Support groupBy over BigInt and Date

packages/db-ivm/src/index.ts

@@ -2,4 +2,4 @@ export * from './d2.js'
 export * from './multiset.js'
 export * from './operators/index.js'
 export * from './types.js'
-export { compareKeys } from './utils.js'
+export { compareKeys, serializeValue } from './utils.js'

packages/db-ivm/src/operators/groupBy.ts

@@ -1,3 +1,4 @@
+import { serializeValue } from '../utils.js'
 import { map } from './map.js'
 import { reduce } from './reduce.js'
 import type { IStreamBuilder, KeyValue } from '../types.js'
@@ -67,7 +68,7 @@ export function groupBy<
     const withKeysAndValues = stream.pipe(
       map((data) => {
         const key = keyExtractor(data)
-        const keyString = JSON.stringify(key)
+        const keyString = serializeValue(key)
 
         // Create values object with pre-aggregated values
         const values: Record<string, unknown> = {}

packages/db-ivm/src/utils.ts

@@ -192,3 +192,20 @@ export function compareKeys(a: string | number, b: string | number): number {
   // Different types: strings come before numbers
   return typeof a === `string` ? -1 : 1
 }
+
+/**
+ * Serializes a value for use as a key, handling BigInt and Date values that JSON.stringify cannot handle.
+ * Uses JSON.stringify with a replacer function to convert BigInt values to strings and Date values to ISO strings.
+ * This is used for creating string keys in groupBy operations.
+ */
+export function serializeValue(value: unknown): string {
+  return JSON.stringify(value, (_, val) => {
+    if (typeof val === 'bigint') {
+      return val.toString()
+    }
+    if (val instanceof Date) {
+      return val.toISOString()
+    }
+    return val
+  })
+}

packages/db/src/query/compiler/group-by.ts

@@ -1,4 +1,10 @@
-import { filter, groupBy, groupByOperators, map } from '@tanstack/db-ivm'
+import {
+  filter,
+  groupBy,
+  groupByOperators,
+  map,
+  serializeValue,
+} from '@tanstack/db-ivm'
 import { Func, PropRef, getHavingExpression } from '../ir.js'
 import {
   AggregateFunctionNotInSelectError,
@@ -248,7 +254,7 @@ export function processGroupBy(
         for (let i = 0; i < groupByClause.length; i++) {
           keyParts.push(aggregatedRow[`__key_${i}`])
         }
-        finalKey = JSON.stringify(keyParts)
+        finalKey = serializeValue(keyParts)
       }
 
       return [