refactor: add post-index build validation to ensure data count matches index (#6507)

#### What type of PR is this?
/kind improvement
/area core
/milestone 2.19.x

#### What this PR does / why we need it:
构建完索引后增加数据量一致性校验的步骤

#### Does this PR introduce a user-facing change?
```release-note
None
```

application/src/main/java/run/halo/app/extension/ReactiveExtensionClientImpl.java

@@ -480,7 +480,20 @@ public class ReactiveExtensionClientImpl implements ReactiveExtensionClient {
 
         private void createIndexerFor(Scheme scheme) {
             setIndexBuildingStateFor(scheme.groupVersionKind().groupKind(), true);
-            indexerFactory.createIndexerFor(scheme.type(), createExtensionIterator(scheme));
+            var iterator = createExtensionIterator(scheme);
+            indexerFactory.createIndexerFor(scheme.type(), iterator);
+            // ensure data count matches index count
+            var prefix = ExtensionStoreUtil.buildStoreNamePrefix(scheme);
+            var indexedSize = indexedQueryEngine.retrieveAll(scheme.groupVersionKind(),
+                new ListOptions(), Sort.unsorted()).size();
+            long count = client.countByNamePrefix(prefix).blockOptional().orElseThrow();
+            if (count != iterator.size() || count != indexedSize) {
+                log.error("indexedSize: {}, count in db: {}, iterate size: {}", indexedSize, count,
+                    iterator.size());
+                throw new IllegalStateException("The number of indexed records is not equal to the "
+                    + "number of records in the database, this is a serious error, please submit "
+                    + "an issue to halo.");
+            }
             setIndexBuildingStateFor(scheme.groupVersionKind().groupKind(), false);
         }
     }

application/src/main/java/run/halo/app/extension/index/DefaultExtensionIterator.java

@@ -21,6 +21,7 @@ public class DefaultExtensionIterator<E extends Extension> implements ExtensionI
     private Pageable currentPageable;
     private List<E> currentData;
     private int currentIndex;
+    private long size;
 
     public DefaultExtensionIterator(ExtensionPaginatedLister<E> lister) {
         this(PageRequest.of(0, DEFAULT_PAGE_SIZE, Sort.by("name")), lister);
@@ -61,6 +62,12 @@ public class DefaultExtensionIterator<E extends Extension> implements ExtensionI
         if (!hasNext()) {
             throw new NoSuchElementException();
         }
+        this.size++;
         return currentData.get(currentIndex++);
     }
+
+    @Override
+    public long size() {
+        return this.size;
+    }
 }

application/src/main/java/run/halo/app/extension/index/ExtensionIterator.java

@@ -14,4 +14,10 @@ import run.halo.app.extension.Extension;
  */
 public interface ExtensionIterator<E extends Extension> extends Iterator<E> {
 
+    /**
+     * Get the total size of the extensions that this iterator iterates over.
+     *
+     * @return the total size of the extensions.
+     */
+    long size();
 }

application/src/main/java/run/halo/app/extension/store/ReactiveExtensionStoreClient.java

@@ -12,6 +12,8 @@ public interface ReactiveExtensionStoreClient {
 
     Mono<Page<ExtensionStore>> listByNamePrefix(String prefix, Pageable pageable);
 
+    Mono<Long> countByNamePrefix(String prefix);
+
     /**
      * List stores by names and return data according to given names order.
      *

application/src/main/java/run/halo/app/extension/store/ReactiveExtensionStoreClientImpl.java

@@ -34,6 +34,11 @@ public class ReactiveExtensionStoreClientImpl implements ReactiveExtensionStoreC
             .map(p -> new PageImpl<>(p.getT1(), pageable, p.getT2()));
     }
 
+    @Override
+    public Mono<Long> countByNamePrefix(String prefix) {
+        return this.repository.countByNameStartingWith(prefix);
+    }
+
     @Override
     public Flux<ExtensionStore> listByNames(List<String> names) {
         ToIntFunction<ExtensionStore> comparator =