add min scan thread num for workload group's scan thread

Author: wangbo

be/src/common/config.cpp

@@ -250,6 +250,7 @@ DEFINE_Validator(doris_scanner_thread_pool_thread_num, [](const int config) -> b
     }
     return true;
 });
+DEFINE_Int32(doris_scanner_min_thread_pool_thread_num, "8");
 DEFINE_Int32(remote_split_source_batch_size, "10240");
 DEFINE_Int32(doris_max_remote_scanner_thread_pool_thread_num, "-1");
 // number of olap scanner thread pool queue size

be/src/common/config.h

@@ -299,6 +299,7 @@ DECLARE_mInt64(doris_blocking_priority_queue_wait_timeout_ms);
 // number of scanner thread pool size for olap table
 // and the min thread num of remote scanner thread pool
 DECLARE_mInt32(doris_scanner_thread_pool_thread_num);
+DECLARE_mInt32(doris_scanner_min_thread_pool_thread_num);
 // number of batch size to fetch the remote split source
 DECLARE_mInt32(remote_split_source_batch_size);
 // max number of remote scanner thread pool size

be/src/runtime/workload_group/workload_group.cpp

@@ -316,7 +316,7 @@ WorkloadGroupInfo WorkloadGroupInfo::parse_topic_info(
     }
 
     // 11 min remote scan thread num
-    int min_remote_scan_thread_num = vectorized::ScannerScheduler::get_remote_scan_thread_num();
+    int min_remote_scan_thread_num = config::doris_scanner_min_thread_pool_thread_num;
     if (tworkload_group_info.__isset.min_remote_scan_thread_num &&
         tworkload_group_info.min_remote_scan_thread_num > 0) {
         min_remote_scan_thread_num = tworkload_group_info.min_remote_scan_thread_num;
@@ -396,7 +396,7 @@ void WorkloadGroup::upsert_task_scheduler(WorkloadGroupInfo* tg_info, ExecEnv* e
                 std::make_unique<vectorized::SimplifiedScanScheduler>("Scan_" + tg_name,
                                                                       cg_cpu_ctl_ptr);
         Status ret = scan_scheduler->start(config::doris_scanner_thread_pool_thread_num,
-                                           config::doris_scanner_thread_pool_thread_num,
+                                           config::doris_scanner_min_thread_pool_thread_num,
                                            config::doris_scanner_thread_pool_queue_size);
         if (ret.ok()) {
             _scan_task_sched = std::move(scan_scheduler);
@@ -415,7 +415,8 @@ void WorkloadGroup::upsert_task_scheduler(WorkloadGroupInfo* tg_info, ExecEnv* e
         std::unique_ptr<vectorized::SimplifiedScanScheduler> remote_scan_scheduler =
                 std::make_unique<vectorized::SimplifiedScanScheduler>("RScan_" + tg_name,
                                                                       cg_cpu_ctl_ptr);
-        Status ret = remote_scan_scheduler->start(remote_max_thread_num, remote_max_thread_num,
+        Status ret = remote_scan_scheduler->start(remote_max_thread_num,
+                                                  config::doris_scanner_min_thread_pool_thread_num,
                                                   remote_scan_thread_queue_size);
         if (ret.ok()) {
             _remote_scan_task_sched = std::move(remote_scan_scheduler);