[Enhancement] reduce tablet shard read lock holding time when calc pe…

…rsistent index compact score (StarRocks#38299)

Signed-off-by: luohaha <18810541851@163.com>

be/src/storage/olap_server.cpp

@@ -404,9 +404,11 @@ void* StorageEngine::_pk_index_major_compaction_thread_callback(void* arg) {
     while (!_bg_worker_stopped.load(std::memory_order_consume)) {
         SLEEP_IN_BG_WORKER(1);
         // schedule persistent index compaction
-        _update_manager->get_pindex_compaction_mgr()->schedule([&]() {
-            return StorageEngine::instance()->tablet_manager()->pick_tablets_to_do_pk_index_major_compaction();
-        });
+        if (config::enable_pindex_minor_compaction) {
+            _update_manager->get_pindex_compaction_mgr()->schedule([&]() {
+                return StorageEngine::instance()->tablet_manager()->pick_tablets_to_do_pk_index_major_compaction();
+            });
+        }
     }
 
     return nullptr;

be/src/storage/tablet_manager.cpp

@@ -705,6 +705,7 @@ TabletSharedPtr TabletManager::find_best_tablet_to_compaction(CompactionType com
 std::vector<TabletAndScore> TabletManager::pick_tablets_to_do_pk_index_major_compaction() {
     std::vector<TabletAndScore> pick_tablets;
     // 1. pick valid tablet, which score is larger than 0
+    std::vector<TabletSharedPtr> tablet_ptr_list;
     for (const auto& tablets_shard : _tablets_shards) {
         std::shared_lock rlock(tablets_shard.lock);
         for (const auto& [tablet_id, tablet_ptr] : tablets_shard.tablet_map) {
@@ -716,15 +717,18 @@ std::vector<TabletAndScore> TabletManager::pick_tablets_to_do_pk_index_major_com
                 continue;
             }
 
-            double score = tablet_ptr->updates()->get_pk_index_write_amp_score();
-            if (score <= 0) {
-                // score == 0 means this tablet's pk index doesn't need major compaction
-                continue;
-            }
-
-            pick_tablets.emplace_back(tablet_ptr, score);
+            tablet_ptr_list.push_back(tablet_ptr);
         }
     }
+    for (const auto& tablet_ptr : tablet_ptr_list) {
+        double score = tablet_ptr->updates()->get_pk_index_write_amp_score();
+        if (score <= 0) {
+            // score == 0 means this tablet's pk index doesn't need major compaction
+            continue;
+        }
+
+        pick_tablets.emplace_back(tablet_ptr, score);
+    }
     // 2. sort tablet by score, by ascending order.
     std::sort(pick_tablets.begin(), pick_tablets.end(), [](TabletAndScore& a, TabletAndScore& b) {
         // We try to compact tablet with small write amplification score first,