fix(kqp): always take snapshot for queries with stream lookup

Author: ulya-sidorina

ydb/core/kqp/common/kqp_tx.cpp

@@ -184,6 +184,11 @@ bool NeedSnapshot(const TKqpTransactionContext& txCtx, const NYql::TKikimrConfig
         return true;
     }
 
+    // We always need snapshot for stream lookup, besause it's used for dependent reads
+    if (hasStreamLookup) {
+        return true;
+    }
+
     // We don't want snapshot when there are effects at the moment,
     // because it hurts performance when there are multiple single-shard
     // reads and a single distributed commit. Taking snapshot costs

ydb/core/kqp/executer_actor/kqp_tasks_graph.cpp

@@ -365,7 +365,7 @@ void BuildSequencerChannels(TKqpTasksGraph& graph, const TStageInfo& stageInfo,
     }
 }
 
-void BuildStreamLookupChannels(TKqpTasksGraph& graph, const TStageInfo& stageInfo, ui32 inputIndex, // TODO
+void BuildStreamLookupChannels(TKqpTasksGraph& graph, const TStageInfo& stageInfo, ui32 inputIndex,
     const TStageInfo& inputStageInfo, ui32 outputIndex,
     const NKqpProto::TKqpPhyCnStreamLookup& streamLookup, bool enableSpilling, const TChannelLogFunc& logFunc)
 {