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1CREATE TABLE readings (
2  id          BIGSERIAL      PRIMARY KEY,
3  time        TIMESTAMPTZ       NOT NULL,
4  value       DOUBLE PRECISION  NOT NULL,
5  device      VARCHAR(255)      NOT NULL,
6  sensor      VARCHAR(255)      NOT NULL,
7  resolution  VARCHAR(255)      NOT NULL,
8  UNIQUE(time, device, sensor, resolution)
9);
10	
11select MAX(time), device, sensor from readings group by device, sensor
12	
13create index if not exists readings_idx on readings (time, device, sensor, resolution);