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  3. Improving Query Performance in PostgreSQL

Exercise

Previewing a row-oriented table

When working with new tables, it is common to SELECT * to preview the data. However, selecting all the rows from a large table using row-oriented storage is resource intensive and slow. A quick optimization trick is to limit the number of rows returned.

You will be working with air quality data from the United States. This data lives in a Postgres database using row-oriented storage. Familiarize yourself with daily_aqi by previewing the data. First, select all records. Then limit the results to improve speed.

Use the EXPLAIN command to quantify the effect of limiting the rows.

Instructions 1/2

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  • 1

    Check the query cost estimate of a SELECT * statement.

  • 2

    Check the query cost estimate after limiting to 10 records.