Question

I have this linq query i’m using and it’s taking 50 seconds to run when i am running it my asp.net application, however the same query executes in 500ms in LinqPad and Sql Management Studio.

I even took the query from the SQL Profiler and ran it again in SQL Management Studio and it takes around 500ms. What overhead Linq could be doing, that an extra 49s??

Below is the code for reference, thanks for your help.

var rCampaign =
    (from a in db.AdCreative
     join h in db.AdHit on a.ID equals h.AdID into gh
     join l in db.AdGroup_Location on a.AdGroupID equals l.AdGroupID into gj
     from subloc in gj.DefaultIfEmpty()
     from subhits in gh.DefaultIfEmpty()
     where a.AdGroup.AdHost.Select(q => q.ID).Contains(rPlatform.ID) &&
           a.AdGroup.AdPublisher.Select(q => q.ID).Contains(rPublisher.ID) &&
           a.AdDimensionID == AdSize &&
           a.AdGroup.Campaign.Starts <= rNow &&
           a.AdGroup.Campaign.Ends >= rNow &&
           subhits.HitType == 1 &&
           (subloc == null || subloc.LocationID == rLocationID)
     select new {
         ID = a.ID,
         Name = a.Name,
         Spent = (subhits.AdDimension != null) ? ((double)subhits.AdDimension.Credit / 1000) : 0,
         CampaignID = a.AdGroup.Campaign.ID,
         CampaignName = a.AdGroup.Campaign.Name,
         CampaignBudget = a.AdGroup.Campaign.DailyBudget
     }).GroupBy(adgroup => adgroup.ID)
       .Select(adgroup => new {
           ID = adgroup.Key,
           Name = adgroup.FirstOrDefault().Name,
           Spent = adgroup.Sum(q => q.Spent),
           CampaignID = adgroup.FirstOrDefault().CampaignID,
           CampaignName = adgroup.FirstOrDefault().CampaignName,
           CampaignBudget = adgroup.FirstOrDefault().CampaignBudget,
       })
      .GroupBy(q => q.CampaignID)
      .Select(campaigngroup => new {
          CampaignID = campaigngroup.Key,
          DailyBudget = campaigngroup.FirstOrDefault().CampaignBudget,
          Consumed = campaigngroup.Sum(q => q.Spent),
          RemainningCredit = campaigngroup.FirstOrDefault().CampaignBudget - campaigngroup.Sum(q => q.Spent),
          Ads = campaigngroup.Select(ag => new {
              ID = ag.ID,
              Name = ag.Name,
              Spent = ag.Spent
          }).OrderBy(q => q.Spent)
      })
      .Where(q => q.Consumed <= q.DailyBudget).OrderByDescending(q => q.RemainningCredit).First();

Answer 1

There are a few ways you can simplify that query:

• select into lets you keep it all in query syntax.
• The join ... into/from/DefaultIfMany constructs implementing left joins can be replaced with join ... into construcs representing group joins.
• Some of the groups near the end cannot be empty, so FirstOrDefault is unnecessary.
• Some of the where conditions can be moved up to the top before the query gets complicated.

Here’s the stab I took at it. The revisions were significant, so it might need a little debugging:

var rCampaign = ( 
    from a in db.AdCreative

    where a.AdDimensionID == AdSize &&
          a.AdGroup.Campaign.Starts <= rNow &&
          a.AdGroup.Campaign.Ends >= rNow &&
          a.AdGroup.AdHost.Select(q => q.ID).Contains(rPlatform.ID) &&
          a.AdGroup.AdPublisher.Select(q => q.ID).Contains(rPublisher.ID)

    join hit in db.AdHit.Where(h => h.HitType == 1 && h.LocationID == rLocationID)
        on a.ID equals hit.AdID
        into hits

    join loc in db.AdGroup_Location
        on a.AdGroupID equals loc.AdGroupID
        into locs

    where !locs.Any() || locs.Any(l => l.LocationID == rLocationID)

    select new {
        a.ID,
        a.Name,
        Spent = hits.Sum(h => h.AdDimension.Credit / 1000) ?? 0,
        CampaignID = a.AdGroup.Campaign.ID,
        CampaignName = a.AdGroup.Campaign.Name,
        CampaignBudget = a.AdGroup.Campaign.DailyBudget,
    } into adgroup
    group adgroup by adgroup.CampaignID into campaigngroup
    select new
    {
        CampaignID = campaigngroup.Key,
        DailyBudget = campaigngroup.First().CampaignBudget,
        Consumed = campaigngroup.Sum(q => q.Spent),
        RemainingCredit = campaigngroup.First().CampaignBudget - campaigngroup.Sum(q => q.Spent),
        Ads = campaigngroup.Select(ag => new {
            ag.ID,
            ag.Name,
            ag.Spent,
        }).OrderBy(q => q.Spent)
    } into q
    where q.Consumed <= q.DailyBudget
    orderby q.RemainingCredit desc)
    .First()