Allow system sampling in DQ (#7836)

Author: Vadim Averin

ydb/library/yql/providers/yt/gateway/lib/yt_helpers.cpp

@@ -340,12 +340,15 @@ static bool IterateRows(NYT::ITransactionPtr tx,
     }
 
     NYT::TTableReaderOptions readerOptions;
-    if (sampling && sampling->Mode == EYtSampleMode::Bernoulli) {
+    if (sampling) {
         NYT::TNode spec = NYT::TNode::CreateMap();
         spec["sampling_rate"] = sampling->Percentage / 100.;
         if (sampling->Repeat) {
             spec["sampling_seed"] = static_cast<i64>(sampling->Repeat);
         }
+        if (sampling->Mode == EYtSampleMode::System) {
+            spec["sampling_mode"] = "block";
+        }
         readerOptions.Config(spec);
     }
 

ydb/library/yql/providers/yt/provider/yql_yt_dq_hybrid.cpp

@@ -120,10 +120,6 @@ class TYtDqHybridTransformer : public TOptimizeTransformerBase {
             PushSkipStat("NonEmptyKeyFilter", nodeName);
             return false;
         }
-        auto sampleSetting = GetSetting(section.Settings().Ref(), EYtSettingType::Sample);
-        if (sampleSetting && sampleSetting->Child(1)->Child(0)->Content() == "system") {
-            return false;
-        }
         ui64 dataSize = 0ULL, dataChunks = 0ULL;
         for (const auto& path : section.Paths()) {
             const TYtPathInfo info(path);

ydb/library/yql/providers/yt/provider/yql_yt_dq_integration.cpp

@@ -426,11 +426,6 @@ class TYtDqIntegration: public TDqIntegrationBase {
                     AddMessage(ctx, info, skipIssues, State_->PassiveExecution);
                     return false;
                 }
-                auto sampleSetting = GetSetting(section.Settings().Ref(), EYtSettingType::Sample);
-                if (sampleSetting && sampleSetting->Child(1)->Child(0)->Content() == "system") {
-                    AddMessage(ctx, "system sampling", skipIssues, State_->PassiveExecution);
-                    return false;
-                }
                 for (auto path: section.Paths()) {
                     if (!path.Table().Maybe<TYtTable>()) {
                         AddMessage(ctx, "non-table path", skipIssues, State_->PassiveExecution);

ydb/library/yql/providers/yt/provider/yql_yt_mkql_compiler.cpp

@@ -395,11 +395,13 @@ TRuntimeNode BuildDqYtInputCall(
         // All sections have the same sampling settings
         if (samplingSpec.IsUndefined()) {
             if (auto sampling = GetSampleParams(section.Settings().Ref())) {
-                YQL_ENSURE(sampling->Mode != EYtSampleMode::System);
                 samplingSpec["sampling_rate"] = sampling->Percentage / 100.;
                 if (sampling->Repeat) {
                     samplingSpec["sampling_seed"] = static_cast<i64>(sampling->Repeat);
                 }
+                if (sampling->Mode == EYtSampleMode::System) {
+                    samplingSpec["sampling_mode"] = "block";
+                }
             }
         }
     }