chore(embedded/sql): add support for LEFT JOIN

Signed-off-by: Stefano Scafiti <[email protected]>

embedded/sql/engine_test.go

@@ -5986,7 +5986,7 @@ func TestNestedJoins(t *testing.T) {
 	require.NoError(t, err)
 }
 
-func TestLeftRightJoins(t *testing.T) {
+func TestLeftJoins(t *testing.T) {
 	e := setupCommonTest(t)
 
 	_, _, err := e.Exec(
@@ -6055,10 +6055,28 @@ func TestLeftRightJoins(t *testing.T) {
 	)
 	require.NoError(t, err)
 
-	rows, err := e.queryAll(
-		context.Background(),
-		nil,
-		`SELECT
+	assertQueryShouldProduceResults(
+		t,
+		e,
+		`SELECT c.customer_id, c.customer_name, c.email, o.order_id, o.order_date
+		FROM customers c LEFT JOIN orders o ON c.customer_id = o.customer_id
+		ORDER BY c.customer_id, o.order_date;`,
+		`
+		SELECT *
+		FROM (
+			VALUES
+				(1, 'Alice Johnson', '[email protected]', 101, '2024-11-01'::TIMESTAMP),
+				(1, 'Alice Johnson', '[email protected]', 103, '2024-11-03'::TIMESTAMP),
+				(2, 'Bob Smith', '[email protected]', 102, '2024-11-02'::TIMESTAMP),
+				(3, 'Charlie Brown', '[email protected]', NULL, NULL)
+		)`,
+	)
+
+	assertQueryShouldProduceResults(
+		t,
+		e,
+		`
+		SELECT
 			c.customer_name,
 			c.email,
 			o.order_id,
@@ -6073,10 +6091,16 @@ func TestLeftRightJoins(t *testing.T) {
 		LEFT JOIN orders o ON oi.order_id = o.order_id
 		LEFT JOIN customers c ON o.customer_id = c.customer_id
 		ORDER BY o.order_date, c.customer_name;`,
-		nil,
+		`
+		SELECT *
+		FROM (
+			VALUES
+				('Alice Johnson', '[email protected]', 101, '2024-11-01'::TIMESTAMP, 'Laptop', 2, 1200.00, 2400.00),
+				('Alice Johnson', '[email protected]', 101, '2024-11-01'::TIMESTAMP, 'Smartphone', 1, 800.00, 800.00),
+				('Bob Smith', '[email protected]', 102, '2024-11-02'::TIMESTAMP, 'Tablet', 3, 400.00, 1200.00),
+				('Alice Johnson', '[email protected]', 103, '2024-11-03'::TIMESTAMP, 'Smartphone', 2, 800.00, 1600.00)
+		)`,
 	)
-	require.NoError(t, err)
-	require.Len(t, rows, 4)
 }
 
 func TestReOpening(t *testing.T) {
@@ -9527,3 +9551,24 @@ func TestFunctions(t *testing.T) {
 		require.Equal(t, "OBJECT", rows[0].ValuesByPosition[0].RawValue().(string))
 	})
 }
+
+func assertQueryShouldProduceResults(t *testing.T, e *Engine, query, resultQuery string) {
+	queryReader, err := e.Query(context.Background(), nil, query, nil)
+	require.NoError(t, err)
+	defer queryReader.Close()
+
+	resultReader, err := e.Query(context.Background(), nil, resultQuery, nil)
+	require.NoError(t, err)
+	defer resultReader.Close()
+
+	for {
+		row, err := queryReader.Read(context.Background())
+		row1, err1 := resultReader.Read(context.Background())
+		require.Equal(t, err, err1)
+
+		if errors.Is(err, ErrNoMoreRows) {
+			break
+		}
+		require.Equal(t, row1.ValuesByPosition, row.ValuesByPosition)
+	}
+}

embedded/sql/joint_row_reader.go

@@ -38,8 +38,6 @@ func newJointRowReader(rowReader RowReader, joins []*JoinSpec) (*jointRowReader,
 		return nil, ErrIllegalArguments
 	}
 
-	// Sanity check: Ensure that no RIGHT JOINs are specified,
-	// as we assume all RIGHT JOINs to be translated into equivalent LEFT JOINs.
 	for _, jspec := range joins {
 		if jspec.joinType == RightJoin {
 			return nil, ErrUnsupportedJoinType

embedded/sql/stmt.go

@@ -3409,44 +3409,9 @@ func (stmt *SelectStmt) Resolve(ctx context.Context, tx *SQLTx, params map[strin
 			rowReader = newLimitRowReader(rowReader, limit)
 		}
 	}
-
 	return rowReader, nil
 }
 
-// removeRightJoin converts all right joins in the SelectStmt to left joins by swapping the involved data sources.
-func (stmt *SelectStmt) removeRightJoin() {
-	if len(stmt.joins) == 0 {
-		return
-	}
-
-	newJoins := make([]*JoinSpec, len(stmt.joins)+1)
-
-	start := 0
-	end := len(newJoins) - 1
-
-	for i := len(stmt.joins) - 1; i > 0; i-- {
-		jspec := stmt.joins[len(stmt.joins)-1-i]
-
-		if jspec.joinType == RightJoin {
-			newJoins[start] = jspec
-			newJoins[start].joinType = LeftJoin
-			start++
-		} else {
-			newJoins[end] = jspec
-			end--
-		}
-	}
-
-	newJoins[start] = &JoinSpec{ds: stmt.ds}
-	if start == 0 {
-		stmt.joins = newJoins[1:]
-		return
-	}
-
-	for i := start; i > 0; i-- {
-	}
-}
-
 func (stmt *SelectStmt) rearrangeOrdExps(groupByCols, orderByExps []*OrdExp) ([]*OrdExp, []*OrdExp) {
 	if len(groupByCols) > 0 && len(orderByExps) > 0 && !ordExpsHaveAggregations(orderByExps) {
 		if ordExpsHasPrefix(orderByExps, groupByCols, stmt.Alias()) {