Merge pull request #39138 from nickitat/control_block_size_in_aggregator

Control block size in aggregator

src/Interpreters/AggregationUtils.cpp

@@ -0,0 +1,113 @@
+#include <Interpreters/AggregationUtils.h>
+
+namespace DB
+{
+
+namespace ErrorCodes
+{
+    extern const int LOGICAL_ERROR;
+}
+
+OutputBlockColumns prepareOutputBlockColumns(
+    const Aggregator::Params & params,
+    const Aggregator::AggregateFunctionsPlainPtrs & aggregate_functions,
+    const Block & res_header,
+    Arenas & aggregates_pools,
+    bool final,
+    size_t rows)
+{
+    MutableColumns key_columns(params.keys_size);
+    MutableColumns aggregate_columns(params.aggregates_size);
+    MutableColumns final_aggregate_columns(params.aggregates_size);
+    Aggregator::AggregateColumnsData aggregate_columns_data(params.aggregates_size);
+
+    for (size_t i = 0; i < params.keys_size; ++i)
+    {
+        key_columns[i] = res_header.safeGetByPosition(i).type->createColumn();
+        key_columns[i]->reserve(rows);
+    }
+
+    for (size_t i = 0; i < params.aggregates_size; ++i)
+    {
+        if (!final)
+        {
+            const auto & aggregate_column_name = params.aggregates[i].column_name;
+            aggregate_columns[i] = res_header.getByName(aggregate_column_name).type->createColumn();
+
+            /// The ColumnAggregateFunction column captures the shared ownership of the arena with the aggregate function states.
+            ColumnAggregateFunction & column_aggregate_func = assert_cast<ColumnAggregateFunction &>(*aggregate_columns[i]);
+
+            for (auto & pool : aggregates_pools)
+                column_aggregate_func.addArena(pool);
+
+            aggregate_columns_data[i] = &column_aggregate_func.getData();
+            aggregate_columns_data[i]->reserve(rows);
+        }
+        else
+        {
+            final_aggregate_columns[i] = aggregate_functions[i]->getReturnType()->createColumn();
+            final_aggregate_columns[i]->reserve(rows);
+
+            if (aggregate_functions[i]->isState())
+            {
+                /// The ColumnAggregateFunction column captures the shared ownership of the arena with aggregate function states.
+                if (auto * column_aggregate_func = typeid_cast<ColumnAggregateFunction *>(final_aggregate_columns[i].get()))
+                    for (auto & pool : aggregates_pools)
+                        column_aggregate_func->addArena(pool);
+
+                /// Aggregate state can be wrapped into array if aggregate function ends with -Resample combinator.
+                final_aggregate_columns[i]->forEachSubcolumn(
+                    [&aggregates_pools](auto & subcolumn)
+                    {
+                        if (auto * column_aggregate_func = typeid_cast<ColumnAggregateFunction *>(subcolumn.get()))
+                            for (auto & pool : aggregates_pools)
+                                column_aggregate_func->addArena(pool);
+                    });
+            }
+        }
+    }
+
+    if (key_columns.size() != params.keys_size)
+        throw Exception{"Aggregate. Unexpected key columns size.", ErrorCodes::LOGICAL_ERROR};
+
+    std::vector<IColumn *> raw_key_columns;
+    raw_key_columns.reserve(key_columns.size());
+    for (auto & column : key_columns)
+        raw_key_columns.push_back(column.get());
+
+    return {
+        .key_columns = std::move(key_columns),
+        .raw_key_columns = std::move(raw_key_columns),
+        .aggregate_columns = std::move(aggregate_columns),
+        .final_aggregate_columns = std::move(final_aggregate_columns),
+        .aggregate_columns_data = std::move(aggregate_columns_data),
+    };
+}
+
+Block finalizeBlock(const Aggregator::Params & params, const Block & res_header, OutputBlockColumns && out_cols, bool final, size_t rows)
+{
+    auto && [key_columns, raw_key_columns, aggregate_columns, final_aggregate_columns, aggregate_columns_data] = out_cols;
+
+    Block res = res_header.cloneEmpty();
+
+    for (size_t i = 0; i < params.keys_size; ++i)
+        res.getByPosition(i).column = std::move(key_columns[i]);
+
+    for (size_t i = 0; i < params.aggregates_size; ++i)
+    {
+        const auto & aggregate_column_name = params.aggregates[i].column_name;
+        if (final)
+            res.getByName(aggregate_column_name).column = std::move(final_aggregate_columns[i]);
+        else
+            res.getByName(aggregate_column_name).column = std::move(aggregate_columns[i]);
+    }
+
+    /// Change the size of the columns-constants in the block.
+    size_t columns = res_header.columns();
+    for (size_t i = 0; i < columns; ++i)
+        if (isColumnConst(*res.getByPosition(i).column))
+            res.getByPosition(i).column = res.getByPosition(i).column->cut(0, rows);
+
+    return res;
+}
+}

src/Interpreters/AggregationUtils.h

@@ -0,0 +1,27 @@
+#pragma once
+
+#include <Interpreters/Aggregator.h>
+
+namespace DB
+{
+
+struct OutputBlockColumns
+{
+    MutableColumns key_columns;
+    std::vector<IColumn *> raw_key_columns;
+    MutableColumns aggregate_columns;
+    MutableColumns final_aggregate_columns;
+    Aggregator::AggregateColumnsData aggregate_columns_data;
+};
+
+
+OutputBlockColumns prepareOutputBlockColumns(
+    const Aggregator::Params & params,
+    const Aggregator::AggregateFunctionsPlainPtrs & aggregate_functions,
+    const Block & res_header,
+    Arenas & aggregates_pools,
+    bool final,
+    size_t rows);
+
+Block finalizeBlock(const Aggregator::Params & params, const Block & res_header, OutputBlockColumns && out_cols, bool final, size_t rows);
+}

src/Interpreters/Aggregator.cpp

@@ -34,6 +34,8 @@
 
 #include <Parsers/ASTSelectQuery.h>
 
+#include <Interpreters/AggregationUtils.h>
+
 namespace ProfileEvents
 {
     extern const Event ExternalAggregationWritePart;
@@ -1587,16 +1589,10 @@ Block Aggregator::convertOneBucketToBlock(
     bool final,
     size_t bucket) const
 {
-    Block block = prepareBlockAndFill(data_variants, final, method.data.impls[bucket].size(),
+    // Used in ConvertingAggregatedToChunksSource -> ConvertingAggregatedToChunksTransform (expects single chunk for each bucket_id).
-        [bucket, &method, arena, this] (
+    constexpr bool return_single_block = true;
-            MutableColumns & key_columns,
+    Block block = convertToBlockImpl<return_single_block>(
-            AggregateColumnsData & aggregate_columns,
+        method, method.data.impls[bucket], arena, data_variants.aggregates_pools, final, method.data.impls[bucket].size());
-            MutableColumns & final_aggregate_columns,
-            bool final_)
-        {
-            convertToBlockImpl(method, method.data.impls[bucket],
-                key_columns, aggregate_columns, final_aggregate_columns, arena, final_);
-        });
 
     block.info.bucket_num = bucket;
     return block;
@@ -1702,26 +1698,17 @@ bool Aggregator::checkLimits(size_t result_size, bool & no_more_keys) const
 }
 
 
-template <typename Method, typename Table>
+template <bool return_single_block, typename Method, typename Table>
-void Aggregator::convertToBlockImpl(
+Aggregator::ConvertToBlockRes<return_single_block>
-    Method & method,
+Aggregator::convertToBlockImpl(Method & method, Table & data, Arena * arena, Arenas & aggregates_pools, bool final, size_t rows) const
-    Table & data,
-    MutableColumns & key_columns,
-    AggregateColumnsData & aggregate_columns,
-    MutableColumns & final_aggregate_columns,
-    Arena * arena,
-    bool final) const
 {
     if (data.empty())
-        return;
+    {
+        auto && out_cols = prepareOutputBlockColumns(params, aggregate_functions, getHeader(final), aggregates_pools, final, rows);
+        return {finalizeBlock(params, getHeader(final), std::move(out_cols), final, rows)};
+    }
 
-    if (key_columns.size() != params.keys_size)
+    ConvertToBlockRes<return_single_block> res;
-        throw Exception{"Aggregate. Unexpected key columns size.", ErrorCodes::LOGICAL_ERROR};
-
-    std::vector<IColumn *> raw_key_columns;
-    raw_key_columns.reserve(key_columns.size());
-    for (auto & column : key_columns)
-        raw_key_columns.push_back(column.get());
 
     if (final)
     {
@@ -1729,20 +1716,23 @@ void Aggregator::convertToBlockImpl(
         if (compiled_aggregate_functions_holder)
         {
             static constexpr bool use_compiled_functions = !Method::low_cardinality_optimization;
-            convertToBlockImplFinal<Method, use_compiled_functions>(method, data, std::move(raw_key_columns), final_aggregate_columns, arena);
+            res = convertToBlockImplFinal<Method, use_compiled_functions, return_single_block>(method, data, arena, aggregates_pools, rows);
         }
         else
 #endif
         {
-            convertToBlockImplFinal<Method, false>(method, data, std::move(raw_key_columns), final_aggregate_columns, arena);
+            res = convertToBlockImplFinal<Method, false, return_single_block>(method, data, arena, aggregates_pools, rows);
         }
     }
     else
     {
-        convertToBlockImplNotFinal(method, data, std::move(raw_key_columns), aggregate_columns);
+        res = convertToBlockImplNotFinal<return_single_block>(method, data, aggregates_pools, rows);
     }
+
     /// In order to release memory early.
     data.clearAndShrink();
+
+    return res;
 }
 
 
@@ -1811,38 +1801,9 @@ inline void Aggregator::insertAggregatesIntoColumns(Mapped & mapped, MutableColu
 }
 
 
-template <typename Method, bool use_compiled_functions, typename Table>
+template <bool use_compiled_functions>
-void NO_INLINE Aggregator::convertToBlockImplFinal(
+Block Aggregator::insertResultsIntoColumns(PaddedPODArray<AggregateDataPtr> & places, OutputBlockColumns && out_cols, Arena * arena) const
-    Method & method,
-    Table & data,
-    std::vector<IColumn *>  key_columns,
-    MutableColumns & final_aggregate_columns,
-    Arena * arena) const
 {
-    if constexpr (Method::low_cardinality_optimization)
-    {
-        if (data.hasNullKeyData())
-        {
-            key_columns[0]->insertDefault();
-            insertAggregatesIntoColumns(data.getNullKeyData(), final_aggregate_columns, arena);
-        }
-    }
-
-    auto shuffled_key_sizes = method.shuffleKeyColumns(key_columns, key_sizes);
-    const auto & key_sizes_ref = shuffled_key_sizes ? *shuffled_key_sizes :  key_sizes;
-
-    PaddedPODArray<AggregateDataPtr> places;
-    places.reserve(data.size());
-
-    data.forEachValue([&](const auto & key, auto & mapped)
-    {
-        method.insertKeyIntoColumns(key, key_columns, key_sizes_ref);
-        places.emplace_back(mapped);
-
-        /// Mark the cell as destroyed so it will not be destroyed in destructor.
-        mapped = nullptr;
-    });
-
     std::exception_ptr exception;
     size_t aggregate_functions_destroy_index = 0;
 
@@ -1863,7 +1824,7 @@ void NO_INLINE Aggregator::convertToBlockImplFinal(
                 if (!is_aggregate_function_compiled[i])
                     continue;
 
-                auto & final_aggregate_column = final_aggregate_columns[i];
+                auto & final_aggregate_column = out_cols.final_aggregate_columns[i];
                 final_aggregate_column = final_aggregate_column->cloneResized(places.size());
                 columns_data.emplace_back(getColumnData(final_aggregate_column.get()));
             }
@@ -1884,7 +1845,7 @@ void NO_INLINE Aggregator::convertToBlockImplFinal(
                 }
             }
 
-            auto & final_aggregate_column = final_aggregate_columns[aggregate_functions_destroy_index];
+            auto & final_aggregate_column = out_cols.final_aggregate_columns[aggregate_functions_destroy_index];
             size_t offset = offsets_of_aggregate_states[aggregate_functions_destroy_index];
 
             /** We increase aggregate_functions_destroy_index because by function contract if insertResultIntoBatch
@@ -1898,7 +1859,8 @@ void NO_INLINE Aggregator::convertToBlockImplFinal(
             bool is_state = aggregate_functions[destroy_index]->isState();
             bool destroy_place_after_insert = !is_state;
 
-            aggregate_functions[destroy_index]->insertResultIntoBatch(0, places.size(), places.data(), offset, *final_aggregate_column, arena, destroy_place_after_insert);
+            aggregate_functions[destroy_index]->insertResultIntoBatch(
+                0, places.size(), places.data(), offset, *final_aggregate_column, arena, destroy_place_after_insert);
         }
     }
     catch (...)
@@ -1923,125 +1885,155 @@ void NO_INLINE Aggregator::convertToBlockImplFinal(
 
     if (exception)
         std::rethrow_exception(exception);
+
+    return finalizeBlock(params, getHeader(/* final */ true), std::move(out_cols), /* final */ true, places.size());
 }
 
-template <typename Method, typename Table>
+template <typename Method, bool use_compiled_functions, bool return_single_block, typename Table>
-void NO_INLINE Aggregator::convertToBlockImplNotFinal(
+Aggregator::ConvertToBlockRes<return_single_block> NO_INLINE
-    Method & method,
+Aggregator::convertToBlockImplFinal(Method & method, Table & data, Arena * arena, Arenas & aggregates_pools, size_t) const
-    Table & data,
-    std::vector<IColumn *>  key_columns,
-    AggregateColumnsData & aggregate_columns) const
 {
+    const size_t max_block_size = params.max_block_size;
+    const bool final = true;
+    ConvertToBlockRes<return_single_block> res;
+
+    std::optional<OutputBlockColumns> out_cols;
+    std::optional<Sizes> shuffled_key_sizes;
+    PaddedPODArray<AggregateDataPtr> places;
+
+    auto init_out_cols = [&]()
+    {
+        out_cols = prepareOutputBlockColumns(params, aggregate_functions, getHeader(final), aggregates_pools, final, max_block_size);
+
         if constexpr (Method::low_cardinality_optimization)
         {
             if (data.hasNullKeyData())
             {
-            key_columns[0]->insertDefault();
+                out_cols->key_columns[0]->insertDefault();
+                insertAggregatesIntoColumns(data.getNullKeyData(), out_cols->final_aggregate_columns, arena);
+                data.hasNullKeyData() = false;
+            }
+        }
+
+        shuffled_key_sizes = method.shuffleKeyColumns(out_cols->raw_key_columns, key_sizes);
+
+        places.reserve(max_block_size);
+    };
+
+    // should be invoked at least once, because null data might be the only content of the `data`
+    init_out_cols();
+
+    data.forEachValue(
+        [&](const auto & key, auto & mapped)
+        {
+            if (!out_cols.has_value())
+                init_out_cols();
+
+            const auto & key_sizes_ref = shuffled_key_sizes ? *shuffled_key_sizes : key_sizes;
+            method.insertKeyIntoColumns(key, out_cols->raw_key_columns, key_sizes_ref);
+            places.emplace_back(mapped);
+
+            /// Mark the cell as destroyed so it will not be destroyed in destructor.
+            mapped = nullptr;
+
+            if constexpr (!return_single_block)
+            {
+                if (places.size() >= max_block_size)
+                {
+                    res.emplace_back(insertResultsIntoColumns<use_compiled_functions>(places, std::move(out_cols.value()), arena));
+                    places.clear();
+                    out_cols.reset();
+                }
+            }
+        });
+
+    if constexpr (return_single_block)
+    {
+        return insertResultsIntoColumns<use_compiled_functions>(places, std::move(out_cols.value()), arena);
+    }
+    else
+    {
+        if (out_cols.has_value())
+            res.emplace_back(insertResultsIntoColumns<use_compiled_functions>(places, std::move(out_cols.value()), arena));
+        return res;
+    }
+}
+
+template <bool return_single_block, typename Method, typename Table>
+Aggregator::ConvertToBlockRes<return_single_block> NO_INLINE
+Aggregator::convertToBlockImplNotFinal(Method & method, Table & data, Arenas & aggregates_pools, size_t) const
+{
+    const size_t max_block_size = params.max_block_size;
+    const bool final = false;
+    ConvertToBlockRes<return_single_block> res;
+
+    std::optional<OutputBlockColumns> out_cols;
+    std::optional<Sizes> shuffled_key_sizes;
+
+    auto init_out_cols = [&]()
+    {
+        out_cols = prepareOutputBlockColumns(params, aggregate_functions, getHeader(final), aggregates_pools, final, max_block_size);
+
+        if constexpr (Method::low_cardinality_optimization)
+        {
+            if (data.hasNullKeyData())
+            {
+                out_cols->raw_key_columns[0]->insertDefault();
 
                 for (size_t i = 0; i < params.aggregates_size; ++i)
-                aggregate_columns[i]->push_back(data.getNullKeyData() + offsets_of_aggregate_states[i]);
+                    out_cols->aggregate_columns_data[i]->push_back(data.getNullKeyData() + offsets_of_aggregate_states[i]);
 
                 data.getNullKeyData() = nullptr;
+                data.hasNullKeyData() = false;
             }
         }
 
-    auto shuffled_key_sizes = method.shuffleKeyColumns(key_columns, key_sizes);
+        shuffled_key_sizes = method.shuffleKeyColumns(out_cols->raw_key_columns, key_sizes);
-    const auto & key_sizes_ref = shuffled_key_sizes ? *shuffled_key_sizes :  key_sizes;
+    };
 
-    data.forEachValue([&](const auto & key, auto & mapped)
+    // should be invoked at least once, because null data might be the only content of the `data`
+    init_out_cols();
+
+    size_t rows_in_current_block = 0;
+
+    data.forEachValue(
+        [&](const auto & key, auto & mapped)
         {
-        method.insertKeyIntoColumns(key, key_columns, key_sizes_ref);
+            if (!out_cols.has_value())
+                init_out_cols();
+
+            const auto & key_sizes_ref = shuffled_key_sizes ? *shuffled_key_sizes : key_sizes;
+            method.insertKeyIntoColumns(key, out_cols->raw_key_columns, key_sizes_ref);
 
             /// reserved, so push_back does not throw exceptions
             for (size_t i = 0; i < params.aggregates_size; ++i)
-            aggregate_columns[i]->push_back(mapped + offsets_of_aggregate_states[i]);
+                out_cols->aggregate_columns_data[i]->push_back(mapped + offsets_of_aggregate_states[i]);
 
             mapped = nullptr;
-    });
-}
 
+            ++rows_in_current_block;
 
-template <typename Filler>
+            if constexpr (!return_single_block)
-Block Aggregator::prepareBlockAndFill(
-    AggregatedDataVariants & data_variants,
-    bool final,
-    size_t rows,
-    Filler && filler) const
-{
-    MutableColumns key_columns(params.keys_size);
-    MutableColumns aggregate_columns(params.aggregates_size);
-    MutableColumns final_aggregate_columns(params.aggregates_size);
-    AggregateColumnsData aggregate_columns_data(params.aggregates_size);
-
-    Block res_header = getHeader(final);
-
-    for (size_t i = 0; i < params.keys_size; ++i)
             {
-        key_columns[i] = res_header.safeGetByPosition(i).type->createColumn();
+                if (rows_in_current_block >= max_block_size)
-        key_columns[i]->reserve(rows);
+                {
+                    res.emplace_back(finalizeBlock(params, getHeader(final), std::move(out_cols.value()), final, rows_in_current_block));
+                    out_cols.reset();
+                    rows_in_current_block = 0;
                 }
+            }
+        });
 
-    for (size_t i = 0; i < params.aggregates_size; ++i)
+    if constexpr (return_single_block)
     {
-        if (!final)
+        return finalizeBlock(params, getHeader(final), std::move(out_cols).value(), final, rows_in_current_block);
-        {
-            const auto & aggregate_column_name = params.aggregates[i].column_name;
-            aggregate_columns[i] = res_header.getByName(aggregate_column_name).type->createColumn();
-
-            /// The ColumnAggregateFunction column captures the shared ownership of the arena with the aggregate function states.
-            ColumnAggregateFunction & column_aggregate_func = assert_cast<ColumnAggregateFunction &>(*aggregate_columns[i]);
-
-            for (auto & pool : data_variants.aggregates_pools)
-                column_aggregate_func.addArena(pool);
-
-            aggregate_columns_data[i] = &column_aggregate_func.getData();
-            aggregate_columns_data[i]->reserve(rows);
     }
     else
     {
-            final_aggregate_columns[i] = aggregate_functions[i]->getReturnType()->createColumn();
+        if (rows_in_current_block)
-            final_aggregate_columns[i]->reserve(rows);
+            res.emplace_back(finalizeBlock(params, getHeader(final), std::move(out_cols).value(), final, rows_in_current_block));
-
+        return res;
-            if (aggregate_functions[i]->isState())
-            {
-                /// The ColumnAggregateFunction column captures the shared ownership of the arena with aggregate function states.
-                if (auto * column_aggregate_func = typeid_cast<ColumnAggregateFunction *>(final_aggregate_columns[i].get()))
-                    for (auto & pool : data_variants.aggregates_pools)
-                        column_aggregate_func->addArena(pool);
-
-                /// Aggregate state can be wrapped into array if aggregate function ends with -Resample combinator.
-                final_aggregate_columns[i]->forEachSubcolumn([&data_variants](auto & subcolumn)
-                {
-                    if (auto * column_aggregate_func = typeid_cast<ColumnAggregateFunction *>(subcolumn.get()))
-                        for (auto & pool : data_variants.aggregates_pools)
-                            column_aggregate_func->addArena(pool);
-                });
     }
-        }
-    }
-
-    filler(key_columns, aggregate_columns_data, final_aggregate_columns, final);
-
-    Block res = res_header.cloneEmpty();
-
-    for (size_t i = 0; i < params.keys_size; ++i)
-        res.getByPosition(i).column = std::move(key_columns[i]);
-
-    for (size_t i = 0; i < params.aggregates_size; ++i)
-    {
-        const auto & aggregate_column_name = params.aggregates[i].column_name;
-        if (final)
-            res.getByName(aggregate_column_name).column = std::move(final_aggregate_columns[i]);
-        else
-            res.getByName(aggregate_column_name).column = std::move(aggregate_columns[i]);
-    }
-
-    /// Change the size of the columns-constants in the block.
-    size_t columns = res_header.columns();
-    for (size_t i = 0; i < columns; ++i)
-        if (isColumnConst(*res.getByPosition(i).column))
-            res.getByPosition(i).column = res.getByPosition(i).column->cut(0, rows);
-
     return res;
 }
 
@@ -2105,13 +2097,10 @@ void Aggregator::createStatesAndFillKeyColumnsWithSingleKey(
 Block Aggregator::prepareBlockAndFillWithoutKey(AggregatedDataVariants & data_variants, bool final, bool is_overflows) const
 {
     size_t rows = 1;
+    auto && out_cols
+        = prepareOutputBlockColumns(params, aggregate_functions, getHeader(final), data_variants.aggregates_pools, final, rows);
+    auto && [key_columns, raw_key_columns, aggregate_columns, final_aggregate_columns, aggregate_columns_data] = out_cols;
 
-    auto filler = [&data_variants, this](
-        MutableColumns & key_columns,
-        AggregateColumnsData & aggregate_columns,
-        MutableColumns & final_aggregate_columns,
-        bool final_)
-    {
     if (data_variants.type == AggregatedDataVariants::Type::without_key || params.overflow_row)
     {
         AggregatedDataWithoutKey & data = data_variants.without_key;
@@ -2119,10 +2108,10 @@ Block Aggregator::prepareBlockAndFillWithoutKey(AggregatedDataVariants & data_va
         if (!data)
             throw Exception("Wrong data variant passed.", ErrorCodes::LOGICAL_ERROR);
 
-            if (!final_)
+        if (!final)
         {
             for (size_t i = 0; i < params.aggregates_size; ++i)
-                    aggregate_columns[i]->push_back(data + offsets_of_aggregate_states[i]);
+                aggregate_columns_data[i]->push_back(data + offsets_of_aggregate_states[i]);
             data = nullptr;
         }
         else
@@ -2135,9 +2124,8 @@ Block Aggregator::prepareBlockAndFillWithoutKey(AggregatedDataVariants & data_va
             for (size_t i = 0; i < params.keys_size; ++i)
                 key_columns[i]->insertDefault();
     }
-    };
 
-    Block block = prepareBlockAndFill(data_variants, final, rows, filler);
+    Block block = finalizeBlock(params, getHeader(final), std::move(out_cols), final, rows);
 
     if (is_overflows)
         block.info.is_overflows = true;
@@ -2148,29 +2136,22 @@ Block Aggregator::prepareBlockAndFillWithoutKey(AggregatedDataVariants & data_va
     return block;
 }
 
-Block Aggregator::prepareBlockAndFillSingleLevel(AggregatedDataVariants & data_variants, bool final) const
+template <bool return_single_block>
+Aggregator::ConvertToBlockRes<return_single_block>
+Aggregator::prepareBlockAndFillSingleLevel(AggregatedDataVariants & data_variants, bool final) const
 {
-    size_t rows = data_variants.sizeWithoutOverflowRow();
+    const size_t rows = data_variants.sizeWithoutOverflowRow();
-
+#define M(NAME) \
-    auto filler = [&data_variants, this](
-        MutableColumns & key_columns,
-        AggregateColumnsData & aggregate_columns,
-        MutableColumns & final_aggregate_columns,
-        bool final_)
-    {
-    #define M(NAME) \
     else if (data_variants.type == AggregatedDataVariants::Type::NAME) \
-            convertToBlockImpl(*data_variants.NAME, data_variants.NAME->data, \
+    { \
-                key_columns, aggregate_columns, final_aggregate_columns, data_variants.aggregates_pool, final_);
+        return convertToBlockImpl<return_single_block>( \
+            *data_variants.NAME, data_variants.NAME->data, data_variants.aggregates_pool, data_variants.aggregates_pools, final, rows); \
+    }
 
     if (false) {} // NOLINT
     APPLY_FOR_VARIANTS_SINGLE_LEVEL(M)
-    #undef M
+#undef M
-        else
+    else throw Exception("Unknown aggregated data variant.", ErrorCodes::UNKNOWN_AGGREGATED_DATA_VARIANT);
-            throw Exception("Unknown aggregated data variant.", ErrorCodes::UNKNOWN_AGGREGATED_DATA_VARIANT);
-    };
-
-    return prepareBlockAndFill(data_variants, final, rows, filler);
 }
 
 
@@ -2292,7 +2273,7 @@ BlocksList Aggregator::convertToBlocks(AggregatedDataVariants & data_variants, b
     if (data_variants.type != AggregatedDataVariants::Type::without_key)
     {
         if (!data_variants.isTwoLevel())
-            blocks.emplace_back(prepareBlockAndFillSingleLevel(data_variants, final));
+            blocks.splice(blocks.end(), prepareBlockAndFillSingleLevel</* return_single_block */ false>(data_variants, final));
         else
             blocks.splice(blocks.end(), prepareBlocksAndFillTwoLevel(data_variants, final, thread_pool.get()));
     }
@@ -3044,9 +3025,15 @@ Block Aggregator::mergeBlocks(BlocksList & blocks, bool final)
 
     Block block;
     if (result.type == AggregatedDataVariants::Type::without_key || is_overflows)
+    {
         block = prepareBlockAndFillWithoutKey(result, final, is_overflows);
+    }
     else
-        block = prepareBlockAndFillSingleLevel(result, final);
+    {
+        // Used during memory efficient merging (SortingAggregatedTransform expects single chunk for each bucket_id).
+        constexpr bool return_single_block = true;
+        block = prepareBlockAndFillSingleLevel<return_single_block>(result, final);
+    }
     /// NOTE: two-level data is not possible here - chooseAggregationMethod chooses only among single-level methods.
 
     if (!final)
@@ -3247,4 +3234,6 @@ void Aggregator::destroyAllAggregateStates(AggregatedDataVariants & result) cons
 }
 
 
+template Aggregator::ConvertToBlockRes<false>
+Aggregator::prepareBlockAndFillSingleLevel<false>(AggregatedDataVariants & data_variants, bool final) const;
 }

src/Interpreters/Aggregator.h

@@ -1,8 +1,9 @@
 #pragma once
 
-#include <mutex>
-#include <memory>
 #include <functional>
+#include <memory>
+#include <mutex>
+#include <type_traits>
 
 #include <Common/logger_useful.h>
 
@@ -872,6 +873,7 @@ using ManyAggregatedDataVariantsPtr = std::shared_ptr<ManyAggregatedDataVariants
 
 class CompiledAggregateFunctionsHolder;
 class NativeWriter;
+struct OutputBlockColumns;
 
 /** How are "total" values calculated with WITH TOTALS?
   * (For more details, see TotalsHavingTransform.)
@@ -933,6 +935,8 @@ public:
         bool compile_aggregate_expressions;
         size_t min_count_to_compile_aggregate_expression;
 
+        size_t max_block_size;
+
         bool only_merge;
 
         struct StatsCollectingParams
@@ -969,6 +973,7 @@ public:
             size_t min_free_disk_space_,
             bool compile_aggregate_expressions_,
             size_t min_count_to_compile_aggregate_expression_,
+            size_t max_block_size_,
             bool only_merge_ = false, // true for projections
             const StatsCollectingParams & stats_collecting_params_ = {})
             : keys(keys_)
@@ -987,15 +992,16 @@ public:
             , min_free_disk_space(min_free_disk_space_)
             , compile_aggregate_expressions(compile_aggregate_expressions_)
             , min_count_to_compile_aggregate_expression(min_count_to_compile_aggregate_expression_)
+            , max_block_size(max_block_size_)
             , only_merge(only_merge_)
             , stats_collecting_params(stats_collecting_params_)
         {
         }
 
         /// Only parameters that matter during merge.
-        Params(const Names & keys_, const AggregateDescriptions & aggregates_, bool overflow_row_, size_t max_threads_)
+        Params(const Names & keys_, const AggregateDescriptions & aggregates_, bool overflow_row_, size_t max_threads_, size_t max_block_size_)
             : Params(
-                keys_, aggregates_, overflow_row_, 0, OverflowMode::THROW, 0, 0, 0, false, nullptr, max_threads_, 0, false, 0, true, {})
+                keys_, aggregates_, overflow_row_, 0, OverflowMode::THROW, 0, 0, 0, false, nullptr, max_threads_, 0, false, 0, max_block_size_, true, {})
         {
         }
 
@@ -1277,15 +1283,12 @@ private:
     void mergeSingleLevelDataImpl(
         ManyAggregatedDataVariants & non_empty_data) const;
 
-    template <typename Method, typename Table>
+    template <bool return_single_block>
-    void convertToBlockImpl(
+    using ConvertToBlockRes = std::conditional_t<return_single_block, Block, BlocksList>;
-        Method & method,
+
-        Table & data,
+    template <bool return_single_block, typename Method, typename Table>
-        MutableColumns & key_columns,
+    ConvertToBlockRes<return_single_block>
-        AggregateColumnsData & aggregate_columns,
+    convertToBlockImpl(Method & method, Table & data, Arena * arena, Arenas & aggregates_pools, bool final, size_t rows) const;
-        MutableColumns & final_aggregate_columns,
-        Arena * arena,
-        bool final) const;
 
     template <typename Mapped>
     void insertAggregatesIntoColumns(
@@ -1293,27 +1296,16 @@ private:
         MutableColumns & final_aggregate_columns,
         Arena * arena) const;
 
-    template <typename Method, bool use_compiled_functions, typename Table>
+    template <bool use_compiled_functions>
-    void convertToBlockImplFinal(
+    Block insertResultsIntoColumns(PaddedPODArray<AggregateDataPtr> & places, OutputBlockColumns && out_cols, Arena * arena) const;
-        Method & method,
-        Table & data,
-        std::vector<IColumn *> key_columns,
-        MutableColumns & final_aggregate_columns,
-        Arena * arena) const;
 
-    template <typename Method, typename Table>
+    template <typename Method, bool use_compiled_functions, bool return_single_block, typename Table>
-    void convertToBlockImplNotFinal(
+    ConvertToBlockRes<return_single_block>
-        Method & method,
+    convertToBlockImplFinal(Method & method, Table & data, Arena * arena, Arenas & aggregates_pools, size_t rows) const;
-        Table & data,
-        std::vector<IColumn *>  key_columns,
-        AggregateColumnsData & aggregate_columns) const;
 
-    template <typename Filler>
+    template <bool return_single_block, typename Method, typename Table>
-    Block prepareBlockAndFill(
+    ConvertToBlockRes<return_single_block>
-        AggregatedDataVariants & data_variants,
+    convertToBlockImplNotFinal(Method & method, Table & data, Arenas & aggregates_pools, size_t rows) const;
-        bool final,
-        size_t rows,
-        Filler && filler) const;
 
     template <typename Method>
     Block convertOneBucketToBlock(
@@ -1331,9 +1323,11 @@ private:
         std::atomic<bool> * is_cancelled = nullptr) const;
 
     Block prepareBlockAndFillWithoutKey(AggregatedDataVariants & data_variants, bool final, bool is_overflows) const;
-    Block prepareBlockAndFillSingleLevel(AggregatedDataVariants & data_variants, bool final) const;
     BlocksList prepareBlocksAndFillTwoLevel(AggregatedDataVariants & data_variants, bool final, ThreadPool * thread_pool) const;
 
+    template <bool return_single_block>
+    ConvertToBlockRes<return_single_block> prepareBlockAndFillSingleLevel(AggregatedDataVariants & data_variants, bool final) const;
+
     template <typename Method>
     BlocksList prepareBlocksAndFillTwoLevelImpl(
         AggregatedDataVariants & data_variants,

src/Interpreters/InterpreterSelectQuery.cpp

@@ -1763,7 +1763,7 @@ static void executeMergeAggregatedImpl(
       *  but it can work more slowly.
       */
 
-    Aggregator::Params params(keys, aggregates, overflow_row, settings.max_threads);
+    Aggregator::Params params(keys, aggregates, overflow_row, settings.max_threads, settings.max_block_size);
 
     auto merging_aggregated = std::make_unique<MergingAggregatedStep>(
         query_plan.getCurrentDataStream(),
@@ -2359,6 +2359,7 @@ static Aggregator::Params getAggregatorParams(
         settings.min_free_disk_space_for_temporary_data,
         settings.compile_aggregate_expressions,
         settings.min_count_to_compile_aggregate_expression,
+        settings.max_block_size,
         /* only_merge */ false,
         stats_collecting_params
     };

src/Processors/QueryPlan/AggregatingStep.cpp

@@ -182,6 +182,7 @@ void AggregatingStep::transformPipeline(QueryPipelineBuilder & pipeline, const B
                     transform_params->params.min_free_disk_space,
                     transform_params->params.compile_aggregate_expressions,
                     transform_params->params.min_count_to_compile_aggregate_expression,
+                    transform_params->params.max_block_size,
                     /* only_merge */ false,
                     transform_params->params.stats_collecting_params};
                 auto transform_params_for_set = std::make_shared<AggregatingTransformParams>(src_header, std::move(params_for_set), final);
@@ -376,16 +377,15 @@ void AggregatingStep::transformPipeline(QueryPipelineBuilder & pipeline, const B
         });
 
         /// We add the explicit resize here, but not in case of aggregating in order, since AIO don't use two-level hash tables and thus returns only buckets with bucket_number = -1.
-        pipeline.resize(should_produce_results_in_order_of_bucket_number ? 1 : pipeline.getNumStreams(), true /* force */);
+        pipeline.resize(should_produce_results_in_order_of_bucket_number ? 1 : params.max_threads, true /* force */);
 
         aggregating = collector.detachProcessors(0);
     }
     else
     {
-        pipeline.addSimpleTransform([&](const Block & header)
+        pipeline.addSimpleTransform([&](const Block & header) { return std::make_shared<AggregatingTransform>(header, transform_params); });
-        {
+
-            return std::make_shared<AggregatingTransform>(header, transform_params);
+        pipeline.resize(should_produce_results_in_order_of_bucket_number ? 1 : params.max_threads, false /* force */);
-        });
 
         aggregating = collector.detachProcessors(0);
     }

src/Processors/TTL/TTLAggregationAlgorithm.cpp

@@ -38,7 +38,8 @@ TTLAggregationAlgorithm::TTLAggregationAlgorithm(
         settings.max_threads,
         settings.min_free_disk_space_for_temporary_data,
         settings.compile_aggregate_expressions,
-        settings.min_count_to_compile_aggregate_expression);
+        settings.min_count_to_compile_aggregate_expression,
+        settings.max_block_size);
 
     aggregator = std::make_unique<Aggregator>(header, params);
 

src/Processors/Transforms/AggregatingInOrderTransform.cpp

@@ -182,7 +182,8 @@ void AggregatingInOrderTransform::consume(Chunk chunk)
             if (cur_block_size >= max_block_size || cur_block_bytes + current_memory_usage >= max_block_bytes)
             {
                 if (group_by_key)
-                    group_by_block = params->aggregator.prepareBlockAndFillSingleLevel(variants, /* final= */ false);
+                    group_by_block
+                        = params->aggregator.prepareBlockAndFillSingleLevel</* return_single_block */ true>(variants, /* final= */ false);
                 cur_block_bytes += current_memory_usage;
                 finalizeCurrentChunk(std::move(chunk), key_end);
                 return;
@@ -293,7 +294,8 @@ void AggregatingInOrderTransform::generate()
     if (cur_block_size && is_consume_finished)
     {
         if (group_by_key)
-            group_by_block = params->aggregator.prepareBlockAndFillSingleLevel(variants, /* final= */ false);
+            group_by_block
+                = params->aggregator.prepareBlockAndFillSingleLevel</* return_single_block */ true>(variants, /* final= */ false);
         else
             params->aggregator.addSingleKeyToAggregateColumns(variants, res_aggregate_columns);
         variants.invalidate();

src/Processors/Transforms/AggregatingTransform.cpp

@@ -203,7 +203,7 @@ public:
     {
         auto & output = outputs.front();
 
-        if (finished && !has_input)
+        if (finished && single_level_chunks.empty())
         {
             output.finish();
             return Status::Finished;
@@ -230,7 +230,7 @@ public:
         if (!processors.empty())
             return Status::ExpandPipeline;
 
-        if (has_input)
+        if (!single_level_chunks.empty())
             return preparePushToOutput();
 
         /// Single level case.
@@ -244,11 +244,14 @@ public:
 private:
     IProcessor::Status preparePushToOutput()
     {
-        auto & output = outputs.front();
+        if (single_level_chunks.empty())
-        output.push(std::move(current_chunk));
+            throw Exception(ErrorCodes::LOGICAL_ERROR, "Some ready chunks expected");
-        has_input = false;
 
-        if (finished)
+        auto & output = outputs.front();
+        output.push(std::move(single_level_chunks.back()));
+        single_level_chunks.pop_back();
+
+        if (finished && single_level_chunks.empty())
         {
             output.finish();
             return Status::Finished;
@@ -268,17 +271,17 @@ private:
             {
                 auto chunk = input.pull();
                 auto bucket = getInfoFromChunk(chunk)->bucket_num;
-                chunks[bucket] = std::move(chunk);
+                two_level_chunks[bucket] = std::move(chunk);
             }
         }
 
         if (!shared_data->is_bucket_processed[current_bucket_num])
             return Status::NeedData;
 
-        if (!chunks[current_bucket_num])
+        if (!two_level_chunks[current_bucket_num])
             return Status::NeedData;
 
-        output.push(std::move(chunks[current_bucket_num]));
+        output.push(std::move(two_level_chunks[current_bucket_num]));
 
         ++current_bucket_num;
         if (current_bucket_num == NUM_BUCKETS)
@@ -298,27 +301,16 @@ private:
     size_t num_threads;
 
     bool is_initialized = false;
-    bool has_input = false;
     bool finished = false;
 
-    Chunk current_chunk;
+    Chunks single_level_chunks;
 
     UInt32 current_bucket_num = 0;
     static constexpr Int32 NUM_BUCKETS = 256;
-    std::array<Chunk, NUM_BUCKETS> chunks;
+    std::array<Chunk, NUM_BUCKETS> two_level_chunks;
 
     Processors processors;
 
-    void setCurrentChunk(Chunk chunk)
-    {
-        if (has_input)
-            throw Exception("Current chunk was already set in "
-                            "ConvertingAggregatedToChunksTransform.", ErrorCodes::LOGICAL_ERROR);
-
-        has_input = true;
-        current_chunk = std::move(chunk);
-    }
-
     void initialize()
     {
         is_initialized = true;
@@ -339,7 +331,7 @@ private:
             auto block = params->aggregator.prepareBlockAndFillWithoutKey(
                 *first, params->final, first->type != AggregatedDataVariants::Type::without_key);
 
-            setCurrentChunk(convertToChunk(block));
+            single_level_chunks.emplace_back(convertToChunk(block));
         }
     }
 
@@ -364,9 +356,10 @@ private:
         else
             throw Exception("Unknown aggregated data variant.", ErrorCodes::UNKNOWN_AGGREGATED_DATA_VARIANT);
 
-        auto block = params->aggregator.prepareBlockAndFillSingleLevel(*first, params->final);
+        auto blocks = params->aggregator.prepareBlockAndFillSingleLevel</* return_single_block */ false>(*first, params->final);
+        for (auto & block : blocks)
+            single_level_chunks.emplace_back(convertToChunk(block));
 
-        setCurrentChunk(convertToChunk(block));
         finished = true;
     }
 

src/Storages/MergeTree/MergeTreeDataSelectExecutor.cpp

@@ -313,6 +313,7 @@ QueryPlanPtr MergeTreeDataSelectExecutor::read(
                 settings.min_free_disk_space_for_temporary_data,
                 settings.compile_aggregate_expressions,
                 settings.min_count_to_compile_aggregate_expression,
+                settings.max_block_size,
                 only_merge);
 
             return std::make_pair(params, only_merge);

tests/performance/queries_over_aggregation.xml

@@ -1,4 +1,8 @@
 <test>
+  <query>select sipHash64(number) from numbers(1e7) group by number format Null</query>
+  <query>select * from (select * from numbers(1e7) group by number) group by number format Null</query>
+  <query>select * from (select * from numbers(1e7) group by number) order by number format Null</query>
+
   <query>select * from (select * from numbers_mt(1e7) group by number) group by number format Null</query>
   <query>select * from (select * from numbers_mt(1e7) group by number) order by number format Null</query>
   <query>select * from (select * from numbers_mt(1e7) group by number) group by number format Null settings max_bytes_before_external_group_by = 1</query>

tests/queries/0_stateless/01064_incremental_streaming_from_2_src_with_feedback.sql

@@ -1,4 +1,5 @@
 SET joined_subquery_requires_alias = 0;
+SET max_threads = 1;
 
 -- incremental streaming usecase
 -- that has sense only if data filling order has guarantees of chronological order

tests/queries/0_stateless/01091_num_threads.sql

@@ -28,7 +28,7 @@ WITH
         ORDER BY event_time DESC
         LIMIT 1
     ) AS id
-SELECT uniqExact(thread_id)
+SELECT uniqExact(thread_id) > 2
 FROM system.query_thread_log
 WHERE (event_date >= (today() - 1)) AND (query_id = id) AND (thread_id != master_thread_id);
 

tests/queries/0_stateless/01281_group_by_limit_memory_tracking.sh

@@ -1,5 +1,5 @@
 #!/usr/bin/env bash
-# Tags: no-replicated-database, no-parallel, no-fasttest, no-tsan, no-asan, no-random-settings, no-s3-storage
+# Tags: no-replicated-database, no-parallel, no-fasttest, no-tsan, no-asan, no-random-settings, no-s3-storage, no-msan
 # Tag no-fasttest: max_memory_usage_for_user can interfere another queries running concurrently
 
 # Regression for MemoryTracker that had been incorrectly accounted

tests/queries/0_stateless/01524_do_not_merge_across_partitions_select_final.reference

@@ -6,4 +6,4 @@
 2020-01-01 00:00:00	2	
 1
 499999
-5
+18

tests/queries/0_stateless/01524_do_not_merge_across_partitions_select_final.sql

@@ -1,7 +1,7 @@
 DROP TABLE IF EXISTS select_final;
 
 SET do_not_merge_across_partitions_select_final = 1;
-SET max_threads = 0;
+SET max_threads = 16;
 
 CREATE TABLE select_final (t DateTime, x Int32, string String) ENGINE = ReplacingMergeTree() PARTITION BY toYYYYMM(t) ORDER BY (x, t);
 

tests/queries/0_stateless/01671_aggregate_function_group_bitmap_data.reference

@@ -1,27 +1,12 @@
 1	50	50	1	0	49
 1	50	50	1	0	49
 1	50	50	1	0	49
-1	50	51	0	1	51
-1	50	50	1	0	49
-1	50	51	0	1	51
-1	50	50	1	0	49
-1	50	50	1	0	49
-1	50	50	1	0	49
 1	50	50	1	0	49
 1	50	50	1	0	49
-1	50	51	0	1	51
-1	50	50	1	0	49
-1	50	51	0	1	51
-1	50	50	1	0	49
-1	50	51	0	1	51
-1	50	50	1	0	49
-1	50	51	0	1	51
 1	50	50	1	0	49
 1	50	50	1	0	49
 1	50	50	1	0	49
-1	50	51	0	1	51
 1	50	50	1	0	49
-1	50	51	0	1	51
 1	50	50	1	0	49
 1	50	50	1	0	49
 1	50	50	1	0	49
@@ -29,32 +14,47 @@
 1	50	50	1	0	49
 1	50	50	1	0	49
 1	50	50	1	0	49
-1	50	51	0	1	51
+1	50	50	1	0	49
+1	50	50	1	0	49
+1	50	50	1	0	49
+1	50	50	1	0	49
+1	50	50	1	0	49
+1	50	50	1	0	49
+1	50	50	1	0	49
+1	50	50	1	0	49
+1	50	50	1	0	49
+1	50	50	1	0	49
+1	50	50	1	0	49
+1	50	50	1	0	49
+1	50	50	1	0	49
+1	50	50	1	0	49
+1	50	50	1	0	49
+1	50	50	1	0	49
+1	50	50	1	0	49
+1	50	50	1	0	49
+1	50	50	1	0	49
+1	50	50	1	0	49
+1	50	50	1	0	49
+1	50	50	1	0	49
+1	50	50	1	0	49
 1	50	50	1	0	49
 1	50	51	0	1	51
-1	50	50	1	0	49
 1	50	51	0	1	51
 1	50	51	0	1	51
-1	50	50	1	0	49
-1	50	50	1	0	49
-1	50	50	1	0	49
-1	50	51	0	1	51
-1	50	50	1	0	49
-1	50	50	1	0	49
 1	50	51	0	1	51
 1	50	51	0	1	51
-1	50	50	1	0	49
-1	50	51	0	1	51
-1	50	50	1	0	49
-1	50	50	1	0	49
-1	50	50	1	0	49
-1	50	50	1	0	49
 1	50	51	0	1	51
 1	50	51	0	1	51
-1	50	50	1	0	49
-1	50	50	1	0	49
 1	50	51	0	1	51
-1	50	50	1	0	49
+1	50	51	0	1	51
-1	50	50	1	0	49
+1	50	51	0	1	51
-1	50	50	1	0	49
+1	50	51	0	1	51
+1	50	51	0	1	51
+1	50	51	0	1	51
+1	50	51	0	1	51
+1	50	51	0	1	51
+1	50	51	0	1	51
+1	50	51	0	1	51
+1	50	51	0	1	51
+1	50	51	0	1	51
 1	50	51	0	1	51

tests/queries/0_stateless/01671_aggregate_function_group_bitmap_data.sql

@@ -52,6 +52,7 @@ ALL LEFT JOIN
     FROM group_bitmap_data_test
     WHERE pickup_date = '2019-01-01'
     GROUP BY city_id
-) AS js2 USING (city_id);
+) AS js2 USING (city_id)
+ORDER BY today_users, before_users, ll_users, old_users, new_users, diff_users;
 
 DROP TABLE IF EXISTS group_bitmap_data_test;

tests/queries/0_stateless/01730_distributed_group_by_no_merge_order_by_long.sql

@@ -12,7 +12,7 @@ select * from remote('127.{2..11}', view(select * from numbers(1e6))) group by n
 -- and the query with GROUP BY on remote servers will first do GROUP BY and then send the block,
 -- so the initiator will first receive all blocks from remotes and only after start merging,
 -- and will hit the memory limit.
-select * from remote('127.{2..11}', view(select * from numbers(1e6))) group by number order by number limit 1e6 settings distributed_group_by_no_merge=2, max_memory_usage='100Mi'; -- { serverError 241 }
+select * from remote('127.{2..11}', view(select * from numbers(1e6))) group by number order by number limit 1e6 settings distributed_group_by_no_merge=2, max_memory_usage='100Mi', max_block_size=1e12; -- { serverError 241 }
 
 -- with optimize_aggregation_in_order=1 remote servers will produce blocks more frequently,
 -- since they don't need to wait until the aggregation will be finished,

tests/queries/0_stateless/02343_aggregation_pipeline.reference

@@ -1,5 +1,22 @@
 -- { echoOn }
 
+explain pipeline select * from (select * from numbers(1e8) group by number) group by number;
+(Expression)
+ExpressionTransform × 16
+  (Aggregating)
+  Resize 16 → 16
+    AggregatingTransform × 16
+      StrictResize 16 → 16
+        (Expression)
+        ExpressionTransform × 16
+          (Aggregating)
+          Resize 1 → 16
+            AggregatingTransform
+              (Expression)
+              ExpressionTransform
+                (ReadFromStorage)
+                Limit
+                  Numbers 0 → 1
 explain pipeline select * from (select * from numbers_mt(1e8) group by number) group by number;
 (Expression)
 ExpressionTransform × 16

tests/queries/0_stateless/02343_aggregation_pipeline.sql

@@ -1,9 +1,12 @@
 set max_threads = 16;
 set prefer_localhost_replica = 1;
 set optimize_aggregation_in_order = 0;
+set max_block_size = 65505;
 
 -- { echoOn }
 
+explain pipeline select * from (select * from numbers(1e8) group by number) group by number;
+
 explain pipeline select * from (select * from numbers_mt(1e8) group by number) group by number;
 
 explain pipeline select * from (select * from numbers_mt(1e8) group by number) order by number;

tests/queries/0_stateless/02355_control_block_size_in_aggregator.reference

@@ -0,0 +1 @@
+1

tests/queries/0_stateless/02355_control_block_size_in_aggregator.sql

@@ -0,0 +1,9 @@
+SET max_block_size = 4213;
+
+SELECT DISTINCT (blockSize() <= 4213)
+FROM
+(
+    SELECT number
+    FROM numbers(100000)
+    GROUP BY number
+);