ClickHouse/dbms/Functions/PositionImpl.h

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#include "FunctionsStringSearch.h"
#include <string>
#include <vector>
#include <Poco/UTF8String.h>
#include <Common/Volnitsky.h>
namespace DB
{
namespace ErrorCodes
{
extern const int ILLEGAL_COLUMN;
}
/** Implementation details for functions of 'position' family depending on ASCII/UTF8 and case sensitiveness.
*/
struct PositionCaseSensitiveASCII
{
/// For searching single substring inside big-enough contiguous chunk of data. Coluld have slightly expensive initialization.
using SearcherInBigHaystack = Volnitsky;
/// For search many substrings in one string
using MultiSearcherInBigHaystack = MultiVolnitsky;
/// For searching single substring, that is different each time. This object is created for each row of data. It must have cheap initialization.
using SearcherInSmallHaystack = LibCASCIICaseSensitiveStringSearcher;
static SearcherInBigHaystack createSearcherInBigHaystack(const char * needle_data, size_t needle_size, size_t haystack_size_hint)
{
return SearcherInBigHaystack(needle_data, needle_size, haystack_size_hint);
}
static SearcherInSmallHaystack createSearcherInSmallHaystack(const char * needle_data, size_t needle_size)
{
return SearcherInSmallHaystack(needle_data, needle_size);
}
static MultiSearcherInBigHaystack createMultiSearcherInBigHaystack(const std::vector<StringRef> & needles)
{
return MultiSearcherInBigHaystack(needles);
}
/// Number of code points between 'begin' and 'end' (this has different behaviour for ASCII and UTF-8).
static size_t countChars(const char * begin, const char * end) { return end - begin; }
/// Convert string to lowercase. Only for case-insensitive search.
/// Implementation is permitted to be inefficient because it is called for single string.
static void toLowerIfNeed(std::string &) { }
};
struct PositionCaseInsensitiveASCII
{
/// `Volnitsky` is not used here, because one person has measured that this is better. It will be good if you question it.
using SearcherInBigHaystack = ASCIICaseInsensitiveStringSearcher;
using MultiSearcherInBigHaystack = MultiVolnitskyCaseInsensitive;
using SearcherInSmallHaystack = LibCASCIICaseInsensitiveStringSearcher;
static SearcherInBigHaystack createSearcherInBigHaystack(const char * needle_data, size_t needle_size, size_t /*haystack_size_hint*/)
{
return SearcherInBigHaystack(needle_data, needle_size);
}
static SearcherInSmallHaystack createSearcherInSmallHaystack(const char * needle_data, size_t needle_size)
{
return SearcherInSmallHaystack(needle_data, needle_size);
}
static MultiSearcherInBigHaystack createMultiSearcherInBigHaystack(const std::vector<StringRef> & needles)
{
return MultiSearcherInBigHaystack(needles);
}
static size_t countChars(const char * begin, const char * end) { return end - begin; }
static void toLowerIfNeed(std::string & s) { std::transform(std::begin(s), std::end(s), std::begin(s), tolower); }
};
struct PositionCaseSensitiveUTF8
{
using SearcherInBigHaystack = VolnitskyUTF8;
using MultiSearcherInBigHaystack = MultiVolnitskyUTF8;
using SearcherInSmallHaystack = LibCASCIICaseSensitiveStringSearcher;
static SearcherInBigHaystack createSearcherInBigHaystack(const char * needle_data, size_t needle_size, size_t haystack_size_hint)
{
return SearcherInBigHaystack(needle_data, needle_size, haystack_size_hint);
}
static SearcherInSmallHaystack createSearcherInSmallHaystack(const char * needle_data, size_t needle_size)
{
return SearcherInSmallHaystack(needle_data, needle_size);
}
static MultiSearcherInBigHaystack createMultiSearcherInBigHaystack(const std::vector<StringRef> & needles)
{
return MultiSearcherInBigHaystack(needles);
}
static size_t countChars(const char * begin, const char * end)
{
size_t res = 0;
for (auto it = begin; it != end; ++it)
if (!UTF8::isContinuationOctet(static_cast<UInt8>(*it)))
++res;
return res;
}
static void toLowerIfNeed(std::string &) { }
};
struct PositionCaseInsensitiveUTF8
{
using SearcherInBigHaystack = VolnitskyCaseInsensitiveUTF8;
using MultiSearcherInBigHaystack = MultiVolnitskyCaseInsensitiveUTF8;
using SearcherInSmallHaystack = UTF8CaseInsensitiveStringSearcher; /// TODO Very suboptimal.
static SearcherInBigHaystack createSearcherInBigHaystack(const char * needle_data, size_t needle_size, size_t haystack_size_hint)
{
return SearcherInBigHaystack(needle_data, needle_size, haystack_size_hint);
}
static SearcherInSmallHaystack createSearcherInSmallHaystack(const char * needle_data, size_t needle_size)
{
return SearcherInSmallHaystack(needle_data, needle_size);
}
static MultiSearcherInBigHaystack createMultiSearcherInBigHaystack(const std::vector<StringRef> & needles)
{
return MultiSearcherInBigHaystack(needles);
}
static size_t countChars(const char * begin, const char * end)
{
size_t res = 0;
for (auto it = begin; it != end; ++it)
if (!UTF8::isContinuationOctet(static_cast<UInt8>(*it)))
++res;
return res;
}
static void toLowerIfNeed(std::string & s) { Poco::UTF8::toLowerInPlace(s); }
};
template <typename Impl>
struct PositionImpl
{
static constexpr bool use_default_implementation_for_constants = false;
using ResultType = UInt64;
/// Find one substring in many strings.
static void vectorConstant(
const ColumnString::Chars & data, const ColumnString::Offsets & offsets, const std::string & needle, PaddedPODArray<UInt64> & res)
{
const UInt8 * begin = data.data();
const UInt8 * pos = begin;
const UInt8 * end = pos + data.size();
/// Current index in the array of strings.
size_t i = 0;
typename Impl::SearcherInBigHaystack searcher = Impl::createSearcherInBigHaystack(needle.data(), needle.size(), end - pos);
/// We will search for the next occurrence in all strings at once.
while (pos < end && end != (pos = searcher.search(pos, end - pos)))
{
/// Determine which index it refers to.
while (begin + offsets[i] <= pos)
{
res[i] = 0;
++i;
}
/// We check that the entry does not pass through the boundaries of strings.
if (pos + needle.size() < begin + offsets[i])
res[i] = 1 + Impl::countChars(reinterpret_cast<const char *>(begin + offsets[i - 1]), reinterpret_cast<const char *>(pos));
else
res[i] = 0;
pos = begin + offsets[i];
++i;
}
if (i < res.size())
memset(&res[i], 0, (res.size() - i) * sizeof(res[0]));
}
/// Search for substring in string.
static void constantConstant(std::string data, std::string needle, UInt64 & res)
{
Impl::toLowerIfNeed(data);
Impl::toLowerIfNeed(needle);
res = data.find(needle);
if (res == std::string::npos)
res = 0;
else
res = 1 + Impl::countChars(data.data(), data.data() + res);
}
/// Search each time for a different single substring inside each time different string.
static void vectorVector(
const ColumnString::Chars & haystack_data,
const ColumnString::Offsets & haystack_offsets,
const ColumnString::Chars & needle_data,
const ColumnString::Offsets & needle_offsets,
PaddedPODArray<UInt64> & res)
{
ColumnString::Offset prev_haystack_offset = 0;
ColumnString::Offset prev_needle_offset = 0;
size_t size = haystack_offsets.size();
for (size_t i = 0; i < size; ++i)
{
size_t needle_size = needle_offsets[i] - prev_needle_offset - 1;
size_t haystack_size = haystack_offsets[i] - prev_haystack_offset - 1;
if (0 == needle_size)
{
/// An empty string is always at the very beginning of `haystack`.
res[i] = 1;
}
else
{
/// It is assumed that the StringSearcher is not very difficult to initialize.
typename Impl::SearcherInSmallHaystack searcher = Impl::createSearcherInSmallHaystack(
reinterpret_cast<const char *>(&needle_data[prev_needle_offset]),
needle_offsets[i] - prev_needle_offset - 1); /// zero byte at the end
/// searcher returns a pointer to the found substring or to the end of `haystack`.
size_t pos = searcher.search(&haystack_data[prev_haystack_offset], &haystack_data[haystack_offsets[i] - 1])
- &haystack_data[prev_haystack_offset];
if (pos != haystack_size)
{
res[i] = 1
+ Impl::countChars(
reinterpret_cast<const char *>(&haystack_data[prev_haystack_offset]),
reinterpret_cast<const char *>(&haystack_data[prev_haystack_offset + pos]));
}
else
res[i] = 0;
}
prev_haystack_offset = haystack_offsets[i];
prev_needle_offset = needle_offsets[i];
}
}
/// Find many substrings in single string.
static void constantVector(
const String & haystack,
const ColumnString::Chars & needle_data,
const ColumnString::Offsets & needle_offsets,
PaddedPODArray<UInt64> & res)
{
// NOTE You could use haystack indexing. But this is a rare case.
ColumnString::Offset prev_needle_offset = 0;
size_t size = needle_offsets.size();
for (size_t i = 0; i < size; ++i)
{
size_t needle_size = needle_offsets[i] - prev_needle_offset - 1;
if (0 == needle_size)
{
res[i] = 1;
}
else
{
typename Impl::SearcherInSmallHaystack searcher = Impl::createSearcherInSmallHaystack(
reinterpret_cast<const char *>(&needle_data[prev_needle_offset]), needle_offsets[i] - prev_needle_offset - 1);
size_t pos = searcher.search(
reinterpret_cast<const UInt8 *>(haystack.data()),
reinterpret_cast<const UInt8 *>(haystack.data()) + haystack.size())
- reinterpret_cast<const UInt8 *>(haystack.data());
if (pos != haystack.size())
{
res[i] = 1 + Impl::countChars(haystack.data(), haystack.data() + pos);
}
else
res[i] = 0;
}
prev_needle_offset = needle_offsets[i];
}
}
template <typename... Args>
static void vectorFixedConstant(Args &&...)
{
throw Exception("Functions 'position' don't support FixedString haystack argument", ErrorCodes::ILLEGAL_COLUMN);
}
};
}