Support WITHIN GROUP for aggregate expressions (#47)

Co-authored-by: Akshay Gupta <kitallis@gmail.com>

Author: scimetfoo

README.md

@@ -24,19 +24,22 @@ The query creation and usage is exactly the same as honeysql.
   - [pattern matching](#pattern-matching)
   - [except](#except)
   - [filter](#filter)
+  - [within group](#within-group)
   - [SQL functions](#sql-functions)
 - [License](#license)
 
 ## Usage
 
 ### REPL
+
 ```clojure
 (require '[honeysql.core :as sql]
          '[honeysql.helpers :refer :all :as sqlh]
          '[honeysql-postgres.helpers :as psqlh])
 ```
 
 ### distinct-on
+
 `select` can be written with a `distinct on` clause
 ``` clojure
 (-> (select :column-1 :column-2 :column-3)
@@ -47,6 +50,7 @@ The query creation and usage is exactly the same as honeysql.
 ```
 
 ### upsert
+
 `upsert` can be written either way. You can make use of `do-update-set!` over `do-update-set`, if you want to modify the some column values in case of conflicts.
 ```clojure
 (-> (insert-into :distributors)
@@ -69,6 +73,7 @@ The query creation and usage is exactly the same as honeysql.
 ```
 
 ### insert into with alias
+
 `insert-into-as` can be used to write insert statements with table name aliased.
 ```clojure
 (-> (psqlh/insert-into-as :distributors :d)
@@ -84,6 +89,7 @@ The query creation and usage is exactly the same as honeysql.
 ```
 
 ### over
+
 You can make use of `over` to write window functions where it takes in vectors with aggregator functions and window functions along with optional alias like `(over [aggregator-function window-function alias])`, the can be coupled with the `window` clause to write window-function functions with alias that is later defines the window-function, like `(-> (over [aggregator-function :w]) (window :w window-function))`.
 ```clojure
 (-> (select :id)
@@ -108,6 +114,7 @@ You can make use of `over` to write window functions where it takes in vectors w
 ```
 
 ### create table
+
 `create-table` and `with-columns` can be used to create tables along with the SQL functions, where `create-table` takes a table name as argument and `with-columns` takes a vector of vectors as argument, where the vectors describe the column properties as `[:column-name :datatype :constraints ... ]`.
 ```clojure
 (-> (psqlh/create-table :films)
@@ -122,13 +129,15 @@ You can make use of `over` to write window functions where it takes in vectors w
 ```
 
 ### drop table
+
 `drop-table` is used to drop tables
 ```clojure
 (sql/format (psqlh/drop-table :cities :towns :vilages))
 => ["DROP TABLE cities, towns, vilages"]
 ```
 
 ### alter table
+
 use `alter-table` along with `add-column` & `drop-column` to modify table level details
 ```clojure
 (-> (psqlh/alter-table :employees)
@@ -143,6 +152,7 @@ use `alter-table` along with `add-column` & `drop-column` to modify table level
 ```
 
 ### create-extension
+
 `create-extension` can be used to create extensions with a given keyword.
 ```clojure
 (-> (psqlh/create-extension :uuid-ossp :if-not-exists? true)
@@ -161,6 +171,7 @@ use `alter-table` along with `add-column` & `drop-column` to modify table level
 ```
 
 ### pattern matching
+
 The `ilike` and `not-ilike` operators can be used to query data using a pattern matching technique.
 - like
 ```clojure
@@ -180,6 +191,7 @@ The `ilike` and `not-ilike` operators can be used to query data using a pattern
 ```
 
 ### except
+
 ```clojure
 (sql/format
   {:except
@@ -200,7 +212,19 @@ The `ilike` and `not-ilike` operators can be used to query data using a pattern
 => ["SELECT count(*) , count(*) FILTER (WHERE i < ?) AS foo, count(*) FILTER (WHERE i BETWEEN ? AND ?) AS bar FROM generate_series(1,10) AS s(i)" 5 3 10]
 ```
 
+### within group
+
+``` clojure
+(-> (select (sql/call :count :*))
+    (within-group [(sql/call :percentile_disc (hsql-types/array [0.25 0.5 0.75])) (order-by :s.i) :alias])
+    (from (sql/raw "generate_series(1,10) AS s(i)"))
+    (sql/format))
+=> ["SELECT count(*) , percentile_disc(ARRAY[?, ?, ?]) WITHIN GROUP (ORDER BY s.i) AS alias FROM generate_series(1,10) AS s(i)"
+    0.25 0.50 0.75]
+```
+
 ### SQL functions
+
 The following are the SQL functions added in `honeysql-postgres`
 - not
 ```clojure
@@ -257,7 +281,7 @@ The following are the SQL functions added in `honeysql-postgres`
 => ["CHECK(a = b)"]
 
 (sql/format (sql/call :check [:= :a :b] [:= :c :d]))
-["CHECK(a = b AND c = d)"]
+=> ["CHECK(a = b AND c = d)"]
 ```
 
 ## License

src/honeysql_postgres/format.cljc

@@ -13,7 +13,8 @@
    :add-column 30
    :drop-column 40
    :create-view 40
-   :filter 54
+   :filter 55
+   :within-group 55
    :over 55
    :insert-into-as 60
    :partition-by 165
@@ -236,6 +237,19 @@
   (binding [sqlf/*subquery?* false]
     (string/join " EXCEPT ALL " (map sqlf/to-sql maps))))
 
+(defmethod format-clause :within-group [[_ expr] m]
+  (let [format (fn [expr]
+                 (let [[expression clause alias] (map sqlf/to-sql expr)]
+                   (->> alias
+                        (str " AS ")
+                        (when alias)
+                        (str expression " WITHIN GROUP " clause))))]
+    (-> m
+        :select
+        seq
+        (when ", ")
+        (str (sqlf/comma-join (map format expr))))))
+
 (override-default-clause-priority)
 
 (defmethod format-modifiers :distinct-on [[_ & fields]]

src/honeysql_postgres/helpers.cljc

@@ -72,6 +72,9 @@
 (defhelper insert-into-as [m fields]
   (assoc m :insert-into-as (sqlh/collify fields)))
 
+(defhelper within-group [m args]
+  (assoc m :within-group (sqlh/collify args)))
+
 (defhelper create-extension [m extension-name]
   (assoc m :create-extension (sqlh/collify extension-name)))
 

test/honeysql_postgres/postgres_test.cljc

@@ -1,18 +1,52 @@
 (ns honeysql-postgres.postgres-test
   (:refer-clojure :exclude [update partition-by filter])
-  (:require [honeysql-postgres.helpers :as sqlph :refer [upsert on-conflict do-nothing on-conflict-constraint
-                                                         returning do-update-set do-update-set!
-                                                         alter-table rename-column drop-column
-                                                         add-column partition-by insert-into-as
-                                                         create-table rename-table drop-table
-                                                         window create-view over with-columns
-                                                         create-extension drop-extension filter]]
-            [honeysql.helpers :as sqlh :refer [insert-into values where select columns
-                                               from order-by update sset query-values
-                                               modifiers]]
-            [honeysql.core :as sql]
+  (:require [clojure.string :as str]
             [clojure.test :as test :refer [deftest is testing]]
-            [clojure.string :as str]))
+            [honeysql-postgres.helpers
+             :as
+             sqlph
+             :refer
+             [add-column
+              alter-table
+              create-extension
+              create-table
+              create-view
+              do-nothing
+              do-update-set
+              do-update-set!
+              drop-column
+              drop-extension
+              drop-table
+              filter
+              insert-into-as
+              on-conflict
+              on-conflict-constraint
+              over
+              partition-by
+              rename-column
+              rename-table
+              returning
+              upsert
+              window
+              with-columns
+              within-group]]
+            [honeysql.core :as sql]
+            [honeysql.helpers
+             :as
+             sqlh
+             :refer
+             [columns
+              from
+              insert-into
+              modifiers
+              order-by
+              query-values
+              select
+              sset
+              update
+              values
+              where]]
+            [honeysql.types :as hsql-types]))
 
 (deftest upsert-test
   (testing "upsert sql generation for postgresql"
@@ -272,6 +306,16 @@
                (modifiers :distinct-on :a :b)
                (sql/format :quoting :ansi))))))
 
+(deftest within-group-test
+  (is (= ["rank() WITHIN GROUP (ORDER BY i)"]
+         (sql/format (within-group [(sql/call :rank) (order-by :i)]))))
+
+  (is (= ["SELECT count(*) , percentile_disc(ARRAY[?, ?, ?]) WITHIN GROUP (ORDER BY s.i) AS alias FROM generate_series(1,10) AS s(i)"
+          0.25 0.50 0.75]
+         (-> (select (sql/call :count :*))
+             (within-group [(sql/call :percentile_disc (hsql-types/array [0.25 0.5 0.75])) (order-by :s.i) :alias])
+             (from (sql/raw "generate_series(1,10) AS s(i)"))
+             (sql/format)))))
 (deftest create-extension-test
   (testing "create extension"
     (is (= ["CREATE EXTENSION \"uuid-ossp\""]