ClickHouse/src/Interpreters/ArithmeticOperationsInAgrFuncOptimize.cpp

#include <Common/typeid_cast.h>
#include <Parsers/ASTLiteral.h>
#include <Parsers/ASTFunction.h>
#include <Interpreters/ArithmeticOperationsInAgrFuncOptimize.h>
#include <IO/WriteHelpers.h>
#include <Parsers/ASTTablesInSelectQuery.h>

namespace DB
{

namespace ErrorCodes
{
    extern const int LOGICAL_ERROR;
    extern const int NUMBER_OF_ARGUMENTS_DOESNT_MATCH;
    extern const int UNEXPECTED_AST_STRUCTURE;
}

namespace
{

constexpr const char * min = "min";
constexpr const char * max = "max";
constexpr const char * mul = "multiply";
constexpr const char * plus = "plus";
constexpr const char * sum = "sum";


bool isConstantField(const Field & field)
{
    return field.getType() == Field::Types::Int64 ||
           field.getType() == Field::Types::UInt64 ||
           field.getType() == Field::Types::Int128 ||
           field.getType() == Field::Types::UInt128;
}

bool onlyConstsInside(const ASTFunction * func_node)
{
    return !(func_node->arguments->children[0]->as<ASTFunction>()) &&
           (func_node->arguments->children.size() == 2 &&
           !(func_node->arguments->children[1]->as<ASTFunction>()));
}

bool inappropriateNameInside(const ASTFunction * func_node, const char * inter_func_name)
{
    return (func_node->arguments->children[0]->as<ASTFunction>() &&
           strcmp(inter_func_name, func_node->arguments->children[0]->as<ASTFunction>()->name.c_str()) != 0) ||
           (func_node->arguments->children.size() == 2 &&
           func_node->arguments->children[1]->as<ASTFunction>() &&
           strcmp(inter_func_name, func_node->arguments->children[1]->as<ASTFunction>()->name.c_str()) != 0);
}

bool isInappropriate(const ASTPtr & node, const char * inter_func_name)
{
    return !node->as<ASTFunction>() || (strcmp(inter_func_name, node->as<ASTFunction>()->name.c_str()) != 0);
}

ASTFunction * getInternalFunction(const ASTFunction * f_n)
{
    const auto * function_args = f_n->arguments->as<ASTExpressionList>();
    if (!function_args || function_args->children.size() != 1)
        throw Exception("Wrong number of arguments for function " + f_n->name + "(" + toString(function_args->children.size()) + " instead of 1)",
                        ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);

    return f_n->arguments->children[0]->as<ASTFunction>();
}

ASTFunction * treeFiller(ASTFunction * old_tree, const ASTs & nodes_array, size_t size, const char * name, bool flag)
{
    if (flag)
        --size;
    for (size_t i = 0; i < size; ++i)
    {
        old_tree->arguments->children = {};
        old_tree->arguments->children.push_back(nodes_array[i]);

        old_tree->arguments->children.push_back(makeASTFunction(name));
        old_tree = old_tree->arguments->children[1]->as<ASTFunction>();
    }
    return old_tree;
}

/// scalar values from the first level
std::pair<ASTs, ASTs> tryGetConst(const char * name, const ASTs & arguments)
{
    ASTs const_num;
    ASTs not_const;

    for (const auto & arg : arguments)
    {
        if (const auto * literal = arg->as<ASTLiteral>())
        {
            if (isConstantField(literal->value))
                const_num.push_back(arg);
            else
                not_const.push_back(arg);
        }
        else
            not_const.push_back(arg);
    }

    if ((strcmp(name, plus) == 0 || strcmp(name, mul) == 0) && const_num.size() + not_const.size() != 2)
        throw Exception("Wrong number of arguments for function 'plus' or 'multiply' (" + toString(const_num.size() + not_const.size()) + " instead of 2)",
                        ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);

    return {const_num, not_const};
}

std::pair<ASTs, ASTs> findAllConsts(const ASTFunction * func_node, const char * inter_func_name)
{
    if (func_node->arguments->children.empty())
    {
        if (strcmp(func_node->name.c_str(), plus) == 0 || strcmp(func_node->name.c_str(), mul) == 0)
            throw Exception("Wrong number of arguments for function" + func_node->name + "(0 instead of 2)",
                        ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
        else
            return {};
    }

    if (onlyConstsInside(func_node))
        return tryGetConst(func_node->name.c_str(), func_node->arguments->children);
    else if (inappropriateNameInside(func_node, inter_func_name))
    {
        bool first_child_is_const = func_node->arguments->children[0]->as<ASTLiteral>() &&
                                    isConstantField(func_node->arguments->children[0]->as<ASTLiteral>()->value);
        bool second_child_is_const = func_node->arguments->children.size() == 2 &&
                                     func_node->arguments->children[1]->as<ASTLiteral>() &&
                                     isConstantField(func_node->arguments->children[1]->as<ASTLiteral>()->value);
        if (first_child_is_const)
            return {{func_node->arguments->children[0]}, {func_node->arguments->children[1]}};
        else if (second_child_is_const)
            return {{func_node->arguments->children[1]}, {func_node->arguments->children[0]}};

        if (isInappropriate(func_node->arguments->children[0], inter_func_name)
            && isInappropriate(func_node->arguments->children[1], inter_func_name))
        {
            return {{}, {func_node->arguments->children[0], func_node->arguments->children[1]}};
        }
        else if (isInappropriate(func_node->arguments->children[0], inter_func_name))
        {
            std::pair<ASTs, ASTs> ans = findAllConsts(func_node->arguments->children[1]->as<ASTFunction>(), inter_func_name);
            ans.second.push_back(func_node->arguments->children[0]);
            return ans;
        }

        std::pair<ASTs, ASTs> ans = findAllConsts(func_node->arguments->children[0]->as<ASTFunction>(), inter_func_name);
        ans.second.push_back(func_node->arguments->children[1]);
        return ans;
    }

    std::pair<ASTs, ASTs> fl = tryGetConst(func_node->name.c_str(), func_node->arguments->children);
    ASTs first_lvl_consts = fl.first;
    ASTs first_lvl_not_consts = fl.second;
    if (first_lvl_not_consts.empty() || !first_lvl_not_consts[0]->as<ASTFunction>())
        return {first_lvl_consts, first_lvl_not_consts};

    std::pair<ASTs, ASTs> ans = findAllConsts(first_lvl_not_consts[0]->as<ASTFunction>(), inter_func_name);
    ASTs all_consts = ans.first;
    ASTs all_not_consts = ans.second;

    if (first_lvl_consts.size() == 1)
    {
        if (!first_lvl_not_consts[0]->as<ASTFunction>())
            all_not_consts.push_back(first_lvl_not_consts[0]);

        all_consts.push_back(first_lvl_consts[0]);
    }
    else if (first_lvl_consts.empty())
    {
        /// if node is inappropriate to go into it, we just add this node to all_not_consts vector
        bool first_node_inappropriate_to_go_into = isInappropriate(first_lvl_not_consts[0], inter_func_name);
        bool second_node_inappropriate_to_go_into = first_lvl_not_consts.size() == 2 &&
                                                    isInappropriate(first_lvl_not_consts[1], inter_func_name);
        if (first_node_inappropriate_to_go_into)
            all_not_consts.push_back(first_lvl_not_consts[0]);

        if (second_node_inappropriate_to_go_into)
            all_not_consts.push_back(first_lvl_not_consts[1]);
    }
    else
        throw Exception("did not expect that", ErrorCodes::UNEXPECTED_AST_STRUCTURE);
    return {all_consts, all_not_consts};
}

/// rebuilds tree, all scalar values now outside the main func
void buildTree(ASTFunction * cur_node, const char * func_name, const char * intro_func, const std::pair<ASTs, ASTs> & tree_comp)
{
    ASTs cons_val = tree_comp.first;
    ASTs non_cons = tree_comp.second;

    bool not_const_empty = non_cons.empty();

    cur_node->name = intro_func;
    cur_node = treeFiller(cur_node, cons_val, cons_val.size(), intro_func, not_const_empty);
    cur_node->name = func_name;

    if (non_cons.empty())
        cur_node->arguments->children.push_back(cons_val[cons_val.size() - 1]);
    else if (non_cons.size() == 1)
        cur_node->arguments->children.push_back(non_cons[0]);
    else
    {
        cur_node->arguments->children.push_back(makeASTFunction(intro_func));
        cur_node = cur_node->arguments->children[0]->as<ASTFunction>();
        cur_node = treeFiller(cur_node, non_cons, non_cons.size() - 2, intro_func, not_const_empty);
        cur_node->arguments->children = {non_cons[non_cons.size() - 2], non_cons[non_cons.size() - 1]};
    }
}

void sumOptimize(ASTFunction * f_n)
{
    const auto * function_args = f_n->arguments->as<ASTExpressionList>();

    if (!function_args || function_args->children.size() != 1)
        throw Exception("Wrong number of arguments for function 'sum' (" + toString(function_args->children.size()) + " instead of 1)",
                        ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);

    ASTFunction * inter_node = getInternalFunction(f_n);
    if (inter_node && inter_node->name == mul)
    {
        std::pair<ASTs, ASTs> nodes = findAllConsts(f_n, mul);

        if (nodes.first.empty())
            return;

        buildTree(f_n, sum, mul, nodes);
    }
}

void minOptimize(ASTFunction * f_n)
{
    ASTFunction * inter_node = getInternalFunction(f_n);
    if (inter_node && inter_node->name == mul)
    {
        int sign = 1;
        std::pair<ASTs, ASTs> nodes = findAllConsts(f_n, mul);

        if (nodes.first.empty())
            return;

        for (const auto & arg : nodes.first)
        {
            Int128 num = applyVisitor(FieldVisitorConvertToNumber<Int128>(), arg->as<ASTLiteral>()->value);

            /// if multiplication is negative, min function becomes max

            if ((arg->as<ASTLiteral>()->value.getType() == Field::Types::Int64 ||
                 arg->as<ASTLiteral>()->value.getType() == Field::Types::Int128) && num < static_cast<Int128>(0))
                sign *= -1;
        }

        if (sign == -1)
            buildTree(f_n, max, mul, nodes);
        else
            buildTree(f_n, min, mul, nodes);
    }
    else if (inter_node && inter_node->name == plus)
    {
        std::pair<ASTs, ASTs> nodes = findAllConsts(f_n, plus);
        buildTree(f_n, min, plus, nodes);
    }
}

void maxOptimize(ASTFunction * f_n)
{
    ASTFunction * inter_node = getInternalFunction(f_n);
    if (inter_node && inter_node->name == mul)
    {
        int sign = 1;
        std::pair<ASTs, ASTs> nodes = findAllConsts(f_n, mul);

        if (nodes.first.empty())
            return;

        for (const auto & arg: nodes.first)
        {
            Int128 num = applyVisitor(FieldVisitorConvertToNumber<Int128>(), arg->as<ASTLiteral>()->value);

            /// if multiplication is negative, max function becomes min
            if ((arg->as<ASTLiteral>()->value.getType() == Field::Types::Int64 ||
                    arg->as<ASTLiteral>()->value.getType() == Field::Types::Int128) && num < static_cast<Int128>(0))
                sign *= -1;
        }

        if (sign == -1)
            buildTree(f_n, min, mul, nodes);
        else
            buildTree(f_n, max, mul, nodes);
    }
    else if (inter_node && inter_node->name == plus)
    {
        std::pair<ASTs, ASTs> nodes = findAllConsts(f_n, plus);
        buildTree(f_n, max, plus, nodes);
    }
}

}

/// optimize for min, max, sum is ready, ToDo: groupBitAnd, groupBitOr, groupBitXor
void ArithmeticOperationsInAgrFuncMatcher::visit(ASTFunction * function_node, Data data)
{
    data = {};
    if (function_node->name == sum)
        sumOptimize(function_node);
    else if (function_node->name == min)
        minOptimize(function_node);
    else if (function_node->name == max)
        maxOptimize(function_node);
}

void ArithmeticOperationsInAgrFuncMatcher::visit(const ASTPtr & current_ast, Data data)
{
    if (!current_ast)
        return;

    if (auto * function_node = current_ast->as<ASTFunction>())
        visit(function_node, data);
}

bool ArithmeticOperationsInAgrFuncMatcher::needChildVisit(const ASTPtr & node, const ASTPtr & child)
{
    if (!child)
        throw Exception("AST item should not have nullptr in children", ErrorCodes::LOGICAL_ERROR);

    return !(node->as<ASTTableExpression>() || node->as<ASTArrayJoin>());
}

}