Add window functions and enhanced aggregations to QuerySchema

Co-authored-by: hotlong <50353452+hotlong@users.noreply.github.com>

Author: Copilot

packages/core/src/query/query-ast.ts

@@ -19,6 +19,7 @@ import type {
   WindowNode,
   WindowFunction,
   WindowFrame,
+  WindowConfig,
   FieldNode,
   LiteralNode,
   OperatorNode,
@@ -81,8 +82,10 @@ export class QueryASTBuilder {
       fields.push(...query.aggregations.map(agg => this.buildAggregation(agg)));
     }
 
-    // Add window functions if they exist (future extension point)
-    // query.windows?.forEach(win => fields.push(this.buildWindow(win)));
+    // Add window functions (ObjectStack Spec v0.7.1)
+    if (query.windows && query.windows.length > 0) {
+      fields.push(...query.windows.map(win => this.buildWindow(win)));
+    }
 
     return {
       type: 'select',
@@ -289,16 +292,7 @@ export class QueryASTBuilder {
   /**
    * Build window function node (ObjectStack Spec v0.7.1)
    */
-  private buildWindow(config: {
-    function: WindowFunction;
-    field?: string;
-    alias: string;
-    partitionBy?: string[];
-    orderBy?: Array<{ field: string; direction: 'asc' | 'desc' }>;
-    frame?: WindowFrame;
-    offset?: number;
-    defaultValue?: any;
-  }): WindowNode {
+  private buildWindow(config: WindowConfig): WindowNode {
     const node: WindowNode = {
       type: 'window',
       function: config.function,

packages/types/src/data-protocol.ts

@@ -340,6 +340,11 @@ export interface QuerySchema {
    */
   group_by?: string[];
 
+  /**
+   * Window functions (ObjectStack Spec v0.7.1)
+   */
+  windows?: WindowConfig[];
+  
   /**
    * Related objects to expand
    */
@@ -375,10 +380,40 @@ export interface JoinConfig {
  * Aggregation configuration
  */
 export interface AggregationConfig {
-  function: 'count' | 'sum' | 'avg' | 'min' | 'max';
+  function: 'count' | 'sum' | 'avg' | 'min' | 'max' | 'count_distinct' | 'array_agg' | 'string_agg';
   field?: string;
   alias?: string;
   distinct?: boolean;
+  separator?: string; // For string_agg function
+}
+
+/**
+ * Window function configuration (ObjectStack Spec v0.7.1)
+ */
+export interface WindowConfig {
+  /** Window function name */
+  function: WindowFunction;
+  
+  /** Field to operate on (not required for row_number, rank, etc.) */
+  field?: string;
+  
+  /** Result alias */
+  alias: string;
+  
+  /** PARTITION BY fields */
+  partitionBy?: string[];
+  
+  /** ORDER BY clause */
+  orderBy?: Array<{ field: string; direction: 'asc' | 'desc' }>;
+  
+  /** Window frame specification */
+  frame?: WindowFrame;
+  
+  /** Offset for lag/lead functions */
+  offset?: number;
+  
+  /** Default value for lag/lead when no previous/next row */
+  defaultValue?: any;
 }
 
 /**

packages/types/src/index.ts

@@ -384,6 +384,7 @@ export type {
   QuerySortConfig,
   JoinConfig,
   AggregationConfig,
+  WindowConfig,
   // Filter Schema (Phase 3.4)
   AdvancedFilterSchema,
   AdvancedFilterCondition,