executor: remove Next function for prepared.go (pingcap#6003)

executor/prepared.go

@@ -93,18 +93,8 @@ func NewPrepareExec(ctx sessionctx.Context, is infoschema.InfoSchema, sqlTxt str
 	}
 }
 
-// Next implements the Executor Next interface.
-func (e *PrepareExec) Next(ctx context.Context) (Row, error) {
-	return nil, errors.Trace(e.DoPrepare())
-}
-
 // NextChunk implements the Executor NextChunk interface.
 func (e *PrepareExec) NextChunk(ctx context.Context, chk *chunk.Chunk) error {
-	return errors.Trace(e.DoPrepare())
-}
-
-// DoPrepare prepares the statement, it can be called multiple times without side effect.
-func (e *PrepareExec) DoPrepare() error {
 	vars := e.ctx.GetSessionVars()
 	if e.ID != 0 {
 		// Must be the case when we retry a prepare.
@@ -194,12 +184,6 @@ type ExecuteExec struct {
 	plan      plan.Plan
 }
 
-// Next implements the Executor Next interface.
-// It will never be called.
-func (e *ExecuteExec) Next(ctx context.Context) (Row, error) {
-	return nil, nil
-}
-
 // NextChunk implements the Executor NextChunk interface.
 func (e *ExecuteExec) NextChunk(ctx context.Context, chk *chunk.Chunk) error {
 	return nil
@@ -236,17 +220,8 @@ type DeallocateExec struct {
 	Name string
 }
 
-// Next implements the Executor Next interface.
-func (e *DeallocateExec) Next(ctx context.Context) (Row, error) {
-	return nil, errors.Trace(e.run(ctx))
-}
-
 // NextChunk implements the Executor NextChunk interface.
 func (e *DeallocateExec) NextChunk(ctx context.Context, chk *chunk.Chunk) error {
-	return errors.Trace(e.run(ctx))
-}
-
-func (e *DeallocateExec) run(ctx context.Context) error {
 	vars := e.ctx.GetSessionVars()
 	id, ok := vars.PreparedStmtNameToID[e.Name]
 	if !ok {

session.go

@@ -859,7 +859,7 @@ func (s *session) PrepareStmt(sql string) (stmtID uint32, paramCount int, fields
 	// So we have to call PrepareTxnCtx here.
 	s.PrepareTxnCtx(ctx)
 	prepareExec := executor.NewPrepareExec(s, executor.GetInfoSchema(s), sql)
-	err = prepareExec.DoPrepare()
+	err = prepareExec.NextChunk(ctx, nil)
 	if err != nil {
 		err = errors.Trace(err)
 		return