1 files changed, 215 insertions, 0 deletions
diff --git a/src/Jellyfin.Database/Jellyfin.Database.Implementations/QueryPartitionHelpers.cs b/src/Jellyfin.Database/Jellyfin.Database.Implementations/QueryPartitionHelpers.cs
new file mode 100644
index 000000000..bb66bddca
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+++ b/src/Jellyfin.Database/Jellyfin.Database.Implementations/QueryPartitionHelpers.cs
@@ -0,0 +1,215 @@
+using System;
+using System.Buffers;
+using System.Collections.Generic;
+using System.Linq;
+using System.Runtime.CompilerServices;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.EntityFrameworkCore;
+
+namespace Jellyfin.Database.Implementations;
+
+/// <summary>
+/// Contains helpers to partition EFCore queries.
+/// </summary>
+public static class QueryPartitionHelpers
+{
+    /// <summary>
+    /// Adds a callback to any directly following calls of Partition for every partition thats been invoked.
+    /// </summary>
+    /// <typeparam name="TEntity">The entity to load.</typeparam>
+    /// <param name="query">The source query.</param>
+    /// <param name="beginPartition">The callback invoked for partition before enumerating items.</param>
+    /// <param name="endPartition">The callback invoked for partition after enumerating items.</param>
+    /// <returns>A queryable that can be used to partition.</returns>
+    public static ProgressablePartitionReporting<TEntity> WithPartitionProgress<TEntity>(this IOrderedQueryable<TEntity> query, Action<int>? beginPartition = null, Action<int, TimeSpan>? endPartition = null)
+    {
+        var progressable = new ProgressablePartitionReporting<TEntity>(query);
+        progressable.OnBeginPartition = beginPartition;
+        progressable.OnEndPartition = endPartition;
+        return progressable;
+    }
+
+    /// <summary>
+    /// Adds a callback to any directly following calls of Partition for every item thats been invoked.
+    /// </summary>
+    /// <typeparam name="TEntity">The entity to load.</typeparam>
+    /// <param name="query">The source query.</param>
+    /// <param name="beginItem">The callback invoked for each item before processing.</param>
+    /// <param name="endItem">The callback invoked for each item after processing.</param>
+    /// <returns>A queryable that can be used to partition.</returns>
+    public static ProgressablePartitionReporting<TEntity> WithItemProgress<TEntity>(this IOrderedQueryable<TEntity> query, Action<TEntity, int, int>? beginItem = null, Action<TEntity, int, int, TimeSpan>? endItem = null)
+    {
+        var progressable = new ProgressablePartitionReporting<TEntity>(query);
+        progressable.OnBeginItem = beginItem;
+        progressable.OnEndItem = endItem;
+        return progressable;
+    }
+
+    /// <summary>
+    /// Adds a callback to any directly following calls of Partition for every partition thats been invoked.
+    /// </summary>
+    /// <typeparam name="TEntity">The entity to load.</typeparam>
+    /// <param name="progressable">The source query.</param>
+    /// <param name="beginPartition">The callback invoked for partition before enumerating items.</param>
+    /// <param name="endPartition">The callback invoked for partition after enumerating items.</param>
+    /// <returns>A queryable that can be used to partition.</returns>
+    public static ProgressablePartitionReporting<TEntity> WithPartitionProgress<TEntity>(this ProgressablePartitionReporting<TEntity> progressable, Action<int>? beginPartition = null, Action<int, TimeSpan>? endPartition = null)
+    {
+        progressable.OnBeginPartition = beginPartition;
+        progressable.OnEndPartition = endPartition;
+        return progressable;
+    }
+
+    /// <summary>
+    /// Adds a callback to any directly following calls of Partition for every item thats been invoked.
+    /// </summary>
+    /// <typeparam name="TEntity">The entity to load.</typeparam>
+    /// <param name="progressable">The source query.</param>
+    /// <param name="beginItem">The callback invoked for each item before processing.</param>
+    /// <param name="endItem">The callback invoked for each item after processing.</param>
+    /// <returns>A queryable that can be used to partition.</returns>
+    public static ProgressablePartitionReporting<TEntity> WithItemProgress<TEntity>(this ProgressablePartitionReporting<TEntity> progressable, Action<TEntity, int, int>? beginItem = null, Action<TEntity, int, int, TimeSpan>? endItem = null)
+    {
+        progressable.OnBeginItem = beginItem;
+        progressable.OnEndItem = endItem;
+        return progressable;
+    }
+
+    /// <summary>
+    /// Enumerates the source query by loading the entities in partitions in a lazy manner reading each item from the database as its requested.
+    /// </summary>
+    /// <typeparam name="TEntity">The entity to load.</typeparam>
+    /// <param name="partitionInfo">The source query.</param>
+    /// <param name="partitionSize">The number of elements to load per partition.</param>
+    /// <param name="cancellationToken">The cancelation token.</param>
+    /// <returns>A enumerable representing the whole of the query.</returns>
+    public static async IAsyncEnumerable<TEntity> PartitionAsync<TEntity>(this ProgressablePartitionReporting<TEntity> partitionInfo, int partitionSize, [EnumeratorCancellation] CancellationToken cancellationToken = default)
+    {
+        await foreach (var item in partitionInfo.Source.PartitionAsync(partitionSize, partitionInfo, cancellationToken).ConfigureAwait(false))
+        {
+            yield return item;
+        }
+    }
+
+    /// <summary>
+    /// Enumerates the source query by loading the entities in partitions directly into memory.
+    /// </summary>
+    /// <typeparam name="TEntity">The entity to load.</typeparam>
+    /// <param name="partitionInfo">The source query.</param>
+    /// <param name="partitionSize">The number of elements to load per partition.</param>
+    /// <param name="cancellationToken">The cancelation token.</param>
+    /// <returns>A enumerable representing the whole of the query.</returns>
+    public static async IAsyncEnumerable<TEntity> PartitionEagerAsync<TEntity>(this ProgressablePartitionReporting<TEntity> partitionInfo, int partitionSize, [EnumeratorCancellation] CancellationToken cancellationToken = default)
+    {
+        await foreach (var item in partitionInfo.Source.PartitionEagerAsync(partitionSize, partitionInfo, cancellationToken).ConfigureAwait(false))
+        {
+            yield return item;
+        }
+    }
+
+    /// <summary>
+    /// Enumerates the source query by loading the entities in partitions in a lazy manner reading each item from the database as its requested.
+    /// </summary>
+    /// <typeparam name="TEntity">The entity to load.</typeparam>
+    /// <param name="query">The source query.</param>
+    /// <param name="partitionSize">The number of elements to load per partition.</param>
+    /// <param name="progressablePartition">Reporting helper.</param>
+    /// <param name="cancellationToken">The cancelation token.</param>
+    /// <returns>A enumerable representing the whole of the query.</returns>
+    public static async IAsyncEnumerable<TEntity> PartitionAsync<TEntity>(
+        this IOrderedQueryable<TEntity> query,
+        int partitionSize,
+        ProgressablePartitionReporting<TEntity>? progressablePartition = null,
+        [EnumeratorCancellation] CancellationToken cancellationToken = default)
+    {
+        var iterator = 0;
+        int itemCounter;
+        do
+        {
+            progressablePartition?.BeginPartition(iterator);
+            itemCounter = 0;
+            await foreach (var item in query
+                .Skip(partitionSize * iterator)
+                .Take(partitionSize)
+                .AsAsyncEnumerable()
+                .WithCancellation(cancellationToken)
+                .ConfigureAwait(false))
+            {
+                progressablePartition?.BeginItem(item, iterator, itemCounter);
+                yield return item;
+                progressablePartition?.EndItem(item, iterator, itemCounter);
+                itemCounter++;
+            }
+
+            progressablePartition?.EndPartition(iterator);
+            iterator++;
+        } while (itemCounter == partitionSize && !cancellationToken.IsCancellationRequested);
+    }
+
+    /// <summary>
+    /// Enumerates the source query by loading the entities in partitions directly into memory.
+    /// </summary>
+    /// <typeparam name="TEntity">The entity to load.</typeparam>
+    /// <param name="query">The source query.</param>
+    /// <param name="partitionSize">The number of elements to load per partition.</param>
+    /// <param name="progressablePartition">Reporting helper.</param>
+    /// <param name="cancellationToken">The cancelation token.</param>
+    /// <returns>A enumerable representing the whole of the query.</returns>
+    public static async IAsyncEnumerable<TEntity> PartitionEagerAsync<TEntity>(
+        this IOrderedQueryable<TEntity> query,
+        int partitionSize,
+        ProgressablePartitionReporting<TEntity>? progressablePartition = null,
+        [EnumeratorCancellation] CancellationToken cancellationToken = default)
+    {
+        var iterator = 0;
+        int itemCounter;
+        var items = ArrayPool<TEntity>.Shared.Rent(partitionSize);
+        try
+        {
+            do
+            {
+                progressablePartition?.BeginPartition(iterator);
+                itemCounter = 0;
+                await foreach (var item in query
+                    .Skip(partitionSize * iterator)
+                    .Take(partitionSize)
+                    .AsAsyncEnumerable()
+                    .WithCancellation(cancellationToken)
+                    .ConfigureAwait(false))
+                {
+                    items[itemCounter++] = item;
+                }
+
+                for (int i = 0; i < itemCounter; i++)
+                {
+                    progressablePartition?.BeginItem(items[i], iterator, itemCounter);
+                    yield return items[i];
+                    progressablePartition?.EndItem(items[i], iterator, itemCounter);
+                }
+
+                progressablePartition?.EndPartition(iterator);
+                iterator++;
+            } while (itemCounter == partitionSize && !cancellationToken.IsCancellationRequested);
+        }
+        finally
+        {
+            ArrayPool<TEntity>.Shared.Return(items);
+        }
+    }
+
+    /// <summary>
+    /// Adds an Index to the enumeration of the async enumerable.
+    /// </summary>
+    /// <typeparam name="TEntity">The entity to load.</typeparam>
+    /// <param name="query">The source query.</param>
+    /// <returns>The source list with an index added.</returns>
+    public static async IAsyncEnumerable<(TEntity Item, int Index)> WithIndex<TEntity>(this IAsyncEnumerable<TEntity> query)
+    {
+        var index = 0;
+        await foreach (var item in query.ConfigureAwait(false))
+        {
+            yield return (item, index++);
+        }
+    }
+}