refactor: Deprecate how="outer" join type in favour of more correct…

… `how="full"` (left/right are *also* outer joins)

crates/polars-lazy/src/frame/mod.rs

@@ -1072,7 +1072,7 @@ impl LazyFrame {
         self.join(other, vec![], vec![], JoinArgs::new(JoinType::Cross))
     }
 
-    /// Left join this query with another lazy query.
+    /// Left outer join this query with another lazy query.
     ///
     /// Matches on the values of the expressions `left_on` and `right_on`. For more
     /// flexible join logic, see [`join`](LazyFrame::join) or
@@ -1122,7 +1122,7 @@ impl LazyFrame {
         )
     }
 
-    /// Outer join this query with another lazy query.
+    /// Full outer join this query with another lazy query.
     ///
     /// Matches on the values of the expressions `left_on` and `right_on`. For more
     /// flexible join logic, see [`join`](LazyFrame::join) or
@@ -1133,17 +1133,17 @@ impl LazyFrame {
     /// ```rust
     /// use polars_core::prelude::*;
     /// use polars_lazy::prelude::*;
-    /// fn outer_join_dataframes(ldf: LazyFrame, other: LazyFrame) -> LazyFrame {
+    /// fn full_join_dataframes(ldf: LazyFrame, other: LazyFrame) -> LazyFrame {
     ///         ldf
-    ///         .outer_join(other, col("foo"), col("bar"))
+    ///         .full_join(other, col("foo"), col("bar"))
     /// }
     /// ```
-    pub fn outer_join<E: Into<Expr>>(self, other: LazyFrame, left_on: E, right_on: E) -> LazyFrame {
+    pub fn full_join<E: Into<Expr>>(self, other: LazyFrame, left_on: E, right_on: E) -> LazyFrame {
         self.join(
             other,
             [left_on.into()],
             [right_on.into()],
-            JoinArgs::new(JoinType::Outer),
+            JoinArgs::new(JoinType::Full),
         )
     }
 

crates/polars-lazy/src/physical_plan/streaming/checks.rs

@@ -35,7 +35,7 @@ pub(super) fn streamable_join(args: &JoinArgs) -> bool {
                 JoinCoalesce::JoinSpecific | JoinCoalesce::CoalesceColumns
             )
         },
-        JoinType::Outer { .. } => true,
+        JoinType::Full { .. } => true,
         _ => false,
     };
     supported && !args.validation.needs_checks()

crates/polars-lazy/src/tests/streaming.rs

@@ -297,7 +297,7 @@ fn test_streaming_partial() -> PolarsResult<()> {
         .left_on([col("a")])
         .right_on([col("a")])
         .suffix("_foo")
-        .how(JoinType::Outer)
+        .how(JoinType::Full)
         .coalesce(JoinCoalesce::CoalesceColumns)
         .finish();
 
@@ -400,7 +400,7 @@ fn test_sort_maintain_order_streaming() -> PolarsResult<()> {
 }
 
 #[test]
-fn test_streaming_outer_join() -> PolarsResult<()> {
+fn test_streaming_full_outer_join() -> PolarsResult<()> {
     let lf_left = df![
          "a"=> [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19],
         "b"=> [0, 0, 0, 3, 0, 1, 3, 3, 3, 1, 4, 4, 2, 1, 1, 3, 1, 4, 2, 2],
@@ -414,7 +414,7 @@ fn test_streaming_outer_join() -> PolarsResult<()> {
     .lazy();
 
     let q = lf_left
-        .outer_join(lf_right, col("a"), col("a"))
+        .full_join(lf_right, col("a"), col("a"))
         .sort_by_exprs([all()], SortMultipleOptions::default());
 
     // Toggle so that the join order is swapped.

crates/polars-ops/src/frame/join/args.rs

@@ -46,7 +46,7 @@ impl JoinCoalesce {
             Left | Inner => {
                 matches!(self, JoinSpecific | CoalesceColumns)
             },
-            Outer { .. } => {
+            Full { .. } => {
                 matches!(self, CoalesceColumns)
             },
             #[cfg(feature = "asof_join")]
@@ -96,9 +96,9 @@ impl JoinArgs {
 #[derive(Clone, PartialEq, Eq, Hash)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub enum JoinType {
-    Left,
     Inner,
-    Outer,
+    Left,
+    Full,
     #[cfg(feature = "asof_join")]
     AsOf(AsOfOptions),
     Cross,
@@ -120,7 +120,7 @@ impl Display for JoinType {
         let val = match self {
             Left => "LEFT",
             Inner => "INNER",
-            Outer { .. } => "OUTER",
+            Full { .. } => "FULL",
             #[cfg(feature = "asof_join")]
             AsOf(_) => "ASOF",
             Cross => "CROSS",
@@ -189,7 +189,7 @@ impl JoinValidation {
         if !self.needs_checks() {
             return Ok(());
         }
-        polars_ensure!(matches!(join_type, JoinType::Inner | JoinType::Outer{..} | JoinType::Left),
+        polars_ensure!(matches!(join_type, JoinType::Inner | JoinType::Full{..} | JoinType::Left),
                       ComputeError: "{self} validation on a {join_type} join is not supported");
         Ok(())
     }

crates/polars-ops/src/frame/join/general.rs

@@ -46,7 +46,7 @@ pub fn _finish_join(
     Ok(df_left)
 }
 
-pub fn _coalesce_outer_join(
+pub fn _coalesce_full_join(
     mut df: DataFrame,
     keys_left: &[&str],
     keys_right: &[&str],

crates/polars-ops/src/frame/join/hash_join/mod.rs

@@ -242,7 +242,7 @@ pub trait JoinDispatch: IntoDf {
         // indices are in bounds
         Ok(unsafe { ca_self._finish_anti_semi_join(&idx, slice) })
     }
-    fn _outer_join_from_series(
+    fn _full_join_from_series(
         &self,
         other: &DataFrame,
         s_left: &Series,
@@ -271,10 +271,10 @@ pub trait JoinDispatch: IntoDf {
             || unsafe { other.take_unchecked(&idx_ca_r) },
         );
 
-        let coalesce = args.coalesce.coalesce(&JoinType::Outer);
+        let coalesce = args.coalesce.coalesce(&JoinType::Full);
         let out = _finish_join(df_left, df_right, args.suffix.as_deref());
         if coalesce {
-            Ok(_coalesce_outer_join(
+            Ok(_coalesce_full_join(
                 out?,
                 &[s_left.name()],
                 &[s_right.name()],

crates/polars-ops/src/frame/join/mod.rs

@@ -25,7 +25,7 @@ pub use cross_join::CrossJoin;
 use either::Either;
 #[cfg(feature = "chunked_ids")]
 use general::create_chunked_index_mapping;
-pub use general::{_coalesce_outer_join, _finish_join, _join_suffix_name};
+pub use general::{_coalesce_full_join, _finish_join, _join_suffix_name};
 pub use hash_join::*;
 use hashbrown::hash_map::{Entry, RawEntryMut};
 #[cfg(feature = "merge_sorted")]
@@ -199,7 +199,7 @@ pub trait DataFrameJoinOps: IntoDf {
                     ._inner_join_from_series(other, s_left, s_right, args, _verbose, drop_names),
                 JoinType::Left => left_df
                     ._left_join_from_series(other, s_left, s_right, args, _verbose, drop_names),
-                JoinType::Outer => left_df._outer_join_from_series(other, s_left, s_right, args),
+                JoinType::Full => left_df._full_join_from_series(other, s_left, s_right, args),
                 #[cfg(feature = "semi_anti_join")]
                 JoinType::Anti => left_df._semi_anti_join_from_series(
                     s_left,
@@ -271,14 +271,14 @@ pub trait DataFrameJoinOps: IntoDf {
             JoinType::Cross => {
                 unreachable!()
             },
-            JoinType::Outer => {
+            JoinType::Full => {
                 let names_left = selected_left.iter().map(|s| s.name()).collect::<Vec<_>>();
                 args.coalesce = JoinCoalesce::KeepColumns;
                 let suffix = args.suffix.clone();
-                let out = left_df._outer_join_from_series(other, &lhs_keys, &rhs_keys, args);
+                let out = left_df._full_join_from_series(other, &lhs_keys, &rhs_keys, args);
 
                 if should_coalesce {
-                    Ok(_coalesce_outer_join(
+                    Ok(_coalesce_full_join(
                         out?,
                         &names_left,
                         drop_names.as_ref().unwrap(),
@@ -341,7 +341,7 @@ pub trait DataFrameJoinOps: IntoDf {
         self.join(other, left_on, right_on, JoinArgs::new(JoinType::Inner))
     }
 
-    /// Perform a left join on two DataFrames
+    /// Perform a left outer join on two DataFrames
     /// # Example
     ///
     /// ```no_run
@@ -384,27 +384,22 @@ pub trait DataFrameJoinOps: IntoDf {
         self.join(other, left_on, right_on, JoinArgs::new(JoinType::Left))
     }
 
-    /// Perform an outer join on two DataFrames
+    /// Perform a full outer join on two DataFrames
     /// # Example
     ///
     /// ```
     /// # use polars_core::prelude::*;
     /// # use polars_ops::prelude::*;
     /// fn join_dfs(left: &DataFrame, right: &DataFrame) -> PolarsResult<DataFrame> {
-    ///     left.outer_join(right, ["join_column_left"], ["join_column_right"])
+    ///     left.full_join(right, ["join_column_left"], ["join_column_right"])
     /// }
     /// ```
-    fn outer_join<I, S>(
-        &self,
-        other: &DataFrame,
-        left_on: I,
-        right_on: I,
-    ) -> PolarsResult<DataFrame>
+    fn full_join<I, S>(&self, other: &DataFrame, left_on: I, right_on: I) -> PolarsResult<DataFrame>
     where
         I: IntoIterator<Item = S>,
         S: AsRef<str>,
     {
-        self.join(other, left_on, right_on, JoinArgs::new(JoinType::Outer))
+        self.join(other, left_on, right_on, JoinArgs::new(JoinType::Full))
     }
 }
 

crates/polars-pipe/src/executors/sinks/joins/generic_build.rs

@@ -14,7 +14,7 @@ use smartstring::alias::String as SmartString;
 use super::*;
 use crate::executors::operators::PlaceHolder;
 use crate::executors::sinks::joins::generic_probe_inner_left::GenericJoinProbe;
-use crate::executors::sinks::joins::generic_probe_outer::GenericOuterJoinProbe;
+use crate::executors::sinks::joins::generic_probe_outer::GenericFullOuterJoinProbe;
 use crate::executors::sinks::utils::{hash_rows, load_vec};
 use crate::executors::sinks::HASHMAP_INIT_SIZE;
 use crate::expressions::PhysicalPipedExpr;
@@ -337,9 +337,9 @@ impl<K: ExtraPayload> Sink for GenericBuild<K> {
                 self.placeholder.replace(Box::new(probe_operator));
                 Ok(FinalizedSink::Operator)
             },
-            JoinType::Outer => {
-                let coalesce = self.join_args.coalesce.coalesce(&JoinType::Outer);
-                let probe_operator = GenericOuterJoinProbe::new(
+            JoinType::Full => {
+                let coalesce = self.join_args.coalesce.coalesce(&JoinType::Full);
+                let probe_operator = GenericFullOuterJoinProbe::new(
                     left_df,
                     materialized_join_cols,
                     suffix,

crates/polars-pipe/src/executors/sinks/joins/generic_probe_outer.rs

@@ -6,7 +6,7 @@ use polars_core::prelude::*;
 use polars_core::series::IsSorted;
 use polars_ops::chunked_array::DfTake;
 use polars_ops::frame::join::_finish_join;
-use polars_ops::prelude::_coalesce_outer_join;
+use polars_ops::prelude::_coalesce_full_join;
 use smartstring::alias::String as SmartString;
 
 use crate::executors::sinks::joins::generic_build::*;
@@ -18,7 +18,7 @@ use crate::expressions::PhysicalPipedExpr;
 use crate::operators::{DataChunk, Operator, OperatorResult, PExecutionContext};
 
 #[derive(Clone)]
-pub struct GenericOuterJoinProbe<K: ExtraPayload> {
+pub struct GenericFullOuterJoinProbe<K: ExtraPayload> {
     /// all chunks are stacked into a single dataframe
     /// the dataframe is not rechunked.
     df_a: Arc<DataFrame>,
@@ -58,7 +58,7 @@ pub struct GenericOuterJoinProbe<K: ExtraPayload> {
     key_names_right: Arc<[SmartString]>,
 }
 
-impl<K: ExtraPayload> GenericOuterJoinProbe<K> {
+impl<K: ExtraPayload> GenericFullOuterJoinProbe<K> {
     #[allow(clippy::too_many_arguments)]
     pub(super) fn new(
         df_a: DataFrame,
@@ -75,7 +75,7 @@ impl<K: ExtraPayload> GenericOuterJoinProbe<K> {
         key_names_left: Arc<[SmartString]>,
         key_names_right: Arc<[SmartString]>,
     ) -> Self {
-        GenericOuterJoinProbe {
+        GenericFullOuterJoinProbe {
             df_a: Arc::new(df_a),
             df_b_dummy: None,
             materialized_join_cols,
@@ -152,7 +152,7 @@ impl<K: ExtraPayload> GenericOuterJoinProbe<K> {
                 .iter()
                 .map(|s| s.as_str())
                 .collect::<Vec<_>>();
-            Ok(_coalesce_outer_join(
+            Ok(_coalesce_full_join(
                 out,
                 &l,
                 &r,
@@ -287,7 +287,7 @@ impl<K: ExtraPayload> GenericOuterJoinProbe<K> {
     }
 }
 
-impl<K: ExtraPayload> Operator for GenericOuterJoinProbe<K> {
+impl<K: ExtraPayload> Operator for GenericFullOuterJoinProbe<K> {
     fn execute(
         &mut self,
         context: &PExecutionContext,
@@ -310,6 +310,6 @@ impl<K: ExtraPayload> Operator for GenericOuterJoinProbe<K> {
         Box::new(new)
     }
     fn fmt(&self) -> &str {
-        "generic_outer_join_probe"
+        "generic_full_join_probe"
     }
 }

crates/polars-pipe/src/pipeline/convert.rs

@@ -299,7 +299,7 @@ where
                                 placeholder,
                             )) as Box<dyn SinkTrait>
                         },
-                        JoinType::Outer { .. } => {
+                        JoinType::Full { .. } => {
                             // First get the names before we (potentially) swap.
                             let key_names_left = join_columns_left
                                 .iter()

crates/polars-plan/src/logical_plan/optimizer/predicate_pushdown/join.rs

@@ -70,15 +70,15 @@ fn join_produces_null(how: &JoinType) -> LeftRight<bool> {
     {
         match how {
             JoinType::Left => LeftRight(false, true),
-            JoinType::Outer { .. } | JoinType::Cross | JoinType::AsOf(_) => LeftRight(true, true),
+            JoinType::Full { .. } | JoinType::Cross | JoinType::AsOf(_) => LeftRight(true, true),
             _ => LeftRight(false, false),
         }
     }
     #[cfg(not(feature = "asof_join"))]
     {
         match how {
             JoinType::Left => LeftRight(false, true),
-            JoinType::Outer { .. } | JoinType::Cross => LeftRight(true, true),
+            JoinType::Full { .. } | JoinType::Cross => LeftRight(true, true),
             _ => LeftRight(false, false),
         }
     }

crates/polars-plan/src/logical_plan/optimizer/projection_pushdown/joins.rs

@@ -257,11 +257,11 @@ pub(super) fn process_join(
             .unwrap();
             already_added_local_to_local_projected.insert(local_name);
         }
-        // In outer joins both columns remain. So `add_local=true` also for the right table
-        let add_local = matches!(options.args.how, JoinType::Outer)
+        // In full outer joins both columns remain. So `add_local=true` also for the right table
+        let add_local = matches!(options.args.how, JoinType::Full)
             && !options.args.coalesce.coalesce(&options.args.how);
         for e in &right_on {
-            // In case of outer joins we also add the columns.
+            // In case of full outer joins we also add the columns.
             // But before we do that we must check if the column wasn't already added by the lhs.
             let add_local = if add_local {
                 !already_added_local_to_local_projected.contains(e.output_name())

crates/polars-plan/src/logical_plan/schema.rs

@@ -221,7 +221,7 @@ pub fn set_estimated_row_counts(
                         let (known_size, estimated_size) = options.rows_left;
                         (known_size, estimated_size, filter_count_left)
                     },
-                    JoinType::Cross | JoinType::Outer { .. } => {
+                    JoinType::Cross | JoinType::Full { .. } => {
                         let (known_size_left, estimated_size_left) = options.rows_left;
                         let (known_size_right, estimated_size_right) = options.rows_right;
                         match (known_size_left, known_size_right) {

crates/polars-sql/src/context.rs

@@ -319,7 +319,7 @@ impl SQLContext {
                 lf = match &tbl.join_operator {
                     JoinOperator::CrossJoin => lf.cross_join(rf),
                     JoinOperator::FullOuter(constraint) => {
-                        process_join(lf, rf, constraint, &l_name, &r_name, JoinType::Outer)?
+                        process_join(lf, rf, constraint, &l_name, &r_name, JoinType::Full)?
                     },
                     JoinOperator::Inner(constraint) => {
                         process_join(lf, rf, constraint, &l_name, &r_name, JoinType::Inner)?

crates/polars/src/docs/eager.rs

@@ -395,7 +395,7 @@
 //! // join on a single column
 //! temp.left_join(&rain, ["days"], ["days"]);
 //! temp.inner_join(&rain, ["days"], ["days"]);
-//! temp.outer_join(&rain, ["days"], ["days"]);
+//! temp.full_join(&rain, ["days"], ["days"]);
 //!
 //! // join on multiple columns
 //! temp.join(&rain, vec!["days", "other"], vec!["days", "other"], JoinArgs::new(JoinType::Left));

crates/polars/src/docs/lazy.rs

@@ -145,7 +145,7 @@
 //! let lf_a = df_a.clone().lazy();
 //! let lf_b = df_b.clone().lazy();
 //!
-//! let joined = lf_a.join(lf_b, vec![col("a")], vec![col("foo")], JoinArgs::new(JoinType::Outer)).collect()?;
+//! let joined = lf_a.join(lf_b, vec![col("a")], vec![col("foo")], JoinArgs::new(JoinType::Full)).collect()?;
 //! // joined:
 //!
 //! // ╭─────┬─────┬─────┬──────┬─────────╮
@@ -172,7 +172,7 @@
 //!
 //! # let lf_a = df_a.clone().lazy();
 //! # let lf_b = df_b.clone().lazy();
-//! let outer = lf_a.outer_join(lf_b, col("a"), col("foo")).collect()?;
+//! let outer = lf_a.full_join(lf_b, col("a"), col("foo")).collect()?;
 //!
 //! # let lf_a = df_a.clone().lazy();
 //! # let lf_b = df_b.clone().lazy();