Postgres/TimescaleDB

• Postgres

Setup

CREATE TABLE sensor_data (
        time TIMESTAMPTZ NOT NULL,
        topic TEXT,
        value DOUBLE PRECISION
);

SELECT create_hypertable('sensor_data', 'time');

Insert data via Node-RED

INSERT INTO sensor_data (time, topic, value) VALUES (
    now(),
    '{{{ msg.topic }}}',
    '{{{ msg.payload }}}'
);

Get table size

SELECT hypertable_size('sensor_data');

Query

Grafana timefilter macro

• limits query to timeframe selected in grafana

SELECT * 
FROM sensor_data 
WHERE (topic = 'home/modbus-meter/sensor/total_system_power_w/state' 
AND $__timeFilter("time")) 

Time buckets

• https://docs.timescale.com/use-timescale/latest/time-buckets/about-time-buckets/
• https://docs.timescale.com/use-timescale/latest/time-buckets/use-time-buckets/
• 15min average time_buckets

SELECT time_bucket('1 hour', timestamp) as time,
  avg(value) AS avg_value
FROM sensor_data
WHERE
  topic = 'home/modbus-meter/sensor/total_system_power_w/state'
  AND 
  $__timeFilter("timestamp")
GROUP by time

Counters

• https://github.com/timescale/timescaledb-toolkit/blob/main/docs/counter_agg.md
• https://stackoverflow.com/questions/76774353/get-complete-hours-time-buckets-with-timescaledb :

SELECT time_bucket('1 hour', time) as bucket,
 first(time,time) as period_begin,
 last(time,time) as period_end,
 MAX(counter) - MIN(counter) as total_consumption
FROM 
GROUP BY 1;

Grafana > Dashboards > Settings > Variables

• topic = SELECT DISTINCT topic FROM "sensor_data"

Continuous aggregates

• https://docs.timescale.com/tutorials/latest/energy-data/dataset-energy/

Links

• https://docs.timescale.com/
• https://www.timescale.com/learn/time-series-basics
• https://www.timescale.com/learn/timescale-basics