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use polars_error::{polars_ensure, polars_err, PolarsResult};
use polars_utils::aliases::PlHashSet;
use super::Column;
use crate::datatypes::AnyValue;
use crate::frame::DataFrame;
use crate::prelude::PlSmallStr;
fn check_hstack(
col: &Column,
names: &mut PlHashSet<PlSmallStr>,
height: usize,
is_empty: bool,
) -> PolarsResult<()> {
polars_ensure!(
col.len() == height || is_empty,
ShapeMismatch: "unable to hstack Series of length {} and DataFrame of height {}",
col.len(), height,
);
polars_ensure!(
names.insert(col.name().clone()),
Duplicate: "unable to hstack, column with name {:?} already exists", col.name().as_str(),
);
Ok(())
}
impl DataFrame {
/// Add columns horizontally.
///
/// # Safety
/// The caller must ensure:
/// - the length of all [`Column`] is equal to the height of this [`DataFrame`]
/// - the columns names are unique
pub unsafe fn hstack_mut_unchecked(&mut self, columns: &[Column]) -> &mut Self {
// If we don't have any columns yet, copy the height from the given columns.
if let Some(fst) = columns.first() {
if self.width() == 0 {
// SAFETY: The functions invariants asks for all columns to be the same length so
// that makes that a valid height.
unsafe { self.set_height(fst.len()) };
}
}
self.clear_schema();
self.columns.extend_from_slice(columns);
self
}
/// Add multiple [`Column`] to a [`DataFrame`].
/// The added `Series` are required to have the same length.
///
/// # Example
///
/// ```rust
/// # use polars_core::prelude::*;
/// fn stack(df: &mut DataFrame, columns: &[Column]) {
/// df.hstack_mut(columns);
/// }
/// ```
pub fn hstack_mut(&mut self, columns: &[Column]) -> PolarsResult<&mut Self> {
let mut names = self
.columns
.iter()
.map(|c| c.name().clone())
.collect::<PlHashSet<_>>();
let height = self.height();
let is_empty = self.is_empty();
// first loop check validity. We don't do this in a single pass otherwise
// this DataFrame is already modified when an error occurs.
for col in columns {
check_hstack(col, &mut names, height, is_empty)?;
}
drop(names);
Ok(unsafe { self.hstack_mut_unchecked(columns) })
}
}
/// Concat [`DataFrame`]s horizontally.
/// Concat horizontally and extend with null values if lengths don't match
pub fn concat_df_horizontal(dfs: &[DataFrame], check_duplicates: bool) -> PolarsResult<DataFrame> {
let output_height = dfs
.iter()
.map(|df| df.height())
.max()
.ok_or_else(|| polars_err!(ComputeError: "cannot concat empty dataframes"))?;
let owned_df;
// if not all equal length, extend the DataFrame with nulls
let dfs = if !dfs.iter().all(|df| df.height() == output_height) {
owned_df = dfs
.iter()
.cloned()
.map(|mut df| {
if df.height() != output_height {
let diff = output_height - df.height();
// SAFETY: We extend each column with nulls to the point of being of length
// `output_height`. Then, we set the height of the resulting dataframe.
unsafe { df.get_columns_mut() }.iter_mut().for_each(|c| {
*c = c.extend_constant(AnyValue::Null, diff).unwrap();
});
df.clear_schema();
unsafe {
df.set_height(output_height);
}
}
df
})
.collect::<Vec<_>>();
owned_df.as_slice()
} else {
dfs
};
let mut first_df = dfs[0].clone();
let height = first_df.height();
let is_empty = first_df.is_empty();
let mut names = if check_duplicates {
first_df
.columns
.iter()
.map(|s| s.name().clone())
.collect::<PlHashSet<_>>()
} else {
Default::default()
};
for df in &dfs[1..] {
let cols = df.get_columns();
if check_duplicates {
for col in cols {
check_hstack(col, &mut names, height, is_empty)?;
}
}
unsafe { first_df.hstack_mut_unchecked(cols) };
}
Ok(first_df)
}