Improve perfomance when select list

Question

I have method as below:

public static IList<MedicalRecord> UpdateServicePrice(
                         IList<MedicalRecord> mListMedicalRecord, 
                         IList<ServicePrice> listAllServicePrice)
{
    foreach (MedicalRecord medical in mListMedicalRecord)
    {
        medical.mListServicePrice =
            (from p in listAllServicePrice
             where p.MedicalRecordID == medical.MedicalRecordID
            select p).ToList();
    }
    return mListMedicalRecord;
}

but it run very slow. Any one can help me for improve performance of above method? Thank a lot.

Have you tried rewriting it imperatively with `for` loops? – Honza Brestan Nov 29 '12 at 14:15 — Honza Brestan, Nov 29 '12 at 14:15
is this using entity framework/linqtosql? – Daniel A. White Nov 29 '12 at 14:16 — Daniel A. White, Nov 29 '12 at 14:16

score 3 · Accepted Answer · answered Nov 29 '12 at 14:27

Here's a Join-based method that should achieve the same thing, but faster:

public static IList<MedicalRecord> UpdateServicePrice(
    IList<MedicalRecord> mListMedicalRecord,
    IList<ServicePrice> listAllServicePrice)
{
    foreach (var j in mListMedicalRecord.GroupJoin(listAllServicePrice,
        mr => mr.MedicalRecordID,
        sp => sp.MedicalRecordID,
        (mr, sps) => new { Record = mr, Prices = sps }))
    {
        j.Record.mListServicePrice = j.Prices.ToList();
    }
    return mListMedicalRecord;
}

Your code loops through the ServicesPrices once for each MedicalRecord. Join goes through the prices once, grouping them by the record ID, and then joins them to the correct record.

Your solution is great ! Thank you. The time change from 267s -> 90ms — user1863463, Nov 29 '12 at 15:27
Golden rule of trying to improve performance: always time before and after to see if it's actually helped :) — Rawling, Nov 30 '12 at 09:43

score 0 · Answer 2 · answered Nov 29 '12 at 14:16

0

You might get significant improvement by replacing the 'where' with a 'join' clause.

answered Nov 29 '12 at 14:16

JohnC

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4
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1

@ssg, this: http://stackoverflow.com/questions/5551264/why-is-linq-join-so-much-faster-than-linking-with-where – tranceporter Nov 29 '12 at 14:19
@tranceporter: thanks I know about the behavior. I wasn't sure JohnC was referring to it. http://stackoverflow.com/questions/649444/testing-equality-of-arrays-in-c-sharp#comment3006817_649476 – Sedat Kapanoglu Nov 29 '12 at 18:39

Improve perfomance when select list

2 Answers2