refactor: using indexes to query post lists

api/src/main/java/run/halo/app/core/extension/content/Snapshot.java

@@ -84,4 +84,7 @@ public static boolean isBaseSnapshot(@NonNull Snapshot snapshot) {
         return Boolean.parseBoolean(annotations.get(Snapshot.KEEP_RAW_ANNO));
     }
 
+    public static String toSubjectRefKey(Ref subjectRef) {
+        return subjectRef.getGroup() + "/" + subjectRef.getKind() + "/" + subjectRef.getName();
+    }
 }

api/src/main/java/run/halo/app/extension/ListResult.java

@@ -8,6 +8,7 @@
 import java.util.Collections;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Optional;
 import java.util.function.Supplier;
 import java.util.stream.Stream;
 import lombok.Data;
@@ -144,6 +145,15 @@ public static <T> List<T> subList(List<T> list, int page, int size) {
         return listSort;
     }
 
+    /**
+     * Gets the first element of the list result.
+     */
+    public static <T> Optional<T> first(ListResult<T> listResult) {
+        return Optional.ofNullable(listResult)
+            .map(ListResult::getItems)
+            .map(list -> list.isEmpty() ? null : list.get(0));
+    }
+
     @Override
     public Stream<T> get() {
         return items.stream();

api/src/main/java/run/halo/app/extension/router/selector/FieldSelector.java

@@ -1,15 +1,26 @@
 package run.halo.app.extension.router.selector;
 
 import java.util.Objects;
+import org.springframework.lang.NonNull;
+import org.springframework.util.Assert;
 import run.halo.app.extension.index.query.Query;
 import run.halo.app.extension.index.query.QueryFactory;
 
-public record FieldSelector(Query query) {
+public record FieldSelector(@NonNull Query query) {
     public FieldSelector(Query query) {
         this.query = Objects.requireNonNullElseGet(query, QueryFactory::all);
     }
 
     public static FieldSelector of(Query query) {
         return new FieldSelector(query);
     }
+
+    public static FieldSelector all() {
+        return new FieldSelector(QueryFactory.all());
+    }
+
+    public FieldSelector andQuery(Query other) {
+        Assert.notNull(other, "Query must not be null");
+        return of(QueryFactory.and(query(), other));
+    }
 }

api/src/main/java/run/halo/app/extension/router/selector/LabelSelector.java

@@ -24,6 +24,22 @@ public boolean test(@NonNull Map<String, String> labels) {
             .allMatch(matcher -> matcher.test(labels.get(matcher.getKey())));
     }
 
+    /**
+     * Returns a new label selector that is the result of ANDing the current selector with the
+     * given selector.
+     *
+     * @param other the selector to AND with
+     * @return a new label selector
+     */
+    public LabelSelector and(LabelSelector other) {
+        var labelSelector = new LabelSelector();
+        var matchers = new ArrayList<SelectorMatcher>();
+        matchers.addAll(this.matchers);
+        matchers.addAll(other.matchers);
+        labelSelector.setMatchers(matchers);
+        return labelSelector;
+    }
+
     public static LabelSelectorBuilder builder() {
         return new LabelSelectorBuilder();
     }

api/src/main/java/run/halo/app/extension/router/selector/SelectorUtil.java

@@ -96,6 +96,8 @@ public static ListOptions labelAndFieldSelectorToListOptions(
         listOptions.setLabelSelector(new LabelSelector().setMatchers(labelMatchers));
         if (!fieldQuery.isEmpty()) {
             listOptions.setFieldSelector(FieldSelector.of(QueryFactory.and(fieldQuery)));
+        } else {
+            listOptions.setFieldSelector(FieldSelector.all());
         }
         return listOptions;
     }