Join between Polars dataframes with inequality conditions

[andrearota]

Research

• I have searched the above polars tags on Stack Overflow for similar questions.

• I have asked my usage related question on Stack Overflow.

Link to question on Stack Overflow

https://stackoverflow.com/questions/75399353/join-between-polars-dataframes-with-inequality-conditions

Question about Polars

I would like to do a join between two dataframes, using as join condition an inequality condition, i.e. greater than.

Given two dataframes, I would like to get the result equivalent to the SQL written below.

stock_market_value = pl.DataFrame(
    {
        "date": [date(2022, 1, 1), date(2022, 2, 1), date(2022, 3, 1)],
        "price": [10.00, 12.00, 14.00]

    }
)

my_stock_orders = pl.DataFrame(
    {
        "date": [date(2022, 1, 15), date(2022, 2, 15)],
        "quantity": [2, 5] 
    }
)

I have read that Polars supports join of type asof, but I don't think it applies to my case (maybe putting tolerance equal to infinity?).

SELECT m.date, m.price * o.quantity AS portfolio_value
FROM stock_market_value m LEFT JOIN my_stock_orders o
  ON m.date >= o.date

Thanks!

[ritchie46]

I answered on SO

[andrearota]

Hi @ritchie46, thanks. I read your answer, but I believe it does not apply. A SO user added an example to clarify the expected result to the original question.