code: func (e *DeallocateExec) Next(ctx context.Context, req *chunk.RecordBatch) error {
  	vars := e.ctx.GetSessionVars()
  	id, ok := vars.PreparedStmtNameToID[e.Name]
  	if !ok {
  		return errors.Trace(plannercore.ErrStmtNotFound)
  	}
  	delete(vars.PreparedStmtNameToID, e.Name)
  	if plannercore.PreparedPlanCacheEnabled() {
  		e.ctx.PreparedPlanCache().Delete(plannercore.NewPSTMTPlanCacheKey(
  			vars, id, vars.PreparedStmts[id].SchemaVersion,
  		))
  	}
  	vars.RemovePreparedStmt(id)
  	return nil
  }
docs: // Next implements the Executor Next interface.