幾十萬數據，分頁查詢10行，花了30秒，太離譜！
改進
1、連表查詢拆分成兩個查詢，在內存中連表。
從30秒，變3秒
2、日期查詢改成區間查詢
airHourly.Date 數據舉例：2015-01-01 02:00:00.000
System.Data.Entity.DbFunctions.TruncateTime(airHourly.Date) == dateHour
改成：(airHourly.Date >= dateHour && airHourly.Date < dateEnd)
3秒變100毫秒。
若僅改2，也是100毫秒。
說明主要原因是2。
public JsonResult StreetStationHourlyData(int page, int rows, string sort, string order, DateTime dateHour, string stations)//, string param, string stationsType
{
PageModel pageInfo = new PageModel();
pageInfo.Page = page;
pageInfo.Rows = rows;
pageInfo.Order = order;
pageInfo.Sort = sort;
string[] stationArray = null;
if (stations != null)
{
stationArray = stations.Split(',');
}
ResultModel result = new ResultModel();
if (pageInfo.Page <= 0)
{
pageInfo.Page = 1;
}
if (pageInfo.Rows <= 0)
{
pageInfo.Rows = 20;
}
dateHour = dateHour.Date;
var dateEnd = dateHour.Date.AddDays(1);
var data = from airHourly in dbq.T_AirStreetDataHourly2
join station in dbq.T_AirStreetStation2
on airHourly.StationID equals station.StationID
where airHourly.StationID != null && (airHourly.Date >= dateHour && airHourly.Date < dateEnd) && stationArray.Contains(airHourly.StationID)
orderby airHourly.StationID, airHourly.Date
select new AirStreetDataDaily2 { O3 = airHourly.O3, PM10 = airHourly.PM10, PM25 = airHourly.PM25, Date = airHourly.Date, Hour = airHourly.Date.Hour, StationName = station.StationName, StationID = station.StationID, Hierarchy = station.Hierarchy, SeatType = station.SeatType, PointNature = station.PointNature, IsStreet = station.IsStreet };
//var data =
// from airHourly in dbq.T_AirStreetDataHourly2
// where airHourly.StationID != null && (airHourly.Date >= dateHour && airHourly.Date < dateEnd) && stationArray.Contains(airHourly.StationID)
// //where stationArray.Contains(airHourly.StationID) && System.Data.Entity.DbFunctions.TruncateTime(airHourly.Date) == dateHour
// orderby airHourly.StationID, airHourly.Date.Hour
// select new AirStreetDataDaily2 { StationID = airHourly.StationID, O3 = airHourly.O3, PM10 = airHourly.PM10, PM25 = airHourly.PM25, Date = airHourly.Date, Hour = airHourly.Date.Hour };
//排序
if (pageInfo.Order != null && pageInfo.Sort != null)
{
bool isAsc = pageInfo.Order == "asc";
data = data.OrderBy(new[] { pageInfo.Sort }, new[] { isAsc });
}
var data1 = data.Skip((pageInfo.Page - 1) * pageInfo.Rows).Take(pageInfo.Rows).ToList();
//var dataB = (from station in dbq.T_AirStreetStation2
// where stationArray.Contains(station.StationID)
// select new AirStreetDataDaily2 { StationName = station.StationName, StationID = station.StationID, Hierarchy = station.Hierarchy, SeatType = station.SeatType, PointNature = station.PointNature, IsStreet = station.IsStreet }
//).ToList();
foreach (var item in data1)
{
//var station2= dataB.Where(d => d.StationID == item.StationID).Select(d=>d).FirstOrDefault();
//item.StationName = station2.StationName;
//item.StationID = station2.StationID;
//item.Hierarchy = station2.Hierarchy;
//item.SeatType = station2.SeatType;
//item.PointNature = station2.PointNature;
//item.IsStreet = station2.IsStreet;
if (item.O3 != null)
{
item.O3 = Math.Round((double)item.O3, 2, MidpointRounding.AwayFromZero);
}
if (item.PM10 != null)
{
item.PM10 = Math.Round((double)item.PM10, 2, MidpointRounding.AwayFromZero);
}
if (item.PM25 != null)
{
item.PM25 = Math.Round((double)item.PM25, 2, MidpointRounding.AwayFromZero);
}
}
result.rows = data1;
result.total = data.Count();
result.success = true;
return Json(result);//, JsonRequestBehavior.AllowGet
}