ClickHouse/src/Functions/MultiSearchFirstPositionImpl.h

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#pragma once
#include <vector>
#include <Columns/ColumnArray.h>
#include <Columns/ColumnString.h>
namespace DB
{
namespace ErrorCodes
{
extern const int NUMBER_OF_ARGUMENTS_DOESNT_MATCH;
}
template <typename Name, typename Impl>
struct MultiSearchFirstPositionImpl
{
using ResultType = UInt64;
/// Variable for understanding, if we used offsets for the output, most
/// likely to determine whether the function returns ColumnVector of ColumnArray.
static constexpr bool is_column_array = false;
static constexpr auto name = Name::name;
static auto getReturnType() { return std::make_shared<DataTypeNumber<ResultType>>(); }
static void vectorConstant(
const ColumnString::Chars & haystack_data,
const ColumnString::Offsets & haystack_offsets,
const Array & needles_arr,
PaddedPODArray<UInt64> & res,
PaddedPODArray<UInt64> & /*offsets*/,
bool /*allow_hyperscan*/,
size_t /*max_hyperscan_regexp_length*/,
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size_t /*max_hyperscan_regexp_total_length*/,
bool /*reject_expensive_hyperscan_regexps*/)
{
// For performance of Volnitsky search, it is crucial to save only one byte for pattern number.
if (needles_arr.size() > std::numeric_limits<UInt8>::max())
throw Exception(ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH,
"Number of arguments for function {} doesn't match: passed {}, should be at most {}",
name, std::to_string(needles_arr.size()), std::to_string(std::numeric_limits<UInt8>::max()));
std::vector<std::string_view> needles;
needles.reserve(needles_arr.size());
for (const auto & needle : needles_arr)
needles.emplace_back(needle.get<String>());
auto res_callback = [](const UInt8 * start, const UInt8 * end) -> UInt64
{
return 1 + Impl::countChars(reinterpret_cast<const char *>(start), reinterpret_cast<const char *>(end));
};
auto searcher = Impl::createMultiSearcherInBigHaystack(needles);
const size_t haystack_size = haystack_offsets.size();
res.resize(haystack_size);
size_t iteration = 0;
while (searcher.hasMoreToSearch())
{
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size_t prev_haystack_offset = 0;
for (size_t j = 0; j < haystack_size; ++j)
{
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const auto * haystack = &haystack_data[prev_haystack_offset];
const auto * haystack_end = haystack + haystack_offsets[j] - prev_haystack_offset - 1;
if (iteration == 0 || res[j] == 0)
res[j] = searcher.searchOneFirstPosition(haystack, haystack_end, res_callback);
else
{
UInt64 result = searcher.searchOneFirstPosition(haystack, haystack_end, res_callback);
if (result != 0)
res[j] = std::min(result, res[j]);
}
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prev_haystack_offset = haystack_offsets[j];
}
++iteration;
}
if (iteration == 0)
std::fill(res.begin(), res.end(), 0);
}
static void vectorVector(
const ColumnString::Chars & haystack_data,
const ColumnString::Offsets & haystack_offsets,
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const IColumn & needles_data,
const ColumnArray::Offsets & needles_offsets,
PaddedPODArray<ResultType> & res,
PaddedPODArray<UInt64> & /*offsets*/,
bool /*allow_hyperscan*/,
size_t /*max_hyperscan_regexp_length*/,
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size_t /*max_hyperscan_regexp_total_length*/,
bool /*reject_expensive_hyperscan_regexps*/)
{
const size_t haystack_size = haystack_offsets.size();
res.resize(haystack_size);
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size_t prev_haystack_offset = 0;
size_t prev_needles_offset = 0;
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const ColumnString * needles_data_string = checkAndGetColumn<ColumnString>(&needles_data);
std::vector<std::string_view> needles;
auto res_callback = [](const UInt8 * start, const UInt8 * end) -> UInt64
{
return 1 + Impl::countChars(reinterpret_cast<const char *>(start), reinterpret_cast<const char *>(end));
};
for (size_t i = 0; i < haystack_size; ++i)
{
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needles.reserve(needles_offsets[i] - prev_needles_offset);
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for (size_t j = prev_needles_offset; j < needles_offsets[i]; ++j)
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{
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needles.emplace_back(needles_data_string->getDataAt(j).toView());
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}
auto searcher = Impl::createMultiSearcherInBigHaystack(needles); // sub-optimal
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const auto * const haystack = &haystack_data[prev_haystack_offset];
const auto * haystack_end = haystack + haystack_offsets[i] - prev_haystack_offset - 1;
size_t iteration = 0;
while (searcher.hasMoreToSearch())
{
if (iteration == 0 || res[i] == 0)
{
res[i] = searcher.searchOneFirstPosition(haystack, haystack_end, res_callback);
}
else
{
UInt64 result = searcher.searchOneFirstPosition(haystack, haystack_end, res_callback);
if (result != 0)
{
res[i] = std::min(result, res[i]);
}
}
++iteration;
}
if (iteration == 0)
{
res[i] = 0;
}
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prev_haystack_offset = haystack_offsets[i];
prev_needles_offset = needles_offsets[i];
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needles.clear();
}
}
};
}