From 0e6e7e45f476a4eacbe1f4b44c149cf35c47e263 Mon Sep 17 00:00:00 2001
From: Paul Trowbridge <paul@hptrow.me>
Date: Tue, 26 May 2020 12:43:46 -0400
Subject: [PATCH] create aggregate function that unwraps 2 arrays and returns
 one with distinct values from both provided

---
 postgres/concat_distinct_array_values.sql | 27 +++++++++++++++++++++++
 postgres/jsonb_arr_aggcd.sql              | 27 +++++++++++++++++++++++
 2 files changed, 54 insertions(+)
 create mode 100644 postgres/concat_distinct_array_values.sql
 create mode 100644 postgres/jsonb_arr_aggcd.sql

diff --git a/postgres/concat_distinct_array_values.sql b/postgres/concat_distinct_array_values.sql
new file mode 100644
index 0000000..a4ca3b0
--- /dev/null
+++ b/postgres/concat_distinct_array_values.sql
@@ -0,0 +1,27 @@
+DO $$
+DECLARE
+
+_a1 jsonb;
+_a2 jsonb;
+_a3 jsonb;
+
+BEGIN
+
+_a1 := (select '["A","B","A"]'::jsonb);
+_a2 := (select '["A","B","A"]'::jsonb);
+SELECT 
+    jsonb_agg(DISTINCT x.ae)
+INTO
+    _a3
+FROM
+    (
+    SELECT jsonb_array_elements(_a1) ae
+    UNION ALL 
+    SELECT jsonb_array_elements(_a2) ae
+) x;
+
+raise notice '%', _a3;
+
+END;
+$$
+language plpgsql
diff --git a/postgres/jsonb_arr_aggcd.sql b/postgres/jsonb_arr_aggcd.sql
new file mode 100644
index 0000000..79bc18a
--- /dev/null
+++ b/postgres/jsonb_arr_aggcd.sql
@@ -0,0 +1,27 @@
+CREATE OR REPLACE FUNCTION public.jsonb_concat_distinct_arr(
+    state jsonb,
+    concat jsonb)
+  RETURNS jsonb AS
+$BODY$
+BEGIN
+    --RAISE notice 'state is %', state;
+    --RAISE notice 'concat is %', concat;
+    RETURN 
+    jsonb_agg(DISTINCT ae) 
+    FROM
+    (
+        SELECT jsonb_array_elements(state) ae
+        UNION ALL 
+        SELECT jsonb_array_elements(concat) ae
+    ) x;
+END;
+$BODY$
+LANGUAGE plpgsql;
+
+DROP AGGREGATE IF EXISTS public.jsonb_arr_aggcd(jsonb);
+CREATE AGGREGATE public.jsonb_arr_aggcd(jsonb) (
+  SFUNC=public.jsonb_concat_distinct_arr,
+  STYPE=jsonb,
+  INITCOND='[]'
+);
+