EDNA实时数据库两种取历史数据值的方式

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1. DnaGetNextHistUTC函数：根据游标一个一个值取

 int i = EzDNAApiNet.EzDnaApi.History.DnaGetHistDirectRawUTC(szServer,szPoint, Start, End, ref key);  

if (i == 0)
                {
                    long l1 = DateTime.Now.Ticks / 10000;

                    int s = 0;

                    int i1 = 0;

                    while (i1 == 0)
                    {
                        i1 = EzDNAApiNet.EzDnaApi.History.DnaGetNextHistUTC(key, ref pdValue, ref ptTime, szStatus, 20);

                        if (pdValue >= dHighLimit)
                        {
                            m_ulHighCount++;
                        }

                        if (pdValue<= dLowLimit)
                        {
                            m_ulLowCount++;
                        }
                       

                        if (i1 == 0)
                        {                           

                            //记住开始时间
                            if (s == 0)
                            {
                                EzDNAApiNet.EzDnaApi.Translator.UCTToStringTime(ptTime, szTime, 30);

                                sStart = szTime.ToString();
                            }  
                       
                            s++;
                        }
                    }

                    //记住结束时间
                    EzDNAApiNet.EzDnaApi.Translator.UCTToStringTime(ptTime, szTime, 30);
                    sEnd = szTime.ToString();

                    long l2 = DateTime.Now.Ticks / 10000 - l1;

    }

2. DnaGetNextHistBlockSmall函数：一次读取批量数据

int i = EzDNAApiNet.EzDnaApi.History.DnaGetHistDirectRawUTC(szServer,szPoint, Start, End, ref key);
 StringBuilder szTime = new StringBuilder(30);

            double[] pszValueList = new double[1000000];
            int[] pszTimeList = new int[1000000];
            ushort[] pszStatusList = new ushort[1000000];

            string sStart = "";
            string eEnd = "";

  if (i == 0)
            {
                long l1 = DateTime.Now.Ticks / 10000;

                int s = 0;

                do
                {

                    i1 = EzDNAApiNet.EzDnaApi.History.DnaGetNextHistBlockSmall(key, 1000000, out pnCount,   pszValueList, pszTimeList, pszStatusList);

                    if (0 == i1)
                    {
                        for (int j = 0; j < pnCount; j++)
                        {
                            //开始时间
                            if (j == 0)
                            {

                                EzDNAApiNet.EzDnaApi.Translator.UCTToStringTime(pszTimeList[j], szTime, 30);
                               
                                sStart = szTime.ToString();

                            }
                            else if (j == pnCount-1)
                            { 
                                //结束时间
                                EzDNAApiNet.EzDnaApi.Translator.UCTToStringTime(pszTimeList[j], szTime, 30);
                                eEnd = szTime.ToString();
                           
                            }
 

                            s++;
                        }

                    }
                }
                while (0 == i1);      

                long l2 = DateTime.Now.Ticks / 10000 - l1;

方式2比方式1性能有10倍的提高。当然，历史数据查询与磁盘IO性能有很大关系。