/// <summary>Returns a Key Selector pair that defines the range of all items contained under this tuple</summary>
public static KeySelectorPair ToSelectorPair([NotNull] this ITuple tuple)
{
if (tuple == null)
{
throw new ArgumentNullException(nameof(tuple));
}
return(KeySelectorPair.StartsWith(tuple.ToSlice()));
}
private static async Task BenchMergeSortAsync(IFdbDatabase db, int N, int K, int B, CancellationToken ct)
{
Console.WriteLine($"=== BenchMergeSort(N={N:N0}, K={K:N0}, B={B:N0}) ===");
// create multiple lists
var location = db.GlobalSpace.Partition.ByKey("MergeSort");
await db.ClearRangeAsync(location, ct);
var sources = Enumerable.Range(0, K).Select(i => 'A' + i).ToArray();
var rnd = new Random();
// insert a number of random number lists
Console.Write($"> Inserting {(K * N):N0} items... ");
foreach (var source in sources)
{
using (var tr = db.BeginTransaction(ct))
{
var list = location.Partition.ByKey(source);
for (int i = 0; i < N; i++)
{
tr.Set(list.Keys.Encode(rnd.Next()), Slice.FromInt32(i));
}
await tr.CommitAsync();
}
}
Console.WriteLine("Done");
// merge/sort them to get only one (hopefully sorted) list
using (var tr = db.BeginTransaction(ct))
{
var mergesort = tr
.MergeSort(
sources.Select(source => KeySelectorPair.StartsWith(location.Keys.Encode(source))),
(kvp) => location.Keys.DecodeLast <int>(kvp.Key)
)
.Take(B)
.Select(kvp => location.Keys.Unpack(kvp.Key));
Console.Write($"> MergeSort with limit {B:N0}... ");
var sw = Stopwatch.StartNew();
var results = await mergesort.ToListAsync();
sw.Stop();
Console.WriteLine("Done");
Console.WriteLine($"Took {FormatTimeMilli(sw.Elapsed.TotalMilliseconds)} to merge sort {results.Count:N0} results from {K} lists of {N} items each");
//foreach (var result in results)
//{
// Console.WriteLine(result.Get<int>(-1));
//}
}
Console.WriteLine();
}
public static FdbQueryRangeExpression RangeStartsWith(Slice prefix, FdbRangeOptions options = null)
{
// starts_with('A') means ['A', B')
return(Range(KeySelectorPair.StartsWith(prefix), options));
}