Creating and using an index
You are working with the US air quality index (AQI) data. AQI data captures four pollutants: ozone, particle pollution, carbon monoxide, and sulfur dioxide. You want to know if one of these pollutants is the main source of poor air quality.
The daily_aqi table contains daily AQI measurements. The defining_parameter field describes which of the four pollutants was the worst for that day.
You will be writing a lot of queries using the pollutant type as a filter. Before you dig into the data, you want to check if defining_parameter has an index on it. If not, you want to add one.
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Improving Query Performance in PostgreSQL
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SELECT indexname
FROM ___
___ tablename = ___; -- Filter condition