Optimizing query for search using nspredicates - ios

Question

This issue has been brought up a lot but I can't seem to optimize this piece of search code any further.
this filterSet array has about 1000 items and it's taking 8 seconds to reproduce results on a non-simulator iPad (simulator shows results in less than a second):
for(NSString *rowID in [self.filterSet array]) {
self.rowResults = [self.filteredResults filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:#"rowID = %#", rowID]];
self.rowResults = [self.rowResults valueForKey:#"value"];
self.duplicateValueSet = [NSOrderedSet orderedSetWithArray:self.rowResults];
filterCount = [[self.resultsArray filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:#"SELF = %#", rowID]] count];
if([self.duplicateValueSet count] != filterCount)
filterCount -= abs([self.duplicateValueSet count] - filterCount);
if(filterCount == matchingCount)
[self.results addObject:rowID];
}
any suggestions to optimizing this query? The majority of the search is taken up in all the filters and predicate sorting. thanks.
edit: so i removed a lot of the code in the for loop and found the culprit to be the first line
self.rowResults = [self.filteredResults filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:#"rowID = %#", rowID]];
this is for some reason taking 7 seconds to execute. Is there a faster/more efficient way to create a predicate to match the rowID string? I've thought about using the makeobjectsperformselector NSArray method but for some reason I get the NSCFNumber unrecognized selector issue (which is saying my array has NSNumbers instead of NSStrings)

Answer 1

so my initial algorithm was running at O(N^2) which is pretty much as bad as it gets (realistically).
I've ended up using an NSDictionary to map keys/values so that I can easily reference them within the first for loop's first pass:
NSMutableDictionary *filteredResultsDict = [[[NSMutableDictionary alloc] init] autorelease];
for (int i = 0; i < [filteredResults count]; i++) {
NSString *key = [[filteredResults objectAtIndex:i] valueForKey:#"rowID"];
NSMutableArray *filtersArray = [NSMutableArray array];
NSMutableArray *tempArray = [filteredResultsDict objectForKey:key];
if (tempArray != nil || [tempArray count] > 0) {
[tempArray addObject:[filteredResults objectAtIndex:i]];
[filteredResultsDict setValue:tempArray forKey:key];
}
else {
[filtersArray addObject:[filteredResults objectAtIndex:i]];
[filteredResultsDict setValue:filtersArray forKey:key];
}
}
and then in my actual for loop, I can call this in place of the previous rowResults:
NSNumber *rowIDNum = [NSNumber numberWithInteger: [rowID integerValue]];
rowResults = [[filteredResultsDict objectForKey:rowIDNum] valueForKey:#"value"];