/**
 * Method to test Fernando's F' map trick
 */

// Query a 1000 records
Account[] records = [SELECT Id,Name FROM Account WHERE Name LIKE 'Test Account - %' LIMIT 1000];

// Use Fernando's MapCreator Method to 
Integer fst = Limits.getCpuTime();
Map<String, SObject> fMap = (Map<String, SObject>) MapCreator.createMapByIndex(records, 'Name' );
Integer fet = Limits.getCpuTime();
System.debug('"Fernanados" method: ' + (fet-fst) + 'ms - Number of records:' + fMap.size());


// Use a traditional for loop
Integer tst = Limits.getCpuTime();
Map<String, SObject> tMap = new Map<String, SObject>();
for(Integer i=0,max=records.size();i<max;i++){
    tMap.put(records[i].name,records[i]);
}
Integer tet = Limits.getCpuTime();
System.debug('"Traditional" method: ' + (tet-tst) + 'ms - Number of records:' + tMap.size());



/**
 * https://learnsf.wordpress.com/2014/12/29/trick-how-to-obtain-a-map-indexed-by-any-field-not-just-id-faster-and-without-loops/
 */
public class MapCreator {
    
    public static Map<String, SObject> createMapByIndex(List<SObject> aList, String indexField ) {
    
        // get the list in JSON format
        String jsonList = JSON.serialize( aList );
        
        // remove enclosing []
        jsonList = jsonList.substring( 1, jsonList.length() - 1 );
        
        // copy the indexField value in front of each
        // {} group using RegEx substitution
        // example result: value:{…"indexField":"value"…}
        jsonList = '{' + jsonList.replaceAll('(\\{.*?"' + indexField + '":"(.*?)"(,".*?")*\\},?)', '"$2":$1' ) + '}';
        
        // create map from the modified JSON
        Map<String, SObject> changedMap = (Map<String, SObject>) JSON.deserialize( jsonList, Map<String, SObject>.class );
        
        return changedMap;
    }
}