feat: 添加字段引用模式和连接执行策略，优化聚合节点的过滤条件

Author: hotlong

packages/spec/src/data/filter.zod.ts

@@ -22,6 +22,21 @@ import { z } from 'zod';
  * 4. Convention over Configuration: Implicit syntax for common queries
  */
 
+/**
+ * Field Reference
+ * Represents a reference to another field/column instead of a literal value.
+ * Used for joins (ON clause) and cross-field comparisons.
+ * 
+ * @example
+ * // user.id = order.owner_id
+ * { "$eq": { "$field": "order.owner_id" } }
+ */
+export const FieldReferenceSchema = z.object({
+  $field: z.string().describe('Field Reference/Column Name')
+});
+
+export type FieldReference = z.infer<typeof FieldReferenceSchema>;
+
 // ============================================================================
 // 3.1 Comparison Operators
 // ============================================================================
@@ -44,16 +59,16 @@ export const EqualityOperatorSchema = z.object({
  */
 export const ComparisonOperatorSchema = z.object({
   /** Greater than - SQL: > | MongoDB: $gt */
-  $gt: z.union([z.number(), z.date()]).optional(),
+  $gt: z.union([z.number(), z.date(), FieldReferenceSchema]).optional(),
 
   /** Greater than or equal to - SQL: >= | MongoDB: $gte */
-  $gte: z.union([z.number(), z.date()]).optional(),
+  $gte: z.union([z.number(), z.date(), FieldReferenceSchema]).optional(),
 
   /** Less than - SQL: < | MongoDB: $lt */
-  $lt: z.union([z.number(), z.date()]).optional(),
+  $lt: z.union([z.number(), z.date(), FieldReferenceSchema]).optional(),
 
   /** Less than or equal to - SQL: <= | MongoDB: $lte */
-  $lte: z.union([z.number(), z.date()]).optional(),
+  $lte: z.union([z.number(), z.date(), FieldReferenceSchema]).optional(),
 });
 
 // ============================================================================
@@ -78,8 +93,8 @@ export const SetOperatorSchema = z.object({
 export const RangeOperatorSchema = z.object({
   /** Between (inclusive) - takes [min, max] array */
   $between: z.tuple([
-    z.union([z.number(), z.date()]),
-    z.union([z.number(), z.date()])
+    z.union([z.number(), z.date(), FieldReferenceSchema]),
+    z.union([z.number(), z.date(), FieldReferenceSchema])
   ]).optional(),
 });
 
@@ -131,17 +146,17 @@ export const FieldOperatorsSchema = z.object({
   $ne: z.any().optional(),
 
   // Comparison (numeric/date)
-  $gt: z.union([z.number(), z.date()]).optional(),
-  $gte: z.union([z.number(), z.date()]).optional(),
-  $lt: z.union([z.number(), z.date()]).optional(),
-  $lte: z.union([z.number(), z.date()]).optional(),
+  $gt: z.union([z.number(), z.date(), FieldReferenceSchema]).optional(),
+  $gte: z.union([z.number(), z.date(), FieldReferenceSchema]).optional(),
+  $lt: z.union([z.number(), z.date(), FieldReferenceSchema]).optional(),
+  $lte: z.union([z.number(), z.date(), FieldReferenceSchema]).optional(),
 
   // Set & Range
   $in: z.array(z.any()).optional(),
   $nin: z.array(z.any()).optional(),
   $between: z.tuple([
-    z.union([z.number(), z.date()]),
-    z.union([z.number(), z.date()])
+    z.union([z.number(), z.date(), FieldReferenceSchema]),
+    z.union([z.number(), z.date(), FieldReferenceSchema])
   ]).optional(),
 
   // String-specific

packages/spec/src/data/query.zod.ts

@@ -90,6 +90,7 @@ export const AggregationNodeSchema = z.object({
   field: z.string().optional().describe('Field to aggregate (optional for COUNT(*))'),
   alias: z.string().describe('Result column alias'),
   distinct: z.boolean().optional().describe('Apply DISTINCT before aggregation'),
+  filter: FilterConditionSchema.optional().describe('Filter/Condition to apply to the aggregation (FILTER WHERE clause)'),
 });
 
 /**
@@ -130,6 +131,18 @@ export const AggregationNodeSchema = z.object({
  */
 export const JoinType = z.enum(['inner', 'left', 'right', 'full']);
 
+/**
+ * Join Execution Strategy
+ * Hints to the query engine on how to execute the join.
+ * 
+ * Strategies:
+ * - **auto**: Engine decides best strategy (Default).
+ * - **database**: Push down join to the database (Requires same datasource).
+ * - **hash**: Load both sets into memory and hash join (Cross-datasource, memory intensive).
+ * - **loop**: Nested loop lookup (N+1 safe version). (Good for small right-side lookups).
+ */
+export const JoinStrategy = z.enum(['auto', 'database', 'hash', 'loop']);
+
 /**
  * Join Node
  * Represents table joins for combining data from multiple objects.
@@ -211,6 +224,7 @@ export const JoinType = z.enum(['inner', 'left', 'right', 'full']);
 export const JoinNodeSchema: z.ZodType<any> = z.lazy(() => 
   z.object({
     type: JoinType.describe('Join type'),
+    strategy: JoinStrategy.optional().describe('Execution strategy hint'),
     object: z.string().describe('Object/table to join'),
     alias: z.string().optional().describe('Table alias'),
     on: FilterConditionSchema.describe('Join condition'),