SaveChanges takes a lot of time due to expensive looping in method MetadataHelper.GetAssociationsForEntitySet(EntitySetBase entitySetKey)

This issue was discussed earlier in 2012 on MSDN forums but it didn’t go anywhere. We now have a genuine need to fix this problem as described here:

Entity Model:

Order - root entity OrderItem - 1-M child of Order

Order and OrderItem have a few FK associations with other master entities such as Customer and Product.

Scenario:

We are creating a new Order and many OrderItems (~600,000) within a single instance of DbContext and calling SaveChanges in the end.

We found that DbContext.SaveChanges was taking a lot of time, so we decided to run our application with dotTrace Profiler, which reported following method as a hot-spot taking almost 70% time:

System.Data.Common.Utils.MetadataHelper.GetAssociationsForEntitySet(EntitySetBase)

DBContext Settings:

1. Configuration.AutoDetectChangesEnabled = false;
2. Configuration.ValidateOnSaveEnabled = false;

Potential Solution: We made a small change to this method to avoid looping and use a dictionary instead to lookup for associations.

private static readonly ConcurrentDictionary<EntitySetBase, List<AssociationSet>> _associationSetsForEntitySet = new ConcurrentDictionary<EntitySetBase, List<AssociationSet>>();

Then fixed the method to use the dictionary as follows:

    // requires: entitySet
    // effects: Returns the associations that occur between entitySet
    // and other entitySets. If none is found, returns an empty set
    internal static List<AssociationSet> GetAssociationsForEntitySet(EntitySetBase entitySetKey)
    {
        DebugCheck.NotNull(entitySetKey);

        return _associationSetsForEntitySet.GetOrAdd(
            entitySetKey, entitySet =>
            {
                var result = new List<AssociationSet>();

                foreach (var extent in entitySet.EntityContainer.BaseEntitySets)
                {
                    if (Helper.IsRelationshipSet(extent))
                    {
                        var assocSet = (AssociationSet)extent;
                        if (IsExtentAtSomeRelationshipEnd(assocSet, entitySet))
                        {
                            result.Add(assocSet);
                        }
                    }
                }
                return result;
            });
    }

The performance indeed improved significantly as seen in the attached profiler snapshots:

[ravi-pathak]

@ajcvickers I will submit a pull request soon. Thanks for your comment.

[ajcvickers]

@ravi-pathak Thanks for finding that. We plan to release EF6.2 soon–we have been having some infrastructure issues that has delayed a number of things, but as of the end of last week we seem to be past them, so we’re going to try to get this out soon now.