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-- createlang pgpgsql ebus
CREATE TABLE value_cache ( LIKE value );
DELETE FROM value_cache;
-- Create a function that always returns the first non-NULL item
CREATE OR REPLACE FUNCTION public.first_agg ( anyelement, anyelement ) RETURNS anyelement AS $$
SELECT CASE WHEN $1 IS NULL THEN $2 ELSE $1 END;
$$ LANGUAGE SQL STABLE;
-- And then wrap an aggreagate around it
CREATE AGGREGATE public.first (
sfunc = public.first_agg,
basetype = anyelement,
stype = anyelement
);
DROP FUNCTION value_insert_trigger_func() CASCADE;
CREATE FUNCTION value_insert_trigger_func() RETURNS trigger AS $$
BEGIN
DELETE FROM value_cache
WHERE date_trunc('hour', timestamp) =
(SELECT date_trunc('hour', max(timestamp)) FROM value)
AND sensor_id = (SELECT sensor_id from value where id = (select max(id) from value));
INSERT INTO value_cache
SELECT
COALESCE(0, (select max(id)+1 from value_cache)) as "id" --XXX use seq
,date_trunc('hour', timestamp) AS "timestamp"
,sensor_id AS "sensor_id"
,type AS "type"
,AVG(value_float) AS "value_float"
,AVG(value_int) AS "value_int"
,first(value_string) AS "value_string"
FROM value
WHERE date_trunc('hour', timestamp) = (SELECT date_trunc('hour', max(timestamp)) FROM value)
AND sensor_id = (SELECT sensor_id FROM value WHERE id = (SELECT MAX(id) FROM value))
GROUP BY type, sensor_id, date_trunc('hour', timestamp);
RETURN NULL;
END;
$$ LANGUAGE plpgsql;
-- DROP TRIGGER value_insert_trigger ON value;
CREATE TRIGGER value_insert_trigger
AFTER INSERT ON value FOR EACH STATEMENT EXECUTE PROCEDURE value_insert_trigger_func();
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