/// <summary>
/// Gets the latest videos added to the site.
/// </summary>
public async Task<LatestVideos> GetLastestVideos(GetLatestVideos getVideos)
{
// We may need multiple queries to fill the quota
var results = new List<VideoPreview>();
// Generate a list of all the possibly bucket dates by truncating now to the day, then subtracting days from that day
// going back as many days as we're allowed to query back
DateTimeOffset nowToTheDay = DateTimeOffset.UtcNow.Truncate(TimeSpan.TicksPerDay);
var bucketDates = Enumerable.Range(0, MaxDaysInPastForLatestVideos + 1)
.Select(day => nowToTheDay.Subtract(TimeSpan.FromDays(day)));
// If we're going to include paging parameters for the first query, filter out any bucket dates that are more recent
// than the first video on the page
bool pageFirstQuery = getVideos.FirstVideoOnPageDate.HasValue && getVideos.FirstVideoOnPageVideoId.HasValue;
if (pageFirstQuery)
{
DateTimeOffset maxBucketToTheDay = getVideos.FirstVideoOnPageDate.Value.Truncate(TimeSpan.TicksPerDay);
bucketDates = bucketDates.Where(bucketToTheDay => bucketToTheDay <= maxBucketToTheDay);
}
DateTimeOffset[] bucketDatesArray = bucketDates.ToArray();
// TODO: Run queries in parallel instead of sequentially?
for (var i = 0; i < bucketDatesArray.Length; i++)
{
int recordsStillNeeded = getVideos.PageSize - results.Count;
string bucket = bucketDatesArray[i].ToString("yyyyMMdd");
// If we're processing a paged request, use the appropriate statement
PreparedStatement preparedStatement;
IStatement boundStatement;
if (pageFirstQuery && i == 0)
{
preparedStatement = await _statementCache.NoContext.GetOrAddAsync(
"SELECT * FROM latest_videos WHERE yyyymmdd = ? AND (added_date, videoid) <= (?, ?) LIMIT ?");
boundStatement = preparedStatement.Bind(bucket, getVideos.FirstVideoOnPageDate.Value, getVideos.FirstVideoOnPageVideoId.Value,
recordsStillNeeded);
}
else
{
preparedStatement = await _statementCache.NoContext.GetOrAddAsync("SELECT * FROM latest_videos WHERE yyyymmdd = ? LIMIT ?");
boundStatement = preparedStatement.Bind(bucket, recordsStillNeeded);
}
RowSet rows = await _session.ExecuteAsync(boundStatement).ConfigureAwait(false);
results.AddRange(rows.Select(MapRowToVideoPreview));
// If we've got all the records we need, we can quit querying
if (results.Count >= getVideos.PageSize)
break;
}
return new LatestVideos
{
Videos = results
};
}
/// <summary>
/// Gets the latest videos added to the site.
/// </summary>
public async Task<LatestVideos> GetLastestVideos(GetLatestVideos getVideos)
{
string[] buckets;
int bucketIndex;
string rowPagingState;
// See if we have paging state from a previous page of videos
if (TryParsePagingState(getVideos.PagingState, out buckets, out bucketIndex, out rowPagingState) == false)
{
// Generate a list of all the possibly bucket dates by truncating now to the day, then subtracting days from that day
// going back as many days as we're allowed to query back
DateTimeOffset nowToTheDay = DateTimeOffset.UtcNow.Truncate(TimeSpan.TicksPerDay);
buckets = Enumerable.Range(0, MaxDaysInPastForLatestVideos + 1)
.Select(day => nowToTheDay.Subtract(TimeSpan.FromDays(day)).ToString("yyyyMMdd"))
.ToArray();
bucketIndex = 0;
rowPagingState = null;
}
// We may need multiple queries to fill the quota so build up a list of results
var results = new List<VideoPreview>();
string nextPageState = null;
// TODO: Run queries in parallel?
while (bucketIndex < buckets.Length)
{
int recordsStillNeeded = getVideos.PageSize - results.Count;
string bucket = buckets[bucketIndex];
// Get a page of records but don't automatically load more pages when enumerating the RowSet
PreparedStatement preparedStatement = await _statementCache.NoContext.GetOrAddAsync("SELECT * FROM latest_videos WHERE yyyymmdd = ?");
IStatement boundStatement = preparedStatement.Bind(bucket)
.SetAutoPage(false)
.SetPageSize(recordsStillNeeded);
// Start from where we left off in this bucket
if (string.IsNullOrEmpty(rowPagingState) == false)
boundStatement.SetPagingState(Convert.FromBase64String(rowPagingState));
RowSet rows = await _session.ExecuteAsync(boundStatement).ConfigureAwait(false);
results.AddRange(rows.Select(MapRowToVideoPreview));
// See if we can stop querying
if (results.Count == getVideos.PageSize)
{
// Are there more rows in the current bucket?
if (rows.PagingState != null && rows.PagingState.Length > 0)
{
// Start from where we left off in this bucket if we get the next page
nextPageState = CreatePagingState(buckets, bucketIndex, Convert.ToBase64String(rows.PagingState));
}
else if (bucketIndex != buckets.Length - 1)
{
// Start from the beginning of the next bucket since we're out of rows in this one
nextPageState = CreatePagingState(buckets, bucketIndex + 1, string.Empty);
}
break;
}
bucketIndex++;
}
return new LatestVideos
{
Videos = results,
PagingState = nextPageState
};
}
