feat: Merge Data Source (#3788)

Add the ability to merge two different series queries to generate a complete study query result.  Provides basic support for other types of merges, but those aren't yet added as full features.

babel.config.js

@@ -45,6 +45,7 @@ module.exports = {
         '@babel/plugin-proposal-object-rest-spread',
         '@babel/plugin-syntax-dynamic-import',
         '@babel/plugin-transform-regenerator',
+        '@babel/transform-destructuring',
         '@babel/plugin-transform-runtime',
         '@babel/plugin-transform-typescript',
       ],

extensions/default/babel.config.js

@@ -0,0 +1 @@
+module.exports = require('../../babel.config.js');

extensions/default/jest.config.js

@@ -0,0 +1,17 @@
+const base = require('../../jest.config.base.js');
+const pkg = require('./package');
+
+module.exports = {
+  ...base,
+  name: pkg.name,
+  displayName: pkg.name,
+  moduleNameMapper: {
+    ...base.moduleNameMapper,
+    '@ohif/(.*)': '<rootDir>/../../platform/$1/src',
+  },
+  // rootDir: "../.."
+  // testMatch: [
+  //   //`<rootDir>/platform/${pack.name}/**/*.spec.js`
+  //   "<rootDir>/platform/app/**/*.test.js"
+  // ]
+};

extensions/default/src/CustomizableContextMenu/ContextMenuItemsBuilder.test.js

@@ -1,14 +1,14 @@
-import ContextMenuItemsBuilder from './ContextMenuItemsBuilder';
+import * as ContextMenuItemsBuilder from './ContextMenuItemsBuilder';
 
 const menus = [
   {
     id: 'one',
-    selector: ({ value }) => value === 'one',
+    selector: ({ value } = {}) => value === 'one',
     items: [],
   },
   {
     id: 'two',
-    selector: ({ value }) => value === 'two',
+    selector: ({ value } = {}) => value === 'two',
     items: [],
   },
   {
@@ -17,13 +17,13 @@ const menus = [
   },
 ];
 
-const menuBuilder = new ContextMenuItemsBuilder();
-
 describe('ContextMenuItemsBuilder', () => {
   test('findMenuDefault', () => {
-    expect(menuBuilder.findMenuDefault(menus, {})).toBe(menus[2]);
+    expect(ContextMenuItemsBuilder.findMenuDefault(menus, {})).toBe(menus[2]);
-    expect(menuBuilder.findMenuDefault(menus, { value: 'two' })).toBe(menus[1]);
+    expect(
-    expect(menuBuilder.findMenuDefault([], {})).toBeUndefined();
+      ContextMenuItemsBuilder.findMenuDefault(menus, { selectorProps: { value: 'two' } })
-    expect(menuBuilder.findMenuDefault(undefined, undefined)).toBeNull();
+    ).toBe(menus[1]);
+    expect(ContextMenuItemsBuilder.findMenuDefault([], {})).toBeUndefined();
+    expect(ContextMenuItemsBuilder.findMenuDefault(undefined, undefined)).toBeNull();
   });
 });

extensions/default/src/DicomWebDataSource/index.js

@@ -140,7 +140,7 @@ function createDicomWebApi(dicomWebConfig, userAuthenticationService) {
       instances: {
         search: (studyInstanceUid, queryParameters) => {
           qidoDicomWebClient.headers = getAuthrorizationHeader();
-          qidoSearch.call(undefined, qidoDicomWebClient, studyInstanceUid, null, queryParameters);
+          return qidoSearch.call(undefined, qidoDicomWebClient, studyInstanceUid, null, queryParameters);
         },
       },
     },
@@ -262,7 +262,8 @@ function createDicomWebApi(dicomWebConfig, userAuthenticationService) {
         enableStudyLazyLoad,
         filters,
         sortCriteria,
-        sortFunction
+        sortFunction,
+        dicomWebConfig
       );
 
       // first naturalize the data
@@ -314,6 +315,8 @@ function createDicomWebApi(dicomWebConfig, userAuthenticationService) {
       Object.keys(instancesPerSeries).forEach(seriesInstanceUID =>
         DicomMetadataStore.addInstances(instancesPerSeries[seriesInstanceUID], madeInClient)
       );
+
+      return seriesSummaryMetadata;
     },
 
     _retrieveSeriesMetadataAsync: async (
@@ -333,7 +336,8 @@ function createDicomWebApi(dicomWebConfig, userAuthenticationService) {
           enableStudyLazyLoad,
           filters,
           sortCriteria,
-          sortFunction
+          sortFunction,
+          dicomWebConfig
         );
 
       /**
@@ -444,6 +448,8 @@ function createDicomWebApi(dicomWebConfig, userAuthenticationService) {
       );
       await Promise.all(seriesDeliveredPromises);
       setSuccessFlag();
+
+      return seriesSummaryMetadata;
     },
     deleteStudyMetadataPromise,
     getImageIdsForDisplaySet(displaySet) {

extensions/default/src/DicomWebDataSource/retrieveStudyMetadata.js

@@ -25,7 +25,8 @@ export function retrieveStudyMetadata(
   enableStudyLazyLoad,
   filters,
   sortCriteria,
-  sortFunction
+  sortFunction,
+  dicomWebConfig = {}
 ) {
   // @TODO: Whenever a study metadata request has failed, its related promise will be rejected once and for all
   // and further requests for that metadata will always fail. On failure, we probably need to remove the
@@ -38,9 +39,11 @@ export function retrieveStudyMetadata(
     throw new Error(`${moduleName}: Required 'StudyInstanceUID' parameter not provided.`);
   }
 
+  const promiseId = `${dicomWebConfig.name}:${StudyInstanceUID}`;
+
   // Already waiting on result? Return cached promise
-  if (StudyMetaDataPromises.has(StudyInstanceUID)) {
+  if (StudyMetaDataPromises.has(promiseId)) {
-    return StudyMetaDataPromises.get(StudyInstanceUID);
+    return StudyMetaDataPromises.get(promiseId);
   }
 
   let promise;
@@ -71,7 +74,7 @@ export function retrieveStudyMetadata(
   }
 
   // Store the promise in cache
-  StudyMetaDataPromises.set(StudyInstanceUID, promise);
+  StudyMetaDataPromises.set(promiseId, promise);
 
   return promise;
 }

extensions/default/src/MergeDataSource/index.test.js

@@ -0,0 +1,203 @@
+import { DicomMetadataStore, IWebApiDataSource } from '@ohif/core';
+import {
+  mergeMap,
+  callForAllDataSourcesAsync,
+  callForAllDataSources,
+  callForDefaultDataSource,
+  callByRetrieveAETitle,
+  createMergeDataSourceApi,
+} from './index';
+
+jest.mock('@ohif/core');
+
+describe('MergeDataSource', () => {
+  let path,
+    sourceName,
+    mergeConfig,
+    extensionManager,
+    series1,
+    series2,
+    series3,
+    series4,
+    mergeKey,
+    tagFunc,
+    dataSourceAndSeriesMap,
+    dataSourceAndUIDsMap,
+    dataSourceAndDSMap,
+    pathSync;
+
+  beforeAll(() => {
+    path = 'query.series.search';
+    pathSync = 'getImageIdsForInstance';
+    tagFunc = jest.fn((data, sourceName) =>
+      data.map(item => ({ ...item, RetrieveAETitle: sourceName }))
+    );
+    sourceName = 'dicomweb1';
+    mergeKey = 'seriesInstanceUid';
+    series1 = { [mergeKey]: '123' };
+    series2 = { [mergeKey]: '234' };
+    series3 = { [mergeKey]: '345' };
+    series4 = { [mergeKey]: '456' };
+    mergeConfig = {
+      seriesMerge: {
+        dataSourceNames: ['dicomweb1', 'dicomweb2'],
+        defaultDataSourceName: 'dicomweb1',
+      },
+    };
+    dataSourceAndSeriesMap = {
+      dataSource1: series1,
+      dataSource2: series2,
+      dataSource3: series3,
+    };
+    dataSourceAndUIDsMap = {
+      dataSource1: ['123'],
+      dataSource2: ['234'],
+      dataSource3: ['345'],
+    };
+    dataSourceAndDSMap = {
+      dataSource1: {
+        displaySet: {
+          StudyInstanceUID: '123',
+          SeriesInstanceUID: '123',
+        },
+      },
+      dataSource2: {
+        displaySet: {
+          StudyInstanceUID: '234',
+          SeriesInstanceUID: '234',
+        },
+      },
+      dataSource3: {
+        displaySet: {
+          StudyInstanceUID: '345',
+          SeriesInstanceUID: '345',
+        },
+      },
+    };
+    extensionManager = {
+      dataSourceDefs: {
+        dataSource1: {
+          sourceName: 'dataSource1',
+          configuration: {},
+        },
+        dataSource2: {
+          sourceName: 'dataSource2',
+          configuration: {},
+        },
+        dataSource3: {
+          sourceName: 'dataSource3',
+          configuration: {},
+        },
+      },
+      getDataSources: jest.fn(dataSourceName => [
+        {
+          [path]: jest.fn().mockResolvedValue([dataSourceAndSeriesMap[dataSourceName]]),
+        },
+      ]),
+    };
+  });
+
+  afterEach(() => {
+    jest.clearAllMocks();
+  });
+
+  describe('callForAllDataSourcesAsync', () => {
+    it('should call the correct functions and return the merged data', async () => {
+      /** Arrange */
+      extensionManager.getDataSources = jest.fn(dataSourceName => [
+        {
+          [path]: jest.fn().mockResolvedValue([dataSourceAndSeriesMap[dataSourceName]]),
+        },
+      ]);
+
+      /** Act */
+      const data = await callForAllDataSourcesAsync({
+        mergeMap,
+        path,
+        args: [],
+        extensionManager,
+        dataSourceNames: ['dataSource1', 'dataSource2'],
+      });
+
+      /** Assert */
+      expect(extensionManager.getDataSources).toHaveBeenCalledTimes(2);
+      expect(extensionManager.getDataSources).toHaveBeenCalledWith('dataSource1');
+      expect(extensionManager.getDataSources).toHaveBeenCalledWith('dataSource2');
+      expect(data).toEqual([series1, series2]);
+    });
+  });
+
+  describe('callForAllDataSources', () => {
+    it('should call the correct functions and return the merged data', () => {
+      /** Arrange */
+      extensionManager.getDataSources = jest.fn(dataSourceName => [
+        {
+          [pathSync]: () => dataSourceAndUIDsMap[dataSourceName],
+        },
+      ]);
+
+      /** Act */
+      const data = callForAllDataSources({
+        path: pathSync,
+        args: [],
+        extensionManager,
+        dataSourceNames: ['dataSource2', 'dataSource3'],
+      });
+
+      /** Assert */
+      expect(extensionManager.getDataSources).toHaveBeenCalledTimes(2);
+      expect(extensionManager.getDataSources).toHaveBeenCalledWith('dataSource2');
+      expect(extensionManager.getDataSources).toHaveBeenCalledWith('dataSource3');
+      expect(data).toEqual(['234', '345']);
+    });
+  });
+
+  describe('callForDefaultDataSource', () => {
+    it('should call the correct function and return the data', () => {
+      /** Arrange */
+      extensionManager.getDataSources = jest.fn(dataSourceName => [
+        {
+          [pathSync]: () => dataSourceAndUIDsMap[dataSourceName],
+        },
+      ]);
+
+      /** Act */
+      const data = callForDefaultDataSource({
+        path: pathSync,
+        args: [],
+        extensionManager,
+        defaultDataSourceName: 'dataSource2',
+      });
+
+      /** Assert */
+      expect(extensionManager.getDataSources).toHaveBeenCalledTimes(1);
+      expect(extensionManager.getDataSources).toHaveBeenCalledWith('dataSource2');
+      expect(data).toEqual(['234']);
+    });
+  });
+
+  describe('callByRetrieveAETitle', () => {
+    it('should call the correct function and return the data', () => {
+      /** Arrange */
+      DicomMetadataStore.getSeries.mockImplementationOnce(() => [series2]);
+      extensionManager.getDataSources = jest.fn(dataSourceName => [
+        {
+          [pathSync]: () => dataSourceAndUIDsMap[dataSourceName],
+        },
+      ]);
+
+      /** Act */
+      const data = callByRetrieveAETitle({
+        path: pathSync,
+        args: [dataSourceAndDSMap['dataSource2']],
+        extensionManager,
+        defaultDataSourceName: 'dataSource2',
+      });
+
+      /** Assert */
+      expect(extensionManager.getDataSources).toHaveBeenCalledTimes(1);
+      expect(extensionManager.getDataSources).toHaveBeenCalledWith('dataSource2');
+      expect(data).toEqual(['234']);
+    });
+  });
+});

extensions/default/src/MergeDataSource/index.ts

@@ -0,0 +1,252 @@
+import { DicomMetadataStore, IWebApiDataSource } from '@ohif/core';
+import { get, uniqBy } from 'lodash';
+import {
+  MergeConfig,
+  CallForAllDataSourcesAsyncOptions,
+  CallForAllDataSourcesOptions,
+  CallForDefaultDataSourceOptions,
+  CallByRetrieveAETitleOptions,
+  MergeMap,
+} from './types';
+
+export const mergeMap: MergeMap = {
+  'query.studies.search': {
+    mergeKey: 'studyInstanceUid',
+    tagFunc: x => x,
+  },
+  'query.series.search': {
+    mergeKey: 'seriesInstanceUid',
+    tagFunc: (series, sourceName) => {
+      series.forEach(series => {
+        series.RetrieveAETitle = sourceName;
+        DicomMetadataStore.updateSeriesMetadata(series);
+      });
+      return series;
+    },
+  },
+};
+
+/**
+ * Calls all data sources asynchronously and merges the results.
+ * @param {CallForAllDataSourcesAsyncOptions} options - The options for calling all data sources.
+ * @param {string} options.path - The path to the function to be called on each data source.
+ * @param {unknown[]} options.args - The arguments to be passed to the function.
+ * @param {ExtensionManager} options.extensionManager - The extension manager.
+ * @param {string[]} options.dataSourceNames - The names of the data sources to be called.
+ * @returns {Promise<unknown[]>} - A promise that resolves to the merged data from all data sources.
+ */
+export const callForAllDataSourcesAsync = async ({
+  mergeMap,
+  path,
+  args,
+  extensionManager,
+  dataSourceNames,
+}: CallForAllDataSourcesAsyncOptions) => {
+  const { mergeKey, tagFunc } = mergeMap[path] || { tagFunc: x => x };
+
+  const dataSourceDefs = Object.values(extensionManager.dataSourceDefs);
+  const promises = [];
+  const mergedData = [];
+
+  for (const dataSourceDef of dataSourceDefs) {
+    const { configuration, sourceName } = dataSourceDef;
+    if (!!configuration && dataSourceNames.includes(sourceName)) {
+      const [dataSource] = extensionManager.getDataSources(sourceName);
+      const func = get(dataSource, path);
+      const promise = func.apply(dataSource, args);
+      promises.push(promise.then(data => mergedData.push(tagFunc(data, sourceName))));
+    }
+  }
+
+  await Promise.allSettled(promises);
+
+  return uniqBy(mergedData.flat(), obj => obj[mergeKey]);
+};
+
+/**
+ * Calls all data sources that match the provided names and merges their data.
+ * @param options - The options for calling all data sources.
+ * @param options.path - The path to the function to be called on each data source.
+ * @param options.args - The arguments to be passed to the function.
+ * @param options.extensionManager - The extension manager instance.
+ * @param options.dataSourceNames - The names of the data sources to be called.
+ * @returns The merged data from all the matching data sources.
+ */
+export const callForAllDataSources = ({
+  path,
+  args,
+  extensionManager,
+  dataSourceNames,
+}: CallForAllDataSourcesOptions) => {
+  const dataSourceDefs = Object.values(extensionManager.dataSourceDefs);
+  const mergedData = [];
+  for (const dataSourceDef of dataSourceDefs) {
+    const { configuration, sourceName } = dataSourceDef;
+    if (!!configuration && dataSourceNames.includes(sourceName)) {
+      const [dataSource] = extensionManager.getDataSources(sourceName);
+      const func = get(dataSource, path);
+      const data = func.apply(dataSource, args);
+      mergedData.push(data);
+    }
+  }
+  return mergedData.flat();
+};
+
+/**
+ * Calls the default data source function specified by the given path with the provided arguments.
+ * @param {CallForDefaultDataSourceOptions} options - The options for calling the default data source.
+ * @param {string} options.path - The path to the function within the default data source.
+ * @param {unknown[]} options.args - The arguments to pass to the function.
+ * @param {string} options.defaultDataSourceName - The name of the default data source.
+ * @param {ExtensionManager} options.extensionManager - The extension manager instance.
+ * @returns {unknown} - The result of calling the default data source function.
+ */
+export const callForDefaultDataSource = ({
+  path,
+  args,
+  defaultDataSourceName,
+  extensionManager,
+}: CallForDefaultDataSourceOptions) => {
+  const [dataSource] = extensionManager.getDataSources(defaultDataSourceName);
+  const func = get(dataSource, path);
+  return func.apply(dataSource, args);
+};
+
+/**
+ * Calls the data source specified by the RetrieveAETitle of the given display set.
+ * @typedef {Object} CallByRetrieveAETitleOptions
+ * @property {string} path - The path of the method to call on the data source.
+ * @property {unknown[]} args - The arguments to pass to the method.
+ * @property {string} defaultDataSourceName - The name of the default data source.
+ * @property {ExtensionManager} extensionManager - The extension manager.
+ */
+export const callByRetrieveAETitle = ({
+  path,
+  args,
+  defaultDataSourceName,
+  extensionManager,
+}: CallByRetrieveAETitleOptions) => {
+  const [displaySet] = args;
+  const seriesMetadata = DicomMetadataStore.getSeries(
+    displaySet.StudyInstanceUID,
+    displaySet.SeriesInstanceUID
+  );
+  const [dataSource] = extensionManager.getDataSources(
+    seriesMetadata.RetrieveAETitle || defaultDataSourceName
+  );
+  return dataSource[path](...args);
+};
+
+function createMergeDataSourceApi(
+  mergeConfig: MergeConfig,
+  UserAuthenticationService: unknown,
+  extensionManager
+) {
+  const { seriesMerge } = mergeConfig;
+  const { dataSourceNames, defaultDataSourceName } = seriesMerge;
+
+  const implementation = {
+    initialize: (...args: unknown[]) =>
+      callForAllDataSources({ path: 'initialize', args, extensionManager, dataSourceNames }),
+    query: {
+      studies: {
+        search: (...args: unknown[]) =>
+          callForAllDataSourcesAsync({
+            mergeMap,
+            path: 'query.studies.search',
+            args,
+            extensionManager,
+            dataSourceNames,
+          }),
+      },
+      series: {
+        search: (...args: unknown[]) =>
+          callForAllDataSourcesAsync({
+            mergeMap,
+            path: 'query.series.search',
+            args,
+            extensionManager,
+            dataSourceNames,
+          }),
+      },
+      instances: {
+        search: (...args: unknown[]) =>
+          callForAllDataSourcesAsync({
+            mergeMap,
+            path: 'query.instances.search',
+            args,
+            extensionManager,
+            dataSourceNames,
+          }),
+      },
+    },
+    retrieve: {
+      bulkDataURI: (...args: unknown[]) =>
+        callForAllDataSourcesAsync({
+          mergeMap,
+          path: 'retrieve.bulkDataURI',
+          args,
+          extensionManager,
+          dataSourceNames,
+        }),
+      directURL: (...args: unknown[]) =>
+        callForDefaultDataSource({
+          path: 'retrieve.directURL',
+          args,
+          defaultDataSourceName,
+          extensionManager,
+        }),
+      series: {
+        metadata: (...args: unknown[]) =>
+          callForAllDataSourcesAsync({
+            mergeMap,
+            path: 'retrieve.series.metadata',
+            args,
+            extensionManager,
+            dataSourceNames,
+          }),
+      },
+    },
+    store: {
+      dicom: (...args: unknown[]) =>
+        callForDefaultDataSource({
+          path: 'store.dicom',
+          args,
+          defaultDataSourceName,
+          extensionManager,
+        }),
+    },
+    deleteStudyMetadataPromise: (...args: unknown[]) =>
+      callForAllDataSources({
+        path: 'deleteStudyMetadataPromise',
+        args,
+        extensionManager,
+        dataSourceNames,
+      }),
+    getImageIdsForDisplaySet: (...args: unknown[]) =>
+      callByRetrieveAETitle({
+        path: 'getImageIdsForDisplaySet',
+        args,
+        defaultDataSourceName,
+        extensionManager,
+      }),
+    getImageIdsForInstance: (...args: unknown[]) =>
+      callByRetrieveAETitle({
+        path: 'getImageIdsForDisplaySet',
+        args,
+        defaultDataSourceName,
+        extensionManager,
+      }),
+    getStudyInstanceUIDs: (...args: unknown[]) =>
+      callForAllDataSources({
+        path: 'getStudyInstanceUIDs',
+        args,
+        extensionManager,
+        dataSourceNames,
+      }),
+  };
+
+  return IWebApiDataSource.create(implementation);
+}
+
+export { createMergeDataSourceApi };

extensions/default/src/MergeDataSource/types.ts

@@ -0,0 +1,44 @@
+import { ExtensionManager } from '@ohif/core';
+
+export type MergeMap = {
+  [key: string]: {
+    mergeKey: string;
+    tagFunc: (data: unknown[], sourceName: string) => unknown[];
+  };
+};
+
+export type CallForAllDataSourcesAsyncOptions = {
+  mergeMap: object;
+  path: string;
+  args: unknown[];
+  dataSourceNames: string[];
+  extensionManager: ExtensionManager;
+};
+
+export type CallForAllDataSourcesOptions = {
+  path: string;
+  args: unknown[];
+  dataSourceNames: string[];
+  extensionManager: ExtensionManager;
+};
+
+export type CallForDefaultDataSourceOptions = {
+  path: string;
+  args: unknown[];
+  defaultDataSourceName: string;
+  extensionManager: ExtensionManager;
+};
+
+export type CallByRetrieveAETitleOptions = {
+  path: string;
+  args: unknown[];
+  defaultDataSourceName: string;
+  extensionManager: ExtensionManager;
+};
+
+export type MergeConfig = {
+  seriesMerge: {
+    dataSourceNames: string[];
+    defaultDataSourceName: string;
+  };
+};

extensions/default/src/getDataSourcesModule.js

@@ -6,6 +6,7 @@ import { createDicomWebApi } from './DicomWebDataSource/index.js';
 import { createDicomJSONApi } from './DicomJSONDataSource/index.js';
 import { createDicomLocalApi } from './DicomLocalDataSource/index.js';
 import { createDicomWebProxyApi } from './DicomWebProxyDataSource/index.js';
+import { createMergeDataSourceApi } from './MergeDataSource/index';
 
 /**
  *
@@ -32,6 +33,11 @@ function getDataSourcesModule() {
       type: 'localApi',
       createDataSource: createDicomLocalApi,
     },
+    {
+      name: 'merge',
+      type: 'mergeApi',
+      createDataSource: createMergeDataSourceApi,
+    },
   ];
 }
 

platform/core/src/extensions/ExtensionManager.ts

@@ -464,7 +464,8 @@ export default class ExtensionManager extends PubSubService {
     const { userAuthenticationService } = this._servicesManager.services;
     const dataSourceInstance = module.createDataSource(
       dataSourceDef.configuration,
-      userAuthenticationService
+      userAuthenticationService,
+      this
     );
 
     this.dataSourceMap[dataSourceDef.sourceName] = [dataSourceInstance];

platform/core/src/services/DicomMetadataStore/DicomMetadataStore.ts

@@ -186,6 +186,18 @@ const BaseImplementation = {
       madeInClient,
     });
   },
+  updateSeriesMetadata(seriesMetadata) {
+    const { StudyInstanceUID, SeriesInstanceUID } = seriesMetadata;
+    const series = _getSeries(StudyInstanceUID, SeriesInstanceUID);
+    if (!series) {
+      return;
+    }
+
+    const study = _getStudy(StudyInstanceUID);
+    if (study) {
+      study.setSeriesMetadata(SeriesInstanceUID, seriesMetadata);
+    }
+  },
   addSeriesMetadata(seriesSummaryMetadata, madeInClient = false) {
     if (!seriesSummaryMetadata || !seriesSummaryMetadata.length || !seriesSummaryMetadata[0]) {
       return;

platform/docs/docs/platform/extensions/modules/data-source.md

@@ -81,7 +81,6 @@ You can take a look at `dicomweb` data source implementation to get an idea
 `extensions/default/src/DicomWebDataSource/index.js` but here here are some
 important api endpoints that you need to implement:
 
-
 - `initialize`: This method is called when the data source is first created in the mode.tsx, it is used to initialize the data source and set the configuration. For instance, `dicomwebDatasource` uses this method to grab the StudyInstanceUID from the URL and set it as the active study, as opposed to `dicomJSONDatasource` which uses url in the browser to fetch the data and store it in a cache
 - `query.studies.search`: This is used in the study panel on the left to fetch the prior studies for the same MRN which is then used to display on the `All` tab. it is also used in the Worklist to show all the studies from the server.
 - `query.series.search`: This is used to fetch the series information for a given study that is expanded in the Worklist.
@@ -89,8 +88,6 @@ important api endpoints that you need to implement:
 - `retrieve.series.metadata`: It is a crucial end point that is used to fetch series level metadata which for hanging displaySets and displaySet creation.
 - `store.dicom`: If you don't need store functionality, you can skip this method. This is used to store the data in the backend.
 
-
-
 ## Static WADO Client
 
 If the configuration for the data source has the value staticWado set, then it
@@ -172,3 +169,44 @@ extensionManager.updateDataSourceConfiguration( "dicomweb",
   },
 );
 ```
+
+## Merge Data Source
+The built-in merge data source is a useful tool for combining results from multiple data sources.
+Currently, this data source only supports merging at the series level. This means that series from data source 'A'
+and series from data source 'B' will be retrieved under the same study. If the same series exists in both data sources,
+the first series arrived is the one that gets stored, and any other conflicting series will be ignored.
+
+The merge data source is particularly useful when dealing with derived data that is generated and stored in different servers.
+For example, it can be used to retrieve annotation series from one data source and input data (images) from another data source.
+
+A default data source can be defined as shown below. This allows defining which of the servers should be the
+fallback server in case something goes wrong.
+
+Configuration Example:
+```js
+window.config = {
+  ...
+  dataSources: [
+    {
+      sourceName: 'merge',
+      namespace: '@ohif/extension-default.dataSourcesModule.merge',
+      configuration: {
+        name: 'merge',
+        friendlyName: 'Merge dicomweb-1 and dicomweb-2 data at the series level',
+        seriesMerge: {
+          dataSourceNames: ['dicomweb-1', 'dicomweb-2'],
+          defaultDataSourceName: 'dicomweb-1'
+        },
+      },
+    },
+    {
+      sourceName: 'dicomweb-1',
+      ...
+    },
+    {
+      sourceName: 'dicomweb-2',
+      ...
+    },
+  ],
+};
+```