Question

I have set of ‘codes’ Z that are valid in a certain time period.

Since I need them a lot of times in a large loop (million+) and every time I have to lookup the corresponding code I cache them in a List<>. After finding the correct codes, i’m inserting (using SqlBulkCopy) a million rows.

I lookup the id with the following code (l_z is a List<T>)

var z_fk = (from z in l_z
            where z.CODE == lookupCode &&
                  z.VALIDFROM <= lookupDate &&
                  z.VALIDUNTIL >= lookupDate 
            select z.id).SingleOrDefault();

In other situations I have used a Dictionary with superb performance, but in those cases I only had to lookup the id based on the code.

But now with searching on the combination of fields, I am stuck.

Any ideas? Thanks in advance.

Answer 1

Create a Dictionary that stores a List of items per lookup code – Dictionary<string, List<Code>> (assuming that lookup code is a string and the objects are of type Code).

Then when you need to query based on lookupDate, you can run your query directly off of dict[lookupCode]:

var z_fk = (from z in dict[lookupCode]
            where z.VALIDFROM <= lookupDate &&
                  z.VALIDUNTIL >= lookupDate 
            select z.id).SingleOrDefault();

Then just make sure that whenever you have a new Code object, that it gets added to the List<Code> collection in the dict corresponding to the lookupCode (and if one doesn’t exist, then create it).