Added support for cross joins - closes #56

CHANGELOG.md

@@ -3,6 +3,7 @@
 - Updated Polars to 0.38.3
 - Added support for writing JSON to string
 - Added support for writing Parquet to `StringIO`
+- Added support for cross joins
 - Added `data_page_size` option to `write_parquet` method
 - Added `truncate_ragged_lines` option to `read_csv`, `read_csv_batched`, and `scan_csv` methods
 - Added precompiled gem for Linux x86-64 MUSL

ext/polars/Cargo.toml

@@ -34,6 +34,7 @@ features = [
     "binary_encoding",
     "concat_str",
     "cov",
+    "cross_join",
     "cse",
     "csv",
     "cum_agg",

ext/polars/src/conversion/mod.rs

@@ -737,8 +737,7 @@ impl TryConvert for Wrap<JoinType> {
             "outer_coalesce" => JoinType::Outer { coalesce: true },
             "semi" => JoinType::Semi,
             "anti" => JoinType::Anti,
-            // #[cfg(feature = "cross_join")]
-            // "cross" => JoinType::Cross,
+            "cross" => JoinType::Cross,
             v => {
                 return Err(RbValueError::new_err(format!(
                 "how must be one of {{'inner', 'left', 'outer', 'semi', 'anti', 'cross'}}, got {}",

lib/polars/lazy_frame.rb

@@ -1839,7 +1839,7 @@ def join(
       if how == "cross"
         return _from_rbldf(
           _ldf.join(
-            other._ldf, [], [], allow_parallel, force_parallel, how, suffix
+            other._ldf, [], [], allow_parallel, join_nulls, force_parallel, how, suffix
           )
         )
       end

test/data_frame_test.rb

@@ -430,6 +430,13 @@ def test_join_outer
     assert_frame expected, df4
   end
 
+  def test_join_cross
+    df1 = Polars::DataFrame.new({a: [1, 2]})
+    df2 = Polars::DataFrame.new({b: ["three", "four"]})
+    expected = Polars::DataFrame.new({a: [1, 1, 2, 2], b: ["three", "four", "three", "four"]})
+    assert_frame expected, df1.join(df2, how: "cross")
+  end
+
   def test_with_column
   end