How should I search through this json structure? - json

Question

I'm working with PHP, I have a json structure which looks like that :
{
"events": [
{
"timestamp": 1468774519,
"id": 75964,
},
{
"timestamp": 1468771410,
"id": 24891,
},
// etc
I need to fetch 5 events in a row, but starting from one specific id, so my first idea is to loop every event from the beginning and check if the id is the offset i'm looking for, and then when i get it i can loop the next 5 events.
But is there a better way to do so ? It could possibly loop through hundreds of events so maybe there's a better way to get there ? thanks

Answer 1

Since the ids aren't in numeric order, you can't use a binary search, so you need to use a sequential search. Here's an example in JavaScript. Also note this code assumes the id is present and there are at least four more events after it in the array.
var index = 0;
var id = 12345; // for example
var json = {...}; // whatever that object was
while(json.events[index].id!=id) {
index++;
}
// found the one, do something with the next five
for(var i=0; i<5; i++) {
var event = json.events[index+i];
// do something
}

Answer 2

In my opinion, you can only take one loop over the events with a filter event.id >= theId,and then check if the filtered array contains theId. if you get it, you can sort this smaller array and take the 5 events.

Answer 3

First I would make a key:value hash object (a lookup object), where the key would be the id from your structure, and the value would be the reference to the event. As a result, you iterate over the structure only once and then get all the events from the lookup structure, by just accessing them by their keys.
You could sort it as well(ideally, you could get it already sorted by id from your source of data) and then use a binary search algorithm.