Merge pull request #3210 from dolthub/angela/lateraljoin

Copy parent row in lateralJoinIterator.buildRow

Author: angelamayxie

enginetest/queries/join_queries.go

@@ -1429,4 +1429,20 @@ LATERAL (
 			},
 		},
 	},
+	{
+		// https://github.com/dolthub/dolt/issues/9820
+		Name: "lateral cross join with subquery",
+		SetUpScript: []string{
+			"create table t0(c0 boolean)",
+			"create table t1(c0 int)",
+			"insert into t0 values (true)",
+			"insert into t1 values(0)",
+		},
+		Assertions: []ScriptTestAssertion{
+			{
+				Query:    "select v.c0, t1.c0 from t0 cross join lateral (select 1 as c0) as v join t1 on v.c0 > t1.c0",
+				Expected: []sql.Row{{1, 0}},
+			},
+		},
+	},
 }

sql/rowexec/join_iters.go

@@ -688,7 +688,7 @@ func (i *crossJoinIterator) Close(ctx *sql.Context) (err error) {
 	return err
 }
 
-// lateralJoinIter is an iterator that performs a lateral join.
+// lateralJoinIterator is an iterator that performs a lateral join.
 // A LateralJoin is a join where the right side is a subquery that can reference the left side, like through a filter.
 // MySQL Docs: https://dev.mysql.com/doc/refman/8.0/en/lateral-derived-tables.html
 // Example:
@@ -716,18 +716,18 @@ func (i *crossJoinIterator) Close(ctx *sql.Context) (err error) {
 // +---+---+
 // cond is passed to the filter iter to be evaluated.
 type lateralJoinIterator struct {
-	lIter      sql.RowIter
-	rIter      sql.RowIter
-	rNode      sql.Node
-	cond       sql.Expression
-	b          sql.NodeExecBuilder
-	pRow       sql.Row
-	lRow       sql.Row
-	rRow       sql.Row
-	rowSize    int
-	scopeLen   int
-	jType      plan.JoinType
-	foundMatch bool
+	primary       sql.RowIter
+	secondary     sql.RowIter
+	secondaryNode sql.Node
+	cond          sql.Expression
+	b             sql.NodeExecBuilder
+	parentRow     sql.Row
+	primaryRow    sql.Row
+	secondaryRow  sql.Row
+	rowSize       int
+	scopeLen      int
+	jType         plan.JoinType
+	foundMatch    bool
 }
 
 func newLateralJoinIter(ctx *sql.Context, b sql.NodeExecBuilder, j *plan.JoinNode, row sql.Row) (sql.RowIter, error) {
@@ -755,105 +755,106 @@ func newLateralJoinIter(ctx *sql.Context, b sql.NodeExecBuilder, j *plan.JoinNod
 	}
 
 	return sql.NewSpanIter(span, &lateralJoinIterator{
-		pRow:     row,
-		lIter:    l,
-		rNode:    j.Right(),
-		cond:     j.Filter,
-		jType:    j.Op,
-		rowSize:  len(row) + len(j.Left().Schema()) + len(j.Right().Schema()),
-		scopeLen: j.ScopeLen,
-		b:        b,
+		parentRow:     row,
+		primary:       l,
+		secondaryNode: j.Right(),
+		cond:          j.Filter,
+		jType:         j.Op,
+		rowSize:       len(row) + len(j.Left().Schema()) + len(j.Right().Schema()),
+		scopeLen:      j.ScopeLen,
+		b:             b,
 	}), nil
 }
 
-func (i *lateralJoinIterator) loadLeft(ctx *sql.Context) error {
-	if i.lRow == nil {
-		lRow, err := i.lIter.Next(ctx)
+func (i *lateralJoinIterator) loadPrimary(ctx *sql.Context) error {
+	if i.primaryRow == nil {
+		lRow, err := i.primary.Next(ctx)
 		if err != nil {
 			return err
 		}
-		i.lRow = lRow
+		i.primaryRow = lRow
 		i.foundMatch = false
 	}
 	return nil
 }
 
-func (i *lateralJoinIterator) buildRight(ctx *sql.Context) error {
-	if i.rIter == nil {
-		prepended, _, err := transform.Node(i.rNode, plan.PrependRowInPlan(i.lRow, true))
+func (i *lateralJoinIterator) buildSecondary(ctx *sql.Context) error {
+	if i.secondary == nil {
+		prepended, _, err := transform.Node(i.secondaryNode, plan.PrependRowInPlan(i.primaryRow, true))
 		if err != nil {
 			return err
 		}
-		iter, err := i.b.Build(ctx, prepended, i.lRow)
+		iter, err := i.b.Build(ctx, prepended, i.primaryRow)
 		if err != nil {
 			return err
 		}
-		i.rIter = iter
+		i.secondary = iter
 	}
 	return nil
 }
 
-func (i *lateralJoinIterator) loadRight(ctx *sql.Context) error {
-	if i.rRow == nil {
-		rRow, err := i.rIter.Next(ctx)
+func (i *lateralJoinIterator) loadSecondary(ctx *sql.Context) error {
+	if i.secondaryRow == nil {
+		sRow, err := i.secondary.Next(ctx)
 		if err != nil {
 			return err
 		}
-		i.rRow = rRow[len(i.lRow):]
+		i.secondaryRow = sRow[len(i.primaryRow):]
 	}
 	return nil
 }
 
-func (i *lateralJoinIterator) buildRow(lRow, rRow sql.Row) sql.Row {
+func (i *lateralJoinIterator) buildRow(primaryRow, secondaryRow sql.Row) sql.Row {
 	row := make(sql.Row, i.rowSize)
-	copy(row, lRow)
-	copy(row[len(lRow):], rRow)
+	copy(row, i.parentRow)
+	copy(row[len(i.parentRow):], primaryRow)
+	copy(row[len(i.parentRow)+len(primaryRow):], secondaryRow)
 	return row
 }
 
 func (i *lateralJoinIterator) removeParentRow(r sql.Row) sql.Row {
-	copy(r[i.scopeLen:], r[len(i.pRow):])
-	r = r[:len(r)-len(i.pRow)+i.scopeLen]
+	copy(r[i.scopeLen:], r[len(i.parentRow):])
+	r = r[:len(r)-len(i.parentRow)+i.scopeLen]
 	return r
 }
 
 func (i *lateralJoinIterator) reset(ctx *sql.Context) (err error) {
-	if i.rIter != nil {
-		err = i.rIter.Close(ctx)
-		i.rIter = nil
+	if i.secondary != nil {
+		err = i.secondary.Close(ctx)
+		i.secondary = nil
 	}
-	i.lRow = nil
-	i.rRow = nil
+	i.primaryRow = nil
+	i.secondaryRow = nil
 	return
 }
 
 func (i *lateralJoinIterator) Next(ctx *sql.Context) (sql.Row, error) {
 	for {
-		if err := i.loadLeft(ctx); err != nil {
+		if err := i.loadPrimary(ctx); err != nil {
 			return nil, err
 		}
-		if err := i.buildRight(ctx); err != nil {
+		if err := i.buildSecondary(ctx); err != nil {
 			return nil, err
 		}
-		if err := i.loadRight(ctx); err != nil {
+		if err := i.loadSecondary(ctx); err != nil {
 			if errors.Is(err, io.EOF) {
 				if !i.foundMatch && i.jType == plan.JoinTypeLateralLeft {
-					res := i.buildRow(i.lRow, nil)
-					if rerr := i.reset(ctx); rerr != nil {
-						return nil, rerr
+					res := i.buildRow(i.primaryRow, nil)
+					if resetErr := i.reset(ctx); resetErr != nil {
+						return nil, resetErr
 					}
 					return i.removeParentRow(res), nil
 				}
-				if rerr := i.reset(ctx); rerr != nil {
-					return nil, rerr
+				if resetErr := i.reset(ctx); resetErr != nil {
+					return nil, resetErr
 				}
 				continue
 			}
 			return nil, err
 		}
 
-		row := i.buildRow(i.lRow, i.rRow)
-		i.rRow = nil
+		row := i.buildRow(i.primaryRow, i.secondaryRow)
+		i.secondaryRow = nil
 		if i.cond != nil {
 			if res, err := sql.EvaluateCondition(ctx, i.cond, row); err != nil {
 				return nil, err
@@ -868,18 +869,18 @@ func (i *lateralJoinIterator) Next(ctx *sql.Context) (sql.Row, error) {
 }
 
 func (i *lateralJoinIterator) Close(ctx *sql.Context) error {
-	var lerr, rerr error
-	if i.lIter != nil {
-		lerr = i.lIter.Close(ctx)
+	var pErr, sErr error
+	if i.primary != nil {
+		pErr = i.primary.Close(ctx)
 	}
-	if i.rIter != nil {
-		rerr = i.rIter.Close(ctx)
+	if i.secondary != nil {
+		sErr = i.secondary.Close(ctx)
 	}
-	if lerr != nil {
-		return lerr
+	if pErr != nil {
+		return pErr
 	}
-	if rerr != nil {
-		return rerr
+	if sErr != nil {
+		return sErr
 	}
 	return nil
 }