fix(scan): preserve partition listing and exact-hit test coverage

Author: wangyong9999

src/paimon/core/operation/append_only_file_store_scan_test.cpp

@@ -1112,7 +1112,11 @@ TEST(AppendOnlyFileStoreScanTest, PartitionPruningAcrossCacheModes) {
                 scan->partition_filter_ = counting;
                 ASSERT_OK_AND_ASSIGN(auto plan, scan->CreatePlan());
                 ASSERT_EQ(counting->row_calls_.load(), 2);
-                ASSERT_GT(counting->stats_calls_.load(), 0);
+                if (mode == 2 && scans > 0) {
+                    ASSERT_EQ(counting->stats_calls_.load(), 0);
+                } else {
+                    ASSERT_GT(counting->stats_calls_.load(), 0);
+                }
                 ASSERT_EQ(plan->Files().size(), partition == 99 ? 0 : 1);
                 if (partition != 99) {
                     ASSERT_EQ(plan->Files()[0].Partition().GetInt(0), partition);
@@ -1190,7 +1194,7 @@ TEST(AppendOnlyFileStoreScanTest, PartitionPruningSkipsExcludedMetadataInCreateP
         if (mode == 2) {
             // Seed the complete snapshot directly: rebuilding must decode every partition.
             SnapshotLiveManifestEntries entries(8);
-            entries.Put(1, {kept, excluded});
+            entries.Put(1, {kept, excluded}, /*total_data_files=*/2);
             ASSERT_OK(scan->StoreSnapshotLiveManifestEntries(0, entries));
         }
         for (int32_t attempt = 0; attempt < 2; ++attempt) {

src/paimon/core/operation/file_store_scan.cpp

@@ -152,10 +152,11 @@ FileStoreScan::RawPlan::GroupFiles FileStoreScan::RawPlan::GroupByPartFiles(
 }
 
 Result<std::vector<PartitionEntry>> FileStoreScan::ReadPartitionEntries() const {
-    PAIMON_ASSIGN_OR_RAISE(std::optional<Snapshot> snapshot, ReadSnapshot());
-    int64_t all_data_files = 0;
+    std::optional<Snapshot> snapshot;
     std::vector<ManifestFileMeta> all_manifest_file_metas;
     std::vector<ManifestFileMeta> filtered_manifest_file_metas;
+    PAIMON_RETURN_NOT_OK(
+        ReadManifests(&snapshot, &all_manifest_file_metas, &filtered_manifest_file_metas));
     std::vector<ManifestEntry> manifest_entries;
     PAIMON_RETURN_NOT_OK(ReadFileEntries(filtered_manifest_file_metas, &manifest_entries,
                                          /*apply_scan_filter=*/true));