Fast-path filter on sorted data

The historical analysis team needs every checkout record from before 2021. The CSV is already sorted by date, so if you tell Polars about that, it can stop scanning as soon as the first 2021 row appears.

This exercise is part of the course

Scaling and Optimizing Data Pipelines with Polars

View Course

Exercise instructions

Mark the date column as sorted so Polars can use a fast-path scan.
Filter to rows where date is before January 1, 2021.
Execute the lazy query.

Hands-on interactive exercise

Have a go at this exercise by completing this sample code.

result = (
    library
    # Mark date as sorted to enable the fast-path scan
    .____("date")
    # Filter to rows before 2021-01-01
    .filter(pl.col("date") < pl.____(2021, 1, 1))
    # Execute the lazy query
    .____()
)
print(result.head())

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