code: func NewPrepareExec(ctx sessionctx.Context, is infoschema.InfoSchema, sqlTxt string) *PrepareExec {
  	base := newBaseExecutor(ctx, nil, prepareStmtLabel)
  	base.initCap = chunk.ZeroCapacity
  	return &PrepareExec{
  		baseExecutor: base,
  		is:           is,
  		sqlText:      sqlTxt,
  	}
  }
docs: // NewPrepareExec creates a new PrepareExec.