// Licensed to the Apache Software Foundation (ASF) under one

// or more contributor license agreements. See the NOTICE file

// distributed with this work for additional information

// regarding copyright ownership. The ASF licenses this file

// to you under the Apache License, Version 2.0 (the

// "License"); you may not use this file except in compliance

// with the License. You may obtain a copy of the License at

//

// http://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing,

// software distributed under the License is distributed on an

// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY

// KIND, either express or implied. See the License for the

// specific language governing permissions and limitations

// under the License.

#include <algorithm>

#include <array>

#include <limits>

#include <string_view>

#include <unordered_map>

#include <vector>

#include "common/status.h"

#include "core/custom_allocator.h"

#include "core/data_type/data_type_number.h"

#include "core/pod_array.h"

#include "core/string_ref.h"

#include "exprs/function/function_totype.h"

#include "exprs/function/simple_function_factory.h"

#include "util/simd/vstring_function.h"

namespace doris {

struct NameLevenshtein {

static constexpr auto name = "levenshtein";

};

struct NameDamerauLevenshteinDistance {

static constexpr auto name = "damerau_levenshtein_distance";

};

// 64MB limit for the distance matrix.

static constexpr size_t MAX_DAMERAU_LEVENSHTEIN_MATRIX_CELLS = 16 * 1024 * 1024;

using Utf8Offsets = DorisVector<size_t>;

static StringRef string_ref_at(const ColumnString::Chars& data,

const ColumnString::Offsets& offsets, size_t i) {

DCHECK_LT(i, offsets.size());

const auto previous_offset = i == 0 ? 0 : offsets[i - 1];

return StringRef(data.data() + previous_offset, offsets[i] - previous_offset)

.trim_tail_padding_zero();

}

static void get_utf8_char_offsets(const StringRef& ref, Utf8Offsets& offsets) {

offsets.clear();

offsets.reserve(ref.size);

for (size_t i = 0, char_size = 0; i < ref.size; i += char_size) {

char_size = UTF8_BYTE_LENGTH[static_cast<unsigned char>(ref.data[i])];

offsets.push_back(i);

}

}

struct LevenshteinDistance {

static Status ascii(const StringRef& left, const StringRef& right, Int32& result) {

const StringRef* left_ref = &left;

const StringRef* right_ref = &right;

size_t m = left.size;

size_t n = right.size;

if (n > m) {

std::swap(left_ref, right_ref);

std::swap(m, n);

}

std::vector<Int32> prev(n + 1);

std::vector<Int32> curr(n + 1);

for (size_t j = 0; j <= n; ++j) {

prev[j] = static_cast<Int32>(j);

}

for (size_t i = 1; i <= m; ++i) {

curr[0] = static_cast<Int32>(i);

const char left_char = left_ref->data[i - 1];

for (size_t j = 1; j <= n; ++j) {

const Int32 cost = left_char == right_ref->data[j - 1] ? 0 : 1;

const Int32 insert_cost = curr[j - 1] + 1;

const Int32 delete_cost = prev[j] + 1;

const Int32 replace_cost = prev[j - 1] + cost;

curr[j] = std::min(std::min(insert_cost, delete_cost), replace_cost);

}

std::swap(prev, curr);

}

result = prev[n];

return Status::OK();

}

static Status utf8(const StringRef& left, const Utf8Offsets& left_offsets,

const StringRef& right, const Utf8Offsets& right_offsets, Int32& result) {

const StringRef* left_ref = &left;

const StringRef* right_ref = &right;

const Utf8Offsets* left_offsets_ref = &left_offsets;

const Utf8Offsets* right_offsets_ref = &right_offsets;

if (right_offsets_ref->size() > left_offsets_ref->size()) {

std::swap(left_offsets_ref, right_offsets_ref);

std::swap(left_ref, right_ref);

}

const size_t m = left_offsets_ref->size();

const size_t n = right_offsets_ref->size();

std::vector<Int32> prev(n + 1);

std::vector<Int32> curr(n + 1);

for (size_t j = 0; j <= n; ++j) {

prev[j] = static_cast<Int32>(j);

}

for (size_t i = 1; i <= m; ++i) {

curr[0] = static_cast<Int32>(i);

const size_t left_off = (*left_offsets_ref)[i - 1];

const size_t left_next = i < m ? (*left_offsets_ref)[i] : left_ref->size;

for (size_t j = 1; j <= n; ++j) {

const size_t right_off = (*right_offsets_ref)[j - 1];

const size_t right_next = j < n ? (*right_offsets_ref)[j] : right_ref->size;

const Int32 cost =

simd::VStringFunctions::utf8_char_equal(*left_ref, left_off, left_next,

*right_ref, right_off, right_next)

? 0

: 1;

const Int32 insert_cost = curr[j - 1] + 1;

const Int32 delete_cost = prev[j] + 1;

const Int32 replace_cost = prev[j - 1] + cost;

curr[j] = std::min(std::min(insert_cost, delete_cost), replace_cost);

}

std::swap(prev, curr);

}

result = prev[n];

return Status::OK();

}

};

struct DamerauLevenshteinDistance {

using SymbolId = Int32;

using SymbolVector = DorisVector<SymbolId>;

using SymbolMap =

std::unordered_map<std::string_view, SymbolId, std::hash<std::string_view>,

std::equal_to<std::string_view>,

CustomStdAllocator<std::pair<const std::string_view, SymbolId>>>;

// Do not use absl::strings_internal::CappedDamerauLevenshteinDistance here:

// 1. It is capped: distances greater than cutoff return cutoff + 1, not exact distance.

// 2. It returns uint8_t and is intended for short strings.

// 3. It implements the restricted/OSA variant, not full Damerau-Levenshtein.

// 4. It works on bytes, cannot handle UTF-8 characters.

static Status ascii(const StringRef& left, const StringRef& right, Int32& result) {

const size_t m = left.size;

const size_t n = right.size;

if (m == 0) {

result = static_cast<Int32>(n);

return Status::OK();

}

if (n == 0) {

result = static_cast<Int32>(m);

return Status::OK();

}

size_t matrix_cells = 0;

RETURN_IF_ERROR(get_matrix_cell_count(m, n, matrix_cells));

const Int32 max_distance = static_cast<Int32>(m + n);

std::array<Int32, 256> last_row {};

PaddedPODArray<Int32> dist;

dist.resize_fill(matrix_cells, 0);

auto at = [&](size_t i, size_t j) -> Int32& { return dist[i * (n + 2) + j]; };

at(0, 0) = max_distance;

for (size_t i = 0; i <= m; ++i) {

at(i + 1, 0) = max_distance;

at(i + 1, 1) = static_cast<Int32>(i);

}

for (size_t j = 0; j <= n; ++j) {

at(0, j + 1) = max_distance;

at(1, j + 1) = static_cast<Int32>(j);

}

for (size_t i = 1; i <= m; ++i) {

Int32 last_match_col = 0;

const auto left_symbol = static_cast<unsigned char>(left.data[i - 1]);

for (size_t j = 1; j <= n; ++j) {

const auto right_symbol = static_cast<unsigned char>(right.data[j - 1]);

const Int32 last_match_row = last_row[right_symbol];

const Int32 transposition_col = last_match_col;

Int32 cost = 1;

if (left_symbol == right_symbol) {

cost = 0;

last_match_col = static_cast<Int32>(j);

}

const Int32 replace_cost = at(i, j) + cost;

const Int32 insert_cost = at(i + 1, j) + 1;

const Int32 delete_cost = at(i, j + 1) + 1;

const Int32 transpose_cost = at(last_match_row, transposition_col) +

static_cast<Int32>(i - last_match_row - 1) + 1 +

static_cast<Int32>(j - transposition_col - 1);

at(i + 1, j + 1) = std::min(std::min(replace_cost, insert_cost),

std::min(delete_cost, transpose_cost));

}

last_row[left_symbol] = static_cast<Int32>(i);

}

result = at(m + 1, n + 1);

return Status::OK();

}

/*

* Keep the UTF-8 symbol mapping path. The benchmark below shows that mapping each UTF-8

* character to an integer symbol first is faster than comparing UTF-8 slices inside the

* dp loop, because the hot loop only needs integer equality and indexed last-row lookup.

*

* --------------------------------------------------------------------------

* Benchmark Time CPU

* --------------------------------------------------------------------------

* BM_DamerauLevenshtein_UTF8/SymbolMapped_16 1.85 us 1.82 us

* BM_DamerauLevenshtein_UTF8/DirectCompare_16 6.48 us 6.43 us

* BM_DamerauLevenshtein_UTF8/SymbolMapped_64 12.6 us 12.6 us

* BM_DamerauLevenshtein_UTF8/DirectCompare_64 119 us 118 us

* BM_DamerauLevenshtein_UTF8/SymbolMapped_128 43.4 us 43.1 us

* BM_DamerauLevenshtein_UTF8/DirectCompare_128 478 us 475 us

* BM_DamerauLevenshtein_UTF8/SymbolMapped_256 160 us 159 us

* BM_DamerauLevenshtein_UTF8/DirectCompare_256 1892 us 1882 us

*/

static Status utf8(const StringRef& left, const Utf8Offsets& left_offsets,

const StringRef& right, const Utf8Offsets& right_offsets, Int32& result) {

SymbolVector left_symbols;

SymbolVector right_symbols;

SymbolMap symbol_ids;

symbol_ids.reserve(left_offsets.size() + right_offsets.size());

SymbolId next_symbol = 0;

append_utf8_symbols(left, left_offsets, left_symbols, symbol_ids, next_symbol);

append_utf8_symbols(right, right_offsets, right_symbols, symbol_ids, next_symbol);

return by_symbols(left_symbols, right_symbols, next_symbol, result);

}

private:

static Status by_symbols(const SymbolVector& left, const SymbolVector& right,

size_t alphabet_size, Int32& result) {

const size_t m = left.size();

const size_t n = right.size();

if (m == 0) {

result = static_cast<Int32>(n);

return Status::OK();

}

if (n == 0) {

result = static_cast<Int32>(m);

return Status::OK();

}

size_t matrix_cells = 0;

RETURN_IF_ERROR(get_matrix_cell_count(m, n, matrix_cells));

const Int32 max_distance = static_cast<Int32>(m + n);

DorisVector<Int32> last_row(alphabet_size, 0);

PaddedPODArray<Int32> dist;

dist.resize_fill(matrix_cells, 0);

auto at = [&](size_t i, size_t j) -> Int32& { return dist[i * (n + 2) + j]; };

at(0, 0) = max_distance;

for (size_t i = 0; i <= m; ++i) {

at(i + 1, 0) = max_distance;

at(i + 1, 1) = static_cast<Int32>(i);

}

for (size_t j = 0; j <= n; ++j) {

at(0, j + 1) = max_distance;

at(1, j + 1) = static_cast<Int32>(j);

}

for (size_t i = 1; i <= m; ++i) {

Int32 last_match_col = 0;

for (size_t j = 1; j <= n; ++j) {

const Int32 last_match_row = last_row[right[j - 1]];

const Int32 transposition_col = last_match_col;

Int32 cost = 1;

if (left[i - 1] == right[j - 1]) {

cost = 0;

last_match_col = static_cast<Int32>(j);

}

const Int32 replace_cost = at(i, j) + cost;

const Int32 insert_cost = at(i + 1, j) + 1;

const Int32 delete_cost = at(i, j + 1) + 1;

const Int32 transpose_cost = at(last_match_row, transposition_col) +

static_cast<Int32>(i - last_match_row - 1) + 1 +

static_cast<Int32>(j - transposition_col - 1);

at(i + 1, j + 1) = std::min(std::min(replace_cost, insert_cost),

std::min(delete_cost, transpose_cost));

}

last_row[left[i - 1]] = static_cast<Int32>(i);

}

result = at(m + 1, n + 1);

return Status::OK();

}

static Status get_matrix_cell_count(size_t m, size_t n, size_t& matrix_cells) {

const auto max_size = std::numeric_limits<size_t>::max();

if (m > max_size - 2 || n > max_size - 2) {

return Status::InvalidArgument(

"damerau_levenshtein_distance input is too large to allocate distance matrix");

}

const size_t rows = m + 2;

const size_t cols = n + 2;

if (rows > max_size / cols) {

return Status::InvalidArgument(

"damerau_levenshtein_distance distance matrix size overflows");

}

matrix_cells = rows * cols;

if (matrix_cells > MAX_DAMERAU_LEVENSHTEIN_MATRIX_CELLS) {

return Status::InvalidArgument(

"damerau_levenshtein_distance distance matrix is too large: {} cells exceeds "

"limit {}",

matrix_cells, MAX_DAMERAU_LEVENSHTEIN_MATRIX_CELLS);

}

return Status::OK();

}

static void append_utf8_symbols(const StringRef& str, const Utf8Offsets& offsets,

SymbolVector& symbols, SymbolMap& symbol_ids,

SymbolId& next_symbol) {

symbols.reserve(symbols.size() + offsets.size());

for (size_t i = 0; i < offsets.size(); ++i) {

const size_t offset = offsets[i];

const size_t next_offset = i + 1 < offsets.size() ? offsets[i + 1] : str.size;

const std::string_view symbol(str.data + offset, next_offset - offset);

auto [it, inserted] = symbol_ids.emplace(symbol, next_symbol);

if (inserted) {

++next_symbol;

}

symbols.push_back(it->second);

}

}

};

template <typename Distance>

struct StringDistanceImplBase {

using ResultDataType = DataTypeInt32;

using ResultPaddedPODArray = PaddedPODArray<Int32>;

static Status vector_vector(const ColumnString::Chars& ldata,

const ColumnString::Offsets& loffsets,

const ColumnString::Chars& rdata,

const ColumnString::Offsets& roffsets, ResultPaddedPODArray& res) {

DCHECK_EQ(loffsets.size(), roffsets.size());

const size_t size = loffsets.size();

res.resize(size);

Utf8Offsets left_offsets;

Utf8Offsets right_offsets;

for (size_t i = 0; i < size; ++i) {

RETURN_IF_ERROR(distance(string_ref_at(ldata, loffsets, i),

string_ref_at(rdata, roffsets, i), left_offsets, right_offsets,

res[i]));

}

return Status::OK();

}

static Status vector_scalar(const ColumnString::Chars& data,

const ColumnString::Offsets& offsets, const StringRef& constant,

ResultPaddedPODArray& res) {

return vector_const(data, offsets, constant, res);

}

static Status scalar_vector(const StringRef& constant, const ColumnString::Chars& data,

const ColumnString::Offsets& offsets, ResultPaddedPODArray& res) {

return vector_const(data, offsets, constant, res);

}

private:

static Status vector_const(const ColumnString::Chars& data,

const ColumnString::Offsets& offsets, const StringRef& constant,

ResultPaddedPODArray& res) {

const size_t size = offsets.size();

res.resize(size);

const auto constant_ref = constant.trim_tail_padding_zero();

const bool constant_ascii = simd::VStringFunctions::is_ascii(constant_ref);

Utf8Offsets constant_offsets;

get_utf8_char_offsets(constant_ref, constant_offsets);

Utf8Offsets value_offsets;

for (size_t i = 0; i < size; ++i) {

RETURN_IF_ERROR(distance_with_const_offsets(string_ref_at(data, offsets, i),

value_offsets, constant_ref,

constant_offsets, constant_ascii, res[i]));

}

return Status::OK();

}

static Status distance(const StringRef& left, const StringRef& right, Utf8Offsets& left_offsets,

Utf8Offsets& right_offsets, Int32& result) {

const bool left_ascii = simd::VStringFunctions::is_ascii(left);

const bool right_ascii = simd::VStringFunctions::is_ascii(right);

if (left_ascii && right_ascii) {

return Distance::ascii(left, right, result);

}

if (left.size == 0) {

result = static_cast<Int32>(

simd::VStringFunctions::get_char_len(right.data, right.size));

return Status::OK();

}

if (right.size == 0) {

result = static_cast<Int32>(simd::VStringFunctions::get_char_len(left.data, left.size));

return Status::OK();

}

get_utf8_char_offsets(left, left_offsets);

get_utf8_char_offsets(right, right_offsets);

return Distance::utf8(left, left_offsets, right, right_offsets, result);

}

static Status distance_with_const_offsets(const StringRef& value, Utf8Offsets& value_offsets,

const StringRef& constant,

const Utf8Offsets& constant_offsets,

bool constant_ascii, Int32& result) {

const bool value_ascii = simd::VStringFunctions::is_ascii(value);

if (value_ascii && constant_ascii) {

return Distance::ascii(value, constant, result);

}

if (value.size == 0) {

result = static_cast<Int32>(constant_offsets.size());

return Status::OK();

}

if (constant.size == 0) {

result = value_ascii ? static_cast<Int32>(value.size)

: static_cast<Int32>(simd::VStringFunctions::get_char_len(

value.data, value.size));

return Status::OK();

}

get_utf8_char_offsets(value, value_offsets);

return Distance::utf8(value, value_offsets, constant, constant_offsets, result);

}

};

template <typename LeftDataType, typename RightDataType>

struct LevenshteinImpl : public StringDistanceImplBase<LevenshteinDistance> {};

template <typename LeftDataType, typename RightDataType>

struct DamerauLevenshteinDistanceImpl : public StringDistanceImplBase<DamerauLevenshteinDistance> {

};

using FunctionLevenshtein =

FunctionBinaryToType<DataTypeString, DataTypeString, LevenshteinImpl, NameLevenshtein>;

using FunctionDamerauLevenshteinDistance =

FunctionBinaryToType<DataTypeString, DataTypeString, DamerauLevenshteinDistanceImpl,

NameDamerauLevenshteinDistance>;

void register_function_levenshtein(SimpleFunctionFactory& factory) {

factory.register_function<FunctionLevenshtein>();

factory.register_alias(FunctionLevenshtein::name, "levenshtein_distance");

factory.register_alias(FunctionLevenshtein::name, "edit_distance");

factory.register_function<FunctionDamerauLevenshteinDistance>();

}

} // namespace doris