Fix forecast accuracy values and improve performance Forecast accuracy should be based only on the most recent predictions. Generally consider measurements and predictions older than 14 days as outdated and irrelevant. This also implies a performance gain, since it saves a full scan of gauge_measurements and the extra index for this purpose. Adding an extra subquery level for calculation of the forecast accuracy per row instead of the function call as a FROM item saves a (nested loop) join, which is another performance gain.