starting to remove exchange

Author: James Cor

engine.go

@@ -447,7 +447,7 @@ func (e *Engine) QueryWithBindings(ctx *sql.Context, query string, parsed sqlpar
 		return nil, nil, nil, err
 	}
 
-	iter = finalizeIters(analyzed, qFlags, iter)
+	iter = finalizeIters(e.Analyzer, analyzed, qFlags, iter)
 
 	return analyzed.Schema(), iter, qFlags, nil
 }
@@ -482,7 +482,7 @@ func (e *Engine) PrepQueryPlanForExecution(ctx *sql.Context, _ string, plan sql.
 		return nil, nil, nil, err
 	}
 
-	iter = finalizeIters(plan, nil, iter)
+	iter = finalizeIters(e.Analyzer, plan, nil, iter)
 
 	return plan.Schema(), iter, nil, nil
 }
@@ -705,7 +705,7 @@ func clearAutocommitTransaction(ctx *sql.Context) error {
 		return nil
 	}
 
-	autocommit, err := plan.IsSessionAutocommit(ctx)
+	autocommit, err := rowexec.IsSessionAutocommit(ctx)
 	if err != nil {
 		return err
 	}
@@ -725,7 +725,7 @@ func (e *Engine) CloseSession(connID uint32) {
 }
 
 func (e *Engine) beginTransaction(ctx *sql.Context) error {
-	beginNewTransaction := ctx.GetTransaction() == nil || plan.ReadCommitted(ctx)
+	beginNewTransaction := ctx.GetTransaction() == nil || rowexec.ReadCommitted(ctx)
 	if beginNewTransaction {
 		ctx.GetLogger().Tracef("beginning new transaction")
 		ts, ok := ctx.Session.(sql.TransactionSession)
@@ -830,7 +830,7 @@ func (e *Engine) executeEvent(ctx *sql.Context, dbName, createEventStatement, us
 		return err
 	}
 
-	iter = finalizeIters(definitionNode, nil, iter)
+	iter = finalizeIters(e.Analyzer, definitionNode, nil, iter)
 
 	// Drain the iterate to execute the event body/definition
 	// NOTE: No row data is returned for an event; we just need to execute the statements
@@ -865,8 +865,9 @@ func findCreateEventNode(planTree sql.Node) (*plan.CreateEvent, error) {
 }
 
 // finalizeIters applies the final transformations on sql.RowIter before execution.
-func finalizeIters(analyzed sql.Node, qFlags *sql.QueryFlags, iter sql.RowIter) sql.RowIter {
-	iter = rowexec.AddTransactionCommittingIter(iter, qFlags)
+func finalizeIters(analyzer *analyzer.Analyzer, analyzed sql.Node, qFlags *sql.QueryFlags, iter sql.RowIter) sql.RowIter {
+	iter = rowexec.AddTransactionCommittingIter(qFlags, iter)
+	iter = rowexec.AddExchangeRowIter(analyzer.Parallelism, analyzed, iter)
 	iter = rowexec.AddExpressionCloser(analyzed, iter)
 	return iter
 }

sql/plan/transaction_committing_iter.go

@@ -398,6 +398,14 @@ type exchangeRowIter struct {
 
 var _ sql.RowIter = (*exchangeRowIter)(nil)
 
+func AddExchangeRowIter(parallelism int, node sql.Node, iter sql.RowIter) sql.RowIter {
+	if parallelism <= 1 {
+		return iter
+	}
+
+	return iter
+}
+
 func (i *exchangeRowIter) Next(ctx *sql.Context) (sql.Row, error) {
 	if i.rows == nil {
 		panic("Next called for a Next2 iterator")

sql/rowexec/other_iters.go

@@ -74,17 +74,17 @@ type TransactionCommittingIter struct {
 	transactionDatabase string
 }
 
-func AddTransactionCommittingIter(child sql.RowIter, qFlags *sql.QueryFlags) sql.RowIter {
+func AddTransactionCommittingIter(qFlags *sql.QueryFlags, iter sql.RowIter) sql.RowIter {
 	// TODO: This is a bit of a hack. Need to figure out better relationship between new transaction node and warnings.
 	if qFlags != nil && qFlags.IsSet(sql.QFlagShowWarnings) {
-		return child
+		return iter
 	}
 	// TODO: remove this once trackedRowIter is moved out of planbuilder
 	// Insert TransactionCommittingIter as child of TrackedRowIter
-	if trackedRowIter, ok := child.(*plan.TrackedRowIter); ok {
+	if trackedRowIter, ok := iter.(*plan.TrackedRowIter); ok {
 		return trackedRowIter.WithChildIter(&TransactionCommittingIter{childIter: trackedRowIter.GetIter()})
 	}
-	return &TransactionCommittingIter{childIter: child}
+	return &TransactionCommittingIter{childIter: iter}
 }
 
 func (t *TransactionCommittingIter) Next(ctx *sql.Context) (sql.Row, error) {
@@ -102,9 +102,9 @@ func (t *TransactionCommittingIter) Close(ctx *sql.Context) error {
 
 	tx := ctx.GetTransaction()
 	// TODO: In the future we should ensure that analyzer supports implicit commits instead of directly
-	// accessing autocommit here.
+	//   accessing autocommit here.
 	// cc. https://dev.mysql.com/doc/refman/8.0/en/implicit-commit.html
-	autocommit, err := plan.IsSessionAutocommit(ctx)
+	autocommit, err := IsSessionAutocommit(ctx)
 	if err != nil {
 		return err
 	}
@@ -137,3 +137,31 @@ func (t *TransactionCommittingIter) WithChildIter(childIter sql.RowIter) sql.Row
 	nt.childIter = childIter
 	return &nt
 }
+
+// IsSessionAutocommit returns true if the current session is using implicit transaction management
+// through autocommit.
+func IsSessionAutocommit(ctx *sql.Context) (bool, error) {
+	if ReadCommitted(ctx) {
+		return true, nil
+	}
+
+	autoCommitSessionVar, err := ctx.GetSessionVariable(ctx, sql.AutoCommitSessionVar)
+	if err != nil {
+		return false, err
+	}
+	return sql.ConvertToBool(ctx, autoCommitSessionVar)
+}
+
+func ReadCommitted(ctx *sql.Context) bool {
+	val, err := ctx.GetSessionVariable(ctx, "transaction_isolation")
+	if err != nil {
+		return false
+	}
+
+	valStr, ok := val.(string)
+	if !ok {
+		return false
+	}
+
+	return valStr == "READ-COMMITTED"
+}