Added last values for table datapoint, update to current latest values and trigger for future values

sql/00026.sql

@@ -0,0 +1,56 @@
+/* Adding last values to the datapoint table since they are a regularly used value. */
+ALTER TABLE public.datapoint ADD COLUMN last_value_int int8 NULL;
+ALTER TABLE public.datapoint ADD COLUMN last_value_string varchar NULL;
+ALTER TABLE public.datapoint ADD COLUMN last_value_datetime timestamptz NULL;
+
+
+
+/* Once-run query to update it to the latest, to avoid user having to wait for the next entry. */
+UPDATE public.datapoint AS dp
+SET
+    last_value_int = dpv.value_int,
+    last_value_string = dpv.value_string,
+    last_value_datetime = dpv.value_datetime
+FROM (
+	SELECT
+		dp.id AS datapoint_id,
+		dpv.value_int,
+		dpv.value_string,
+		dpv.value_datetime
+	FROM public.datapoint dp
+	LEFT JOIN (
+		SELECT
+			*, 
+			row_number() OVER (PARTITION BY "datapoint_id" ORDER BY ts DESC) AS rn
+		FROM datapoint_value
+	) dpv ON dpv.datapoint_id = dp.id AND rn = 1
+) AS dpv
+WHERE
+	dpv.datapoint_id = dp.id;
+
+
+
+/* A trigger keeps the value current without bugs introduced in software missing the entry. */
+CREATE OR REPLACE FUNCTION datapoint_entry()
+	RETURNS TRIGGER 
+	LANGUAGE PLPGSQL
+	AS
+$$
+BEGIN
+	UPDATE public.datapoint
+	SET
+		last_value_int      = NEW.value_int,
+		last_value_string   = NEW.value_string,
+		last_value_datetime = NEW.value_datetime
+	WHERE
+		id = NEW.datapoint_id;
+
+	RETURN NEW;
+END;
+$$;
+
+CREATE TRIGGER datapoint_entry
+	AFTER INSERT
+	ON public.datapoint_value
+	FOR EACH ROW
+	EXECUTE PROCEDURE datapoint_entry();