ClickHouse/dbms/src/Functions/IFunction.cpp

#include <Functions/IFunctionAdaptors.h>

#include <Common/config.h>
#include <Common/typeid_cast.h>
#include <Common/assert_cast.h>
#include <Common/LRUCache.h>
#include <Columns/ColumnConst.h>
#include <Columns/ColumnNullable.h>
#include <Columns/ColumnArray.h>
#include <Columns/ColumnTuple.h>
#include <Columns/ColumnLowCardinality.h>
#include <DataTypes/DataTypeNothing.h>
#include <DataTypes/DataTypeNullable.h>
#include <DataTypes/DataTypeTuple.h>
#include <DataTypes/Native.h>
#include <DataTypes/DataTypeLowCardinality.h>
#include <DataTypes/getLeastSupertype.h>
#include <Functions/FunctionHelpers.h>
#include <Interpreters/ExpressionActions.h>
#include <IO/WriteHelpers.h>
#include <ext/range.h>
#include <ext/collection_cast.h>
#include <cstdlib>
#include <memory>
#include <optional>

#if USE_EMBEDDED_COMPILER
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunused-parameter"
#include <llvm/IR/IRBuilder.h>
#pragma GCC diagnostic pop
#endif


namespace DB
{

namespace ErrorCodes
{
    extern const int NUMBER_OF_ARGUMENTS_DOESNT_MATCH;
    extern const int ILLEGAL_COLUMN;
}


/// Cache for functions result if it was executed on low cardinality column.
/// It's LRUCache which stores function result executed on dictionary and index mapping.
/// It's expected that cache_size is a number of reading streams (so, will store single cached value per thread).
class ExecutableFunctionLowCardinalityResultCache
{
public:
    /// Will assume that dictionaries with same hash has the same keys.
    /// Just in case, check that they have also the same size.
    struct DictionaryKey
    {
        UInt128 hash;
        UInt64 size;

        bool operator== (const DictionaryKey & other) const { return hash == other.hash && size == other.size; }
    };

    struct DictionaryKeyHash
    {
        size_t operator()(const DictionaryKey & key) const
        {
            SipHash hash;
            hash.update(key.hash.low);
            hash.update(key.hash.high);
            hash.update(key.size);
            return hash.get64();
        }
    };

    struct CachedValues
    {
        /// Store ptr to dictionary to be sure it won't be deleted.
        ColumnPtr dictionary_holder;
        ColumnUniquePtr function_result;
        /// Remap positions. new_pos = index_mapping->index(old_pos);
        ColumnPtr index_mapping;
    };

    using CachedValuesPtr = std::shared_ptr<CachedValues>;

    explicit ExecutableFunctionLowCardinalityResultCache(size_t cache_size) : cache(cache_size) {}

    CachedValuesPtr get(const DictionaryKey & key) { return cache.get(key); }
    void set(const DictionaryKey & key, const CachedValuesPtr & mapped) { cache.set(key, mapped); }
    CachedValuesPtr getOrSet(const DictionaryKey & key, const CachedValuesPtr & mapped)
    {
        return cache.getOrSet(key, [&]() { return mapped; }).first;
    }

private:
    using Cache = LRUCache<DictionaryKey, CachedValues, DictionaryKeyHash>;
    Cache cache;
};


void ExecutableFunctionAdaptor::createLowCardinalityResultCache(size_t cache_size)
{
    if (!low_cardinality_result_cache)
        low_cardinality_result_cache = std::make_shared<ExecutableFunctionLowCardinalityResultCache>(cache_size);
}


ColumnPtr wrapInNullable(const ColumnPtr & src, const Block & block, const ColumnNumbers & args, size_t result, size_t input_rows_count)
{
    ColumnPtr result_null_map_column;

    /// If result is already nullable.
    ColumnPtr src_not_nullable = src;

    if (src->onlyNull())
        return src;
    else if (auto * nullable = checkAndGetColumn<ColumnNullable>(*src))
    {
        src_not_nullable = nullable->getNestedColumnPtr();
        result_null_map_column = nullable->getNullMapColumnPtr();
    }

    for (const auto & arg : args)
    {
        const ColumnWithTypeAndName & elem = block.getByPosition(arg);
        if (!elem.type->isNullable())
            continue;

        /// Const Nullable that are NULL.
        if (elem.column->onlyNull())
        {
            auto result_type = block.getByPosition(result).type;
            assert(result_type->isNullable());
            return result_type->createColumnConstWithDefaultValue(input_rows_count);
        }

        if (isColumnConst(*elem.column))
            continue;

        if (auto * nullable = checkAndGetColumn<ColumnNullable>(*elem.column))
        {
            const ColumnPtr & null_map_column = nullable->getNullMapColumnPtr();
            if (!result_null_map_column)
            {
                result_null_map_column = null_map_column;
            }
            else
            {
                MutableColumnPtr mutable_result_null_map_column = (*std::move(result_null_map_column)).mutate();

                NullMap & result_null_map = assert_cast<ColumnUInt8 &>(*mutable_result_null_map_column).getData();
                const NullMap & src_null_map = assert_cast<const ColumnUInt8 &>(*null_map_column).getData();

                for (size_t i = 0, size = result_null_map.size(); i < size; ++i)
                    if (src_null_map[i])
                        result_null_map[i] = 1;

                result_null_map_column = std::move(mutable_result_null_map_column);
            }
        }
    }

    if (!result_null_map_column)
        return makeNullable(src);

    return ColumnNullable::create(src_not_nullable->convertToFullColumnIfConst(), result_null_map_column);
}


namespace
{

struct NullPresence
{
    bool has_nullable = false;
    bool has_null_constant = false;
};

NullPresence getNullPresense(const Block & block, const ColumnNumbers & args)
{
    NullPresence res;

    for (const auto & arg : args)
    {
        const auto & elem = block.getByPosition(arg);

        if (!res.has_nullable)
            res.has_nullable = elem.type->isNullable();
        if (!res.has_null_constant)
            res.has_null_constant = elem.type->onlyNull();
    }

    return res;
}

NullPresence getNullPresense(const ColumnsWithTypeAndName & args)
{
    NullPresence res;

    for (const auto & elem : args)
    {
        if (!res.has_nullable)
            res.has_nullable = elem.type->isNullable();
        if (!res.has_null_constant)
            res.has_null_constant = elem.type->onlyNull();
    }

    return res;
}

bool allArgumentsAreConstants(const Block & block, const ColumnNumbers & args)
{
    for (auto arg : args)
        if (!isColumnConst(*block.getByPosition(arg).column))
            return false;
    return true;
}
}

bool ExecutableFunctionAdaptor::defaultImplementationForConstantArguments(
    Block & block, const ColumnNumbers & args, size_t result, size_t input_rows_count, bool dry_run)
{
    ColumnNumbers arguments_to_remain_constants = impl->getArgumentsThatAreAlwaysConstant();

    /// Check that these arguments are really constant.
    for (auto arg_num : arguments_to_remain_constants)
        if (arg_num < args.size() && !isColumnConst(*block.getByPosition(args[arg_num]).column))
            throw Exception("Argument at index " + toString(arg_num) + " for function " + getName() + " must be constant", ErrorCodes::ILLEGAL_COLUMN);

    if (args.empty() || !impl->useDefaultImplementationForConstants() || !allArgumentsAreConstants(block, args))
        return false;

    Block temporary_block;
    bool have_converted_columns = false;

    size_t arguments_size = args.size();
    for (size_t arg_num = 0; arg_num < arguments_size; ++arg_num)
    {
        const ColumnWithTypeAndName & column = block.getByPosition(args[arg_num]);

        if (arguments_to_remain_constants.end() != std::find(arguments_to_remain_constants.begin(), arguments_to_remain_constants.end(), arg_num))
        {
            temporary_block.insert({column.column->cloneResized(1), column.type, column.name});
        }
        else
        {
            have_converted_columns = true;
            temporary_block.insert({ assert_cast<const ColumnConst *>(column.column.get())->getDataColumnPtr(), column.type, column.name });
        }
    }

    /** When using default implementation for constants, the function requires at least one argument
      *  not in "arguments_to_remain_constants" set. Otherwise we get infinite recursion.
      */
    if (!have_converted_columns)
        throw Exception("Number of arguments for function " + getName() + " doesn't match: the function requires more arguments",
            ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);

    temporary_block.insert(block.getByPosition(result));

    ColumnNumbers temporary_argument_numbers(arguments_size);
    for (size_t i = 0; i < arguments_size; ++i)
        temporary_argument_numbers[i] = i;

    executeWithoutLowCardinalityColumns(temporary_block, temporary_argument_numbers, arguments_size, temporary_block.rows(), dry_run);

    ColumnPtr result_column;
    /// extremely rare case, when we have function with completely const arguments
    /// but some of them produced by non isDeterministic function
    if (temporary_block.getByPosition(arguments_size).column->size() > 1)
        result_column = temporary_block.getByPosition(arguments_size).column->cloneResized(1);
    else
        result_column = temporary_block.getByPosition(arguments_size).column;

    block.getByPosition(result).column = ColumnConst::create(result_column, input_rows_count);
    return true;
}


bool ExecutableFunctionAdaptor::defaultImplementationForNulls(
    Block & block, const ColumnNumbers & args, size_t result, size_t input_rows_count, bool dry_run)
{
    if (args.empty() || !impl->useDefaultImplementationForNulls())
        return false;

    NullPresence null_presence = getNullPresense(block, args);

    if (null_presence.has_null_constant)
    {
        auto & result_column = block.getByPosition(result).column;
        auto result_type = block.getByPosition(result).type;
        // Default implementation for nulls returns null result for null arguments,
        // so the result type must be nullable.
        assert(result_type->isNullable());

        result_column = result_type->createColumnConstWithDefaultValue(input_rows_count);
        return true;
    }

    if (null_presence.has_nullable)
    {
        Block temporary_block = createBlockWithNestedColumns(block, args, result);
        executeWithoutLowCardinalityColumns(temporary_block, args, result, temporary_block.rows(), dry_run);
        block.getByPosition(result).column = wrapInNullable(temporary_block.getByPosition(result).column, block, args,
                                                            result, input_rows_count);
        return true;
    }

    return false;
}

void ExecutableFunctionAdaptor::executeWithoutLowCardinalityColumns(
    Block & block, const ColumnNumbers & args, size_t result, size_t input_rows_count, bool dry_run)
{
    if (defaultImplementationForConstantArguments(block, args, result, input_rows_count, dry_run))
        return;

    if (defaultImplementationForNulls(block, args, result, input_rows_count, dry_run))
        return;

    if (dry_run)
        impl->executeDryRun(block, args, result, input_rows_count);
    else
        impl->execute(block, args, result, input_rows_count);
}

static const ColumnLowCardinality * findLowCardinalityArgument(const Block & block, const ColumnNumbers & args)
{
    const ColumnLowCardinality * result_column = nullptr;

    for (auto arg : args)
    {
        const ColumnWithTypeAndName & column = block.getByPosition(arg);
        if (auto * low_cardinality_column = checkAndGetColumn<ColumnLowCardinality>(column.column.get()))
        {
            if (result_column)
                throw Exception("Expected single dictionary argument for function.", ErrorCodes::LOGICAL_ERROR);

            result_column = low_cardinality_column;
        }
    }

    return result_column;
}

static ColumnPtr replaceLowCardinalityColumnsByNestedAndGetDictionaryIndexes(
    Block & block, const ColumnNumbers & args, bool can_be_executed_on_default_arguments, size_t input_rows_count)
{
    size_t num_rows = input_rows_count;
    ColumnPtr indexes;

    /// Find first LowCardinality column and replace it to nested dictionary.
    for (auto arg : args)
    {
        ColumnWithTypeAndName & column = block.getByPosition(arg);
        if (auto * low_cardinality_column = checkAndGetColumn<ColumnLowCardinality>(column.column.get()))
        {
            /// Single LowCardinality column is supported now.
            if (indexes)
                throw Exception("Expected single dictionary argument for function.", ErrorCodes::LOGICAL_ERROR);

            auto * low_cardinality_type = checkAndGetDataType<DataTypeLowCardinality>(column.type.get());

            if (!low_cardinality_type)
                throw Exception("Incompatible type for low cardinality column: " + column.type->getName(),
                                ErrorCodes::LOGICAL_ERROR);

            if (can_be_executed_on_default_arguments)
            {
                /// Normal case, when function can be executed on values's default.
                column.column = low_cardinality_column->getDictionary().getNestedColumn();
                indexes = low_cardinality_column->getIndexesPtr();
            }
            else
            {
                /// Special case when default value can't be used. Example: 1 % LowCardinality(Int).
                /// LowCardinality always contains default, so 1 % 0 will throw exception in normal case.
                auto dict_encoded = low_cardinality_column->getMinimalDictionaryEncodedColumn(0, low_cardinality_column->size());
                column.column = dict_encoded.dictionary;
                indexes = dict_encoded.indexes;
            }

            num_rows = column.column->size();
            column.type = low_cardinality_type->getDictionaryType();
        }
    }

    /// Change size of constants.
    for (auto arg : args)
    {
        ColumnWithTypeAndName & column = block.getByPosition(arg);
        if (auto * column_const = checkAndGetColumn<ColumnConst>(column.column.get()))
        {
            column.column = column_const->removeLowCardinality()->cloneResized(num_rows);
            column.type = removeLowCardinality(column.type);
        }
    }

#ifndef NDEBUG
    block.checkNumberOfRows(true);
#endif

    return indexes;
}

static void convertLowCardinalityColumnsToFull(Block & block, const ColumnNumbers & args)
{
    for (auto arg : args)
    {
        ColumnWithTypeAndName & column = block.getByPosition(arg);

        column.column = recursiveRemoveLowCardinality(column.column);
        column.type = recursiveRemoveLowCardinality(column.type);
    }
}

void ExecutableFunctionAdaptor::execute(Block & block, const ColumnNumbers & args, size_t result, size_t input_rows_count, bool dry_run)
{
    if (impl->useDefaultImplementationForLowCardinalityColumns())
    {
        auto & res = block.safeGetByPosition(result);
        Block block_without_low_cardinality = block.cloneWithoutColumns();

        for (auto arg : args)
            block_without_low_cardinality.safeGetByPosition(arg).column = block.safeGetByPosition(arg).column;

        if (auto * res_low_cardinality_type = typeid_cast<const DataTypeLowCardinality *>(res.type.get()))
        {
            const auto * low_cardinality_column = findLowCardinalityArgument(block, args);
            bool can_be_executed_on_default_arguments = impl->canBeExecutedOnDefaultArguments();
            bool use_cache = low_cardinality_result_cache && can_be_executed_on_default_arguments
                             && low_cardinality_column && low_cardinality_column->isSharedDictionary();
            ExecutableFunctionLowCardinalityResultCache::DictionaryKey key;

            if (use_cache)
            {
                const auto & dictionary = low_cardinality_column->getDictionary();
                key = {dictionary.getHash(), dictionary.size()};

                auto cached_values = low_cardinality_result_cache->get(key);
                if (cached_values)
                {
                    auto indexes = cached_values->index_mapping->index(low_cardinality_column->getIndexes(), 0);
                    res.column = ColumnLowCardinality::create(cached_values->function_result, indexes, true);
                    return;
                }
            }

            block_without_low_cardinality.safeGetByPosition(result).type = res_low_cardinality_type->getDictionaryType();
            ColumnPtr indexes = replaceLowCardinalityColumnsByNestedAndGetDictionaryIndexes(
                    block_without_low_cardinality, args, can_be_executed_on_default_arguments, input_rows_count);

            executeWithoutLowCardinalityColumns(block_without_low_cardinality, args, result, block_without_low_cardinality.rows(), dry_run);

            auto keys = block_without_low_cardinality.safeGetByPosition(result).column->convertToFullColumnIfConst();

            auto res_mut_dictionary = DataTypeLowCardinality::createColumnUnique(*res_low_cardinality_type->getDictionaryType());
            ColumnPtr res_indexes = res_mut_dictionary->uniqueInsertRangeFrom(*keys, 0, keys->size());
            ColumnUniquePtr res_dictionary = std::move(res_mut_dictionary);

            if (indexes)
            {
                if (use_cache)
                {
                    auto cache_values = std::make_shared<ExecutableFunctionLowCardinalityResultCache::CachedValues>();
                    cache_values->dictionary_holder = low_cardinality_column->getDictionaryPtr();
                    cache_values->function_result = res_dictionary;
                    cache_values->index_mapping = res_indexes;

                    cache_values = low_cardinality_result_cache->getOrSet(key, cache_values);
                    res_dictionary = cache_values->function_result;
                    res_indexes = cache_values->index_mapping;
                }

                res.column = ColumnLowCardinality::create(res_dictionary, res_indexes->index(*indexes, 0), use_cache);
            }
            else
            {
                res.column = ColumnLowCardinality::create(res_dictionary, res_indexes);
            }
        }
        else
        {
            convertLowCardinalityColumnsToFull(block_without_low_cardinality, args);
            executeWithoutLowCardinalityColumns(block_without_low_cardinality, args, result, input_rows_count, dry_run);
            res.column = block_without_low_cardinality.safeGetByPosition(result).column;
        }
    }
    else
        executeWithoutLowCardinalityColumns(block, args, result, input_rows_count, dry_run);
}

void FunctionOverloadResolverAdaptor::checkNumberOfArguments(size_t number_of_arguments) const
{
    if (isVariadic())
        return;

    size_t expected_number_of_arguments = getNumberOfArguments();

    if (number_of_arguments != expected_number_of_arguments)
        throw Exception("Number of arguments for function " + getName() + " doesn't match: passed "
                        + toString(number_of_arguments) + ", should be " + toString(expected_number_of_arguments),
                        ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
}

DataTypePtr FunctionOverloadResolverAdaptor::getReturnTypeWithoutLowCardinality(const ColumnsWithTypeAndName & arguments) const
{
    checkNumberOfArguments(arguments.size());

    if (!arguments.empty() && impl->useDefaultImplementationForNulls())
    {
        NullPresence null_presence = getNullPresense(arguments);

        if (null_presence.has_null_constant)
        {
            return makeNullable(std::make_shared<DataTypeNothing>());
        }
        if (null_presence.has_nullable)
        {
            Block nested_block = createBlockWithNestedColumns(Block(arguments), ext::collection_cast<ColumnNumbers>(ext::range(0, arguments.size())));
            auto return_type = impl->getReturnType(ColumnsWithTypeAndName(nested_block.begin(), nested_block.end()));
            return makeNullable(return_type);

        }
    }

    return impl->getReturnType(arguments);
}

#if USE_EMBEDDED_COMPILER

static std::optional<DataTypes> removeNullables(const DataTypes & types)
{
    for (const auto & type : types)
    {
        if (!typeid_cast<const DataTypeNullable *>(type.get()))
            continue;
        DataTypes filtered;
        for (const auto & sub_type : types)
            filtered.emplace_back(removeNullable(sub_type));
        return filtered;
    }
    return {};
}

bool IFunction::isCompilable(const DataTypes & arguments) const
{
    if (useDefaultImplementationForNulls())
        if (auto denulled = removeNullables(arguments))
            return isCompilableImpl(*denulled);
    return isCompilableImpl(arguments);
}

llvm::Value * IFunction::compile(llvm::IRBuilderBase & builder, const DataTypes & arguments, ValuePlaceholders values) const
{
    if (useDefaultImplementationForNulls())
    {
        if (auto denulled = removeNullables(arguments))
        {
            /// FIXME: when only one column is nullable, this can actually be slower than the non-jitted version
            ///        because this involves copying the null map while `wrapInNullable` reuses it.
            auto & b = static_cast<llvm::IRBuilder<> &>(builder);
            auto * fail = llvm::BasicBlock::Create(b.GetInsertBlock()->getContext(), "", b.GetInsertBlock()->getParent());
            auto * join = llvm::BasicBlock::Create(b.GetInsertBlock()->getContext(), "", b.GetInsertBlock()->getParent());
            auto * zero = llvm::Constant::getNullValue(toNativeType(b, makeNullable(getReturnTypeImpl(*denulled))));
            for (size_t i = 0; i < arguments.size(); i++)
            {
                if (!arguments[i]->isNullable())
                    continue;
                /// Would be nice to evaluate all this lazily, but that'd change semantics: if only unevaluated
                /// arguments happen to contain NULLs, the return value would not be NULL, though it should be.
                auto * value = values[i]();
                auto * ok = llvm::BasicBlock::Create(b.GetInsertBlock()->getContext(), "", b.GetInsertBlock()->getParent());
                b.CreateCondBr(b.CreateExtractValue(value, {1}), fail, ok);
                b.SetInsertPoint(ok);
                values[i] = [value = b.CreateExtractValue(value, {0})]() { return value; };
            }
            auto * result = b.CreateInsertValue(zero, compileImpl(builder, *denulled, std::move(values)), {0});
            auto * result_block = b.GetInsertBlock();
            b.CreateBr(join);
            b.SetInsertPoint(fail);
            auto * null = b.CreateInsertValue(zero, b.getTrue(), {1});
            b.CreateBr(join);
            b.SetInsertPoint(join);
            auto * phi = b.CreatePHI(result->getType(), 2);
            phi->addIncoming(result, result_block);
            phi->addIncoming(null, fail);
            return phi;
        }
    }
    return compileImpl(builder, arguments, std::move(values));
}

#endif

DataTypePtr FunctionOverloadResolverAdaptor::getReturnType(const ColumnsWithTypeAndName & arguments) const
{
    if (impl->useDefaultImplementationForLowCardinalityColumns())
    {
        bool has_low_cardinality = false;
        size_t num_full_low_cardinality_columns = 0;
        size_t num_full_ordinary_columns = 0;

        ColumnsWithTypeAndName args_without_low_cardinality(arguments);

        for (ColumnWithTypeAndName & arg : args_without_low_cardinality)
        {
            bool is_const = arg.column && isColumnConst(*arg.column);
            if (is_const)
                arg.column = assert_cast<const ColumnConst &>(*arg.column).removeLowCardinality();

            if (auto * low_cardinality_type = typeid_cast<const DataTypeLowCardinality *>(arg.type.get()))
            {
                arg.type = low_cardinality_type->getDictionaryType();
                has_low_cardinality = true;

                if (!is_const)
                    ++num_full_low_cardinality_columns;
            }
            else if (!is_const)
                ++num_full_ordinary_columns;
        }

        for (auto & arg : args_without_low_cardinality)
        {
            arg.column = recursiveRemoveLowCardinality(arg.column);
            arg.type = recursiveRemoveLowCardinality(arg.type);
        }

        auto type_without_low_cardinality = getReturnTypeWithoutLowCardinality(args_without_low_cardinality);

        if (impl->canBeExecutedOnLowCardinalityDictionary() && has_low_cardinality
            && num_full_low_cardinality_columns <= 1 && num_full_ordinary_columns == 0
            && type_without_low_cardinality->canBeInsideLowCardinality())
            return std::make_shared<DataTypeLowCardinality>(type_without_low_cardinality);
        else
            return type_without_low_cardinality;
    }

    return getReturnTypeWithoutLowCardinality(arguments);
}
}