* prevent selecting all fields of entity TRevision by casting `IQue…

…ryable<TRevision>` to `IQueryable<TBaseRevision>` then project to `RevisionIdWithDuplicateIndexProjectionFactory()`

* quick exit when param `newRevisions` is empty to prevent execute sql with WHERE FALSE clause
@ `AddRevisionsWithDuplicateIndex()`

+ method `RevisionIdWithDuplicateIndexProjectionFactory()` & nested class `RevisionIdWithDuplicateIndexProjection`
* rename method `IsRevisionEntityIdEqualsExpression()` & `RevisionEntityIdSelector()` to `IsRevisionIdEqualsExpression()` & `RevisionIdSelector()`
* rename type param `TEntityId` to `TRevisionId` and constrained to `struct`
@ SaverWithRevision.cs
@ c#/crawler

c#/crawler/src/Tieba/Crawl/Saver/Post/PostSaver.cs

@@ -10,6 +10,7 @@ public abstract class PostSaver<TPost, TBaseRevision, TPostId>(
     : SaverWithRevision<TBaseRevision, TPostId>(logger), IPostSaver<TPost>
     where TPost : BasePost
     where TBaseRevision : BaseRevisionWithSplitting
+    where TPostId : struct
 {
     protected delegate void PostSaveHandler();
 

c#/crawler/src/Tieba/Crawl/Saver/Post/ReplySaver.cs

@@ -46,10 +46,13 @@ public override SaverChangeSet<ReplyPost> Save(CrawlerDbContext db)
         return changeSet;
     }
 
-    protected override Pid RevisionEntityIdSelector(BaseReplyRevision entity) => entity.Pid;
+    protected override Pid RevisionIdSelector(BaseReplyRevision entity) => entity.Pid;
     protected override Expression<Func<BaseReplyRevision, bool>>
-        IsRevisionEntityIdEqualsExpression(BaseReplyRevision newRevision) =>
+        IsRevisionIdEqualsExpression(BaseReplyRevision newRevision) =>
         existingRevision => existingRevision.Pid == newRevision.Pid;
+    protected override Expression<Func<BaseReplyRevision, RevisionIdWithDuplicateIndexProjection>>
+        RevisionIdWithDuplicateIndexProjectionFactory() =>
+        e => new() {RevisionId = e.Pid, DuplicateIndex = e.DuplicateIndex};
 
     protected override bool FieldUpdateIgnorance
         (string propName, object? oldValue, object? newValue) => propName switch

c#/crawler/src/Tieba/Crawl/Saver/Post/SubReplySaver.cs

@@ -43,10 +43,13 @@ public override SaverChangeSet<SubReplyPost> Save(CrawlerDbContext db)
         return changeSet;
     }
 
-    protected override Spid RevisionEntityIdSelector(BaseSubReplyRevision entity) => entity.Spid;
+    protected override Spid RevisionIdSelector(BaseSubReplyRevision entity) => entity.Spid;
     protected override Expression<Func<BaseSubReplyRevision, bool>>
-        IsRevisionEntityIdEqualsExpression(BaseSubReplyRevision newRevision) =>
+        IsRevisionIdEqualsExpression(BaseSubReplyRevision newRevision) =>
         existingRevision => existingRevision.Spid == newRevision.Spid;
+    protected override Expression<Func<BaseSubReplyRevision, RevisionIdWithDuplicateIndexProjection>>
+        RevisionIdWithDuplicateIndexProjectionFactory() =>
+        e => new() {RevisionId = e.Spid, DuplicateIndex = e.DuplicateIndex};
 
     protected override NullFieldsBitMask GetRevisionNullFieldBitMask(string fieldName) => 0;
 }

c#/crawler/src/Tieba/Crawl/Saver/Post/ThreadSaver.cs

@@ -35,10 +35,13 @@ public override SaverChangeSet<ThreadPost> Save(CrawlerDbContext db) =>
             th => new ThreadRevision {TakenAt = th.UpdatedAt ?? th.CreatedAt, Tid = th.Tid},
             PredicateBuilder.New<ThreadPost>(th => Posts.Keys.Contains(th.Tid)));
 
-    protected override Tid RevisionEntityIdSelector(BaseThreadRevision entity) => entity.Tid;
+    protected override Tid RevisionIdSelector(BaseThreadRevision entity) => entity.Tid;
     protected override Expression<Func<BaseThreadRevision, bool>>
-        IsRevisionEntityIdEqualsExpression(BaseThreadRevision newRevision) =>
+        IsRevisionIdEqualsExpression(BaseThreadRevision newRevision) =>
         existingRevision => existingRevision.Tid == newRevision.Tid;
+    protected override Expression<Func<BaseThreadRevision, RevisionIdWithDuplicateIndexProjection>>
+        RevisionIdWithDuplicateIndexProjectionFactory() =>
+        e => new() {RevisionId = e.Tid, DuplicateIndex = e.DuplicateIndex};
 
     protected override bool FieldUpdateIgnorance
         (string propName, object? oldValue, object? newValue) => propName switch

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

@@ -2,10 +2,11 @@
 
 namespace tbm.Crawler.Tieba.Crawl.Saver;
 
-public abstract partial class SaverWithRevision<TBaseRevision, TEntityId>(
-    ILogger<SaverWithRevision<TBaseRevision, TEntityId>> logger)
+public abstract partial class SaverWithRevision<TBaseRevision, TRevisionId>(
+    ILogger<SaverWithRevision<TBaseRevision, TRevisionId>> logger)
     : IRevisionProperties
     where TBaseRevision : BaseRevisionWithSplitting
+    where TRevisionId : struct
 {
     protected delegate void AddSplitRevisionsDelegate(CrawlerDbContext db, IEnumerable<TBaseRevision> revisions);
     protected abstract Lazy<Dictionary<Type, AddSplitRevisionsDelegate>>
@@ -15,6 +16,7 @@ protected void AddRevisionsWithDuplicateIndex<TRevision>(CrawlerDbContext db, IE
         where TRevision : TBaseRevision
     {
         var newRevisions = revisions.OfType<TRevision>().ToList();
+        if (newRevisions.Count == 0) return; // quick exit to prevent execute sql with WHERE FALSE clause
         var dbSet = db.Set<TRevision>();
         var visitor = new ReplaceParameterTypeVisitor<TBaseRevision, TRevision>();
 
@@ -26,11 +28,13 @@ protected void AddRevisionsWithDuplicateIndex<TRevision>(CrawlerDbContext db, IE
                 (predicate, newRevision) => predicate.Or(LinqKit.PredicateBuilder
                     .New<TRevision>(existingRevision => existingRevision.TakenAt == newRevision.TakenAt)
                     .And((Expression<Func<TRevision, bool>>)visitor
-                        .Visit(IsRevisionEntityIdEqualsExpression(newRevision))))))
+                        .Visit(IsRevisionIdEqualsExpression(newRevision))))))
+            .Cast<TBaseRevision>()
+            .Select(RevisionIdWithDuplicateIndexProjectionFactory())
             .ToList();
         (from existingRevision in existingRevisions
                 join newRevision in newRevisions
-                    on RevisionEntityIdSelector(existingRevision) equals RevisionEntityIdSelector(newRevision)
+                    on existingRevision.RevisionId equals RevisionIdSelector(newRevision)
                 select (existingRevision, newRevision))
             .ForEach(t =>
                 t.newRevision.DuplicateIndex = (ushort)(t.existingRevision.DuplicateIndex + 1));
@@ -39,9 +43,18 @@ on RevisionEntityIdSelector(existingRevision) equals RevisionEntityIdSelector(ne
 
     protected abstract NullFieldsBitMask GetRevisionNullFieldBitMask(string fieldName);
 
-    protected abstract TEntityId RevisionEntityIdSelector(TBaseRevision entity);
+    protected abstract TRevisionId RevisionIdSelector(TBaseRevision entity);
     protected abstract Expression<Func<TBaseRevision, bool>>
-        IsRevisionEntityIdEqualsExpression(TBaseRevision newRevision);
+        IsRevisionIdEqualsExpression(TBaseRevision newRevision);
+
+    protected abstract Expression<Func<TBaseRevision, RevisionIdWithDuplicateIndexProjection>>
+        RevisionIdWithDuplicateIndexProjectionFactory();
+    [SuppressMessage("ReSharper", "PropertyCanBeMadeInitOnly.Global")]
+    protected class RevisionIdWithDuplicateIndexProjection
+    {
+        public TRevisionId RevisionId { get; set; }
+        public ushort DuplicateIndex { get; set; }
+    }
 
     protected virtual bool ShouldIgnoreEntityRevision(string propName, PropertyEntry propEntry, EntityEntry entityEntry) => false;
     protected virtual bool FieldUpdateIgnorance(string propName, object? oldValue, object? newValue) => false;
@@ -52,7 +65,7 @@ protected abstract Expression<Func<TBaseRevision, bool>>
         _ => false
     };
 }
-public abstract partial class SaverWithRevision<TBaseRevision, TEntityId>
+public abstract partial class SaverWithRevision<TBaseRevision, TRevisionId>
 {
     protected void SaveEntitiesWithRevision<TEntity, TRevision>(
         CrawlerDbContext db,

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

@@ -14,10 +14,13 @@ protected override Lazy<Dictionary<Type, AddSplitRevisionsDelegate>>
             {typeof(UserRevision.SplitIpGeolocation), AddRevisionsWithDuplicateIndex<UserRevision.SplitIpGeolocation>}
         });
 
-    protected override Uid RevisionEntityIdSelector(BaseUserRevision entity) => entity.Uid;
+    protected override Uid RevisionIdSelector(BaseUserRevision entity) => entity.Uid;
     protected override Expression<Func<BaseUserRevision, bool>>
-        IsRevisionEntityIdEqualsExpression(BaseUserRevision newRevision) =>
+        IsRevisionIdEqualsExpression(BaseUserRevision newRevision) =>
         existingRevision => existingRevision.Uid == newRevision.Uid;
+    protected override Expression<Func<BaseUserRevision, RevisionIdWithDuplicateIndexProjection>>
+        RevisionIdWithDuplicateIndexProjectionFactory() =>
+        e => new() {RevisionId = e.Uid, DuplicateIndex = e.DuplicateIndex};
 
     protected override bool ShouldIgnoreEntityRevision(string propName, PropertyEntry propEntry, EntityEntry entityEntry)
     {