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Return single row for aggregation without keys on empty set: development [#CLICKHOUSE-1920] #51

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This commit is contained in:
Alexey Milovidov 2018-02-18 08:35:48 +03:00
parent a4c10f7499
commit 7415513151
8 changed files with 57 additions and 21 deletions
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7
dbms/src/DataStreams/ParallelAggregatingBlockInputStream.cpp
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@ -197,6 +197,13 @@ void ParallelAggregatingBlockInputStream::execute()
<< "Total aggregated. " << total_src_rows << " rows (from " << total_src_bytes / 1048576.0 << " MiB)"
<< " in " << elapsed_seconds << " sec."
<< " (" << total_src_rows / elapsed_seconds << " rows/sec., " << total_src_bytes / elapsed_seconds / 1048576.0 << " MiB/sec.)");
/// If there was no data, and we aggregate without keys, we must return single row with the result of empty aggregation.
/// To do this, we pass a block with zero rows to aggregate.
if (total_src_rows == 0 && params.keys_size == 0 && !params.empty_result_for_aggregation_by_empty_set)
aggregator.executeOnBlock(children.at(0)->getHeader(), *many_data[0],
threads_data[0].key_columns, threads_data[0].aggregate_columns,
threads_data[0].key, no_more_keys);
}
}

7
dbms/src/Interpreters/Aggregator.cpp
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@ -648,7 +648,7 @@ void NO_INLINE Aggregator::executeWithoutKeyImpl(
}
bool Aggregator::executeOnBlock(Block & block, AggregatedDataVariants & result,
bool Aggregator::executeOnBlock(const Block & block, AggregatedDataVariants & result,
ColumnRawPtrs & key_columns, AggregateColumns & aggregate_columns, StringRefs & key,
bool & no_more_keys)
{
@ -1023,6 +1023,11 @@ void Aggregator::execute(const BlockInputStreamPtr & stream, AggregatedDataVaria
break;
}
/// If there was no data, and we aggregate without keys, and we must return single row with the result of empty aggregation.
/// To do this, we pass a block with zero rows to aggregate.
if (result.empty() && params.keys_size == 0 && !params.empty_result_for_aggregation_by_empty_set)
executeOnBlock(stream->getHeader(), result, key_columns, aggregate_columns, key, no_more_keys);
double elapsed_seconds = watch.elapsedSeconds();
size_t rows = result.sizeWithoutOverflowRow();
LOG_TRACE(log, std::fixed << std::setprecision(3)

16
dbms/src/Interpreters/Aggregator.h
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@ -1009,6 +1009,10 @@ public:
/// Settings to flush temporary data to the filesystem (external aggregation).
const size_t max_bytes_before_external_group_by; /// 0 - do not use external aggregation.
/// Return empty result when aggregating without keys on empty set.
bool empty_result_for_aggregation_by_empty_set;
const std::string tmp_path;
Params(
@ -1017,20 +1021,24 @@ public:
bool overflow_row_, size_t max_rows_to_group_by_, OverflowMode group_by_overflow_mode_,
Compiler * compiler_, UInt32 min_count_to_compile_,
size_t group_by_two_level_threshold_, size_t group_by_two_level_threshold_bytes_,
size_t max_bytes_before_external_group_by_, const std::string & tmp_path_)
size_t max_bytes_before_external_group_by_,
bool empty_result_for_aggregation_by_empty_set_,
const std::string & tmp_path_)
: src_header(src_header_),
keys(keys_), aggregates(aggregates_), keys_size(keys.size()), aggregates_size(aggregates.size()),
overflow_row(overflow_row_), max_rows_to_group_by(max_rows_to_group_by_), group_by_overflow_mode(group_by_overflow_mode_),
compiler(compiler_), min_count_to_compile(min_count_to_compile_),
group_by_two_level_threshold(group_by_two_level_threshold_), group_by_two_level_threshold_bytes(group_by_two_level_threshold_bytes_),
max_bytes_before_external_group_by(max_bytes_before_external_group_by_), tmp_path(tmp_path_)
max_bytes_before_external_group_by(max_bytes_before_external_group_by_),
empty_result_for_aggregation_by_empty_set(empty_result_for_aggregation_by_empty_set_),
tmp_path(tmp_path_)
{
}
/// Only parameters that matter during merge.
Params(const Block & intermediate_header_,
const ColumnNumbers & keys_, const AggregateDescriptions & aggregates_, bool overflow_row_)
: Params(Block(), keys_, aggregates_, overflow_row_, 0, OverflowMode::THROW, nullptr, 0, 0, 0, 0, "")
: Params(Block(), keys_, aggregates_, overflow_row_, 0, OverflowMode::THROW, nullptr, 0, 0, 0, 0, false, "")
{
intermediate_header = intermediate_header_;
}
@ -1050,7 +1058,7 @@ public:
using AggregateFunctionsPlainPtrs = std::vector<IAggregateFunction *>;
/// Process one block. Return false if the processing should be aborted (with group_by_overflow_mode = 'break').
bool executeOnBlock(Block & block, AggregatedDataVariants & result,
bool executeOnBlock(const Block & block, AggregatedDataVariants & result,
ColumnRawPtrs & key_columns, AggregateColumns & aggregate_columns, /// Passed to not create them anew for each block
StringRefs & keys, /// - pass the corresponding objects that are initially empty.
bool & no_more_keys);

18
dbms/src/Interpreters/InterpreterSelectQuery.cpp
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@ -21,7 +21,6 @@
#include <DataStreams/CreatingSetsBlockInputStream.h>
#include <DataStreams/MaterializingBlockInputStream.h>
#include <DataStreams/ConcatBlockInputStream.h>
#include <DataStreams/OneBlockInputStream.h>
#include <Parsers/ASTSelectQuery.h>
#include <Parsers/ASTIdentifier.h>
@ -462,7 +461,7 @@ void InterpreterSelectQuery::executeSingleQuery()
union_within_single_query = false;
/** Take out the data from Storage. from_stage - to what stage the request was completed in Storage. */
/** Read the data from Storage. from_stage - to what stage the request was completed in Storage. */
QueryProcessingStage::Enum from_stage = executeFetchColumns();
LOG_TRACE(log, QueryProcessingStage::toString(from_stage) << " -> " << QueryProcessingStage::toString(to_stage));
@ -864,18 +863,8 @@ QueryProcessingStage::Enum InterpreterSelectQuery::executeFetchColumns()
if (streams.empty())
streams = storage->read(required_columns, query_info, context, from_stage, max_block_size, max_streams);
/// The storage has no data for this query.
if (streams.empty())
{
from_stage = QueryProcessingStage::FetchColumns;
Block header;
for (const auto & name : required_columns)
{
auto type = storage->getDataTypeByName(name);
header.insert({ type->createColumn(), type, name });
}
streams.emplace_back(std::make_shared<OneBlockInputStream>(header));
}
streams.emplace_back(std::make_shared<NullBlockInputStream>(storage->getSampleBlockForColumns(required_columns)));
if (alias_actions)
{
@ -971,7 +960,8 @@ void InterpreterSelectQuery::executeAggregation(const ExpressionActionsPtr & exp
settings.compile ? &context.getCompiler() : nullptr, settings.min_count_to_compile,
allow_to_use_two_level_group_by ? settings.group_by_two_level_threshold : SettingUInt64(0),
allow_to_use_two_level_group_by ? settings.group_by_two_level_threshold_bytes : SettingUInt64(0),
settings.limits.max_bytes_before_external_group_by, context.getTemporaryPath());
settings.limits.max_bytes_before_external_group_by, settings.empty_result_for_aggregation_by_empty_set,
context.getTemporaryPath());
/// If there are several sources, then we perform parallel aggregation
if (streams.size() > 1)

4
dbms/src/Interpreters/Settings.h
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@ -180,7 +180,9 @@ struct Settings
M(SettingSeconds, http_send_timeout, DEFAULT_HTTP_READ_BUFFER_TIMEOUT, "HTTP send timeout") \
M(SettingSeconds, http_receive_timeout, DEFAULT_HTTP_READ_BUFFER_TIMEOUT, "HTTP receive timeout") \
M(SettingBool, optimize_throw_if_noop, false, "If setting is enabled and OPTIMIZE query didn't actually assign a merge then an explanatory exception is thrown") \
M(SettingBool, use_index_for_in_with_subqueries, true, "Try using an index if there is a subquery or a table expression on the right side of the IN operator.")
M(SettingBool, use_index_for_in_with_subqueries, true, "Try using an index if there is a subquery or a table expression on the right side of the IN operator.") \
\
M(SettingBool, empty_result_for_aggregation_by_empty_set, false, "Return empty result when aggregating without keys on empty set.")
/// Possible limits for query execution.

2
dbms/src/Interpreters/tests/aggregate.cpp
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@ -79,7 +79,7 @@ int main(int argc, char ** argv)
Aggregator::Params params(
stream->getHeader(), {0, 1}, aggregate_descriptions,
false, 0, OverflowMode::THROW, nullptr, 0, 0, 0, 0, "");
false, 0, OverflowMode::THROW, nullptr, 0, 0, 0, 0, false, "");
Aggregator aggregator(params);

5
dbms/tests/queries/0_stateless/00572_aggregation_by_empty_set.reference Normal file
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@ -0,0 +1,5 @@
0
0
1
0 0 nan \N [] []
1

19
dbms/tests/queries/0_stateless/00572_aggregation_by_empty_set.sql Normal file
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@ -0,0 +1,19 @@
CREATE TEMPORARY TABLE t (x UInt8);
SET empty_result_for_aggregation_by_empty_set = 0;
SELECT count() FROM system.one WHERE 0;
SELECT count() FROM system.one WHERE rand() < 0;
SELECT count() FROM system.one WHERE 1;
SELECT count(), uniq(x), avg(x), avg(toNullable(x)), groupArray(x), groupUniqArray(x) FROM t;
SELECT x, count(), uniq(x), avg(x), avg(toNullable(x)), groupArray(x), groupUniqArray(x) FROM t GROUP BY x;
SET empty_result_for_aggregation_by_empty_set = 1;
SELECT count() FROM system.one WHERE 0;
SELECT count() FROM system.one WHERE rand() < 0;
SELECT count() FROM system.one WHERE 1;
SELECT count(), uniq(x), avg(x), avg(toNullable(x)), groupArray(x), groupUniqArray(x) FROM t;
SELECT x, count(), uniq(x), avg(x), avg(toNullable(x)), groupArray(x), groupUniqArray(x) FROM t GROUP BY x;