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#include <unordered_set>
#include <Common/typeid_cast.h>
#include <Parsers/ASTLiteral.h>
#include <Parsers/ASTFunction.h>
#include <Parsers/ASTSubquery.h>
#include <Parsers/ASTTablesInSelectQuery.h>
#include <Interpreters/ArithmeticOperationsInAgrFuncOptimize.h>
#include <Poco/String.h>
namespace DB
{
namespace ErrorCodes
{
extern const int BAD_TYPE_OF_FIELD;
}
namespace
{
const ASTFunction * getInternalFunction(const ASTFunction & func)
{
if (func.arguments && func.arguments->children.size() == 1)
return func.arguments->children[0]->as<ASTFunction>();
return nullptr;
}
ASTPtr exchangeExtractFirstArgument(const String & func_name, const ASTFunction & child_func)
{
ASTs new_child_args;
new_child_args.push_back(child_func.arguments->children[1]);
auto new_child = makeASTFunction(func_name, new_child_args);
ASTs new_args;
new_args.push_back(child_func.arguments->children[0]);
new_args.push_back(new_child);
return makeASTFunction(child_func.name, new_args);
}
ASTPtr exchangeExtractSecondArgument(const String & func_name, const ASTFunction & child_func)
{
ASTs new_child_args;
new_child_args.push_back(child_func.arguments->children[0]);
auto new_child = makeASTFunction(func_name, new_child_args);
ASTs new_args;
new_args.push_back(new_child);
new_args.push_back(child_func.arguments->children[1]);
return makeASTFunction(child_func.name, new_args);
}
Field zeroField(const Field & value)
{
switch (value.getType())
{
case Field::Types::UInt64: return static_cast<UInt64>(0);
case Field::Types::Int64: return static_cast<Int64>(0);
case Field::Types::Float64: return static_cast<Float64>(0);
case Field::Types::UInt128: return static_cast<UInt128>(0);
case Field::Types::Int128: return static_cast<Int128>(0);
case Field::Types::UInt256: return static_cast<UInt256>(0);
case Field::Types::Int256: return static_cast<Int256>(0);
default:
break;
}
throw Exception(ErrorCodes::BAD_TYPE_OF_FIELD, "Unexpected literal type in function");
}
ASTPtr tryExchangeFunctions(const ASTFunction & func)
{
static const std::unordered_map<String, std::unordered_set<String>> supported
= {{"sum", {"multiply", "divide"}},
{"min", {"multiply", "divide", "plus", "minus"}},
{"max", {"multiply", "divide", "plus", "minus"}},
{"avg", {"multiply", "divide", "plus", "minus"}}};
/// Aggregate functions[sum|min|max|avg] is case-insensitive, so we use lower cases name
auto lower_name = Poco::toLower(func.name);
const ASTFunction * child_func = getInternalFunction(func);
if (!child_func || !child_func->arguments || child_func->arguments->children.size() != 2 || !supported.contains(lower_name)
|| !supported.find(lower_name)->second.contains(child_func->name))
return {};
auto original_alias = func.tryGetAlias();
const auto & child_func_args = child_func->arguments->children;
const auto * first_literal = child_func_args[0]->as<ASTLiteral>();
const auto * second_literal = child_func_args[1]->as<ASTLiteral>();
ASTPtr optimized_ast;
/** Need reverse max <-> min for:
*
* max(-1*value) -> -1*min(value)
* max(value/-2) -> min(value)/-2
* max(1-value) -> 1-min(value)
*/
auto get_reverse_aggregate_function_name = [](const std::string & aggregate_function_name) -> std::string
{
if (aggregate_function_name == "min")
return "max";
else if (aggregate_function_name == "max")
return "min";
else
return aggregate_function_name;
};
if (first_literal && !second_literal)
{
/// It's possible to rewrite 'sum(1/n)' with 'sum(1) * div(1/n)' but we lose accuracy. Ignored.
if (child_func->name == "divide")
return {};
bool need_reverse
= (child_func->name == "multiply" && first_literal->value < zeroField(first_literal->value)) || child_func->name == "minus";
if (need_reverse)
lower_name = get_reverse_aggregate_function_name(lower_name);
optimized_ast = exchangeExtractFirstArgument(lower_name, *child_func);
}
else if (second_literal) /// second or both are consts
{
bool need_reverse
= (child_func->name == "multiply" || child_func->name == "divide") && second_literal->value < zeroField(second_literal->value);
if (need_reverse)
lower_name = get_reverse_aggregate_function_name(lower_name);
optimized_ast = exchangeExtractSecondArgument(lower_name, *child_func);
}
if (optimized_ast)
{
optimized_ast->setAlias(original_alias);
return optimized_ast;
}
return {};
}
}
void ArithmeticOperationsInAgrFuncMatcher::visit(const ASTFunction & func, ASTPtr & ast, Data & data)
{
if (auto exchanged_funcs = tryExchangeFunctions(func))
{
ast = exchanged_funcs;
/// Main visitor is bottom-up. This is top-down part.
/// We've found an aggregate function an now move it down through others: sum(mul(mul)) -> mul(mul(sum)).
/// It's not dangerous cause main visitor already has visited this part of tree.
auto & expression_list = ast->children[0];
visit(expression_list->children[0], data);
}
}
void ArithmeticOperationsInAgrFuncMatcher::visit(ASTPtr & ast, Data & data)
{
if (const auto * function_node = ast->as<ASTFunction>())
{
if (function_node->is_window_function)
return;
visit(*function_node, ast, data);
}
}
bool ArithmeticOperationsInAgrFuncMatcher::needChildVisit(const ASTPtr & node, const ASTPtr &)
{
return !node->as<ASTSubquery>() &&
!node->as<ASTTableExpression>() &&
!node->as<ASTArrayJoin>();
}
}
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