implement a reduce operator & ZQL group-by on top of it

src/zql/ast-to-ivm/pipeline-builder.ts

@@ -64,7 +64,7 @@ export function applySelect(
   orderBy: Ordering | undefined,
 ) {
   return stream.map(x => {
-    let ret: Partial<Record<string, unknown>>;
+    let ret: Record<string, unknown>;
     if (select.length === 0) {
       ret = {...x};
     } else {

src/zql/integration.test.ts

@@ -6,7 +6,7 @@ import {Replicache, TEST_LICENSE_KEY} from 'replicache';
 import {nanoid} from 'nanoid';
 import fc from 'fast-check';
 import {EntityQuery} from './query/entity-query.js';
-import {agg} from './query/agg.js';
+import * as agg from './query/agg.js';
 
 export async function tickAFewTimes(n = 10, time = 0) {
   for (let i = 0; i < n; i++) {
@@ -406,7 +406,7 @@ test('group by', async () => {
       priority: 'high',
       assignee: 'charles',
       created: new Date('2024-01-01').getTime(),
-      updated: new Date().getTime(),
+      updated: Date.now(),
     },
     {
       id: 'b',
@@ -415,7 +415,7 @@ test('group by', async () => {
       priority: 'medium',
       assignee: 'bob',
       created: new Date('2024-01-02').getTime(),
-      updated: new Date().getTime(),
+      updated: Date.now(),
     },
     {
       id: 'c',
@@ -424,11 +424,10 @@ test('group by', async () => {
       priority: 'low',
       assignee: 'alice',
       created: new Date('2024-01-03').getTime(),
-      updated: new Date().getTime(),
+      updated: Date.now(),
     },
   ] as const;
   await Promise.all(issues.map(r.mutate.initIssue));
-  await new Promise(resolve => setTimeout(resolve, 0));
   const stmt = q
     .select('status', agg.count('status', 'count'))
     .groupBy('status')

src/zql/query/agg.ts

@@ -35,106 +35,110 @@ export type AggArray<Field extends string, Alias extends string> = {
   aggregate: 'array';
 } & AggregateBase<Field, Alias>;
 
-export const agg: {
-  min<Field extends string>(field: Field): Min<Field, Field>;
-  min<Field extends string, Alias extends string>(
-    field: Field,
-    alias: Alias,
-  ): Min<Field, Alias>;
-
-  max<Field extends string>(field: Field): Max<Field, Field>;
-  max<Field extends string, Alias extends string>(
-    field: Field,
-    alias: Alias,
-  ): Max<Field, Alias>;
-
-  sum<Field extends string>(field: Field): Sum<Field, Field>;
-  sum<Field extends string, Alias extends string>(
-    field: Field,
-    alias: Alias,
-  ): Sum<Field, Alias>;
-
-  count<Field extends string>(field: Field): Count<Field, Field>;
-  count<Field extends string, Alias extends string>(
-    field: Field,
-    alias: Alias,
-  ): Count<Field, Alias>;
-
-  avg<Field extends string>(field: Field): Avg<Field, Field>;
-  avg<Field extends string, Alias extends string>(
-    field: Field,
-    alias: Alias,
-  ): Avg<Field, Alias>;
-
-  array<Field extends string>(field: Field): AggArray<Field, Field>;
-  array<Field extends string, Alias extends string>(
-    field: Field,
-    alias: Alias,
-  ): AggArray<Field, Alias>;
-} = {
-  min<Field extends string, Alias extends string>(
-    field: Field,
-    alias?: Alias | undefined,
-  ): Min<Field, Alias> {
-    return {
-      aggregate: 'min',
-      field,
-      alias: alias ?? (field as unknown as Alias),
-    };
-  },
-
-  max<Field extends string, Alias extends string>(
-    field: Field,
-    alias?: Alias | undefined,
-  ): Max<Field, Alias> {
-    return {
-      aggregate: 'max',
-      field,
-      alias: alias ?? (field as unknown as Alias),
-    };
-  },
-
-  sum<Field extends string, Alias extends string>(
-    field: Field,
-    alias?: Alias | undefined,
-  ): Sum<Field, Alias> {
-    return {
-      aggregate: 'sum',
-      field,
-      alias: alias ?? (field as unknown as Alias),
-    };
-  },
-
-  count<Field extends string, Alias extends string>(
-    field: Field,
-    alias?: Alias | undefined,
-  ): Count<Field, Alias> {
-    return {
-      aggregate: 'count',
-      field,
-      alias: alias ?? (field as unknown as Alias),
-    };
-  },
-
-  avg<Field extends string, Alias extends string>(
-    field: Field,
-    alias?: Alias | undefined,
-  ): Avg<Field, Alias> {
-    return {
-      aggregate: 'avg',
-      field,
-      alias: alias ?? (field as unknown as Alias),
-    };
-  },
-
-  array<Field extends string, Alias extends string>(
-    field: Field,
-    alias?: Alias | undefined,
-  ): AggArray<Field, Alias> {
-    return {
-      aggregate: 'array',
-      field,
-      alias: alias ?? (field as unknown as Alias),
-    };
-  },
-};
+export function min<Field extends string>(field: Field): Min<Field, Field>;
+export function min<Field extends string, Alias extends string>(
+  field: Field,
+  alias: Alias,
+): Min<Field, Alias>;
+export function min<Field extends string, Alias extends string>(
+  field: Field,
+  alias?: Alias | undefined,
+): Min<Field, Alias> {
+  return {
+    aggregate: 'min',
+    field,
+    alias: alias ?? (field as unknown as Alias),
+  };
+}
+
+export function max<Field extends string>(field: Field): Max<Field, Field>;
+export function max<Field extends string, Alias extends string>(
+  field: Field,
+  alias: Alias,
+): Max<Field, Alias>;
+export function max<Field extends string, Alias extends string>(
+  field: Field,
+  alias?: Alias | undefined,
+): Max<Field, Alias> {
+  return {
+    aggregate: 'max',
+    field,
+    alias: alias ?? (field as unknown as Alias),
+  };
+}
+
+export function sum<Field extends string>(field: Field): Sum<Field, Field>;
+export function sum<Field extends string, Alias extends string>(
+  field: Field,
+  alias: Alias,
+): Sum<Field, Alias>;
+export function sum<Field extends string, Alias extends string>(
+  field: Field,
+  alias?: Alias | undefined,
+): Sum<Field, Alias> {
+  return {
+    aggregate: 'sum',
+    field,
+    alias: alias ?? (field as unknown as Alias),
+  };
+}
+
+export function count<Field extends string>(field: Field): Count<Field, Field>;
+export function count<Field extends string, Alias extends string>(
+  field: Field,
+  alias: Alias,
+): Count<Field, Alias>;
+export function count<Field extends string, Alias extends string>(
+  field: Field,
+  alias?: Alias | undefined,
+): Count<Field, Alias> {
+  return {
+    aggregate: 'count',
+    field,
+    alias: alias ?? (field as unknown as Alias),
+  };
+}
+
+export function avg<Field extends string>(field: Field): Avg<Field, Field>;
+export function avg<Field extends string, Alias extends string>(
+  field: Field,
+  alias: Alias,
+): Avg<Field, Alias>;
+export function avg<Field extends string, Alias extends string>(
+  field: Field,
+  alias?: Alias | undefined,
+): Avg<Field, Alias> {
+  return {
+    aggregate: 'avg',
+    field,
+    alias: alias ?? (field as unknown as Alias),
+  };
+}
+
+export function array<Field extends string>(
+  field: Field,
+): AggArray<Field, Field>;
+export function array<Field extends string, Alias extends string>(
+  field: Field,
+  alias: Alias,
+): AggArray<Field, Alias>;
+export function array<Field extends string, Alias extends string>(
+  field: Field,
+  alias?: Alias | undefined,
+): AggArray<Field, Alias> {
+  return {
+    aggregate: 'array',
+    field,
+    alias: alias ?? (field as unknown as Alias),
+  };
+}
+
+export function isAggregate<Field extends string, Alias extends string>(
+  x: unknown,
+): x is Aggregate<Field, Alias> {
+  return (
+    x !== null &&
+    typeof x === 'object' &&
+    typeof (x as Record<string, unknown>).aggregate === 'string'
+  );
+}

src/zql/query/entity-query.test.ts

@@ -3,7 +3,7 @@ import {z} from 'zod';
 import {makeTestContext} from '../context/context.js';
 import {Misuse} from '../error/misuse.js';
 import {EntityQuery, astForTesting as ast} from './entity-query.js';
-import {agg} from './agg.js';
+import * as agg from './agg.js';
 
 const context = makeTestContext();
 test('query types', () => {
@@ -53,14 +53,18 @@ test('query types', () => {
   q.where(sym, '==', true);
 
   // @ts-expect-error - 'x' is not a field that we can aggregate on
-  q.select(agg.array('x'));
+  q.select(agg.array('x')).groupBy('id');
 
-  expectTypeOf(q.select('id', agg.array('str')).prepare().exec()).toMatchTypeOf<
-    Promise<readonly {id: string; str: readonly string[]}[]>
-  >();
+  expectTypeOf(
+    q.select('id', agg.array('str')).groupBy('optStr').prepare().exec(),
+  ).toMatchTypeOf<Promise<readonly {id: string; str: readonly string[]}[]>>();
 
   expectTypeOf(
-    q.select('id', agg.array('str', 'alias')).prepare().exec(),
+    q
+      .select('id', agg.array('str', 'alias'))
+      .groupBy('optStr')
+      .prepare()
+      .exec(),
   ).toMatchTypeOf<Promise<readonly {id: string; alias: readonly string[]}[]>>();
 });