How to add pagination and limit to cosmos db - pagination

Question

I want to specify the number of records to return from the database. The only way I've come up with that allows me to do that, is by setting the MaxItemCount = 1, so that each feed response contains only one result, and then readNext from the iterator the wanted number of times. I don't know enough about RUs and what goes on behind the scenes with cosmos db, but I suspect setting MaxItemCount = 1 is bad practice. So is there any other way to do this?
public async Task<(IEnumerable<T> Results, string ContinuationToken)> ReadAsync(Expression<Func<T, bool>> predicate, int limit, string continuationToken)
{
var items = new List<T>();
var options = new QueryRequestOptions { MaxItemCount = 1 };
IQueryable<T> query = _container.GetItemLinqQueryable<T>(true, continuationToken, options).Where(predicate);
using (var iterator = query.ToFeedIterator())
{
while (iterator.HasMoreResults && (limit == -1 || entityList.Count < limit))
{
FeedResponse<T> response = await iterator.ReadNextAsync();
items.AddRange(response.Resource);
continuationToken = response.ContinuationToken;
}
}
return (items, continuationToken);
}

Answer 1

Regarding pagination, your approach is correct. What you could do is maintain an internal records counter and adjust it based on the number of documents received.
Here's the pseudo code to do so:
public async Task<(IEnumerable<T> Results, string ContinuationToken)> ReadAsync(Expression<Func<T, bool>> predicate, int limit, string continuationToken)
{
var items = new List<T>();
int itemsRemaining = limit//Let's say you want to fetch a finite number of items.
do
{
maxItemsCount = Math.Min(itemsRemaining, 100);//assuming you want to fetch a minimum of 100 items at a time
var options = new QueryRequestOptions { MaxItemCount = maxItemsCount };
IQueryable<T> query = _container.GetItemLinqQueryable<T>(true, continuationToken, options).Where(predicate);
using (var iterator = query.ToFeedIterator())
{
while (iterator.HasMoreResults)
{
FeedResponse<T> response = await iterator.ReadNextAsync();
items.AddRange(response.Resource);
continuationToken = response.ContinuationToken;
}
}
itemsRemaining -= items.Count;
}
while (itemsRemaining > 0);
return (items, continuationToken);
}
In the case where you wish to fetch 101 records, your code will iterate at least twice. First time it will fetch 100 records and the next time it will only fetch 1 record (101 - 100).