[Cosmos] Adding check for setting ParallelizeCrossPartitionQuery head…

…er (Azure#31233)

### Packages impacted by this PR
@azure/cosmos

### Issues associated with this PR
Azure#31232

### Describe the problem that is addressed by this PR
Currently during a query if maxDegreeOfParallelism is set as 1,
ParallelizeCrossPartitionQuery header value is set as true. This is
currently resulting error from gateway for simple queries like "Select *
FROM c".

### What are the possible designs available to address the problem? If
there are more than one possible design, why was the one in this PR
chosen?


### Are there test cases added in this PR? _(If not, why?)_
Yes.

### Provide a list of related PRs _(if any)_


### Command used to generate this PR:**_(Applicable only to SDK release
request PRs)_

### Checklists
- [ ] Added impacted package name to the issue description
- [ ] Does this PR needs any fixes in the SDK Generator?** _(If so,
create an Issue in the
[Autorest/typescript](https://github.com/Azure/autorest.typescript)
repository and link it here)_
- [ ] Added a changelog (if necessary)

sdk/cosmosdb/cosmos/CHANGELOG.md

@@ -8,6 +8,8 @@
 
 ### Bugs Fixed
 
+- Fixed issue for incorrect `ParallelizeCrossPartitionQuery` header value. It was set to true if `maxDegreeOfParallelism` was set to 0 or 1 in `FeedOptions` while executing a query. [#31232](https://github.com/Azure/azure-sdk-for-js/issues/31232)
+
 ### Other Changes
 
 ## 4.2.0 (2024-11-19)

sdk/cosmosdb/cosmos/src/request/request.ts

@@ -176,7 +176,11 @@ export async function getHeaders({
     headers[Constants.HttpHeaders.PopulateQueryMetrics] = options.populateQueryMetrics;
   }
 
-  if (options.maxDegreeOfParallelism !== undefined) {
+  if (
+    options.maxDegreeOfParallelism !== undefined &&
+    options.maxDegreeOfParallelism !== 0 &&
+    options.maxDegreeOfParallelism !== 1
+  ) {
     headers[Constants.HttpHeaders.ParallelizeCrossPartitionQuery] = true;
   }
 

sdk/cosmosdb/cosmos/test/internal/unit/getHeader.spec.ts

@@ -0,0 +1,40 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+import assert from "assert";
+import { Constants } from "../../../src/common/constants";
+import { getHeaders } from "../../../src/request/request";
+import { CosmosHeaders, FeedOptions } from "../../../src";
+
+describe("Test x-ms-documentdb-query-parallelizecrosspartitionquery header value", function () {
+  const mockedEndpoint = "https://localhost:8081";
+  function getHeadersFunc(feedOptions: FeedOptions): Promise<CosmosHeaders> {
+    return getHeaders({
+      clientOptions: { endpoint: mockedEndpoint },
+      defaultHeaders: null,
+      verb: null,
+      path: null,
+      resourceId: null,
+      resourceType: null,
+      options: feedOptions,
+      partitionKeyRangeId: null,
+      useMultipleWriteLocations: null,
+      partitionKey: null,
+    });
+  }
+  it("If maxDegreeOfParallelism > 1 then x-ms-documentdb-query-parallelizecrosspartitionquery header should be true", async function () {
+    const headers = await getHeadersFunc({ maxDegreeOfParallelism: 2 });
+    assert.equal(
+      headers[Constants.HttpHeaders.ParallelizeCrossPartitionQuery],
+      true,
+      "incorrect header value",
+    );
+  });
+  it("If maxDegreeOfParallelism == 0 then x-ms-documentdb-query-parallelizecrosspartitionquery header should be null", async function () {
+    const headers = await getHeadersFunc({ maxDegreeOfParallelism: 0 });
+    assert.equal(
+      headers[Constants.HttpHeaders.ParallelizeCrossPartitionQuery],
+      null,
+      "incorrect header value",
+    );
+  });
+});

sdk/cosmosdb/cosmos/test/public/integration/split.spec.ts

@@ -123,7 +123,7 @@ describe("Partition Splits", () => {
         .container(container.id)
         .items.query("SELECT * FROM root r", {
           maxItemCount: 2,
-          maxDegreeOfParallelism: 1,
+          maxDegreeOfParallelism: 2,
         })
         .fetchAll();
       assert.fail("Expected query to fail");
@@ -138,7 +138,7 @@ describe("Partition Splits", () => {
         .container(container.id)
         .items.query("SELECT * FROM root r", {
           maxItemCount: 2,
-          maxDegreeOfParallelism: 1,
+          maxDegreeOfParallelism: 2,
         })
         .fetchNext();
       assert.fail("Expected query to fail");
@@ -153,7 +153,7 @@ describe("Partition Splits", () => {
         .container(container.id)
         .items.query("SELECT * FROM root r", {
           maxItemCount: 2,
-          maxDegreeOfParallelism: 1,
+          maxDegreeOfParallelism: 2,
         })
         .getAsyncIterator();
       const results = [];

sdk/cosmosdb/cosmos/tsconfig.strict.json

@@ -180,6 +180,7 @@
     "test/internal/unit/timeoutFailoverRetryPolicy.spec.ts",
     "test/internal/unit/nonStreamingOrderByMap.spec.ts",
     "test/internal/unit/utils/supportedQueryFeaturesBuilder.spec.ts",
+    "test/internal/unit/getHeader.spec.ts",
     "test/public/common/BaselineTest.PathParser.ts",
     "test/public/common/TestData.ts",
     "test/public/common/setup.ts",