Add within group clause support for aggregate function builder (#1024)

Co-authored-by: Ivashkin Olexiy <[email protected]>
Co-authored-by: Dev K0te <[email protected]>
Co-authored-by: igalklebanov <[email protected]>

Author: 3 people

src/operation-node/aggregate-function-node.ts

@@ -11,6 +11,7 @@ export interface AggregateFunctionNode extends OperationNode {
   readonly aggregated: readonly OperationNode[]
   readonly distinct?: boolean
   readonly orderBy?: OrderByNode
+  readonly withinGroup?: OrderByNode
   readonly filter?: WhereNode
   readonly over?: OverNode
 }
@@ -46,11 +47,14 @@ export const AggregateFunctionNode = freeze({
   cloneWithOrderBy(
     aggregateFunctionNode: AggregateFunctionNode,
     orderItems: ReadonlyArray<OrderByItemNode>,
+    withinGroup = false,
   ): AggregateFunctionNode {
+    const prop = withinGroup ? 'withinGroup' : 'orderBy'
+
     return freeze({
       ...aggregateFunctionNode,
-      orderBy: aggregateFunctionNode.orderBy
-        ? OrderByNode.cloneWithItems(aggregateFunctionNode.orderBy, orderItems)
+      [prop]: aggregateFunctionNode[prop]
+        ? OrderByNode.cloneWithItems(aggregateFunctionNode[prop], orderItems)
         : OrderByNode.create(orderItems),
     })
   },

src/operation-node/operation-node-transformer.ts

@@ -904,11 +904,12 @@ export class OperationNodeTransformer {
   ): AggregateFunctionNode {
     return requireAllProps({
       kind: 'AggregateFunctionNode',
+      func: node.func,
       aggregated: this.transformNodeList(node.aggregated),
       distinct: node.distinct,
       orderBy: this.transformNode(node.orderBy),
+      withinGroup: this.transformNode(node.withinGroup),
       filter: this.transformNode(node.filter),
-      func: node.func,
       over: this.transformNode(node.over),
     })
   }

src/query-builder/aggregate-function-builder.ts

@@ -11,7 +11,7 @@ import {
 } from '../expression/expression.js'
 import {
   ReferenceExpression,
-  StringReference,
+  SimpleReferenceExpression,
 } from '../parser/reference-parser.js'
 import {
   ComparisonOperatorExpression,
@@ -21,7 +21,6 @@ import {
 } from '../parser/binary-operation-parser.js'
 import { SqlBool } from '../util/type-utils.js'
 import { ExpressionOrFactory } from '../parser/expression-parser.js'
-import { DynamicReferenceBuilder } from '../dynamic/dynamic-reference-builder.js'
 import {
   OrderByDirectionExpression,
   parseOrderBy,
@@ -125,7 +124,7 @@ export class AggregateFunctionBuilder<DB, TB extends keyof DB, O = unknown>
    * inner join "pet" ON "pet"."owner_id" = "person"."id"
    * ```
    */
-  orderBy<OE extends StringReference<DB, TB> | DynamicReferenceBuilder<any>>(
+  orderBy<OE extends SimpleReferenceExpression<DB, TB>>(
     orderBy: OE,
     direction?: OrderByDirectionExpression,
   ): AggregateFunctionBuilder<DB, TB, O> {
@@ -138,6 +137,48 @@ export class AggregateFunctionBuilder<DB, TB extends keyof DB, O = unknown>
     })
   }
 
+  /**
+   * Adds a `withing group` clause with a nested `order by` clause after the function.
+   *
+   * This is only supported by some dialects like PostgreSQL or MS SQL Server.
+   *
+   * ### Examples
+   *
+   * Most frequent person name:
+   *
+   * ```ts
+   * const result = await db
+   *   .selectFrom('person')
+   *   .select((eb) => [
+   *     eb.fn
+   *       .agg<string>('mode')
+   *       .withinGroupOrderBy('person.first_name')
+   *       .as('most_frequent_name')
+   *   ])
+   *   .executeTakeFirstOrThrow()
+   * ```
+   *
+   * The generated SQL (PostgreSQL):
+   *
+   * ```sql
+   * select mode() within group (order by "person"."first_name") as "most_frequent_name"
+   * from "person"
+   * ```
+   */
+  withinGroupOrderBy<OE extends SimpleReferenceExpression<DB, TB>>(
+    orderBy: OE,
+    direction?: OrderByDirectionExpression,
+  ): AggregateFunctionBuilder<DB, TB, O> {
+    return new AggregateFunctionBuilder({
+      ...this.#props,
+      aggregateFunctionNode: AggregateFunctionNode.cloneWithOrderBy(
+        this.#props.aggregateFunctionNode,
+        parseOrderBy([orderBy, direction]),
+        true,
+      ),
+    })
+  }
+
   /**
    * Adds a `filter` clause with a nested `where` clause after the function.
    *

src/query-compiler/default-query-compiler.ts

@@ -1418,6 +1418,12 @@ export class DefaultQueryCompiler
 
     this.append(')')
 
+    if (node.withinGroup) {
+      this.append(' within group (')
+      this.visitNode(node.withinGroup)
+      this.append(')')
+    }
+
     if (node.filter) {
       this.append(' filter(')
       this.visitNode(node.filter)

test/node/src/aggregate-function.test.ts

@@ -4,6 +4,7 @@ import {
   SimpleReferenceExpression,
   ReferenceExpression,
   sql,
+  expressionBuilder,
 } from '../../../'
 import {
   Database,
@@ -1108,8 +1109,12 @@ for (const dialect of DIALECTS) {
       await query.execute()
     })
 
-    describe(`should execute order-sensitive aggregate functions`, () => {
-      if (dialect === 'postgres' || dialect === 'mysql' || dialect === 'sqlite') {
+    describe('should execute order-sensitive aggregate functions', () => {
+      if (
+        dialect === 'postgres' ||
+        dialect === 'mysql' ||
+        dialect === 'sqlite'
+      ) {
         const isMySql = dialect === 'mysql'
         const funcName = isMySql ? 'group_concat' : 'string_agg'
         const funcArgs: Array<ReferenceExpression<Database, 'person'>> = [
@@ -1157,6 +1162,39 @@ for (const dialect of DIALECTS) {
           await query.execute()
         })
       }
+
+      if (dialect === 'postgres' || dialect === 'mssql') {
+        it(`should execute a query with within group (order by column) in select clause`, async () => {
+          const query = ctx.db.selectFrom('toy').select((eb) =>
+            eb.fn
+              .agg('percentile_cont', [sql.lit(0.5)])
+              .withinGroupOrderBy('toy.price')
+              .$call((ab) => (dialect === 'mssql' ? ab.over() : ab))
+              .as('median_price'),
+          )
+
+          testSql(query, dialect, {
+            postgres: {
+              sql: [
+                `select percentile_cont(0.5) within group (order by "toy"."price") as "median_price"`,
+                `from "toy"`,
+              ],
+              parameters: [],
+            },
+            mysql: NOT_SUPPORTED,
+            mssql: {
+              sql: [
+                `select percentile_cont(0.5) within group (order by "toy"."price") over() as "median_price"`,
+                `from "toy"`,
+              ],
+              parameters: [],
+            },
+            sqlite: NOT_SUPPORTED,
+          })
+
+          await query.execute()
+        })
+      }
     })
   })
 }