polars.LazyFrame.join#

Add a join operation to the Logical Plan.

Parameters:

other

Lazy DataFrame to join with.

on

Join column of both DataFrames. If set, left_on and right_on should be None.

how{‘inner’, ‘left’, ‘outer’, ‘semi’, ‘anti’, ‘cross’}

Join strategy.

Note

A left join preserves the row order of the left DataFrame.

left_on

Join column of the left DataFrame.

right_on

Join column of the right DataFrame.

suffix

Suffix to append to columns with a duplicate name.

validate: {‘m:m’, ‘m:1’, ‘1:m’, ‘1:1’}

Checks if join is of specified type.

many_to_many
“m:m”: default, does not result in checks

one_to_one
“1:1”: check if join keys are unique in both left and right datasets

one_to_many
“1:m”: check if join keys are unique in left dataset

many_to_one
“m:1”: check if join keys are unique in right dataset

Note

This is currently not supported the streaming engine.
This is only supported when joined by single columns.

allow_parallel

Allow the physical plan to optionally evaluate the computation of both DataFrames up to the join in parallel.

force_parallel

Force the physical plan to evaluate the computation of both DataFrames up to the join in parallel.

See also

join_asof

Examples

>>> lf = pl.LazyFrame(
...     {
...         "foo": [1, 2, 3],
...         "bar": [6.0, 7.0, 8.0],
...         "ham": ["a", "b", "c"],
...     }
... )
>>> other_lf = pl.LazyFrame(
...     {
...         "apple": ["x", "y", "z"],
...         "ham": ["a", "b", "d"],
...     }
... )
>>> lf.join(other_lf, on="ham").collect()
shape: (2, 4)
┌─────┬─────┬─────┬───────┐
│ foo ┆ bar ┆ ham ┆ apple │
│ --- ┆ --- ┆ --- ┆ ---   │
│ i64 ┆ f64 ┆ str ┆ str   │
╞═════╪═════╪═════╪═══════╡
│ 1   ┆ 6.0 ┆ a   ┆ x     │
│ 2   ┆ 7.0 ┆ b   ┆ y     │
└─────┴─────┴─────┴───────┘
>>> lf.join(other_lf, on="ham", how="outer").collect()
shape: (4, 4)
┌──────┬──────┬─────┬───────┐
│ foo  ┆ bar  ┆ ham ┆ apple │
│ ---  ┆ ---  ┆ --- ┆ ---   │
│ i64  ┆ f64  ┆ str ┆ str   │
╞══════╪══════╪═════╪═══════╡
│ 1    ┆ 6.0  ┆ a   ┆ x     │
│ 2    ┆ 7.0  ┆ b   ┆ y     │
│ null ┆ null ┆ d   ┆ z     │
│ 3    ┆ 8.0  ┆ c   ┆ null  │
└──────┴──────┴─────┴───────┘
>>> lf.join(other_lf, on="ham", how="left").collect()
shape: (3, 4)
┌─────┬─────┬─────┬───────┐
│ foo ┆ bar ┆ ham ┆ apple │
│ --- ┆ --- ┆ --- ┆ ---   │
│ i64 ┆ f64 ┆ str ┆ str   │
╞═════╪═════╪═════╪═══════╡
│ 1   ┆ 6.0 ┆ a   ┆ x     │
│ 2   ┆ 7.0 ┆ b   ┆ y     │
│ 3   ┆ 8.0 ┆ c   ┆ null  │
└─────┴─────┴─────┴───────┘
>>> lf.join(other_lf, on="ham", how="semi").collect()
shape: (2, 3)
┌─────┬─────┬─────┐
│ foo ┆ bar ┆ ham │
│ --- ┆ --- ┆ --- │
│ i64 ┆ f64 ┆ str │
╞═════╪═════╪═════╡
│ 1   ┆ 6.0 ┆ a   │
│ 2   ┆ 7.0 ┆ b   │
└─────┴─────┴─────┘
>>> lf.join(other_lf, on="ham", how="anti").collect()
shape: (1, 3)
┌─────┬─────┬─────┐
│ foo ┆ bar ┆ ham │
│ --- ┆ --- ┆ --- │
│ i64 ┆ f64 ┆ str │
╞═════╪═════╪═════╡
│ 3   ┆ 8.0 ┆ c   │
└─────┴─────┴─────┘