diff --git a/.github/scripts/wait-for-postgres.sh b/.github/scripts/wait-for-postgres.sh
new file mode 100755
index 0000000..41d6275
--- /dev/null
+++ b/.github/scripts/wait-for-postgres.sh
@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+until pg_isready &>/dev/null; do
+  sleep 1
+done
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 6a8eef5..57f18a9 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -6,16 +6,20 @@ on:
     branches:
       - main
 
-concurrency:
-  group: ${{ github.workflow }}-${{ github.ref }}
-  cancel-in-progress: true
 
 jobs:
   test:
+    concurrency:
+      group: ${{ github.workflow }}-${{ matrix.pg }}-${{ github.ref }}
+      cancel-in-progress: true
     strategy:
       matrix:
         pg:
-          - v17
+          - default
+          - postgresql_17
+          - postgresql_16
+          - postgresql_15
+          - postgresql_14
     runs-on: namespace-profile-cached-amd64-lg
     steps:
       - uses: actions/checkout@v4
@@ -34,6 +38,6 @@ jobs:
           authToken: "${{ secrets.CACHIX_AUTH_TOKEN }}"
       - run: nix flake check
       - run: nix build .#${{ matrix.pg }}
-      - run: nix run .#devenv -- up -D
-      - run: nix develop -c pg_prove test.sql
-      - run: nix run .#devenv down
+      - run: nix run .#${{ matrix.pg }}-compose -- up -D && nix develop .#${{ matrix.pg }} -c ./.github/scripts/wait-for-postgres.sh
+      - run: nix develop .#${{ matrix.pg }} -c pg_prove test.sql
+      - run: nix run .#${{ matrix.pg }}-compose down
diff --git a/README.md b/README.md
index 2de11f4..b578a52 100644
--- a/README.md
+++ b/README.md
@@ -13,5 +13,6 @@ select jsonb_patch(
 (1 row)
 ```
 
-See [./test.sql] for more examples.
+Compatible (I think) with PostgreSQL 14+.
+See [./test.sql](./test.sql) for more examples.
 I have not yet written tests for A.11-A.15 from the RFC.
diff --git a/flake.nix b/flake.nix
index c8c9b55..5be1e59 100644
--- a/flake.nix
+++ b/flake.nix
@@ -35,50 +35,52 @@
         pkgs,
         system,
         ...
-      }: {
-        devShells.default = pkgs.mkShell {
-          name = "pg_jsonpatch";
-          buildInputs = with pkgs; [
-            postgresql
-            perlPackages.TAPParserSourceHandlerpgTAP # pg_prove
-          ];
-          PGDATA = "data/default";
-          PGHOST = "localhost";
-          PGDATABASE = "postgres";
-        };
-
+      }: let
         packages = {
           default = pkgs.callPackage ./package.nix {inherit (pkgs) postgresql;};
-          v17 = pkgs.callPackage ./package.nix {postgresql = pkgs.postgresql_17;};
-          v16 = pkgs.callPackage ./package.nix {postgresql = pkgs.postgresql_16;};
-          v15 = pkgs.callPackage ./package.nix {postgresql = pkgs.postgresql_15;};
-          v14 = pkgs.callPackage ./package.nix {postgresql = pkgs.postgresql_14;};
+          postgresql_17 = pkgs.callPackage ./package.nix {postgresql = pkgs.postgresql_17;};
+          postgresql_16 = pkgs.callPackage ./package.nix {postgresql = pkgs.postgresql_16;};
+          postgresql_15 = pkgs.callPackage ./package.nix {postgresql = pkgs.postgresql_15;};
+          postgresql_14 = pkgs.callPackage ./package.nix {postgresql = pkgs.postgresql_14;};
         };
+      in {
+        devShells = builtins.mapAttrs (name: drv:
+          pkgs.mkShell {
+            name = "pg_jsonpatch";
+            buildInputs = [
+              drv.passthru.postgresql
+              pkgs.perlPackages.TAPParserSourceHandlerpgTAP # pg_prove
+            ];
+            PGDATA = "data/${name}";
+            PGHOST = "localhost";
+            PGDATABASE = "postgres";
+          })
+        packages;
 
-        process-compose.devenv = {
-          imports = [
-            inputs.services.processComposeModules.default
-          ];
+        inherit packages;
 
-          cli.options.no-server = false;
+        process-compose = lib.mapAttrs' (name: drv:
+          lib.nameValuePair "${name}-compose" {
+            imports = [
+              inputs.services.processComposeModules.default
+            ];
 
-          services.postgres.default = {
-            enable = true;
-            extensions = exts:
-              with exts; [
-                config.packages.default
-                pgtap
-              ];
-            initialScript.after = ''
-              create extension pgtap;
-            '';
-            package = config.packages.default.postgresql;
-            settings = {
-              log_statement = "all";
-              logging_collector = false;
+            cli.options.no-server = false;
+
+            services.postgres.${name} = {
+              enable = true;
+              extensions = exts: [drv exts.pgtap];
+              initialScript.after = ''
+                create extension pgtap;
+              '';
+              package = drv.passthru.postgresql;
+              settings = {
+                log_statement = "all";
+                logging_collector = false;
+              };
             };
-          };
-        };
+          })
+        packages;
       };
     };
 }
diff --git a/pg_jsonpatch--1.0.0.sql b/pg_jsonpatch--1.0.0.sql
index 9e742b4..61b64db 100644
--- a/pg_jsonpatch--1.0.0.sql
+++ b/pg_jsonpatch--1.0.0.sql
@@ -3,23 +3,20 @@
 create or replace function jsonb_patch_add(target jsonb, path text[], value jsonb)
 returns jsonb
 as $$
-  with x as (
-    select jsonb_typeof(jsonb_extract_path(target, variadic trim_array(path, 1))) as t
-  )
-  select jsonb_set(target, path, value, true)
-  from x
-  where x.t = 'object'
-  union all
-  select jsonb_insert(target, path, value)
-  from x
-  where x.t = 'array' and path[array_length(path, 1)] is distinct from '-'
-  union all
-  select jsonb_insert(target, trim_array(path, 1) || array['-1'], value, true)
-  from x
-  where x.t = 'array' and path[array_length(path, 1)] = '-'
-  limit 1
-$$
-language sql
+declare
+  target_type text := jsonb_typeof(jsonb_extract_path(target, variadic trim_array(path, 1)));
+begin
+  case
+    when target_type = 'object'
+      then return jsonb_set(target, path, value, true);
+    when target_type = 'array' and path[array_length(path, 1)] = '-'
+      then return jsonb_insert(target, trim_array(path, 1) || array['-1'], value, true);
+    when target_type = 'array'
+      then return jsonb_insert(target, path, value);
+    else return null;
+  end case;
+end $$
+language plpgsql
 immutable;
 
 create or replace function jsonb_patch_remove(target jsonb, path text[])
@@ -36,22 +33,13 @@ immutable;
 
 create or replace function jsonb_patch_move(target jsonb, _from text[], path text[])
 returns jsonb
-as $$
-  with old as (
-    select jsonb_extract_path(target, variadic _from) as value
-  )
-
-  select @extschema@.jsonb_patch_add(@extschema@.jsonb_patch_remove(target, _from), path, value)
-  from old
-$$
+as $$ select @extschema@.jsonb_patch_add(@extschema@.jsonb_patch_remove(target, _from), path, jsonb_extract_path(target, variadic _from)) $$
 language sql
 immutable;
 
 create or replace function jsonb_patch_copy(target jsonb, _from text[], path text[])
 returns jsonb
-as $$
-  select @extschema@.jsonb_patch_add(target, path, jsonb_extract_path(target, variadic _from))
-$$
+as $$ select @extschema@.jsonb_patch_add(target, path, jsonb_extract_path(target, variadic _from)) $$
 language sql
 immutable;
 
@@ -67,53 +55,40 @@ as $$ select array_remove(string_to_array(path, '/'), '') $$
 language sql
 immutable;
 
+-- Apply a single patch operation to an object.
 create or replace function jsonb_patch_apply(target jsonb, patch jsonb)
 returns jsonb
 as $$
 declare
-  op text := patch->>'op';
   path text[] := @extschema@.jsonb_patch_split_path(patch->>'path');
-  rv jsonb;
 begin
   case patch->>'op'
-    when 'add' then rv := @extschema@.jsonb_patch_add(target, path, patch->'value');
-    when 'remove' then rv := @extschema@.jsonb_patch_remove(target, path);
-    when 'replace' then rv := @extschema@.jsonb_patch_replace(target, path, patch->'value');
-    when 'move' then rv := @extschema@.jsonb_patch_move(target, @extschema@.jsonb_patch_split_path(patch->>'from'), path);
-    when 'copy' then rv := @extschema@.jsonb_patch_copy(target, @extschema@.jsonb_patch_split_path(patch->>'from'), path);
-    when 'test' then rv := @extschema@.jsonb_patch_test(target, path, patch->'value');
+    when 'add' then return @extschema@.jsonb_patch_add(target, path, patch->'value');
+    when 'remove' then return @extschema@.jsonb_patch_remove(target, path);
+    when 'replace' then return @extschema@.jsonb_patch_replace(target, path, patch->'value');
+    when 'move' then return @extschema@.jsonb_patch_move(target, @extschema@.jsonb_patch_split_path(patch->>'from'), path);
+    when 'copy' then return @extschema@.jsonb_patch_copy(target, @extschema@.jsonb_patch_split_path(patch->>'from'), path);
+    when 'test' then return @extschema@.jsonb_patch_test(target, path, patch->'value');
+    else return null;
   end case;
-
-  return rv;
 end $$
 language plpgsql
 immutable;
 
-create or replace function jsonb_coalesce(variadic jsonb[])
-returns jsonb
-as $$
-  select value
-  from unnest($1) as value
-  where value is not null and jsonb_typeof(value) != 'null'
-  limit 1
-$$
-language sql
-immutable;
-
-create or replace function jsonb_patch_agg(target jsonb, patch jsonb, base jsonb)
-returns jsonb
-as $$ select @extschema@.jsonb_patch_apply(@extschema@.jsonb_coalesce(target, base), patch) $$
-language sql
-immutable;
-
-create or replace aggregate jsonb_patch_agg(jsonb, jsonb) (
-  sfunc = @extschema@.jsonb_patch_agg,
-  stype = jsonb,
-  initcond = null
-);
-
 create or replace function jsonb_patch(target jsonb, patches jsonb)
 returns jsonb
-as $$ select jsonb_patch_agg(value, target) from jsonb_array_elements(patches) $$
-language sql
+as $$
+declare
+  patch jsonb;
+  result jsonb := target;
+begin
+  for patch in select * from jsonb_array_elements(patches) loop
+    result := @extschema@.jsonb_patch_apply(result, patch);
+    if result is null then
+      return null;
+    end if;
+  end loop;
+  return result;
+end $$
+language plpgsql
 immutable;
diff --git a/test.sql b/test.sql
index 1e92f3e..0fa7813 100644
--- a/test.sql
+++ b/test.sql
@@ -90,7 +90,8 @@ select
 from (
   values
     ('{"op":"replace","path":"/a/b/c","value":42}'::jsonb),
-    ('{"op":"test","path":"/a/b/c","value":"C"}')
+    ('{"op":"test","path":"/a/b/c","value":"C"}'),
+    ('{"op":"add","path":"/a/b/d","value":"foo"}'::jsonb)
 ) as patches(patch);
 
 select plan(count(*)::int) from test_cases;