From c4d07fba751e312eedd39bd8d32126acd5e6894e Mon Sep 17 00:00:00 2001
From: Scott Twiname <skott.twiname@gmail.com>
Date: Fri, 26 Aug 2022 14:51:51 +1200
Subject: [PATCH 01/13] Add distinctOn to QueryBuilder

---
 .../graphile-build-pg/src/QueryBuilder.d.ts   |  1 +
 .../graphile-build-pg/src/QueryBuilder.js     | 29 ++++++++++++++++++-
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/packages/graphile-build-pg/src/QueryBuilder.d.ts b/packages/graphile-build-pg/src/QueryBuilder.d.ts
index 2baa3ecbc..7f53f9fa7 100644
--- a/packages/graphile-build-pg/src/QueryBuilder.d.ts
+++ b/packages/graphile-build-pg/src/QueryBuilder.d.ts
@@ -51,6 +51,7 @@ export default class QueryBuilder {
   public offset(offsetGen: NumberGen): void;
   public first(first: number): void;
   public last(last: number): void;
+  public distinctOn(exprGen: SQLGen): void;
 
   // ----------------------------------------
 
diff --git a/packages/graphile-build-pg/src/QueryBuilder.js b/packages/graphile-build-pg/src/QueryBuilder.js
index 9ba9e587b..eaf2fde90 100644
--- a/packages/graphile-build-pg/src/QueryBuilder.js
+++ b/packages/graphile-build-pg/src/QueryBuilder.js
@@ -106,6 +106,7 @@ class QueryBuilder {
     offset: ?NumberGen,
     first: ?number,
     last: ?number,
+    distinctOn: Array<SQLGen>,
     beforeLock: {
       [string]: Array<() => void> | null,
     },
@@ -133,6 +134,7 @@ class QueryBuilder {
     offset: ?number,
     first: ?number,
     last: ?number,
+    distinctOn: Array<SQLGen>,
     cursorComparator: ?CursorComparator,
   };
   lockContext: {
@@ -170,6 +172,7 @@ class QueryBuilder {
       last: false,
       limit: false,
       offset: false,
+      distinctOn: false,
     };
     this.finalized = false;
     this.selectedIdentifiers = false;
@@ -192,6 +195,7 @@ class QueryBuilder {
       offset: null,
       first: null,
       last: null,
+      distinctOn: [],
       beforeLock: {
         // As a performance optimisation, we're going to list a number of lock
         // types so that V8 doesn't need to mutate the object too much
@@ -231,6 +235,7 @@ class QueryBuilder {
       offset: null,
       first: null,
       last: null,
+      distinctOn: [],
       cursorComparator: null,
     };
     this._children = new Map();
@@ -511,6 +516,10 @@ ${sql.join(
     }
     this.data.last = last;
   }
+  distinctOn(exprGen: SQLGen) {
+    this.checkLock("distinctOn");
+    this.data.distinctOn.push(exprGen);
+  }
 
   // ----------------------------------------
 
@@ -744,7 +753,14 @@ ${sql.join(
         : this.buildSelectFields();
 
     let fragment = sql.fragment`\
-select ${useAsterisk ? sql.fragment`${this.getTableAlias()}.*` : fields}
+select ${
+      this.compiledData.distinctOn.length &&
+      sql.fragment`distinct on (${sql.join(
+        this.compiledData.distinctOn,
+        ", "
+      )})`
+    }
+${useAsterisk ? sql.fragment`${this.getTableAlias()}.*` : fields}
 ${
   this.compiledData.from &&
   sql.fragment`from ${this.compiledData.from[0]} as ${this.getTableAlias()}`
@@ -868,6 +884,14 @@ order by (row_number() over (partition by 1)) desc`; /* We don't need to factor
       this.locks[type] = isDev ? new Error("Initally locked here").stack : true;
       this.compiledData[type] = data;
     } else if (type === "orderBy") {
+      // Add distinct to existing order by to avoid `SELECT DISTINCT ON expressions must match initial ORDER BY expressions`
+      if (this.data[type].length) {
+        this.data["distinctOn"].forEach(d => {
+          if (!this.data[type].find(([a]) => a === d)) {
+            this.data[type].unshift([d, undefined, undefined]);
+          }
+        });
+      }
       this.compiledData[type] = this.data[type].map(([a, b, c]) => [
         callIfNecessary(a, context),
         b,
@@ -894,6 +918,8 @@ order by (row_number() over (partition by 1)) desc`; /* We don't need to factor
       this.compiledData[type] = this.data[type];
     } else if (type === "last") {
       this.compiledData[type] = this.data[type];
+    } else if (type === "distinctOn") {
+      this.compiledData[type] = callIfNecessaryArray(this.data[type], context);
     } else {
       throw new Error(`Wasn't expecting to lock '${type}'`);
     }
@@ -925,6 +951,7 @@ order by (row_number() over (partition by 1)) desc`; /* We don't need to factor
     this.lock("limit");
     this.lock("first");
     this.lock("last");
+    this.lock("distinctOn");
     // We must execute select after orderBy otherwise we cannot generate a cursor
     this.lock("fixedSelectExpression");
     this.lock("selectCursor");

From b47ddc6e4bf1d749ab3daecc561a5710cbbb3d4a Mon Sep 17 00:00:00 2001
From: Scott Twiname <skott.twiname@gmail.com>
Date: Mon, 29 Aug 2022 09:27:42 +1200
Subject: [PATCH 02/13] Use ternary to avoid inserting `0` into sql

Co-authored-by: Benjie <benjie@jemjie.com>
---
 packages/graphile-build-pg/src/QueryBuilder.js | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/packages/graphile-build-pg/src/QueryBuilder.js b/packages/graphile-build-pg/src/QueryBuilder.js
index eaf2fde90..132c1ff52 100644
--- a/packages/graphile-build-pg/src/QueryBuilder.js
+++ b/packages/graphile-build-pg/src/QueryBuilder.js
@@ -754,11 +754,12 @@ ${sql.join(
 
     let fragment = sql.fragment`\
 select ${
-      this.compiledData.distinctOn.length &&
-      sql.fragment`distinct on (${sql.join(
-        this.compiledData.distinctOn,
-        ", "
-      )})`
+      this.compiledData.distinctOn.length
+      ? sql.fragment`distinct on (${sql.join(
+          this.compiledData.distinctOn,
+          ", "
+        )})`
+      : sql.blank
     }
 ${useAsterisk ? sql.fragment`${this.getTableAlias()}.*` : fields}
 ${

From 341f5b99ed426cea31ef10d7d8d7c593e9c97770 Mon Sep 17 00:00:00 2001
From: Scott Twiname <skott.twiname@gmail.com>
Date: Mon, 29 Aug 2022 13:53:47 +1200
Subject: [PATCH 03/13] Add test for distinctOn

---
 .../postgraphile-core/__tests__/helpers-v5.js |  2 +
 .../__tests__/integration/DistinctOnPlugin.js | 46 +++++++++
 .../__tests__/kitchen-sink-data.sql           |  7 ++
 .../__tests__/kitchen-sink-schema.sql         | 11 +++
 .../base/distinct_query_builder.toys.json5    | 46 +++++++++
 .../base/distinct_query_builder.toys.sql      | 99 +++++++++++++++++++
 .../distinct_query_builder.toys.test.graphql  | 22 +++++
 7 files changed, 233 insertions(+)
 create mode 100644 packages/postgraphile-core/__tests__/integration/DistinctOnPlugin.js
 create mode 100644 packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.json5
 create mode 100644 packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.sql
 create mode 100644 packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.test.graphql

diff --git a/packages/postgraphile-core/__tests__/helpers-v5.js b/packages/postgraphile-core/__tests__/helpers-v5.js
index 40f7fd493..ddd5e0c46 100644
--- a/packages/postgraphile-core/__tests__/helpers-v5.js
+++ b/packages/postgraphile-core/__tests__/helpers-v5.js
@@ -24,6 +24,7 @@ import { withPgClient, getServerVersionNum } from "./helpers";
 import jsonwebtoken from "jsonwebtoken";
 import { createPostGraphileSchema } from "..";
 import { makeExtendSchemaPlugin, gql } from "graphile-utils";
+import DistinctOnPlugin from "./integration/DistinctOnPlugin";
 import ToyCategoriesPlugin from "./integration/ToyCategoriesPlugin";
 
 /**
@@ -468,6 +469,7 @@ const makeSchema = config => {
         appendPlugins: [
           ExtendedPlugin,
           config.ToyCategoriesPlugin ? ToyCategoriesPlugin : null,
+          config.DistinctOnPlugin ? DistinctOnPlugin : null,
         ].filter(isNotNullish),
       }
     );
diff --git a/packages/postgraphile-core/__tests__/integration/DistinctOnPlugin.js b/packages/postgraphile-core/__tests__/integration/DistinctOnPlugin.js
new file mode 100644
index 000000000..630c5b04a
--- /dev/null
+++ b/packages/postgraphile-core/__tests__/integration/DistinctOnPlugin.js
@@ -0,0 +1,46 @@
+module.exports = builder => {
+  builder.hook(
+    "GraphQLObjectType:fields:field:args",
+    (args, build, context) => {
+      const {
+        graphql: { GraphQLString },
+        pgSql: sql,
+      } = build;
+
+      const {
+        Self,
+        scope: { fieldName },
+        addArgDataGenerator,
+      } = context;
+
+      if (!(Self.name === "Query" && fieldName === "allToys")) {
+        return args;
+      }
+
+      addArgDataGenerator(({ distinct }) => {
+        return {
+          pgQuery: queryBuilder => {
+            if (!distinct) {
+              return;
+            }
+            const id = sql.fragment`${queryBuilder.getTableAlias()}.${sql.identifier(
+              distinct
+            )}`;
+
+            queryBuilder.distinctOn(id);
+          },
+        };
+      });
+
+      return build.extend(
+        args,
+        {
+          distinct: {
+            type: GraphQLString,
+          },
+        },
+        "test"
+      );
+    }
+  );
+};
diff --git a/packages/postgraphile-core/__tests__/kitchen-sink-data.sql b/packages/postgraphile-core/__tests__/kitchen-sink-data.sql
index 2070c9671..076fc77f5 100644
--- a/packages/postgraphile-core/__tests__/kitchen-sink-data.sql
+++ b/packages/postgraphile-core/__tests__/kitchen-sink-data.sql
@@ -276,6 +276,13 @@ insert into named_query_builder.toy_categories(toy_id, category_id, approved) va
   (4, 2, true),
   (1, 3, false);
 
+
+insert into distinct_query_builder.toys (id, name, color) values
+  (1, 'Rex', 'green'),
+  (2, 'Toy Soldiers', 'green'),
+  (3, 'Dino-Rocket Launcher', 'red'),
+  (4, 'History of Dinosaurs book', 'red');
+
 --------------------------------------------------------------------------------
 alter sequence enum_tables.letter_descriptions_id_seq restart with 101;
 insert into enum_tables.letter_descriptions(letter, letter_via_view, description) values
diff --git a/packages/postgraphile-core/__tests__/kitchen-sink-schema.sql b/packages/postgraphile-core/__tests__/kitchen-sink-schema.sql
index f26de5d5f..b0d551653 100644
--- a/packages/postgraphile-core/__tests__/kitchen-sink-schema.sql
+++ b/packages/postgraphile-core/__tests__/kitchen-sink-schema.sql
@@ -13,6 +13,7 @@ drop schema if exists
   large_bigint,
   network_types,
   named_query_builder,
+  distinct_query_builder,
   enum_tables,
   geometry
 cascade;
@@ -1140,6 +1141,16 @@ create table named_query_builder.toy_categories (
 
 --------------------------------------------------------------------------------
 
+create schema distinct_query_builder;
+
+create table distinct_query_builder.toys (
+  id serial primary key,
+  name text not null,
+  color text not null
+);
+
+--------------------------------------------------------------------------------
+
 create schema enum_tables;
 create table enum_tables.abcd (letter text primary key, description text);
 comment on column enum_tables.abcd.description is E'@enumDescription';
diff --git a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.json5 b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.json5
new file mode 100644
index 000000000..2f69f1c4e
--- /dev/null
+++ b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.json5
@@ -0,0 +1,46 @@
+{
+  t1: {
+    nodes: [
+      {
+        name: "Dino-Rocket Launcher",
+        color: "red",
+      },
+      {
+        name: "Rex",
+        color: "green",
+      },
+    ],
+  },
+  t2: {
+    nodes: [
+      {
+        name: "Toy Soldiers",
+      },
+      {
+        name: "Rex",
+      },
+      {
+        name: "History of Dinosaurs book",
+      },
+      {
+        name: "Dino-Rocket Launcher",
+      },
+    ],
+  },
+  t3: {
+    nodes: [
+      {
+        name: "Rex",
+      },
+      {
+        name: "Toy Soldiers",
+      },
+      {
+        name: "Dino-Rocket Launcher",
+      },
+      {
+        name: "History of Dinosaurs book",
+      },
+    ],
+  },
+}
diff --git a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.sql b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.sql
new file mode 100644
index 000000000..18e5d58e3
--- /dev/null
+++ b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.sql
@@ -0,0 +1,99 @@
+with __local_0__ as (
+  select to_json(
+    (
+      json_build_object(
+        '__identifiers'::text,
+        json_build_array(__local_1__."id"),
+        'name'::text,
+        (__local_1__."name"),
+        'color'::text,
+        (__local_1__."color")
+      )
+    )
+  ) as "@nodes"
+  from (
+    select distinct on (__local_1__."color") __local_1__.*
+    from "distinct_query_builder"."toys" as __local_1__
+    where (TRUE) and (TRUE)
+    order by __local_1__."color" DESC,
+    __local_1__."id" ASC
+  ) __local_1__
+),
+__local_2__ as (
+  select json_agg(
+    to_json(__local_0__)
+  ) as data
+  from __local_0__
+)
+select coalesce(
+  (
+    select __local_2__.data
+    from __local_2__
+  ),
+  '[]'::json
+) as "data"
+
+with __local_0__ as (
+  select to_json(
+    (
+      json_build_object(
+        '__identifiers'::text,
+        json_build_array(__local_1__."id"),
+        'name'::text,
+        (__local_1__."name")
+      )
+    )
+  ) as "@nodes"
+  from (
+    select distinct on (__local_1__."name") __local_1__.*
+    from "distinct_query_builder"."toys" as __local_1__
+    where (TRUE) and (TRUE)
+    order by __local_1__."name" DESC,
+    __local_1__."id" ASC
+  ) __local_1__
+),
+__local_2__ as (
+  select json_agg(
+    to_json(__local_0__)
+  ) as data
+  from __local_0__
+)
+select coalesce(
+  (
+    select __local_2__.data
+    from __local_2__
+  ),
+  '[]'::json
+) as "data"
+
+with __local_0__ as (
+  select to_json(
+    (
+      json_build_object(
+        '__identifiers'::text,
+        json_build_array(__local_1__."id"),
+        'name'::text,
+        (__local_1__."name")
+      )
+    )
+  ) as "@nodes"
+  from (
+    select __local_1__.*
+    from "distinct_query_builder"."toys" as __local_1__
+    where (TRUE) and (TRUE)
+    order by __local_1__."id" ASC
+  ) __local_1__
+),
+__local_2__ as (
+  select json_agg(
+    to_json(__local_0__)
+  ) as data
+  from __local_0__
+)
+select coalesce(
+  (
+    select __local_2__.data
+    from __local_2__
+  ),
+  '[]'::json
+) as "data"
\ No newline at end of file
diff --git a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.test.graphql b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.test.graphql
new file mode 100644
index 000000000..817c4ad17
--- /dev/null
+++ b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.test.graphql
@@ -0,0 +1,22 @@
+## expect(errors).toBeFalsy();
+#> schema: ["distinct_query_builder"]
+#> subscriptions: true
+#> DistinctOnPlugin: true
+{
+  t1: allToys(distinct: "color") {
+    nodes {
+      name
+      color
+    }
+  }
+  t2: allToys(distinct: "name") {
+    nodes {
+      name
+    }
+  }
+  t3: allToys {
+    nodes {
+      name
+    }
+  }
+}

From 372c8c200df07af20bb266cd732693003112472d Mon Sep 17 00:00:00 2001
From: Scott Twiname <skott.twiname@gmail.com>
Date: Mon, 29 Aug 2022 14:44:43 +1200
Subject: [PATCH 04/13] Specify ASC for order by distinct columns

---
 packages/graphile-build-pg/src/QueryBuilder.js   |  2 +-
 .../base/distinct_query_builder.toys.json5       | 16 ++++++++--------
 .../queries/base/distinct_query_builder.toys.sql |  4 ++--
 3 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/packages/graphile-build-pg/src/QueryBuilder.js b/packages/graphile-build-pg/src/QueryBuilder.js
index 132c1ff52..7fdc104c2 100644
--- a/packages/graphile-build-pg/src/QueryBuilder.js
+++ b/packages/graphile-build-pg/src/QueryBuilder.js
@@ -889,7 +889,7 @@ order by (row_number() over (partition by 1)) desc`; /* We don't need to factor
       if (this.data[type].length) {
         this.data["distinctOn"].forEach(d => {
           if (!this.data[type].find(([a]) => a === d)) {
-            this.data[type].unshift([d, undefined, undefined]);
+            this.data[type].unshift([d, true, undefined]);
           }
         });
       }
diff --git a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.json5 b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.json5
index 2f69f1c4e..78cd37028 100644
--- a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.json5
+++ b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.json5
@@ -1,29 +1,29 @@
 {
   t1: {
     nodes: [
-      {
-        name: "Dino-Rocket Launcher",
-        color: "red",
-      },
       {
         name: "Rex",
         color: "green",
       },
+      {
+        name: "Dino-Rocket Launcher",
+        color: "red",
+      },
     ],
   },
   t2: {
     nodes: [
       {
-        name: "Toy Soldiers",
+        name: "Dino-Rocket Launcher",
       },
       {
-        name: "Rex",
+        name: "History of Dinosaurs book",
       },
       {
-        name: "History of Dinosaurs book",
+        name: "Rex",
       },
       {
-        name: "Dino-Rocket Launcher",
+        name: "Toy Soldiers",
       },
     ],
   },
diff --git a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.sql b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.sql
index 18e5d58e3..645c0a7ca 100644
--- a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.sql
+++ b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.sql
@@ -15,7 +15,7 @@ with __local_0__ as (
     select distinct on (__local_1__."color") __local_1__.*
     from "distinct_query_builder"."toys" as __local_1__
     where (TRUE) and (TRUE)
-    order by __local_1__."color" DESC,
+    order by __local_1__."color" ASC,
     __local_1__."id" ASC
   ) __local_1__
 ),
@@ -48,7 +48,7 @@ with __local_0__ as (
     select distinct on (__local_1__."name") __local_1__.*
     from "distinct_query_builder"."toys" as __local_1__
     where (TRUE) and (TRUE)
-    order by __local_1__."name" DESC,
+    order by __local_1__."name" ASC,
     __local_1__."id" ASC
   ) __local_1__
 ),

From 939d66f65bd1a53d0b37df9a4e5f6af4cf010371 Mon Sep 17 00:00:00 2001
From: Scott Twiname <skott.twiname@gmail.com>
Date: Tue, 30 Aug 2022 13:42:51 +1200
Subject: [PATCH 05/13] Fix merging distinct and order by

---
 .../graphile-build-pg/src/QueryBuilder.js     | 22 +++++++++----------
 .../__tests__/integration/DistinctOnPlugin.js | 17 +++++++-------
 .../base/distinct_query_builder.toys.json5    |  8 +++----
 .../base/distinct_query_builder.toys.sql      |  9 +++++---
 .../distinct_query_builder.toys.test.graphql  |  4 ++--
 5 files changed, 30 insertions(+), 30 deletions(-)

diff --git a/packages/graphile-build-pg/src/QueryBuilder.js b/packages/graphile-build-pg/src/QueryBuilder.js
index 7fdc104c2..78c6d8a26 100644
--- a/packages/graphile-build-pg/src/QueryBuilder.js
+++ b/packages/graphile-build-pg/src/QueryBuilder.js
@@ -3,6 +3,7 @@ import * as sql from "pg-sql2";
 import type { SQL } from "pg-sql2";
 import isSafeInteger from "lodash/isSafeInteger";
 import chunk from "lodash/chunk";
+import isEqual from "lodash/isEqual";
 import type { PgClass, PgType } from "./plugins/PgIntrospectionPlugin";
 
 // eslint-disable-next-line flowtype/no-weak-types
@@ -886,18 +887,15 @@ order by (row_number() over (partition by 1)) desc`; /* We don't need to factor
       this.compiledData[type] = data;
     } else if (type === "orderBy") {
       // Add distinct to existing order by to avoid `SELECT DISTINCT ON expressions must match initial ORDER BY expressions`
-      if (this.data[type].length) {
-        this.data["distinctOn"].forEach(d => {
-          if (!this.data[type].find(([a]) => a === d)) {
-            this.data[type].unshift([d, true, undefined]);
-          }
-        });
-      }
-      this.compiledData[type] = this.data[type].map(([a, b, c]) => [
-        callIfNecessary(a, context),
-        b,
-        c,
-      ]);
+      // Convert distinct fields to order by applying ascending and using existing order by for matching fields
+      const distinctAsOrderBy = this.data["distinctOn"].map(
+        d => this.data[type].find(([a]) => isEqual(a, d)) ?? [d, true, null]
+      );
+
+      // Create a union of the distinct and order by fields
+      this.compiledData[type] = [
+        ...new Set([...distinctAsOrderBy, ...this.data[type]]),
+      ].map(([a, b, c]) => [callIfNecessary(a, context), b, c]);
     } else if (type === "from") {
       if (this.data.from) {
         const f = this.data.from;
diff --git a/packages/postgraphile-core/__tests__/integration/DistinctOnPlugin.js b/packages/postgraphile-core/__tests__/integration/DistinctOnPlugin.js
index 630c5b04a..05efbc6a1 100644
--- a/packages/postgraphile-core/__tests__/integration/DistinctOnPlugin.js
+++ b/packages/postgraphile-core/__tests__/integration/DistinctOnPlugin.js
@@ -3,7 +3,7 @@ module.exports = builder => {
     "GraphQLObjectType:fields:field:args",
     (args, build, context) => {
       const {
-        graphql: { GraphQLString },
+        graphql: { GraphQLString, GraphQLList },
         pgSql: sql,
       } = build;
 
@@ -20,14 +20,13 @@ module.exports = builder => {
       addArgDataGenerator(({ distinct }) => {
         return {
           pgQuery: queryBuilder => {
-            if (!distinct) {
-              return;
-            }
-            const id = sql.fragment`${queryBuilder.getTableAlias()}.${sql.identifier(
-              distinct
-            )}`;
+            distinct?.map(field => {
+              const id = sql.fragment`${queryBuilder.getTableAlias()}.${sql.identifier(
+                field
+              )}`;
 
-            queryBuilder.distinctOn(id);
+              queryBuilder.distinctOn(id);
+            });
           },
         };
       });
@@ -36,7 +35,7 @@ module.exports = builder => {
         args,
         {
           distinct: {
-            type: GraphQLString,
+            type: new GraphQLList(GraphQLString),
           },
         },
         "test"
diff --git a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.json5 b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.json5
index 78cd37028..3f1ed47e9 100644
--- a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.json5
+++ b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.json5
@@ -14,16 +14,16 @@
   t2: {
     nodes: [
       {
-        name: "Dino-Rocket Launcher",
+        name: "Rex",
       },
       {
-        name: "History of Dinosaurs book",
+        name: "Toy Soldiers",
       },
       {
-        name: "Rex",
+        name: "Dino-Rocket Launcher",
       },
       {
-        name: "Toy Soldiers",
+        name: "History of Dinosaurs book",
       },
     ],
   },
diff --git a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.sql b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.sql
index 645c0a7ca..8817aeeaa 100644
--- a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.sql
+++ b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.sql
@@ -45,11 +45,14 @@ with __local_0__ as (
     )
   ) as "@nodes"
   from (
-    select distinct on (__local_1__."name") __local_1__.*
+    select distinct on (
+      __local_1__."id",
+      __local_1__."name"
+    ) __local_1__.*
     from "distinct_query_builder"."toys" as __local_1__
     where (TRUE) and (TRUE)
-    order by __local_1__."name" ASC,
-    __local_1__."id" ASC
+    order by __local_1__."id" ASC,
+    __local_1__."name" ASC
   ) __local_1__
 ),
 __local_2__ as (
diff --git a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.test.graphql b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.test.graphql
index 817c4ad17..a08461a8a 100644
--- a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.test.graphql
+++ b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.test.graphql
@@ -3,13 +3,13 @@
 #> subscriptions: true
 #> DistinctOnPlugin: true
 {
-  t1: allToys(distinct: "color") {
+  t1: allToys(distinct: ["color"]) {
     nodes {
       name
       color
     }
   }
-  t2: allToys(distinct: "name") {
+  t2: allToys(distinct: ["id", "name"]) {
     nodes {
       name
     }

From 28c64e0b039f514aa27655bf5d7b58b886d9c408 Mon Sep 17 00:00:00 2001
From: Scott Twiname <skott.twiname@gmail.com>
Date: Fri, 2 Sep 2022 10:45:07 +1200
Subject: [PATCH 06/13] Apply suggestions from code review

Co-authored-by: Benjie <benjie@jemjie.com>
---
 .../__tests__/integration/DistinctOnPlugin.js                | 3 +++
 .../queries/base/distinct_query_builder.toys.test.graphql    | 5 +++++
 2 files changed, 8 insertions(+)

diff --git a/packages/postgraphile-core/__tests__/integration/DistinctOnPlugin.js b/packages/postgraphile-core/__tests__/integration/DistinctOnPlugin.js
index 05efbc6a1..35574cf44 100644
--- a/packages/postgraphile-core/__tests__/integration/DistinctOnPlugin.js
+++ b/packages/postgraphile-core/__tests__/integration/DistinctOnPlugin.js
@@ -21,6 +21,9 @@ module.exports = builder => {
         return {
           pgQuery: queryBuilder => {
             distinct?.map(field => {
+              // THIS IS AN EXAMPLE FOR THE TESTS. DO NOT USE THIS IN REAL PRODUCTION CODE!
+              // Instead you should use an enum to indicate the allowed identifiers; otherwise
+              // you risk interacting with the system columns and maybe worse.
               const id = sql.fragment`${queryBuilder.getTableAlias()}.${sql.identifier(
                 field
               )}`;
diff --git a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.test.graphql b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.test.graphql
index a08461a8a..a1cb5aa47 100644
--- a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.test.graphql
+++ b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.test.graphql
@@ -5,18 +5,23 @@
 {
   t1: allToys(distinct: ["color"]) {
     nodes {
+      id
       name
       color
     }
   }
   t2: allToys(distinct: ["id", "name"]) {
     nodes {
+      id
       name
+      color
     }
   }
   t3: allToys {
     nodes {
+      id
       name
+      color
     }
   }
 }

From c6c0d54bf12d4c50f0f0d346aa29b5eed3284ab6 Mon Sep 17 00:00:00 2001
From: Scott Twiname <skott.twiname@gmail.com>
Date: Fri, 2 Sep 2022 12:43:54 +1200
Subject: [PATCH 07/13] Address code related comments

---
 .../graphile-build-pg/src/QueryBuilder.js     | 44 ++++++++++++-------
 packages/graphile-build-pg/src/utils.js       | 18 ++++++++
 .../base/distinct_query_builder.toys.json5    | 18 ++++++++
 .../base/distinct_query_builder.toys.sql      | 17 +++++--
 4 files changed, 79 insertions(+), 18 deletions(-)

diff --git a/packages/graphile-build-pg/src/QueryBuilder.js b/packages/graphile-build-pg/src/QueryBuilder.js
index 78c6d8a26..5bd990c81 100644
--- a/packages/graphile-build-pg/src/QueryBuilder.js
+++ b/packages/graphile-build-pg/src/QueryBuilder.js
@@ -3,8 +3,8 @@ import * as sql from "pg-sql2";
 import type { SQL } from "pg-sql2";
 import isSafeInteger from "lodash/isSafeInteger";
 import chunk from "lodash/chunk";
-import isEqual from "lodash/isEqual";
 import type { PgClass, PgType } from "./plugins/PgIntrospectionPlugin";
+import { arraysMatch } from "./utils";
 
 // eslint-disable-next-line flowtype/no-weak-types
 type GraphQLContext = any;
@@ -214,6 +214,7 @@ class QueryBuilder {
         last: [],
         limit: [],
         offset: [],
+        distinctOn: [],
       },
       cursorComparator: null,
       liveConditions: [],
@@ -756,11 +757,11 @@ ${sql.join(
     let fragment = sql.fragment`\
 select ${
       this.compiledData.distinctOn.length
-      ? sql.fragment`distinct on (${sql.join(
-          this.compiledData.distinctOn,
-          ", "
-        )})`
-      : sql.blank
+        ? sql.fragment`distinct on (${sql.join(
+            this.compiledData.distinctOn,
+            ", "
+          )})`
+        : sql.blank
     }
 ${useAsterisk ? sql.fragment`${this.getTableAlias()}.*` : fields}
 ${
@@ -886,16 +887,29 @@ order by (row_number() over (partition by 1)) desc`; /* We don't need to factor
       this.locks[type] = isDev ? new Error("Initally locked here").stack : true;
       this.compiledData[type] = data;
     } else if (type === "orderBy") {
-      // Add distinct to existing order by to avoid `SELECT DISTINCT ON expressions must match initial ORDER BY expressions`
-      // Convert distinct fields to order by applying ascending and using existing order by for matching fields
-      const distinctAsOrderBy = this.data["distinctOn"].map(
-        d => this.data[type].find(([a]) => isEqual(a, d)) ?? [d, true, null]
-      );
+      if (this.data["distinctOn"].length) {
+        // Add distinct to existing order by to avoid `SELECT DISTINCT ON expressions must match initial ORDER BY expressions`
+        // Convert distinct fields to order by applying ascending and using existing order by for matching fields
+        const distinctAsOrderBy = this.data["distinctOn"].map(
+          d =>
+            this.data[type].find(
+              ([a]) =>
+                a === d ||
+                (Array.isArray(a) && Array.isArray(d) && arraysMatch(a, d))
+            ) ?? [d, true, null]
+        );
 
-      // Create a union of the distinct and order by fields
-      this.compiledData[type] = [
-        ...new Set([...distinctAsOrderBy, ...this.data[type]]),
-      ].map(([a, b, c]) => [callIfNecessary(a, context), b, c]);
+        // Create a union of the distinct and order by fields
+        this.compiledData[type] = [
+          ...new Set([...distinctAsOrderBy, ...this.data[type]]),
+        ].map(([a, b, c]) => [callIfNecessary(a, context), b, c]);
+      } else {
+        this.compiledData[type] = this.data[type].map(([a, b, c]) => [
+          callIfNecessary(a, context),
+          b,
+          c,
+        ]);
+      }
     } else if (type === "from") {
       if (this.data.from) {
         const f = this.data.from;
diff --git a/packages/graphile-build-pg/src/utils.js b/packages/graphile-build-pg/src/utils.js
index fec346b24..2b328e2cf 100644
--- a/packages/graphile-build-pg/src/utils.js
+++ b/packages/graphile-build-pg/src/utils.js
@@ -29,3 +29,21 @@ export const parseTags = (str: string) => {
     }
   );
 };
+
+export function arraysMatch<T>(
+  array1: ReadonlyArray<T>,
+  array2: ReadonlyArray<T>,
+  comparator: (val1: T, val2: T) => boolean = (v1, v2) => v1 === v2
+): boolean {
+  const l = array1.length;
+  if (l !== array2.length) {
+    return false;
+  }
+
+  for (let i = 0; i < l; i++) {
+    if (!comparator(array1[i], array2[i])) {
+      return false;
+    }
+  }
+  return true;
+}
diff --git a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.json5 b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.json5
index 3f1ed47e9..e8d03523e 100644
--- a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.json5
+++ b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.json5
@@ -2,10 +2,12 @@
   t1: {
     nodes: [
       {
+        id: 1,
         name: "Rex",
         color: "green",
       },
       {
+        id: 3,
         name: "Dino-Rocket Launcher",
         color: "red",
       },
@@ -14,32 +16,48 @@
   t2: {
     nodes: [
       {
+        id: 1,
         name: "Rex",
+        color: "green",
       },
       {
+        id: 2,
         name: "Toy Soldiers",
+        color: "green",
       },
       {
+        id: 3,
         name: "Dino-Rocket Launcher",
+        color: "red",
       },
       {
+        id: 4,
         name: "History of Dinosaurs book",
+        color: "red",
       },
     ],
   },
   t3: {
     nodes: [
       {
+        id: 1,
         name: "Rex",
+        color: "green",
       },
       {
+        id: 2,
         name: "Toy Soldiers",
+        color: "green",
       },
       {
+        id: 3,
         name: "Dino-Rocket Launcher",
+        color: "red",
       },
       {
+        id: 4,
         name: "History of Dinosaurs book",
+        color: "red",
       },
     ],
   },
diff --git a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.sql b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.sql
index 8817aeeaa..7f4b33ed5 100644
--- a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.sql
+++ b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.sql
@@ -4,6 +4,8 @@ with __local_0__ as (
       json_build_object(
         '__identifiers'::text,
         json_build_array(__local_1__."id"),
+        'id'::text,
+        (__local_1__."id"),
         'name'::text,
         (__local_1__."name"),
         'color'::text,
@@ -39,8 +41,12 @@ with __local_0__ as (
       json_build_object(
         '__identifiers'::text,
         json_build_array(__local_1__."id"),
+        'id'::text,
+        (__local_1__."id"),
         'name'::text,
-        (__local_1__."name")
+        (__local_1__."name"),
+        'color'::text,
+        (__local_1__."color")
       )
     )
   ) as "@nodes"
@@ -52,7 +58,8 @@ with __local_0__ as (
     from "distinct_query_builder"."toys" as __local_1__
     where (TRUE) and (TRUE)
     order by __local_1__."id" ASC,
-    __local_1__."name" ASC
+    __local_1__."name" ASC,
+    __local_1__."id" ASC
   ) __local_1__
 ),
 __local_2__ as (
@@ -75,8 +82,12 @@ with __local_0__ as (
       json_build_object(
         '__identifiers'::text,
         json_build_array(__local_1__."id"),
+        'id'::text,
+        (__local_1__."id"),
         'name'::text,
-        (__local_1__."name")
+        (__local_1__."name"),
+        'color'::text,
+        (__local_1__."color")
       )
     )
   ) as "@nodes"

From 617f8c655b20da479f4311920708cb8231f947c5 Mon Sep 17 00:00:00 2001
From: Scott Twiname <skott.twiname@gmail.com>
Date: Tue, 6 Sep 2022 13:19:25 +1200
Subject: [PATCH 08/13] Lock cursor when distinctOn is used and vice versa

---
 .../graphile-build-pg/src/QueryBuilder.js     | 10 ++++
 .../__tests__/kitchen-sink-data.sql           |  1 -
 .../base/distinct_query_builder.toys.json5    | 15 ++++++
 .../base/distinct_query_builder.toys.sql      | 47 ++++++++++++++++++-
 .../distinct_query_builder.toys.test.graphql  |  8 ++++
 5 files changed, 79 insertions(+), 2 deletions(-)

diff --git a/packages/graphile-build-pg/src/QueryBuilder.js b/packages/graphile-build-pg/src/QueryBuilder.js
index 5bd990c81..5e5051eb4 100644
--- a/packages/graphile-build-pg/src/QueryBuilder.js
+++ b/packages/graphile-build-pg/src/QueryBuilder.js
@@ -265,6 +265,16 @@ class QueryBuilder {
       this.lock("limit");
       this.lock("offset");
     });
+    this.beforeLock("distinctOn", () => {
+      this.lock("selectCursor");
+      this.lock("cursorComparator");
+    });
+    this.beforeLock("selectCursor", () => {
+      this.lock("distinctOn");
+    });
+    this.beforeLock("cursorComparator", () => {
+      this.lock("distinctOn");
+    });
     this.lockContext = Object.freeze({
       queryBuilder: this,
     });
diff --git a/packages/postgraphile-core/__tests__/kitchen-sink-data.sql b/packages/postgraphile-core/__tests__/kitchen-sink-data.sql
index 076fc77f5..672fb1785 100644
--- a/packages/postgraphile-core/__tests__/kitchen-sink-data.sql
+++ b/packages/postgraphile-core/__tests__/kitchen-sink-data.sql
@@ -276,7 +276,6 @@ insert into named_query_builder.toy_categories(toy_id, category_id, approved) va
   (4, 2, true),
   (1, 3, false);
 
-
 insert into distinct_query_builder.toys (id, name, color) values
   (1, 'Rex', 'green'),
   (2, 'Toy Soldiers', 'green'),
diff --git a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.json5 b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.json5
index e8d03523e..c0db957b8 100644
--- a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.json5
+++ b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.json5
@@ -61,4 +61,19 @@
       },
     ],
   },
+  t4: {
+    totalCount: 4,
+    nodes: [
+      {
+        id: 1,
+        name: "Rex",
+        color: "green",
+      },
+      {
+        id: 3,
+        name: "Dino-Rocket Launcher",
+        color: "red",
+      },
+    ],
+  },
 }
diff --git a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.sql b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.sql
index 7f4b33ed5..001119161 100644
--- a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.sql
+++ b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.sql
@@ -110,4 +110,49 @@ select coalesce(
     from __local_2__
   ),
   '[]'::json
-) as "data"
\ No newline at end of file
+) as "data"
+
+with __local_0__ as (
+  select to_json(
+    (
+      json_build_object(
+        '__identifiers'::text,
+        json_build_array(__local_1__."id"),
+        'id'::text,
+        (__local_1__."id"),
+        'name'::text,
+        (__local_1__."name"),
+        'color'::text,
+        (__local_1__."color")
+      )
+    )
+  ) as "@nodes"
+  from (
+    select distinct on (__local_1__."color") __local_1__.*
+    from "distinct_query_builder"."toys" as __local_1__
+    where (TRUE) and (TRUE)
+    order by __local_1__."color" ASC,
+    __local_1__."id" ASC
+  ) __local_1__
+),
+__local_2__ as (
+  select json_agg(
+    to_json(__local_0__)
+  ) as data
+  from __local_0__
+)
+select coalesce(
+  (
+    select __local_2__.data
+    from __local_2__
+  ),
+  '[]'::json
+) as "data",
+(
+  select json_build_object(
+    'totalCount'::text,
+    count(1)
+  )
+  from "distinct_query_builder"."toys" as __local_1__
+  where 1 = 1
+) as "aggregates"
\ No newline at end of file
diff --git a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.test.graphql b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.test.graphql
index a1cb5aa47..b416b00fa 100644
--- a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.test.graphql
+++ b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.test.graphql
@@ -24,4 +24,12 @@
       color
     }
   }
+  t4: allToys(distinct: ["color"]) {
+    totalCount
+    nodes {
+      id
+      name
+      color
+    }
+  }
 }

From f32bd5950d692f6c047f1061d779d9a366c89f04 Mon Sep 17 00:00:00 2001
From: Scott Twiname <skott.twiname@gmail.com>
Date: Thu, 8 Sep 2022 13:47:10 +1200
Subject: [PATCH 09/13] Fix equality check add additional test

---
 .../graphile-build-pg/src/QueryBuilder.js     |  8 +++-
 .../base/distinct_query_builder.toys.json5    | 14 +++++++
 .../base/distinct_query_builder.toys.sql      | 42 +++++++++++++++++--
 .../distinct_query_builder.toys.test.graphql  |  7 ++++
 4 files changed, 67 insertions(+), 4 deletions(-)

diff --git a/packages/graphile-build-pg/src/QueryBuilder.js b/packages/graphile-build-pg/src/QueryBuilder.js
index 5e5051eb4..91ff1b067 100644
--- a/packages/graphile-build-pg/src/QueryBuilder.js
+++ b/packages/graphile-build-pg/src/QueryBuilder.js
@@ -905,7 +905,13 @@ order by (row_number() over (partition by 1)) desc`; /* We don't need to factor
             this.data[type].find(
               ([a]) =>
                 a === d ||
-                (Array.isArray(a) && Array.isArray(d) && arraysMatch(a, d))
+                (Array.isArray(a) &&
+                  Array.isArray(d) &&
+                  arraysMatch(
+                    a,
+                    d,
+                    (v1, v2) => JSON.stringify(v1) === JSON.stringify(v2)
+                  ))
             ) ?? [d, true, null]
         );
 
diff --git a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.json5 b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.json5
index c0db957b8..ba566018a 100644
--- a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.json5
+++ b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.json5
@@ -76,4 +76,18 @@
       },
     ],
   },
+  t5: {
+    nodes: [
+      {
+        id: 3,
+        name: "Dino-Rocket Launcher",
+        color: "red",
+      },
+      {
+        id: 1,
+        name: "Rex",
+        color: "green",
+      },
+    ],
+  },
 }
diff --git a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.sql b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.sql
index 001119161..e4ff10b4f 100644
--- a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.sql
+++ b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.sql
@@ -58,8 +58,7 @@ with __local_0__ as (
     from "distinct_query_builder"."toys" as __local_1__
     where (TRUE) and (TRUE)
     order by __local_1__."id" ASC,
-    __local_1__."name" ASC,
-    __local_1__."id" ASC
+    __local_1__."name" ASC
   ) __local_1__
 ),
 __local_2__ as (
@@ -155,4 +154,41 @@ select coalesce(
   )
   from "distinct_query_builder"."toys" as __local_1__
   where 1 = 1
-) as "aggregates"
\ No newline at end of file
+) as "aggregates"
+
+with __local_0__ as (
+  select to_json(
+    (
+      json_build_object(
+        '__identifiers'::text,
+        json_build_array(__local_1__."id"),
+        'id'::text,
+        (__local_1__."id"),
+        'name'::text,
+        (__local_1__."name"),
+        'color'::text,
+        (__local_1__."color")
+      )
+    )
+  ) as "@nodes"
+  from (
+    select distinct on (__local_1__."color") __local_1__.*
+    from "distinct_query_builder"."toys" as __local_1__
+    where (TRUE) and (TRUE)
+    order by __local_1__."color" DESC,
+    __local_1__."id" ASC
+  ) __local_1__
+),
+__local_2__ as (
+  select json_agg(
+    to_json(__local_0__)
+  ) as data
+  from __local_0__
+)
+select coalesce(
+  (
+    select __local_2__.data
+    from __local_2__
+  ),
+  '[]'::json
+) as "data"
\ No newline at end of file
diff --git a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.test.graphql b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.test.graphql
index b416b00fa..657ce9707 100644
--- a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.test.graphql
+++ b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.test.graphql
@@ -32,4 +32,11 @@
       color
     }
   }
+  t5: allToys(distinct: ["color"], orderBy: COLOR_DESC) {
+    nodes {
+      id
+      name
+      color
+    }
+  }
 }

From e012e1fdbf45a47493788a5bdeb85496032d4823 Mon Sep 17 00:00:00 2001
From: Benjie Gillam <benjie@jemjie.com>
Date: Thu, 5 Oct 2023 12:39:59 +0100
Subject: [PATCH 10/13] Backport sql.isEquivalent from pg-sql2@5

---
 packages/graphile-build-pg/src/utils.js | 18 +------
 packages/pg-sql2/src/index.ts           | 66 +++++++++++++++++++++++++
 2 files changed, 67 insertions(+), 17 deletions(-)

diff --git a/packages/graphile-build-pg/src/utils.js b/packages/graphile-build-pg/src/utils.js
index 2b328e2cf..ef17ba982 100644
--- a/packages/graphile-build-pg/src/utils.js
+++ b/packages/graphile-build-pg/src/utils.js
@@ -30,20 +30,4 @@ export const parseTags = (str: string) => {
   );
 };
 
-export function arraysMatch<T>(
-  array1: ReadonlyArray<T>,
-  array2: ReadonlyArray<T>,
-  comparator: (val1: T, val2: T) => boolean = (v1, v2) => v1 === v2
-): boolean {
-  const l = array1.length;
-  if (l !== array2.length) {
-    return false;
-  }
-
-  for (let i = 0; i < l; i++) {
-    if (!comparator(array1[i], array2[i])) {
-      return false;
-    }
-  }
-  return true;
-}
+export { arraysMatch } from "pg-sql2";
diff --git a/packages/pg-sql2/src/index.ts b/packages/pg-sql2/src/index.ts
index 9add48c74..f2529bf2a 100644
--- a/packages/pg-sql2/src/index.ts
+++ b/packages/pg-sql2/src/index.ts
@@ -1,6 +1,7 @@
 import * as debugFactory from "debug";
 import { QueryConfig } from "pg";
 import LRU from "@graphile/lru";
+import { inspect } from "util";
 
 const debug = debugFactory("pg-sql2");
 
@@ -326,6 +327,71 @@ export function join(items: Array<SQL>, rawSeparator = ""): SQLQuery {
   return currentItems;
 }
 
+export function arraysMatch<T>(
+  array1: ReadonlyArray<T>,
+  array2: ReadonlyArray<T>,
+  comparator?: (val1: T, val2: T) => boolean
+): boolean {
+  if (array1 === array2) return true;
+  const l = array1.length;
+  if (l !== array2.length) {
+    return false;
+  }
+  for (let i = 0; i < l; i++) {
+    if (
+      comparator ? !comparator(array1[i]!, array2[i]!) : array1[i] !== array2[i]
+    ) {
+      return false;
+    }
+  }
+  return true;
+}
+
+export function isEquivalent(
+  sql1: SQL,
+  sql2: SQL,
+  options?: {
+    symbolSubstitutes?: Map<symbol, symbol>;
+  }
+): boolean {
+  if (sql1 === sql2) {
+    return true;
+  } else if (Array.isArray(sql1)) {
+    if (!Array.isArray(sql2)) {
+      return false;
+    }
+    return arraysMatch(sql1, sql2, (a, b) => isEquivalent(a, b, options));
+  } else if (Array.isArray(sql2)) {
+    return false;
+  } else {
+    switch (sql1.type) {
+      case "RAW": {
+        if (sql2.type !== sql1.type) {
+          return false;
+        }
+        return sql1.text === sql2.text;
+      }
+      case "VALUE": {
+        if (sql2.type !== sql1.type) {
+          return false;
+        }
+        return sql1.value === sql2.value;
+      }
+      case "IDENTIFIER": {
+        if (sql2.type !== sql1.type) {
+          return false;
+        }
+        return arraysMatch(sql1.names, sql2.names);
+      }
+      default: {
+        const never: never = sql1;
+        console.error(`Unhandled node type: ${inspect(never)}`);
+        return false;
+      }
+    }
+  }
+}
+
 // Copied from https://github.com/brianc/node-postgres/blob/860cccd53105f7bc32fed8b1de69805f0ecd12eb/lib/client.js#L285-L302
 // Ported from PostgreSQL 9.2.4 source code in src/interfaces/libpq/fe-exec.c
 // Trivial performance optimisations by Benjie.

From b81a04db248d332dcb4846abca9a48c53f7fadd6 Mon Sep 17 00:00:00 2001
From: Benjie Gillam <benjie@jemjie.com>
Date: Thu, 5 Oct 2023 12:40:33 +0100
Subject: [PATCH 11/13] Change how the 'ORDER BY' clause is built

---
 .../graphile-build-pg/src/QueryBuilder.js     | 59 +++++++++----------
 1 file changed, 27 insertions(+), 32 deletions(-)

diff --git a/packages/graphile-build-pg/src/QueryBuilder.js b/packages/graphile-build-pg/src/QueryBuilder.js
index 91ff1b067..1b9cb89ea 100644
--- a/packages/graphile-build-pg/src/QueryBuilder.js
+++ b/packages/graphile-build-pg/src/QueryBuilder.js
@@ -4,7 +4,6 @@ import type { SQL } from "pg-sql2";
 import isSafeInteger from "lodash/isSafeInteger";
 import chunk from "lodash/chunk";
 import type { PgClass, PgType } from "./plugins/PgIntrospectionPlugin";
-import { arraysMatch } from "./utils";
 
 // eslint-disable-next-line flowtype/no-weak-types
 type GraphQLContext = any;
@@ -269,6 +268,9 @@ class QueryBuilder {
       this.lock("selectCursor");
       this.lock("cursorComparator");
     });
+    this.beforeLock("orderBy", () => {
+      this.lock("distinctOn");
+    });
     this.beforeLock("selectCursor", () => {
       this.lock("distinctOn");
     });
@@ -764,6 +766,23 @@ ${sql.join(
           })} as object`
         : this.buildSelectFields();
 
+    const orderBy: Array<[sql.SQL, boolean, boolean | null]> = [];
+    const remainingOrderBy = [...this.compiledData.orderBy];
+    for (const distinctExpression of this.compiledData.distinctOn) {
+      const relevantOrderByIndex = remainingOrderBy.findIndex(o =>
+        sql.isEquivalent(o[0], distinctExpression)
+      );
+      if (relevantOrderByIndex >= 0) {
+        orderBy.push(remainingOrderBy[relevantOrderByIndex]);
+        remainingOrderBy.splice(relevantOrderByIndex, 1);
+      } else {
+        orderBy.push([distinctExpression, true, null]);
+      }
+    }
+    for (const orderSpec of remainingOrderBy) {
+      orderBy.push(orderSpec);
+    }
+
     let fragment = sql.fragment`\
 select ${
       this.compiledData.distinctOn.length
@@ -781,9 +800,9 @@ ${
 ${this.compiledData.join.length && sql.join(this.compiledData.join, " ")}
 where ${this.buildWhereClause(true, true, options)}
 ${
-  this.compiledData.orderBy.length
+  orderBy.length
     ? sql.fragment`order by ${sql.join(
-        this.compiledData.orderBy.map(
+        orderBy.map(
           ([expr, ascending, nullsFirst]) =>
             sql.fragment`${expr} ${
               Number(ascending) ^ Number(flip)
@@ -897,35 +916,11 @@ order by (row_number() over (partition by 1)) desc`; /* We don't need to factor
       this.locks[type] = isDev ? new Error("Initally locked here").stack : true;
       this.compiledData[type] = data;
     } else if (type === "orderBy") {
-      if (this.data["distinctOn"].length) {
-        // Add distinct to existing order by to avoid `SELECT DISTINCT ON expressions must match initial ORDER BY expressions`
-        // Convert distinct fields to order by applying ascending and using existing order by for matching fields
-        const distinctAsOrderBy = this.data["distinctOn"].map(
-          d =>
-            this.data[type].find(
-              ([a]) =>
-                a === d ||
-                (Array.isArray(a) &&
-                  Array.isArray(d) &&
-                  arraysMatch(
-                    a,
-                    d,
-                    (v1, v2) => JSON.stringify(v1) === JSON.stringify(v2)
-                  ))
-            ) ?? [d, true, null]
-        );
-
-        // Create a union of the distinct and order by fields
-        this.compiledData[type] = [
-          ...new Set([...distinctAsOrderBy, ...this.data[type]]),
-        ].map(([a, b, c]) => [callIfNecessary(a, context), b, c]);
-      } else {
-        this.compiledData[type] = this.data[type].map(([a, b, c]) => [
-          callIfNecessary(a, context),
-          b,
-          c,
-        ]);
-      }
+      this.compiledData[type] = this.data[type].map(([a, b, c]) => [
+        callIfNecessary(a, context),
+        b,
+        c,
+      ]);
     } else if (type === "from") {
       if (this.data.from) {
         const f = this.data.from;

From 915cffa9cb29aa1c84e752026284db3e9ec964cb Mon Sep 17 00:00:00 2001
From: Benjie Gillam <benjie@jemjie.com>
Date: Thu, 5 Oct 2023 14:20:13 +0100
Subject: [PATCH 12/13] Move orderBy logic again, and forbid distinctOn with
 last

---
 .../graphile-build-pg/src/QueryBuilder.js     | 45 ++++++++++++-------
 1 file changed, 28 insertions(+), 17 deletions(-)

diff --git a/packages/graphile-build-pg/src/QueryBuilder.js b/packages/graphile-build-pg/src/QueryBuilder.js
index 1b9cb89ea..7296ff51a 100644
--- a/packages/graphile-build-pg/src/QueryBuilder.js
+++ b/packages/graphile-build-pg/src/QueryBuilder.js
@@ -601,6 +601,10 @@ ${sql.join(
         throw new Error("Cannot combine 'last' and 'offset'");
       } else {
         if (this.compiledData.orderBy.length > 0) {
+          if (this.compiledData.distinctOn.length > 0) {
+            // TODO: improve this
+            throw new Error(`'distinctOn' cannot be combined with 'last'`);
+          }
           flip = true;
           limit = this.compiledData.last;
         } else {
@@ -620,9 +624,31 @@ ${sql.join(
   getFinalLimit() {
     return this.getFinalLimitAndOffset().limit;
   }
+  _orderByExpressionsAndDirections: Array<
+    [sql.SQL, boolean, boolean | null]
+  > | null = null;
   getOrderByExpressionsAndDirections() {
     this.lock("orderBy");
-    return this.compiledData.orderBy;
+    if (!this._orderByExpressionsAndDirections) {
+      const orderBy: Array<[sql.SQL, boolean, boolean | null]> = [];
+      const remainingOrderBy = [...this.compiledData.orderBy];
+      for (const distinctExpression of this.compiledData.distinctOn) {
+        const relevantOrderByIndex = remainingOrderBy.findIndex(o =>
+          sql.isEquivalent(o[0], distinctExpression)
+        );
+        if (relevantOrderByIndex >= 0) {
+          orderBy.push(remainingOrderBy[relevantOrderByIndex]);
+          remainingOrderBy.splice(relevantOrderByIndex, 1);
+        } else {
+          orderBy.push([distinctExpression, true, null]);
+        }
+      }
+      for (const orderSpec of remainingOrderBy) {
+        orderBy.push(orderSpec);
+      }
+      this._orderByExpressionsAndDirections = orderBy;
+    }
+    return this._orderByExpressionsAndDirections;
   }
   getSelectFieldsCount() {
     this.lockEverything();
@@ -766,22 +792,7 @@ ${sql.join(
           })} as object`
         : this.buildSelectFields();
 
-    const orderBy: Array<[sql.SQL, boolean, boolean | null]> = [];
-    const remainingOrderBy = [...this.compiledData.orderBy];
-    for (const distinctExpression of this.compiledData.distinctOn) {
-      const relevantOrderByIndex = remainingOrderBy.findIndex(o =>
-        sql.isEquivalent(o[0], distinctExpression)
-      );
-      if (relevantOrderByIndex >= 0) {
-        orderBy.push(remainingOrderBy[relevantOrderByIndex]);
-        remainingOrderBy.splice(relevantOrderByIndex, 1);
-      } else {
-        orderBy.push([distinctExpression, true, null]);
-      }
-    }
-    for (const orderSpec of remainingOrderBy) {
-      orderBy.push(orderSpec);
-    }
+    const orderBy = this.getOrderByExpressionsAndDirections();
 
     let fragment = sql.fragment`\
 select ${

From d7be967605738c993f7bbc2d49ab418e482dbf38 Mon Sep 17 00:00:00 2001
From: Benjie Gillam <benjie@jemjie.com>
Date: Thu, 5 Oct 2023 14:30:01 +0100
Subject: [PATCH 13/13] Add more tests

---
 .../base/distinct_query_builder.toys.json5    |  39 +++
 .../base/distinct_query_builder.toys.sql      | 252 +++++++++++++++++-
 .../distinct_query_builder.toys.test.graphql  |  43 +++
 3 files changed, 333 insertions(+), 1 deletion(-)

diff --git a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.json5 b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.json5
index ba566018a..403985e11 100644
--- a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.json5
+++ b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.json5
@@ -90,4 +90,43 @@
       },
     ],
   },
+  t6: {
+    totalCount: 4,
+    nodes: [
+      {
+        id: 3,
+        name: "Dino-Rocket Launcher",
+        color: "red",
+      },
+    ],
+    pageInfo: {
+      endCursor: "WyJuYW1lX2FzYyIsImNvbG9yX2Rlc2MiLFsicmVkIiwiRGluby1Sb2NrZXQgTGF1bmNoZXIiLDNdXQ==",
+    },
+  },
+  t7: {
+    totalCount: 4,
+    nodes: [
+      {
+        id: 4,
+        name: "History of Dinosaurs book",
+        color: "red",
+      },
+    ],
+    pageInfo: {
+      endCursor: "WyJuYW1lX2FzYyIsImNvbG9yX2Rlc2MiLFsicmVkIiwiSGlzdG9yeSBvZiBEaW5vc2F1cnMgYm9vayIsNF1d",
+    },
+  },
+  t8: {
+    totalCount: 4,
+    nodes: [
+      {
+        id: 3,
+        name: "Dino-Rocket Launcher",
+        color: "red",
+      },
+    ],
+    pageInfo: {
+      endCursor: "WyJuYW1lX2FzYyIsImNvbG9yX2Rlc2MiLFsicmVkIiwiRGluby1Sb2NrZXQgTGF1bmNoZXIiLDNdXQ==",
+    },
+  },
 }
diff --git a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.sql b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.sql
index e4ff10b4f..7debc8d6d 100644
--- a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.sql
+++ b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.sql
@@ -191,4 +191,254 @@ select coalesce(
     from __local_2__
   ),
   '[]'::json
-) as "data"
\ No newline at end of file
+) as "data"
+
+with __local_0__ as (
+  select to_json(
+    (
+      json_build_object(
+        '__identifiers'::text,
+        json_build_array(__local_1__."id"),
+        'id'::text,
+        (__local_1__."id"),
+        'name'::text,
+        (__local_1__."name"),
+        'color'::text,
+        (__local_1__."color")
+      )
+    )
+  ) as "@nodes",
+  to_json(
+    json_build_array(
+      'name_asc',
+      'color_desc',
+      json_build_array(
+        __local_1__."color",
+        __local_1__."name",
+        __local_1__."id"
+      )
+    )
+  ) as "__cursor"
+  from (
+    select distinct on (__local_1__."color") __local_1__.*
+    from "distinct_query_builder"."toys" as __local_1__
+    where (TRUE) and (TRUE)
+    order by __local_1__."color" DESC,
+    __local_1__."name" ASC,
+    __local_1__."id" ASC
+    limit 1
+  ) __local_1__
+),
+__local_2__ as (
+  select json_agg(
+    to_json(__local_0__)
+  ) as data
+  from __local_0__
+)
+select coalesce(
+  (
+    select __local_2__.data
+    from __local_2__
+  ),
+  '[]'::json
+) as "data",
+(
+  select json_build_object(
+    'totalCount'::text,
+    count(1)
+  )
+  from "distinct_query_builder"."toys" as __local_1__
+  where 1 = 1
+) as "aggregates"
+
+with __local_0__ as (
+  select to_json(
+    (
+      json_build_object(
+        '__identifiers'::text,
+        json_build_array(__local_1__."id"),
+        'id'::text,
+        (__local_1__."id"),
+        'name'::text,
+        (__local_1__."name"),
+        'color'::text,
+        (__local_1__."color")
+      )
+    )
+  ) as "@nodes",
+  to_json(
+    json_build_array(
+      'name_asc',
+      'color_desc',
+      json_build_array(
+        __local_1__."color",
+        __local_1__."name",
+        __local_1__."id"
+      )
+    )
+  ) as "__cursor"
+  from (
+    select distinct on (__local_1__."color") __local_1__.*
+    from "distinct_query_builder"."toys" as __local_1__
+    where (
+      (
+        (
+          (
+            (
+              'name_asc',
+              'color_desc'
+            ) = (
+              $1,
+              $2
+            )
+          ) AND (
+            (
+              (
+                __local_1__."color" < $3
+              ) OR (
+                __local_1__."color" = $3 AND (
+                  (
+                    __local_1__."name" > $4
+                  ) OR (
+                    __local_1__."name" = $4 AND (
+                      (
+                        __local_1__."id" > $5
+                      ) OR (
+                        __local_1__."id" = $5 AND false
+                      )
+                    )
+                  )
+                )
+              )
+            )
+          )
+        )
+      )
+    ) and (TRUE)
+    order by __local_1__."color" DESC,
+    __local_1__."name" ASC,
+    __local_1__."id" ASC
+    limit 1
+  ) __local_1__
+),
+__local_2__ as (
+  select json_agg(
+    to_json(__local_0__)
+  ) as data
+  from __local_0__
+)
+select coalesce(
+  (
+    select __local_2__.data
+    from __local_2__
+  ),
+  '[]'::json
+) as "data",
+(
+  select json_build_object(
+    'totalCount'::text,
+    count(1)
+  )
+  from "distinct_query_builder"."toys" as __local_1__
+  where 1 = 1
+) as "aggregates"
+
+with __local_0__ as (
+  select to_json(
+    (
+      json_build_object(
+        '__identifiers'::text,
+        json_build_array(__local_1__."id"),
+        'id'::text,
+        (__local_1__."id"),
+        'name'::text,
+        (__local_1__."name"),
+        'color'::text,
+        (__local_1__."color")
+      )
+    )
+  ) as "@nodes",
+  to_json(
+    json_build_array(
+      'name_asc',
+      'color_desc',
+      json_build_array(
+        __local_1__."color",
+        __local_1__."name",
+        __local_1__."id"
+      )
+    )
+  ) as "__cursor"
+  from (
+    with __local_2__ as (
+      select distinct on (__local_1__."color") __local_1__.*
+      from "distinct_query_builder"."toys" as __local_1__
+      where (TRUE)
+      and (
+        (
+          (
+            (
+              (
+                'name_asc',
+                'color_desc'
+              ) = (
+                $1,
+                $2
+              )
+            ) AND (
+              (
+                (
+                  __local_1__."color" > $3
+                ) OR (
+                  __local_1__."color" = $3 AND (
+                    (
+                      __local_1__."name" < $4
+                    ) OR (
+                      __local_1__."name" = $4 AND (
+                        (
+                          __local_1__."id" < $5
+                        ) OR (
+                          __local_1__."id" = $5 AND false
+                        )
+                      )
+                    )
+                  )
+                )
+              )
+            )
+          )
+        )
+      )
+      order by __local_1__."color" ASC,
+      __local_1__."name" DESC,
+      __local_1__."id" DESC
+      limit 1
+    )
+    select *
+    from __local_2__
+    order by (
+      row_number( ) over (partition by 1)
+    ) desc
+  ) __local_1__
+),
+__local_3__ as (
+  select json_agg(
+    to_json(__local_0__)
+  ) as data
+  from __local_0__
+)
+select coalesce(
+  (
+    select __local_3__.data
+    from __local_3__
+  ),
+  '[]'::json
+) as "data",
+(
+  select json_build_object(
+    'totalCount'::text,
+    count(1)
+  )
+  from "distinct_query_builder"."toys" as __local_1__
+  where 1 = 1
+) as "aggregates"
\ No newline at end of file
diff --git a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.test.graphql b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.test.graphql
index 657ce9707..383fdf3d2 100644
--- a/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.test.graphql
+++ b/packages/postgraphile-core/__tests__/queries/base/distinct_query_builder.toys.test.graphql
@@ -39,4 +39,47 @@
       color
     }
   }
+  t6: allToys(distinct: ["color"], orderBy: [NAME_ASC, COLOR_DESC], first: 1) {
+    totalCount
+    nodes {
+      id
+      name
+      color
+    }
+    pageInfo {
+      endCursor
+    }
+  }
+  t7: allToys(
+    distinct: ["color"]
+    orderBy: [NAME_ASC, COLOR_DESC]
+    first: 1
+    after: "WyJuYW1lX2FzYyIsImNvbG9yX2Rlc2MiLFsicmVkIiwiRGluby1Sb2NrZXQgTGF1bmNoZXIiLDNdXQ==" # cursor from t6
+  ) {
+    totalCount
+    nodes {
+      id
+      name
+      color
+    }
+    pageInfo {
+      endCursor
+    }
+  }
+  t8: allToys(
+    distinct: ["color"]
+    orderBy: [NAME_ASC, COLOR_DESC]
+    last: 1
+    before: "WyJuYW1lX2FzYyIsImNvbG9yX2Rlc2MiLFsicmVkIiwiSGlzdG9yeSBvZiBEaW5vc2F1cnMgYm9vayIsNF1d" # cursor from t7
+  ) {
+    totalCount
+    nodes {
+      id
+      name
+      color
+    }
+    pageInfo {
+      endCursor
+    }
+  }
 }