feat(kqp): add pragma for sequential reads

ydb/core/kqp/opt/physical/kqp_opt_phy_source.cpp

@@ -110,6 +110,11 @@ TExprBase KqpRewriteReadTable(TExprBase node, TExprContext& ctx, const TKqpOptim
         matched->Settings = settings.BuildNode(ctx, matched->Settings.Pos());
     }
 
+    if (kqpCtx.Config->HasMaxSequentialReadsInFlight()) {
+        settings.SequentialInFlight = *kqpCtx.Config->MaxSequentialReadsInFlight.Get();
+        matched->Settings = settings.BuildNode(ctx, matched->Settings.Pos());
+    }
+
     TVector<TExprBase> inputs;
     TVector<TCoArgument> args;
     TNodeOnNodeOwnedMap argReplaces;

ydb/core/kqp/provider/yql_kikimr_settings.cpp

@@ -95,6 +95,7 @@ TKikimrConfiguration::TKikimrConfiguration() {
     REGISTER_SETTING(*this, MaxDPccpDPTableSize);
 
     REGISTER_SETTING(*this, MaxTasksPerStage);
+    REGISTER_SETTING(*this, MaxSequentialReadsInFlight);
 
     /* Runtime */
     REGISTER_SETTING(*this, ScanQuery);
@@ -147,6 +148,10 @@ bool TKikimrSettings::HasOptUseFinalizeByKey() const {
     return GetFlagValue(OptUseFinalizeByKey.Get().GetOrElse(true)) != EOptionalFlag::Disabled;
 }
 
+bool TKikimrSettings::HasMaxSequentialReadsInFlight() const {
+    return !MaxSequentialReadsInFlight.Get().Empty();
+}
+
 EOptionalFlag TKikimrSettings::GetOptPredicateExtract() const {
     return GetOptionalFlagValue(OptEnablePredicateExtract.Get());
 }

ydb/core/kqp/provider/yql_kikimr_settings.h

@@ -72,6 +72,7 @@ struct TKikimrSettings {
 
 
     NCommon::TConfSetting<ui32, false> MaxTasksPerStage;
+    NCommon::TConfSetting<ui32, false> MaxSequentialReadsInFlight;
 
     /* Runtime */
     NCommon::TConfSetting<bool, true> ScanQuery;
@@ -88,6 +89,7 @@ struct TKikimrSettings {
     bool HasOptEnableOlapPushdown() const;
     bool HasOptEnableOlapProvideComputeSharding() const;
     bool HasOptUseFinalizeByKey() const;
+    bool HasMaxSequentialReadsInFlight() const;
 
     EOptionalFlag GetOptPredicateExtract() const;
     EOptionalFlag GetUseLlvm() const;

ydb/core/kqp/ut/opt/kqp_ne_ut.cpp

@@ -4235,7 +4235,46 @@ Y_UNIT_TEST_SUITE(KqpNewEngine) {
         }
     }
 
+    Y_UNIT_TEST_TWIN(SequentialReadsPragma, Enabled) {
+        TKikimrRunner kikimr;
+        auto db = kikimr.GetTableClient();
+        auto session = db.CreateSession().GetValueSync().GetSession();
+
+        NYdb::NTable::TExecDataQuerySettings querySettings;
+        querySettings.CollectQueryStats(ECollectQueryStatsMode::Profile);
+
+        TString query = R"(
+            SELECT Key, Data FROM `/Root/EightShard` 
+                WHERE Text = "Value1" 
+                ORDER BY Key 
+                LIMIT 1;
+        )";
+
+        if (Enabled) {
+            TString pragma = TString(R"(
+                PRAGMA ydb.MaxSequentialReadsInFlight = "1";
+            )");
 
+            query = pragma + query;
+        }
+
+        auto result = session.ExecuteDataQuery(query, TTxControl::BeginTx().CommitTx(), querySettings).GetValueSync();
+        UNIT_ASSERT_C(result.IsSuccess(), result.GetIssues().ToString());
+        CompareYson(R"([[[101u];[1]]])", FormatResultSetYson(result.GetResultSet(0)));
+
+        auto stats = NYdb::TProtoAccessor::GetProto(*result.GetStats());
+        for (const auto& phase : stats.query_phases()) {
+            for (const auto& access : phase.table_access()) {
+                if (access.name() == "/Root/EightShard") {
+                    if (Enabled) {
+                        UNIT_ASSERT_LT(access.partitions_count(), 8);
+                    } else {
+                        UNIT_ASSERT_EQUAL(access.partitions_count(), 8);
+                    }
+                }
+            }
+        }
+    }
 
 }