ios - How do I set up relationship for large core data sets efficiently? -

i have 2 entities drink , breweries. have data in json , building out core data tables each , have relationship set (one 1 drink brewery). however, trying set @ time of building out drink objects slows down process because having query core data every time create new drink (there couple thousand drinks , 1000 breweries). @ moment brewery has unique id matches attribute on drink. best way go without slowing down load time greatly? considering using 1 entity instead , placing breweries in same table though bad db practice.

here code building out drink table json code adding in brewery commented out.

[jsoncategories enumerateobjectsusingblock:^(id obj, nsuinteger idx, bool *stop){     drink *drink = [nsentitydescription insertnewobjectforentityforname:@"drink" inmanagedobjectcontext:importcontext];     //drinktype.id = [obj objectforkey:@"id"];     drink.name = [obj objectforkey:@"name"];     drink.alcoholbyvolume = [obj objectforkey:@"abv"];     drink.drinktype = beerdrinktype;     drink.breweryid = [obj objectforkey:@"brewery_id"];   //        nsarray *fetchedobjects; //        nsfetchrequest *fetch = [[nsfetchrequest alloc]init]; //        nsentitydescription *entitydescription = [nsentitydescription entityforname:@"breweries" inmanagedobjectcontext:importcontext]; //        [fetch setentity:entitydescription]; //        [fetch setpredicate:[nspredicate predicatewithformat:@"id =%@", drink.breweryid]]; //        nserror *errorbrewery; //        [fetch setfetchlimit:1]; //        fetchedobjects = [importcontext executefetchrequest:fetch error:&errorbrewery]; //        if (fetchedobjects && [fetchedobjects count] > 0){ //        breweries *fetchedbrewery = [fetchedobjects objectatindex:0]; //        drink.breweries = fetchedbrewery; //        }  }]; 

you re-fetching brewery list each iteration of jsoncategories elements. adds huge overhead , causes slowness, , unnecessary because assume list not change.

a better design fetch once, , filter needed. i’ve omitted code below , wrote important parts, should able fill in yourself.

nsfetchrequest *fetch = …; // note predicate not set here fetchedbreweries = [importcontext executefetchrequest…]; [jsoncategories enumerateobjectsusingblock:^(id obj, nsuinteger idx, bool *stop){     …     nsarray *matchingbreweries = [fetchedbreweries filteredarrayusingpredicate:…predicate];     drink.breweries = matchingbreweries.firstobject; }]; 

maybe slow, because if fetch breweries, might consume cpu , memory (though i’d first try see if problem).

a further optimization first iterate on jsoncategories , create set of brewery id-s found in results. then, fetch these breweries, , iterate on drink results again add breweries drinks. like

nsmutableset *breweryids = [nsmutableset set]; [jsoncategories enumerateobjectsusingblock:^(id obj, nsuinteger idx, bool *stop){     …     [breweryids addobject:[obj objectforkey:@"brewery_id"]]; }]; nsfetchrequest *fetch = [[nsfetchrequest alloc] init]; [fetch setpredicate:[nspredicate predicatewithformat:@"id in %@", breweryids]]; nsarray *breweries = [importcontext executefetchrequest…] (drink *drink in drinks) {     nsarray *matchingbreweries = [fetchedbreweries filteredarrayusingpredicate:…predicate];     drink.breweries = matchingbreweries.firstobject; } 

hm. need beer now.