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#include <Processors/QueryPlan/Optimizations/Optimizations.h>
#include <Functions/IFunction.h>
#include <Processors/QueryPlan/AggregatingStep.h>
#include <Processors/QueryPlan/ExpressionStep.h>
#include <Processors/QueryPlan/FilterStep.h>
#include <Processors/QueryPlan/Optimizations/actionsDAGUtils.h>
#include <Processors/QueryPlan/ReadFromMergeTree.h>
#include <stack>
#include <unordered_map>
using namespace DB;
namespace
{
using NodeSet = std::unordered_set<const ActionsDAG::Node *>;
using NodeMap = std::unordered_map<const ActionsDAG::Node *, bool>;
struct Frame
{
const ActionsDAG::Node * node = nullptr;
size_t next_child = 0;
};
bool isInjectiveFunction(const ActionsDAG::Node * node)
{
if (node->function_base->isInjective({}))
return true;
size_t fixed_args = 0;
for (const auto & child : node->children)
if (child->type == ActionsDAG::ActionType::COLUMN)
++fixed_args;
static const std::vector<String> injective = {"plus", "minus", "negate", "tuple"};
return (fixed_args + 1 >= node->children.size()) && (std::find(injective.begin(), injective.end(), node->function_base->getName()) != injective.end());
}
void removeInjectiveFunctionsFromResultsRecursively(const ActionsDAG::Node * node, NodeSet & irreducible, NodeSet & visited)
{
if (visited.contains(node))
return;
visited.insert(node);
switch (node->type)
{
case ActionsDAG::ActionType::ALIAS:
assert(node->children.size() == 1);
removeInjectiveFunctionsFromResultsRecursively(node->children.at(0), irreducible, visited);
break;
case ActionsDAG::ActionType::ARRAY_JOIN:
UNREACHABLE();
case ActionsDAG::ActionType::COLUMN:
irreducible.insert(node);
break;
case ActionsDAG::ActionType::FUNCTION:
if (!isInjectiveFunction(node))
{
irreducible.insert(node);
}
else
{
for (const auto & child : node->children)
removeInjectiveFunctionsFromResultsRecursively(child, irreducible, visited);
}
break;
case ActionsDAG::ActionType::INPUT:
irreducible.insert(node);
break;
}
}
/// Our objective is to replace injective function nodes in `actions` results with its children
/// until only the irreducible subset of nodes remains. Against these set of nodes we will match partition key expression
/// to determine if it maps all rows with the same value of group by key to the same partition.
NodeSet removeInjectiveFunctionsFromResultsRecursively(const ActionsDAGPtr & actions)
{
NodeSet irreducible;
NodeSet visited;
for (const auto & node : actions->getOutputs())
removeInjectiveFunctionsFromResultsRecursively(node, irreducible, visited);
return irreducible;
}
bool allOutputsDependsOnlyOnAllowedNodes(
const NodeSet & irreducible_nodes, const MatchedTrees::Matches & matches, const ActionsDAG::Node * node, NodeMap & visited)
{
if (visited.contains(node))
return visited[node];
bool res = false;
/// `matches` maps partition key nodes into nodes in group by actions
if (matches.contains(node))
{
const auto & match = matches.at(node);
/// Function could be mapped into its argument. In this case .monotonicity != std::nullopt (see matchTrees)
if (match.node && match.node->result_name == node->result_name && !match.monotonicity)
res = irreducible_nodes.contains(match.node);
}
if (!res)
{
switch (node->type)
{
case ActionsDAG::ActionType::ALIAS:
assert(node->children.size() == 1);
res = allOutputsDependsOnlyOnAllowedNodes(irreducible_nodes, matches, node->children.at(0), visited);
break;
case ActionsDAG::ActionType::ARRAY_JOIN:
UNREACHABLE();
case ActionsDAG::ActionType::COLUMN:
/// Constants doesn't matter, so let's always consider them matched.
res = true;
break;
case ActionsDAG::ActionType::FUNCTION:
res = true;
for (const auto & child : node->children)
res &= allOutputsDependsOnlyOnAllowedNodes(irreducible_nodes, matches, child, visited);
break;
case ActionsDAG::ActionType::INPUT:
break;
}
}
visited[node] = res;
return res;
}
/// Here we check that partition key expression is a deterministic function of the reduced set of group by key nodes.
/// No need to explicitly check that each function is deterministic, because it is a guaranteed property of partition key expression (checked on table creation).
/// So it is left only to check that each output node depends only on the allowed set of nodes (`irreducible_nodes`).
bool allOutputsDependsOnlyOnAllowedNodes(
const ActionsDAG & partition_actions, const NodeSet & irreducible_nodes, const MatchedTrees::Matches & matches)
{
NodeMap visited;
bool res = true;
for (const auto & node : partition_actions.getOutputs())
if (node->type != ActionsDAG::ActionType::INPUT)
res &= allOutputsDependsOnlyOnAllowedNodes(irreducible_nodes, matches, node, visited);
return res;
}
/// 0. Partition key columns should be a subset of group by key columns.
/// 1. Optimization is applicable if partition by expression is a deterministic function of col1, ..., coln and group by key is injective functions of these col1, ..., coln.
/// 2. To find col1, ..., coln we apply removeInjectiveFunctionsFromResultsRecursively to group by key actions.
/// 3. We match partition key actions with group by key actions to find col1', ..., coln' in partition key actions.
/// 4. We check that partition key is indeed a deterministic function of col1', ..., coln'.
bool isPartitionKeySuitsGroupByKey(
const ReadFromMergeTree & reading, const ActionsDAGPtr & group_by_actions, const AggregatingStep & aggregating)
{
if (aggregating.isGroupingSets())
return false;
if (group_by_actions->hasArrayJoin() || group_by_actions->hasStatefulFunctions() || group_by_actions->hasNonDeterministic())
return false;
/// We are interested only in calculations required to obtain group by keys (and not aggregate function arguments for example).
group_by_actions->removeUnusedActions(aggregating.getParams().keys);
const auto & gb_key_required_columns = group_by_actions->getRequiredColumnsNames();
const auto & partition_actions = reading.getStorageMetadata()->getPartitionKey().expression->getActionsDAG();
/// Check that PK columns is a subset of GBK columns.
for (const auto & col : partition_actions.getRequiredColumnsNames())
if (std::find(gb_key_required_columns.begin(), gb_key_required_columns.end(), col) == gb_key_required_columns.end())
return false;
const auto irreducibe_nodes = removeInjectiveFunctionsFromResultsRecursively(group_by_actions);
const auto matches = matchTrees(*group_by_actions, partition_actions);
return allOutputsDependsOnlyOnAllowedNodes(partition_actions, irreducibe_nodes, matches);
}
}
namespace DB::QueryPlanOptimizations
{
size_t tryAggregatePartitionsIndependently(QueryPlan::Node * node, QueryPlan::Nodes &)
{
if (!node || node->children.size() != 1)
return 0;
auto * aggregating_step = typeid_cast<AggregatingStep *>(node->step.get());
if (!aggregating_step)
return 0;
const auto * expression_node = node->children.front();
const auto * expression_step = typeid_cast<const ExpressionStep *>(expression_node->step.get());
if (!expression_step)
return 0;
auto * maybe_reading_step = expression_node->children.front()->step.get();
if (const auto * filter = typeid_cast<const FilterStep *>(maybe_reading_step))
{
const auto * filter_node = expression_node->children.front();
if (filter_node->children.size() != 1 || !filter_node->children.front()->step)
return 0;
maybe_reading_step = filter_node->children.front()->step.get();
}
auto * reading = typeid_cast<ReadFromMergeTree *>(maybe_reading_step);
if (!reading)
return 0;
if (!reading->willOutputEachPartitionThroughSeparatePort()
&& isPartitionKeySuitsGroupByKey(*reading, expression_step->getExpression()->clone(), *aggregating_step))
{
if (reading->requestOutputEachPartitionThroughSeparatePort())
aggregating_step->skipMerging();
}
return 0;
}
}
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