CODEWITHSUNDEEP
iosobjective-ccore-datansfetchrequest
Savitha
Savitha

Reputation: 561

Count of child in Coredata

I need to find count of children based on logic.

I have table A, it has two relationship B and C. Now i need to find count of B and C. Count = No of B * NO of C.

Data:

A1 
{
    {
    B1a
    },
    {
    C1a,
    C1b
    }
},
A2:
{
    {
    B2a,
    B2b
    },
    {
    C2a,
    C2b
    }
}

Total Count = 6

i have tried with following

NSEntityDescription *entity = [NSEntityDescription entityForName:@"A" inManagedObjectContext:context];
NSArray *allObjects = [context executeFetchRequest:fetchRequest error:&fetchError];
NSInteger totalCount= 0;

for(A *a in allObjects)
{
    NSInteger countOfB = [a.B count];
    NSInteger countOfc = [a.C count];
    totalCount = totalCount + (countOfB * countOfc);
}

This is work fine. But when i have 10000 records it is taking more time. Please suggest me if any alternative ways.

Upvotes: 0

Views: 125

Answers (1)

Wain
Wain

Reputation: 119041

Don't do the multiplication on demand. Each time an A instance has the relationship to B or C changed, calculate the product and store it in a new attribute on A. Now to fetch your total count you can use only a single fetch (returning dictionary type) and then @sum (using the array with a collection operator) and none of the objects need to actually be loaded into memory.

Consider using KVO to monitor for relationship changes and trigger the update to your product.

Upvotes: 1

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