optimize(backend): optimize /api/posts/latest-reply

resolves #554

backend/src/main/java/com/openisle/config/PostDataSyncer.java

@@ -0,0 +1,43 @@
+package com.openisle.config;
+
+import com.openisle.service.CommentService;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.boot.CommandLineRunner;
+import org.springframework.jdbc.core.JdbcTemplate;
+import org.springframework.jdbc.core.RowMapper;
+import org.springframework.stereotype.Component;
+
+import java.time.LocalDateTime;
+import java.util.List;
+
+/**
+ *
+ */
+@Slf4j
+@RequiredArgsConstructor
+@Component
+public class PostDataSyncer  implements CommandLineRunner {
+
+    private final JdbcTemplate jdbcTemplate;
+    private final CommentService commentService;
+    @Override
+    public void run(String... args) {
+
+        // 我们需要处理下历史数据，一些帖子的评论数量和最后回复时间可能为空
+        // 系统下次升级后，可以删掉这些代码
+        List<Long> oldPosts = jdbcTemplate.query("""
+                        select distinct p.id from posts p join comments c on p.id = c.post_id
+                        where last_reply_at is null
+                      """,
+                 (rs, rowNum) -> rs.getLong(1));
+
+        log.info("found {} old posts: {}", oldPosts.size(), oldPosts);
+        oldPosts.forEach(postId -> {
+            long cnt = commentService.countComments(postId);
+            LocalDateTime lastCommentTime = commentService.getLastCommentTime(postId);
+            jdbcTemplate.update("update posts set comment_count = ?, last_reply_at = ? where id = ?", cnt, lastCommentTime, postId);
+            log.info("update post {} success", postId);
+        });
+    }
+}

backend/src/main/java/com/openisle/mapper/PostMapper.java

@@ -60,7 +60,8 @@ public class PostMapper {
         dto.setCategory(categoryMapper.toDto(post.getCategory()));
         dto.setTags(post.getTags().stream().map(tagMapper::toDto).collect(Collectors.toList()));
         dto.setViews(post.getViews());
-        dto.setCommentCount(commentService.countComments(post.getId()));
+        //dto.setCommentCount(commentService.countComments(post.getId()));
+        dto.setCommentCount(post.getCommentCount());
         dto.setStatus(post.getStatus());
         dto.setPinnedAt(post.getPinnedAt());
 

backend/src/main/java/com/openisle/model/Post.java

@@ -67,4 +67,10 @@ public class Post {
     @Column
     private LocalDateTime pinnedAt;
 
+    @Column(nullable = false)
+    private long commentCount = 0;
+
+    @Column
+    private LocalDateTime lastReplyAt;
+
 }

backend/src/main/java/com/openisle/service/CommentService.java

@@ -58,6 +58,11 @@ public class CommentService {
         comment.setContent(content);
         comment = commentRepository.save(comment);
         log.debug("Comment {} saved for post {}", comment.getId(), postId);
+
+        post.setCommentCount(post.getCommentCount() + 1);
+        post.setLastReplyAt(LocalDateTime.now());
+        postRepository.save(post);
+
         imageUploader.addReferences(imageUploader.extractUrls(content));
         if (!author.getId().equals(post.getAuthor().getId())) {
             notificationService.createNotification(post.getAuthor(), NotificationType.COMMENT_REPLY, post, comment, null, null, null, null);
@@ -101,6 +106,13 @@ public class CommentService {
         comment.setContent(content);
         comment = commentRepository.save(comment);
         log.debug("Reply {} saved for parent {}", comment.getId(), parentId);
+
+        Post post = postRepository.findById(parent.getPost().getId())
+                .orElseThrow(() -> new com.openisle.exception.NotFoundException("Post not found"));
+        post.setCommentCount(post.getCommentCount() + 1);
+        post.setLastReplyAt(LocalDateTime.now());
+        postRepository.save(post);
+
         imageUploader.addReferences(imageUploader.extractUrls(content));
         if (!author.getId().equals(parent.getAuthor().getId())) {
             notificationService.createNotification(parent.getAuthor(), NotificationType.COMMENT_REPLY, parent.getPost(), comment, null, null, null, null);

backend/src/main/java/com/openisle/service/PostService.java

@@ -612,7 +612,7 @@ public class PostService {
                 .sorted(java.util.Comparator
                         .comparing(Post::getPinnedAt, java.util.Comparator.nullsLast(java.util.Comparator.reverseOrder()))
                         .thenComparing(p -> {
-                            java.time.LocalDateTime t = commentRepository.findLastCommentTime(p);
+                            java.time.LocalDateTime t = p.getLastReplyAt();
                             return t != null ? t : p.getCreatedAt();
                         }, java.util.Comparator.nullsLast(java.util.Comparator.reverseOrder())))
                 .toList();