* move the update ignorance for BasePost.AuthorUid to a new method …

…`GlobalFieldUpdateIgnorance()`

* move method `IsLatestReplierUser()` to the only implement in `UserSaver` of a new method `ShouldIgnoreEntityRevision()`
@ SaverWithRevision.cs

+ static prop `Instance` @ `User.EqualityComparer`
* move placeholder implement of virtual method `RevisionWithSplitting.IsAllFieldsIsNullExceptSplit()` to its parent declare in `BaseRevisionWithSplitting`
- static field `_dataSourceSingleton` @ CrawlerDbContext.cs
@ crawler

+ static prop `Instance` @ `ByteArrayEqualityComparer`
+ static prop `Instance` @ `NpgsqlCamelCaseNameTranslator`
- merge method `GetNpgsqlDataSourceFactory()` with `GetNpgsqlDataSource` and convert it from `protected virtual` to `private` @ TbmDbContext.cs
@ shared
@ c#

c#/crawler/src/Db/CrawlerDbContext.cs

@@ -10,8 +10,6 @@ namespace tbm.Crawler.Db;
 public class CrawlerDbContext(ILogger<CrawlerDbContext> logger, Fid fid = 0)
     : TbmDbContext<CrawlerDbContext.ModelCacheKeyFactory>(logger)
 {
-    private static Lazy<NpgsqlDataSource>? _dataSourceSingleton;
-
     public delegate CrawlerDbContext NewDefault();
     public delegate CrawlerDbContext New(Fid fid);
 
@@ -108,11 +106,7 @@ protected override void OnModelCreating(ModelBuilder b)
     }
 
     protected override void OnBuildingNpgsqlDataSource(NpgsqlDataSourceBuilder builder) =>
-        builder.MapEnum<PostType>("tbmcr_triggeredBy", new NpgsqlCamelCaseNameTranslator());
-
-    [SuppressMessage("Critical Code Smell", "S2696:Instance members should not write to \"static\" fields")]
-    protected override Lazy<NpgsqlDataSource> GetNpgsqlDataSource(string? connectionString) =>
-        _dataSourceSingleton ??= GetNpgsqlDataSourceFactory(connectionString);
+        builder.MapEnum<PostType>("tbmcr_triggeredBy", NpgsqlCamelCaseNameTranslator.Instance);
 
     public class ModelCacheKeyFactory : IModelCacheKeyFactory
     { // https://stackoverflow.com/questions/51864015/entity-framework-map-model-class-to-table-at-run-time/51899590#51899590

c#/crawler/src/Db/Revision/Splitting/BaseRevisionWithSplitting.cs

@@ -6,5 +6,5 @@ public abstract class BaseRevisionWithSplitting : RowVersionedEntity
 {
     public uint TakenAt { get; set; }
     public ushort? NullFieldsBitMask { get; set; }
-    public abstract bool IsAllFieldsIsNullExceptSplit();
+    public virtual bool IsAllFieldsIsNullExceptSplit() => throw new NotSupportedException();
 }

c#/crawler/src/Db/Revision/Splitting/RevisionWithSplitting.cs

@@ -5,7 +5,6 @@ public abstract class RevisionWithSplitting<TBaseRevision> : BaseRevisionWithSpl
 {
     private readonly Dictionary<Type, TBaseRevision> _splitEntities = [];
     public IReadOnlyDictionary<Type, TBaseRevision> SplitEntities => _splitEntities;
-    public override bool IsAllFieldsIsNullExceptSplit() => throw new NotSupportedException();
 
     protected TValue? GetSplitEntityValue<TSplitEntity, TValue>
         (Func<TSplitEntity, TValue?> valueSelector)

c#/crawler/src/Db/User.cs

@@ -17,12 +17,14 @@ public class User : TimestampedEntity
 
     public class EqualityComparer : EqualityComparer<User>
     {
+        public static EqualityComparer Instance { get; } = new();
+
         public override bool Equals(User? x, User? y) => x == y || (
             x != null && y != null &&
             (x.Uid, x.Name, x.DisplayName, x.Portrait, x.PortraitUpdatedAt, x.Gender, x.FansNickname, x.IpGeolocation)
             == (y.Uid, y.Name, y.DisplayName, y.Portrait, y.PortraitUpdatedAt, y.Gender, y.FansNickname, y.IpGeolocation)
             && (x.Icon == y.Icon
-                || (x.Icon != null && y.Icon != null && new ByteArrayEqualityComparer().Equals(x.Icon, y.Icon))));
+                || (x.Icon != null && y.Icon != null && ByteArrayEqualityComparer.Instance.Equals(x.Icon, y.Icon))));
 
         public override int GetHashCode(User obj)
         {

c#/crawler/src/Tieba/Crawl/Saver/ReplySignatureSaver.cs

@@ -49,7 +49,7 @@ select s
     public sealed record UniqueSignature(uint Id, byte[] XxHash3)
     {
         public bool Equals(UniqueSignature? other) =>
-            other != null && Id == other.Id && new ByteArrayEqualityComparer().Equals(XxHash3, other.XxHash3);
+            other != null && Id == other.Id && ByteArrayEqualityComparer.Instance.Equals(XxHash3, other.XxHash3);
 
         public override int GetHashCode()
         {

c#/crawler/src/Tieba/Crawl/Saver/SaverWithRevision.cs

@@ -11,10 +11,16 @@ public abstract class SaverWithRevision<TBaseRevision>
     protected abstract IReadOnlyDictionary<Type, AddRevisionDelegate> AddRevisionDelegatesKeyBySplitEntityType { get; }
     protected abstract NullFieldsBitMask GetRevisionNullFieldBitMask(string fieldName);
 
+    private static bool GlobalFieldUpdateIgnorance(string propName, object? oldValue, object? newValue) => propName switch
+    { // possible rarely respond with the protoBuf default value 0
+        nameof(BasePost.AuthorUid) when newValue is 0L && oldValue is not null => true,
+        _ => false
+    };
     protected virtual bool FieldUpdateIgnorance(string propName, object? oldValue, object? newValue) => false;
     protected virtual bool FieldRevisionIgnorance(string propName, object? oldValue, object? newValue) => false;
     protected virtual bool UserFieldUpdateIgnorance(string propName, object? oldValue, object? newValue) => false;
     protected virtual bool UserFieldRevisionIgnorance(string propName, object? oldValue, object? newValue) => false;
+    protected virtual bool ShouldIgnoreEntityRevision(string propName, PropertyEntry propEntry, EntityEntry entityEntry) => false;
 
     protected void SaveEntitiesWithRevision<TEntity, TRevision>(
         CrawlerDbContext db,
@@ -51,15 +57,14 @@ bool IsTimestampingFieldName(string name) => name is nameof(BasePost.LastSeenAt)
             {
                 var pName = p.Metadata.Name;
                 if (!p.IsModified || IsTimestampingFieldName(pName)) continue;
+                if (ShouldIgnoreEntityRevision(pName, p, entityEntry)) return null;
 
                 if (FieldUpdateIgnorance(
                         pName, p.OriginalValue, p.CurrentValue)
+                    || SaverWithRevision<TBaseRevision>.GlobalFieldUpdateIgnorance(
+                        pName, p.OriginalValue, p.CurrentValue)
                     || (entryIsUser && UserFieldUpdateIgnorance(
-                        pName, p.OriginalValue, p.CurrentValue))
-
-                    // possible rarely respond with the protoBuf default value 0
-                    || (pName == nameof(BasePost.AuthorUid)
-                        && p is { CurrentValue: 0L, OriginalValue: not null}))
+                        pName, p.OriginalValue, p.CurrentValue)))
                 {
                     p.IsModified = false;
                     continue; // skip following revision check
@@ -70,8 +75,6 @@ bool IsTimestampingFieldName(string name) => name is nameof(BasePost.LastSeenAt)
                         pName, p.OriginalValue, p.CurrentValue)))
                     continue;
 
-                if (IsLatestReplierUser(pName, p, entityEntry)) return null;
-
                 if (!IRevisionProperties.Cache[typeof(TRevision)].TryGetValue(pName, out var revisionProp))
                 {
                     object? ToHexWhenByteArray(object? value) =>
@@ -118,25 +121,4 @@ bool IsTimestampingFieldName(string name) => name is nameof(BasePost.LastSeenAt)
             .GroupBy(pair => pair.Key, pair => pair.Value)
             .ForEach(g => AddRevisionDelegatesKeyBySplitEntityType[g.Key](db, g));
     }
-
-    private static bool IsLatestReplierUser(string pName, PropertyEntry p, EntityEntry entry)
-    {
-        // ThreadCrawlFacade.ParseLatestRepliers() will save users with empty string as portrait
-        // they may soon be updated by (sub) reply crawler after it find out the latest reply
-        // so we should ignore its revision update for all fields
-        // ignore entire record is not possible via IFieldChangeIgnorance.GlobalFieldChangeIgnorance.Revision()
-        // since it can only determine one field at the time
-        if (pName != nameof(User.Portrait) || p.OriginalValue is not "") return false;
-
-        // invokes OriginalValues.ToObject() to get a new instance
-        // since entityInTracking is reference to the changed one
-        var user = (User)entry.OriginalValues.ToObject();
-
-        // create another user instance with only fields of latest replier filled
-        var latestReplier = User.CreateLatestReplier(user.Uid, user.Name, user.DisplayName);
-
-        // if they are same by fields values, the original one is the latest replier
-        // that previously generated by ParseLatestRepliers()
-        return new User.EqualityComparer().Equals(user, latestReplier);
-    }
 }

c#/crawler/src/Tieba/Crawl/Saver/UserSaver.cs

@@ -1,3 +1,5 @@
+using Microsoft.EntityFrameworkCore.ChangeTracking;
+
 namespace tbm.Crawler.Tieba.Crawl.Saver;
 
 public partial class UserSaver
@@ -31,6 +33,27 @@ protected override bool FieldRevisionIgnorance
         _ => false
     };
 
+    protected override bool ShouldIgnoreEntityRevision(string propName, PropertyEntry propEntry, EntityEntry entityEntry)
+    {
+        // ThreadCrawlFacade.ParseLatestRepliers() will save users with empty string as portrait
+        // they may soon be updated by (sub) reply crawler after it find out the latest reply
+        // so we should ignore its revision update for all fields
+        // ignore entire record is not possible via IFieldChangeIgnorance.GlobalFieldChangeIgnorance.Revision()
+        // since it can only determine one field at the time
+        if (propName != nameof(User.Portrait) || propEntry.OriginalValue is not "") return false;
+
+        // invokes OriginalValues.ToObject() to get a new instance
+        // since entityInTracking is reference to the changed one
+        var user = (User)entityEntry.OriginalValues.ToObject();
+
+        // create another user instance with only fields of latest replier filled
+        var latestReplier = User.CreateLatestReplier(user.Uid, user.Name, user.DisplayName);
+
+        // if they are same by fields values, the original one is the latest replier
+        // that previously generated by ParseLatestRepliers()
+        return User.EqualityComparer.Instance.Equals(user, latestReplier);
+    }
+
     protected override Dictionary<Type, AddRevisionDelegate>
         AddRevisionDelegatesKeyBySplitEntityType { get; } = new()
     {

c#/imagePipeline/src/Consumer/MetadataConsumer.cs

@@ -106,7 +106,7 @@ public MetadataConsumer
         return new()
         {
             XxHash3 = xxHash3,
-            RawBytes = commonXxHash3ToIgnore.Contains(xxHash3, new ByteArrayEqualityComparer()) ? null : rawBytes
+            RawBytes = commonXxHash3ToIgnore.Contains(xxHash3, ByteArrayEqualityComparer.Instance) ? null : rawBytes
         };
     }
 

c#/shared/src/ByteArrayEqualityComparer.cs

@@ -2,6 +2,8 @@ namespace tbm.Shared;
 
 public class ByteArrayEqualityComparer : EqualityComparer<byte[]>
 {
+    public static ByteArrayEqualityComparer Instance { get; } = new();
+
     public override bool Equals(byte[]? x, byte[]? y) =>
         x == y || (x != null && y != null && x.AsSpan().SequenceEqual(y.AsSpan()));
 

c#/shared/src/Db/NpgsqlCamelCaseNameTranslator.cs

@@ -4,6 +4,8 @@ namespace tbm.Shared.Db;
 
 public class NpgsqlCamelCaseNameTranslator : INpgsqlNameTranslator
 {
+    public static NpgsqlCamelCaseNameTranslator Instance { get; } = new();
+
     public string TranslateTypeName(string clrName) => TranslateMemberName(clrName);
 
     /// <see>https://github.com/efcore/EFCore.NamingConventions/blob/0d19b13a8e62ec20779c3cca03c27f200b5b7458/EFCore.NamingConventions/Internal/CamelCaseNameRewriter.cs#L13</see>

c#/shared/src/Db/TbmDbContext.cs

@@ -96,6 +96,9 @@ public class TbmDbContext<TModelCacheKeyFactory>(ILogger<TbmDbContext<TModelCach
     : TbmDbContext(logger)
     where TModelCacheKeyFactory : class, IModelCacheKeyFactory
 {
+    [SuppressMessage("ReSharper", "StaticMemberInGenericType")]
+    private static Lazy<NpgsqlDataSource>? _dataSourceSingleton;
+
     // ReSharper disable once UnusedAutoPropertyAccessor.Global
     public required IConfiguration Config { private get; init; }
     public DbSet<ImageInReply> ImageInReplies => Set<ImageInReply>();
@@ -139,13 +142,11 @@ protected override void OnModelCreating(ModelBuilder b)
 
     protected virtual void OnBuildingNpgsqlDataSource(NpgsqlDataSourceBuilder builder) { }
 
-    protected virtual Lazy<NpgsqlDataSource> GetNpgsqlDataSource(string? connectionString) =>
-        throw new NotSupportedException();
-
-    protected Lazy<NpgsqlDataSource> GetNpgsqlDataSourceFactory(string? connectionString) => new(() =>
-    {
-        var dataSourceBuilder = new NpgsqlDataSourceBuilder(connectionString);
-        OnBuildingNpgsqlDataSource(dataSourceBuilder);
-        return dataSourceBuilder.Build();
-    });
+    private Lazy<NpgsqlDataSource> GetNpgsqlDataSource(string? connectionString) =>
+        _dataSourceSingleton ??= new(() =>
+        {
+            var dataSourceBuilder = new NpgsqlDataSourceBuilder(connectionString);
+            OnBuildingNpgsqlDataSource(dataSourceBuilder);
+            return dataSourceBuilder.Build();
+        });
 }