ClickHouse/dbms/Functions/MultiSearchFirstIndexImpl.h

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#pragma once
#include <vector>
#include <Columns/ColumnString.h>
namespace DB
{
template <typename Impl>
struct MultiSearchFirstIndexImpl
{
using ResultType = UInt64;
static constexpr bool is_using_hyperscan = false;
/// 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 auto getReturnType() { return std::make_shared<DataTypeNumber<ResultType>>(); }
static void vectorConstant(
const ColumnString::Chars & haystack_data,
const ColumnString::Offsets & haystack_offsets,
const std::vector<StringRef> & needles,
PaddedPODArray<UInt64> & res,
[[maybe_unused]] PaddedPODArray<UInt64> & offsets)
{
auto searcher = Impl::createMultiSearcherInBigHaystack(needles);
const size_t haystack_string_size = haystack_offsets.size();
res.resize(haystack_string_size);
size_t iteration = 0;
while (searcher.hasMoreToSearch())
{
size_t prev_offset = 0;
for (size_t j = 0; j < haystack_string_size; ++j)
{
const auto * haystack = &haystack_data[prev_offset];
const auto * haystack_end = haystack + haystack_offsets[j] - prev_offset - 1;
/// hasMoreToSearch traverse needles in increasing order
if (iteration == 0 || res[j] == 0)
res[j] = searcher.searchOneFirstIndex(haystack, haystack_end);
prev_offset = haystack_offsets[j];
}
++iteration;
}
}
};
}