Optimize snapshot acquiring when read write statement is spliting

src/observer/table/ob_table_rpc_processor.cpp

@@ -400,6 +400,7 @@ int ObTableApiProcessorBase::setup_tx_snapshot_(transaction::ObTxDesc &trans_des
     SCN weak_read_snapshot;
     if (OB_FAIL(txs->get_weak_read_snapshot_version(
               -1, // system variable : max read stale time for user
+              false,
               weak_read_snapshot))) {
       LOG_WARN("fail to get weak read snapshot", K(ret));
     } else {

src/share/parameter/ob_parameter_seed.ipp

@@ -264,7 +264,7 @@ DEF_TIME_WITH_CHECKER(max_stale_time_for_weak_consistency, OB_TENANT_PARAMETER,
                       "the max data stale time that cluster weak read version behind current timestamp,"
                       "no smaller than weak_read_version_refresh_interval, range: [5s, +∞)",
                       ObParameterAttr(Section::TENANT, Source::DEFAULT, EditLevel::DYNAMIC_EFFECTIVE));
-DEF_BOOL(enable_monotonic_weak_read, OB_TENANT_PARAMETER, "true",
+DEF_BOOL(enable_monotonic_weak_read, OB_TENANT_PARAMETER, "false",
          "specifies observer supportting atomicity and monotonic order read",
         ObParameterAttr(Section::TENANT, Source::DEFAULT, EditLevel::DYNAMIC_EFFECTIVE));
 DEF_DBL(server_cpu_quota_min, OB_CLUSTER_PARAMETER, "1", "[1,16]",

src/sql/ob_sql_trans_control.cpp

@@ -656,7 +656,10 @@ int ObSqlTransControl::stmt_setup_snapshot_(ObSQLSessionInfo *session,
   auto &snapshot = das_ctx.get_snapshot();
   if (cl == ObConsistencyLevel::WEAK || cl == ObConsistencyLevel::FROZEN) {
     SCN snapshot_version = SCN::min_scn();
+    const bool local_single_ls = plan->is_local_plan() &&
+                                 OB_PHY_PLAN_LOCAL == plan->get_location_type();
     if (OB_FAIL(txs->get_weak_read_snapshot_version(session->get_ob_max_read_stale_time(),
+                                                    local_single_ls,
                                                     snapshot_version))) {
       TRANS_LOG(WARN, "get weak read snapshot fail", KPC(txs));
       int64_t stale_time = session->get_ob_max_read_stale_time();

src/storage/concurrency_control/ob_multi_version_garbage_collector.cpp

@@ -444,6 +444,7 @@ int ObMultiVersionGarbageCollector::study_min_unallocated_WRS(
 
   if (OB_FAIL(MTL(transaction::ObTransService*)->get_weak_read_snapshot_version(
                 -1, // system variable : max read stale time for user
+                false,
                 min_unallocated_WRS))) {
     MVCC_LOG(WARN, "fail to get weak read snapshot", K(ret));
     if (OB_REPLICA_NOT_READABLE == ret) {

src/storage/tx/ob_tx_api.cpp

@@ -716,6 +716,7 @@ int ObTransService::get_ls_read_snapshot_version(const share::ObLSID &local_ls_i
 }
 
 int ObTransService::get_weak_read_snapshot_version(const int64_t max_read_stale_us_for_user,
+                                                   const bool local_single_ls,
                                                    SCN &snapshot)
 {
   int ret = OB_SUCCESS;
@@ -724,10 +725,16 @@ int ObTransService::get_weak_read_snapshot_version(const int64_t max_read_stale_
 
     // server weak read version
   if (!ObWeakReadUtil::enable_monotonic_weak_read(tenant_id_)) {
+    if (local_single_ls) {
       if (OB_FAIL(GCTX.weak_read_service_->get_server_version(tenant_id_, wrs_scn))) {
         TRANS_LOG(WARN, "get server read snapshot fail", K(ret), KPC(this));
       }
       monotinic_read = false;
+    } else {
+      if (OB_FAIL(GCTX.weak_read_service_->get_cluster_version(tenant_id_, wrs_scn))) {
+        TRANS_LOG(WARN, "get weak read snapshot fail", K(ret), KPC(this));
+      }
+    }
     // wrs cluster version
   } else if (OB_FAIL(GCTX.weak_read_service_->get_cluster_version(tenant_id_, wrs_scn))) {
     TRANS_LOG(WARN, "get weak read snapshot fail", K(ret), KPC(this));

src/storage/tx/ob_tx_api.h

@@ -235,6 +235,7 @@ int get_ls_read_snapshot_version(const share::ObLSID &local_ls_id,
  * OB_REPLICA_NOT_READABLE - snapshot is too stale
  */
 int get_weak_read_snapshot_version(const int64_t max_read_stale_time,
+                                   const bool local_single_ls,
                                    share::SCN &snapshot_version);
 /*
  * release_snapshot - release snapshot