Add paging to queries

[Arithmomaniac]

Currently, RsapiDao.GetRDOs(Condition) returns a List<T> and pulls all items down at once.

In order to enable handling of large sets, it would be better to use an IEnumerable<T> for queries, and pull results by paging. The general idea can be seen in the following code snippet we have used before at Milyli:

var initialResultSet = repo.Query(query, pageLength);

foreach (var result in initialResultSet.Results)
    yield return result;

string queryToken = initialResultSet.QueryToken;

// Iterate though all remaining pages
var totalCount = initialResultSet.TotalCount;
int currentPosition = pageLength + 1;

while (currentPosition <= totalCount)
{
    var subsetResult = repo.QuerySubset(queryToken, currentPosition, pageLength);
    foreach (var result in subsetResult.Results)
        yield return result;

    currentPosition += pageLength;
}

The paging could be set as a global configuration and/or on the specific call, and fallback to "no paging" if not set.

[Arithmomaniac]

I've started work on this: Arithmomaniac/Gravity/feature/Paging_8

[ggachevski]

Very clean, very useful -- necessary, I should say.

Since I am on the direct-SQL calls wave right now (under #24), this Paging will be well handled by SQL server too, so same method signatures will remain and you will be able to do this as easily (and much more quickly) via a SQL-based implementation, soon.