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Try to apply optimization only if optimizer reaches pre distinct node

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This commit is contained in:
Igor Nikonov 2022-09-14 20:55:49 +00:00
parent bab5744a1d
commit f011f72114
4 changed files with 29 additions and 33 deletions
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2
src/Core/SortDescription.cpp
View File

@ -42,7 +42,7 @@ void SortColumnDescription::explain(JSONBuilder::JSONMap & map) const
map.add("With Fill", with_fill);
}
size_t SortDescription::hasPrefix(const SortDescription & prefix) const
bool SortDescription::hasPrefix(const SortDescription & prefix) const
{
if (prefix.empty())
return true;

2
src/Core/SortDescription.h
View File

@ -121,7 +121,7 @@ public:
size_t min_count_to_compile_sort_description = 3;
bool compile_sort_description = false;
size_t hasPrefix(const SortDescription & prefix) const;
bool hasPrefix(const SortDescription & prefix) const;
};
/** Compile sort description for header_types.

2
src/Processors/QueryPlan/Optimizations/Optimizations.h
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@ -54,7 +54,7 @@ size_t tryExecuteFunctionsAfterSorting(QueryPlan::Node * parent_node, QueryPlan:
/// Update information about prefix sort description in SortingStep.
size_t tryReuseStorageOrderingForWindowFunctions(QueryPlan::Node * parent_node, QueryPlan::Nodes & nodes);
/// TODO: description
/// Reading in order from MergeTree table if DISTINCT columns match or form a prefix of MergeTree sorting key
size_t tryDistinctReadInOrder(QueryPlan::Node * node, QueryPlan::Nodes & nodes);
inline const auto & getOptimizations()

56
src/Processors/QueryPlan/Optimizations/distinctReadInOrder.cpp
View File

@ -11,41 +11,34 @@
namespace DB::QueryPlanOptimizations
{
///
size_t tryDistinctReadInOrder(QueryPlan::Node * parent_node, QueryPlan::Nodes &)
{
/// walk through the plan
/// (1) check if there is preliminary distinct node
/// (2) check if nodes below preliminary distinct preserve sorting
QueryPlan::Node * node = parent_node;
/// check if it is preliminary distinct node
DistinctStep * pre_distinct = nullptr;
QueryPlan::Node * pre_distinct_node = nullptr;
while (!node->children.empty())
if (auto * distinct = typeid_cast<DistinctStep *>(parent_node->step.get()); distinct)
{
if (pre_distinct)
{
/// check if nodes below DISTINCT preserve sorting
const auto * step = dynamic_cast<const ITransformingStep *>(node->step.get());
if (step)
{
const ITransformingStep::DataStreamTraits & traits = step->getDataStreamTraits();
if (!traits.preserves_sorting)
return 0;
}
}
if (auto * tmp = typeid_cast<DistinctStep *>(node->step.get()); tmp)
{
if (tmp->isPreliminary())
{
pre_distinct_node = node;
pre_distinct = tmp;
}
}
node = node->children.front();
if (distinct->isPreliminary())
pre_distinct = distinct;
}
if (!pre_distinct)
return 0;
/// walk through the plan
/// check if nodes below preliminary distinct preserve sorting
QueryPlan::Node * node = parent_node;
while (!node->children.empty())
{
const auto * step = dynamic_cast<const ITransformingStep *>(node->step.get());
if (step)
{
const ITransformingStep::DataStreamTraits & traits = step->getDataStreamTraits();
if (!traits.preserves_sorting)
return 0;
}
node = node->children.front();
}
/// check if we read from MergeTree
auto * read_from_merge_tree = typeid_cast<ReadFromMergeTree *>(node->step.get());
if (!read_from_merge_tree)
return 0;
@ -55,7 +48,7 @@ size_t tryDistinctReadInOrder(QueryPlan::Node * parent_node, QueryPlan::Nodes &)
if (output.sort_scope != DataStream::SortScope::Chunk)
return 0;
const SortDescription & sort_desc = output.sort_description;
/// find non-const columns in DISTINCT
const auto & distinct_columns = pre_distinct->getOutputStream().header.getColumnsWithTypeAndName();
std::vector<std::string_view> non_const_columns;
non_const_columns.reserve(distinct_columns.size());
@ -67,6 +60,7 @@ size_t tryDistinctReadInOrder(QueryPlan::Node * parent_node, QueryPlan::Nodes &)
/// apply optimization only when distinct columns match or form prefix of sorting key
/// todo: check if reading in order optimization would be beneficial when sorting key is prefix of columns in DISTINCT
const SortDescription & sort_desc = output.sort_description;
if (sort_desc.size() < non_const_columns.size())
return 0;
@ -83,14 +77,15 @@ size_t tryDistinctReadInOrder(QueryPlan::Node * parent_node, QueryPlan::Nodes &)
if (distinct_sort_desc.empty())
return 0;
/// update input order info in read_from_merge_tree step
const int direction = 1; /// default direction, ASC
InputOrderInfoPtr order_info
= std::make_shared<const InputOrderInfo>(distinct_sort_desc, distinct_sort_desc.size(), direction, pre_distinct->getLimitHint());
read_from_merge_tree->setQueryInfoInputOrderInfo(order_info);
/// update data stream's sorting properties
/// find all transforms between preliminary distinct step and ReadFromMergeTree
std::vector<ITransformingStep *> steps2update;
node = pre_distinct_node;
node = parent_node;
while (node && node->step.get() != read_from_merge_tree)
{
auto * transform = dynamic_cast<ITransformingStep *>(node->step.get());
@ -103,6 +98,7 @@ size_t tryDistinctReadInOrder(QueryPlan::Node * parent_node, QueryPlan::Nodes &)
node = nullptr;
}
/// update data stream's sorting properties for found transforms
const DataStream * input_stream = &read_from_merge_tree->getOutputStream();
while (!steps2update.empty())
{