Initial sets up of new execution plan comparison result endpoint (#18813)

* Initial sets up of new execution plan comparison result endpoint

* Makes query execution plan endpoint URI's more consistent.

src/sql/azdata.proposed.d.ts

@@ -1268,6 +1268,38 @@ declare module 'azdata' {
 			graphs: ExecutionPlanGraph[]
 		}
 
+		export interface ExecutionGraphComparisonResult {
+			/**
+			 * The base ExecutionPlanNode for the ExecutionGraphComparisonResult.
+			 */
+			baseNode: ExecutionPlanNode;
+			/**
+			 * The children of the ExecutionGraphComparisonResult.
+			 */
+			children: ExecutionGraphComparisonResult[];
+			/**
+			 * The group index of the ExecutionGraphComparisonResult.
+			 */
+			groupIndex: number;
+			/**
+			 * Flag to indicate if the ExecutionGraphComparisonResult has a matching node in the compared execution plan.
+			 */
+			hasMatch: boolean;
+			/**
+			 * List of matching nodes for the ExecutionGraphComparisonResult.
+			 */
+			matchingNodes: ExecutionGraphComparisonResult[];
+			/**
+			 * The parent of the ExecutionGraphComparisonResult.
+			 */
+			parentNode: ExecutionGraphComparisonResult;
+		}
+
+		export interface ExecutionPlanComparisonResult extends ResultStatus {
+			firstComparisonResult: ExecutionGraphComparisonResult;
+			secondComparisonResult: ExecutionGraphComparisonResult;
+		}
+
 		export interface ExecutionPlanProvider extends DataProvider {
 			// execution plan service methods
 
@@ -1276,6 +1308,12 @@ declare module 'azdata' {
 			 * @param planFile file that contains the execution plan
 			 */
 			getExecutionPlan(planFile: ExecutionPlanGraphInfo): Thenable<GetExecutionPlanResult>;
+			/**
+			 * Compares two execution plans and identifies matching regions in both execution plans.
+			 * @param firstPlanFile file that contains the first execution plan.
+			 * @param secondPlanFile file that contains the second execution plan.
+			 */
+			compareExecutionPlanGraph(firstPlanFile: ExecutionPlanGraphInfo, secondPlanFile: ExecutionPlanGraphInfo): Thenable<ExecutionPlanComparisonResult>;
 		}
 	}