69 lines
2.6 KiB
C#
69 lines
2.6 KiB
C#
using System.Diagnostics.CodeAnalysis;
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using Iceshrimp.Backend.Core.Database;
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using Iceshrimp.Backend.Core.Database.Tables;
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using Iceshrimp.Backend.Core.Services;
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using Microsoft.EntityFrameworkCore;
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namespace Iceshrimp.Backend.Core.Extensions;
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public static class QueryableTimelineExtensions
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{
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// Determined empirically in 2023. Ask zotan for the spreadsheet if you're curious.
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private const int Cutoff = 250;
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private const string Prefix = "following-query-heuristic";
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public static IQueryable<Note> FilterByFollowingAndOwn(
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this IQueryable<Note> query, User user, DatabaseContext db, int heuristic
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)
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{
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return heuristic < Cutoff
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? query.FollowingAndOwnLowFreq(user, db)
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: query.Where(note => note.User == user || note.User.IsFollowedBy(user));
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}
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private static IQueryable<Note> FollowingAndOwnLowFreq(this IQueryable<Note> query, User user, DatabaseContext db)
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=> query.Where(note => db.Followings
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.Where(p => p.Follower == user)
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.Select(p => p.FolloweeId)
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.Concat(new[] { user.Id })
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.Contains(note.UserId));
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public static IQueryable<User> NeedsTimelineHeuristicUpdate(
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this IQueryable<User> query, DatabaseContext db, TimeSpan maxRemainingTtl
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)
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{
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var cutoff = DateTime.UtcNow + maxRemainingTtl;
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return query.Where(u => !db.CacheStore.Any(c => c.Key == Prefix + ':' + u.Id && c.Expiry > cutoff));
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}
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public static async Task ResetHeuristicAsync(User user, CacheService cache)
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{
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await cache.ClearAsync($"{Prefix}:{user.Id}");
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}
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public static async Task<int> GetHeuristicAsync(
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User user, DatabaseContext db, CacheService cache, bool forceUpdate = false
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)
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{
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return await cache.FetchValueAsync($"{Prefix}:{user.Id}", TimeSpan.FromHours(24), FetchHeuristicAsync,
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forceUpdate: forceUpdate);
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[SuppressMessage("ReSharper", "EntityFramework.UnsupportedServerSideFunctionCall")]
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async Task<int> FetchHeuristicAsync()
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{
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var latestNote = await db.Notes.OrderByDescending(p => p.Id)
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.Select(p => new { p.CreatedAt })
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.FirstOrDefaultAsync()
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?? new { CreatedAt = DateTime.UtcNow };
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//TODO: maybe we should express this as a ratio between matching and non-matching posts
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return await db.Notes
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.Where(p => p.CreatedAt > latestNote.CreatedAt - TimeSpan.FromDays(7))
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.FollowingAndOwnLowFreq(user, db)
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.OrderByDescending(p => p.Id)
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.Take(Cutoff + 1)
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.CountAsync();
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}
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}
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}
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