how to create and aggregate

postgres/aggregate.md

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+CREATE OR REPLACE FUNCTION public.jsonb_concat(
+    state jsonb,
+    concat jsonb)
+  RETURNS jsonb AS
+$BODY$
+BEGIN
+    --RAISE notice 'state is %', state;
+    --RAISE notice 'concat is %', concat;
+    RETURN state || concat;
+END;
+$BODY$
+  LANGUAGE plpgsql VOLATILE
+  COST 100;
+
+
+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 SELECT jsonb_agg(state || concat;
+END;
+$BODY$
+  LANGUAGE plpgsql VOLATILE
+  COST 100;
+
+
+DROP AGGREGATE IF EXISTS public.jsonb_arr_aggc(jsonb);
+CREATE AGGREGATE public.jsonb_arr_aggc(jsonb) (
+  SFUNC=public.jsonb_concat,
+  STYPE=jsonb,
+  INITCOND='[]'
+);
+
+DROP AGGREGATE IF EXISTS public.jsonb_obj_aggc(jsonb);
+CREATE AGGREGATE public.jsonb_obj_aggc(jsonb) (
+  SFUNC=public.jsonb_concat,
+  STYPE=jsonb,
+  INITCOND='{}'
+);