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#include <Processors/QueryPlan/Optimizations/Optimizations.h>
#include <Processors/QueryPlan/FilterStep.h>
#include <Processors/QueryPlan/ExpressionStep.h>
#include <Interpreters/ActionsDAG.h>
namespace DB::QueryPlanOptimizations
{
size_t tryMergeExpressions(QueryPlan::Node * parent_node, QueryPlan::Nodes &)
{
if (parent_node->children.size() != 1)
return false;
QueryPlan::Node * child_node = parent_node->children.front();
auto & parent = parent_node->step;
auto & child = child_node->step;
auto * parent_expr = typeid_cast<ExpressionStep *>(parent.get());
auto * parent_filter = typeid_cast<FilterStep *>(parent.get());
auto * child_expr = typeid_cast<ExpressionStep *>(child.get());
if (parent_expr && child_expr)
{
const auto & child_actions = child_expr->getExpression();
const auto & parent_actions = parent_expr->getExpression();
/// We cannot combine actions with arrayJoin and stateful function because we not always can reorder them.
/// Example: select rowNumberInBlock() from (select arrayJoin([1, 2]))
/// Such a query will return two zeroes if we combine actions together.
if (child_actions->hasArrayJoin() && parent_actions->hasStatefulFunctions())
return 0;
auto merged = ActionsDAG::merge(std::move(*child_actions), std::move(*parent_actions));
auto expr = std::make_unique<ExpressionStep>(child_expr->getInputStreams().front(), merged);
expr->setStepDescription("(" + parent_expr->getStepDescription() + " + " + child_expr->getStepDescription() + ")");
parent_node->step = std::move(expr);
parent_node->children.swap(child_node->children);
return 1;
}
else if (parent_filter && child_expr)
{
const auto & child_actions = child_expr->getExpression();
const auto & parent_actions = parent_filter->getExpression();
if (child_actions->hasArrayJoin() && parent_actions->hasStatefulFunctions())
return 0;
auto merged = ActionsDAG::merge(std::move(*child_actions), std::move(*parent_actions));
auto filter = std::make_unique<FilterStep>(child_expr->getInputStreams().front(),
merged,
parent_filter->getFilterColumnName(),
parent_filter->removesFilterColumn());
filter->setStepDescription("(" + parent_filter->getStepDescription() + " + " + child_expr->getStepDescription() + ")");
parent_node->step = std::move(filter);
parent_node->children.swap(child_node->children);
return 1;
}
return 0;
}
}
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