggregates.length > 0 && queryInfo.hasSelectValue === false) {
throw new Error("Aggregate queries must use the VALUE keyword");
}
this.queryExecutionContext = new PipelinedQueryExecutionContext(
this.clientContext,
this.resourceLink,
this.query,
this.options,
queryPlan
);
}
private async fetchQueryPlan() {
if (!this.queryPlanPromise && this.resourceType === ResourceType.item) {
return this.clientContext
.getQueryPlan(
getPathFromLink(this.resourceLink) + "/docs",
ResourceType.item,
this.resourceLink,
this.query,
this.options
)
.catch((error: any) => error); // Without this catch, node reports an unhandled rejection. So we stash the promise as resolved even if it errored.
}
return this.queryPlanPromise;
}
private needsQueryPlan(error: any): error is ErrorResponse {
return (
error.code === StatusCodes.BadRequest &&
error.substatus &&
error.substatus === SubStatusCodes.CrossPartitionQueryNotServable
);
}
}