feat: add cross_join (#390)

crates/proof-of-sql/src/base/database/join_util.rs

@@ -0,0 +1,243 @@
+use super::{ColumnRepeatOp, ElementwiseRepeatOp, RepetitionOp, Table, TableOptions};
+use crate::base::scalar::Scalar;
+use bumpalo::Bump;
+
+/// Compute the CROSS JOIN / cartesian product of two tables.
+///
+/// # Panics
+/// The function if written correctly can not actually panic.
+pub fn cross_join<'a, S: Scalar>(
+    left: &Table<'a, S>,
+    right: &Table<'a, S>,
+    alloc: &'a Bump,
+) -> Table<'a, S> {
+    let left_num_rows = left.num_rows();
+    let right_num_rows = right.num_rows();
+    let product_num_rows = left_num_rows * right_num_rows;
+    Table::<'a, S>::try_from_iter_with_options(
+        left.inner_table()
+            .iter()
+            .map(|(&ident, column)| {
+                (
+                    ident,
+                    ColumnRepeatOp::column_op(column, alloc, right_num_rows),
+                )
+            })
+            .chain(right.inner_table().iter().map(|(&ident, column)| {
+                (
+                    ident,
+                    ElementwiseRepeatOp::column_op(column, alloc, left_num_rows),
+                )
+            })),
+        TableOptions::new(Some(product_num_rows)),
+    )
+    .expect("Table creation should not fail")
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::base::{database::Column, scalar::test_scalar::TestScalar};
+
+    #[test]
+    fn we_can_do_cross_joins() {
+        let bump = Bump::new();
+        let a = "a".parse().unwrap();
+        let b = "b".parse().unwrap();
+        let c = "c".parse().unwrap();
+        let d = "d".parse().unwrap();
+        let left = Table::<'_, TestScalar>::try_from_iter_with_options(
+            vec![
+                (a, Column::SmallInt(&[1_i16, 2, 3])),
+                (b, Column::Int(&[4_i32, 5, 6])),
+            ],
+            TableOptions::default(),
+        )
+        .expect("Table creation should not fail");
+        let right = Table::<'_, TestScalar>::try_from_iter_with_options(
+            vec![
+                (c, Column::BigInt(&[7_i64, 8, 9])),
+                (d, Column::Int128(&[10_i128, 11, 12])),
+            ],
+            TableOptions::default(),
+        )
+        .expect("Table creation should not fail");
+        let result = cross_join(&left, &right, &bump);
+        assert_eq!(result.num_rows(), 9);
+        assert_eq!(result.num_columns(), 4);
+        assert_eq!(
+            result.inner_table()[&a].as_smallint().unwrap(),
+            &[1_i16, 2, 3, 1, 2, 3, 1, 2, 3]
+        );
+        assert_eq!(
+            result.inner_table()[&b].as_int().unwrap(),
+            &[4_i32, 5, 6, 4, 5, 6, 4, 5, 6]
+        );
+        assert_eq!(
+            result.inner_table()[&c].as_bigint().unwrap(),
+            &[7_i64, 7, 7, 8, 8, 8, 9, 9, 9]
+        );
+        assert_eq!(
+            result.inner_table()[&d].as_int128().unwrap(),
+            &[10_i128, 10, 10, 11, 11, 11, 12, 12, 12]
+        );
+    }
+
+    #[test]
+    fn we_can_do_cross_joins_if_one_table_has_no_rows() {
+        let bump = Bump::new();
+        let a = "a".parse().unwrap();
+        let b = "b".parse().unwrap();
+        let c = "c".parse().unwrap();
+        let d = "d".parse().unwrap();
+
+        // Right table has no rows
+        let left = Table::<'_, TestScalar>::try_from_iter_with_options(
+            vec![
+                (a, Column::SmallInt(&[1_i16, 2, 3])),
+                (b, Column::Int(&[4_i32, 5, 6])),
+            ],
+            TableOptions::default(),
+        )
+        .expect("Table creation should not fail");
+        let right = Table::<'_, TestScalar>::try_from_iter_with_options(
+            vec![
+                (c, Column::BigInt(&[0_i64; 0])),
+                (d, Column::Int128(&[0_i128; 0])),
+            ],
+            TableOptions::default(),
+        )
+        .expect("Table creation should not fail");
+        let result = cross_join(&left, &right, &bump);
+        assert_eq!(result.num_rows(), 0);
+        assert_eq!(result.num_columns(), 4);
+        assert_eq!(result.inner_table()[&a].as_smallint().unwrap(), &[0_i16; 0]);
+        assert_eq!(result.inner_table()[&b].as_int().unwrap(), &[0_i32; 0]);
+        assert_eq!(result.inner_table()[&c].as_bigint().unwrap(), &[0_i64; 0]);
+        assert_eq!(result.inner_table()[&d].as_int128().unwrap(), &[0_i128; 0]);
+
+        // Left table has no rows
+        let left = Table::<'_, TestScalar>::try_from_iter_with_options(
+            vec![
+                (a, Column::SmallInt(&[0_i16; 0])),
+                (b, Column::Int(&[0_i32; 0])),
+            ],
+            TableOptions::default(),
+        )
+        .expect("Table creation should not fail");
+        let right = Table::<'_, TestScalar>::try_from_iter_with_options(
+            vec![
+                (c, Column::BigInt(&[7_i64, 8, 9])),
+                (d, Column::Int128(&[10_i128, 11, 12])),
+            ],
+            TableOptions::default(),
+        )
+        .expect("Table creation should not fail");
+        let result = cross_join(&left, &right, &bump);
+        assert_eq!(result.num_rows(), 0);
+        assert_eq!(result.num_columns(), 4);
+        assert_eq!(result.inner_table()[&a].as_smallint().unwrap(), &[0_i16; 0]);
+        assert_eq!(result.inner_table()[&b].as_int().unwrap(), &[0_i32; 0]);
+        assert_eq!(result.inner_table()[&c].as_bigint().unwrap(), &[0_i64; 0]);
+        assert_eq!(result.inner_table()[&d].as_int128().unwrap(), &[0_i128; 0]);
+
+        // Both tables have no rows
+        let left = Table::<'_, TestScalar>::try_from_iter_with_options(
+            vec![
+                (a, Column::SmallInt(&[0_i16; 0])),
+                (b, Column::Int(&[0_i32; 0])),
+            ],
+            TableOptions::default(),
+        )
+        .expect("Table creation should not fail");
+        let right = Table::<'_, TestScalar>::try_from_iter_with_options(
+            vec![
+                (c, Column::BigInt(&[0_i64; 0])),
+                (d, Column::Int128(&[0_i128; 0])),
+            ],
+            TableOptions::default(),
+        )
+        .expect("Table creation should not fail");
+        let result = cross_join(&left, &right, &bump);
+        assert_eq!(result.num_rows(), 0);
+        assert_eq!(result.num_columns(), 4);
+        assert_eq!(result.inner_table()[&a].as_smallint().unwrap(), &[0_i16; 0]);
+        assert_eq!(result.inner_table()[&b].as_int().unwrap(), &[0_i32; 0]);
+        assert_eq!(result.inner_table()[&c].as_bigint().unwrap(), &[0_i64; 0]);
+        assert_eq!(result.inner_table()[&d].as_int128().unwrap(), &[0_i128; 0]);
+    }
+
+    #[test]
+    fn we_can_do_cross_joins_if_one_table_has_no_columns() {
+        // Left table has no columns
+        let bump = Bump::new();
+        let a = "a".parse().unwrap();
+        let b = "b".parse().unwrap();
+        let c = "c".parse().unwrap();
+        let d = "d".parse().unwrap();
+        let left =
+            Table::<'_, TestScalar>::try_from_iter_with_options(vec![], TableOptions::new(Some(2)))
+                .expect("Table creation should not fail");
+
+        let right = Table::<'_, TestScalar>::try_from_iter_with_options(
+            vec![
+                (c, Column::BigInt(&[7_i64, 8])),
+                (d, Column::Int128(&[10_i128, 11])),
+            ],
+            TableOptions::default(),
+        )
+        .expect("Table creation should not fail");
+
+        let result = cross_join(&left, &right, &bump);
+        assert_eq!(result.num_rows(), 4);
+        assert_eq!(result.num_columns(), 2);
+        assert_eq!(
+            result.inner_table()[&c].as_bigint().unwrap(),
+            &[7_i64, 7, 8, 8]
+        );
+        assert_eq!(
+            result.inner_table()[&d].as_int128().unwrap(),
+            &[10_i128, 10, 11, 11]
+        );
+
+        // Right table has no columns
+        let left = Table::<'_, TestScalar>::try_from_iter_with_options(
+            vec![
+                (a, Column::SmallInt(&[1_i16, 2])),
+                (b, Column::Int(&[4_i32, 5])),
+            ],
+            TableOptions::default(),
+        )
+        .expect("Table creation should not fail");
+        let right =
+            Table::<'_, TestScalar>::try_from_iter_with_options(vec![], TableOptions::new(Some(0)))
+                .expect("Table creation should not fail");
+        let result = cross_join(&left, &right, &bump);
+        assert_eq!(result.num_rows(), 0);
+        assert_eq!(result.num_columns(), 2);
+        assert_eq!(result.inner_table()[&a].as_smallint().unwrap(), &[0_i16; 0]);
+        assert_eq!(result.inner_table()[&b].as_int().unwrap(), &[0_i32; 0]);
+
+        // Both tables have no columns
+        let left =
+            Table::<'_, TestScalar>::try_from_iter_with_options(vec![], TableOptions::new(Some(2)))
+                .expect("Table creation should not fail");
+        let right =
+            Table::<'_, TestScalar>::try_from_iter_with_options(vec![], TableOptions::new(Some(7)))
+                .expect("Table creation should not fail");
+        let result = cross_join(&left, &right, &bump);
+        assert_eq!(result.num_rows(), 14);
+        assert_eq!(result.num_columns(), 0);
+
+        // Both tables have no columns and no rows
+        let left =
+            Table::<'_, TestScalar>::try_from_iter_with_options(vec![], TableOptions::new(Some(0)))
+                .expect("Table creation should not fail");
+        let right =
+            Table::<'_, TestScalar>::try_from_iter_with_options(vec![], TableOptions::new(Some(0)))
+                .expect("Table creation should not fail");
+        let result = cross_join(&left, &right, &bump);
+        assert_eq!(result.num_rows(), 0);
+        assert_eq!(result.num_columns(), 0);
+    }
+}

crates/proof-of-sql/src/base/database/mod.rs

@@ -26,7 +26,6 @@ pub(super) use column_comparison_operation::{
 };
 
 mod column_repetition_operation;
-#[allow(unused_imports)]
 pub(super) use column_repetition_operation::{ColumnRepeatOp, ElementwiseRepeatOp, RepetitionOp};
 
 mod column_operation_error;
@@ -118,3 +117,6 @@ pub(crate) mod union_util;
 pub(crate) mod order_by_util;
 #[cfg(test)]
 mod order_by_util_test;
+
+#[allow(dead_code)]
+pub(crate) mod join_util;