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#include <Interpreters/ActionsDAG.h>
#include <Processors/QueryPlan/ExpressionStep.h>
#include <Processors/QueryPlan/FillingStep.h>
#include <Processors/QueryPlan/Optimizations/Optimizations.h>
#include <Processors/QueryPlan/SortingStep.h>
#include <Common/Exception.h>
#include <DataTypes/IDataType.h>
namespace DB
{
namespace ErrorCodes
{
extern const int LOGICAL_ERROR;
}
}
namespace
{
const DB::DataStream & getChildOutputStream(DB::QueryPlan::Node & node)
{
if (node.children.size() != 1)
throw DB::Exception(DB::ErrorCodes::LOGICAL_ERROR, "Node \"{}\" is expected to have only one child.", node.step->getName());
return node.children.front()->step->getOutputStream();
}
}
namespace DB::QueryPlanOptimizations
{
/// This is a check that output columns does not have the same name
/// This is ok for DAG, but may introduce a bug in a SotringStep cause columns are selected by name.
static bool areOutputsConvertableToBlock(const ActionsDAG::NodeRawConstPtrs & outputs)
{
std::unordered_set<std::string_view> names;
for (const auto & output : outputs)
{
if (!names.emplace(output->result_name).second)
return false;
}
return true;
}
size_t tryExecuteFunctionsAfterSorting(QueryPlan::Node * parent_node, QueryPlan::Nodes & nodes)
{
if (parent_node->children.size() != 1)
return 0;
QueryPlan::Node * child_node = parent_node->children.front();
auto & parent_step = parent_node->step;
auto & child_step = child_node->step;
auto * sorting_step = typeid_cast<SortingStep *>(parent_step.get());
auto * expression_step = typeid_cast<ExpressionStep *>(child_step.get());
if (!sorting_step || !expression_step)
return 0;
// Filling step position should be preserved
if (!child_node->children.empty())
if (typeid_cast<FillingStep *>(child_node->children.front()->step.get()))
return 0;
NameSet sort_columns;
for (const auto & col : sorting_step->getSortDescription())
sort_columns.insert(col.column_name);
auto [needed_for_sorting, unneeded_for_sorting] = expression_step->getExpression()->splitActionsBySortingDescription(sort_columns);
// No calculations can be postponed.
if (unneeded_for_sorting->trivial())
return 0;
if (!areOutputsConvertableToBlock(needed_for_sorting->getOutputs()))
return 0;
// Sorting (parent_node) -> Expression (child_node)
auto & node_with_needed = nodes.emplace_back();
std::swap(node_with_needed.children, child_node->children);
child_node->children = {&node_with_needed};
node_with_needed.step = std::make_unique<ExpressionStep>(getChildOutputStream(node_with_needed), std::move(needed_for_sorting));
node_with_needed.step->setStepDescription(child_step->getStepDescription());
// Sorting (parent_node) -> so far the origin Expression (child_node) -> NeededCalculations (node_with_needed)
std::swap(parent_step, child_step);
// so far the origin Expression (parent_node) -> Sorting (child_node) -> NeededCalculations (node_with_needed)
sorting_step->updateInputStream(getChildOutputStream(*child_node));
auto description = parent_step->getStepDescription();
parent_step = std::make_unique<DB::ExpressionStep>(child_step->getOutputStream(), std::move(unneeded_for_sorting));
parent_step->setStepDescription(description + " [lifted up part]");
// UneededCalculations (parent_node) -> Sorting (child_node) -> NeededCalculations (node_with_needed)
return 3;
}
}
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