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111 lines
3.7 KiB
C++
111 lines
3.7 KiB
C++
#include <Columns/ColumnString.h>
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#include <DataTypes/DataTypeString.h>
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#include <Functions/FunctionFactory.h>
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#include <Functions/FunctionHelpers.h>
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#include <Functions/IFunctionImpl.h>
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#include <pcg_random.hpp>
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#include <Common/randomSeed.h>
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#include <common/unaligned.h>
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namespace DB
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{
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namespace ErrorCodes
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{
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extern const int NUMBER_OF_ARGUMENTS_DOESNT_MATCH;
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extern const int ILLEGAL_TYPE_OF_ARGUMENT;
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extern const int TOO_LARGE_STRING_SIZE;
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}
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/* Generate random string of specified length with fully random bytes (including zero). */
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class FunctionRandomString : public IFunction
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{
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public:
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static constexpr auto name = "randomString";
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static FunctionPtr create(const Context &) { return std::make_shared<FunctionRandomString>(); }
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String getName() const override { return name; }
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bool isVariadic() const override { return true; }
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size_t getNumberOfArguments() const override { return 0; }
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DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
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{
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if (arguments.empty())
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throw Exception(
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"Function " + getName() + " requires at least one argument: the size of resulting string",
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ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
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if (arguments.size() > 2)
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throw Exception(
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"Function " + getName() + " requires at most two arguments: the size of resulting string and optional disambiguation tag",
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ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
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const IDataType & length_type = *arguments[0];
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if (!isNumber(length_type))
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throw Exception("First argument of function " + getName() + " must have numeric type", ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
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return std::make_shared<DataTypeString>();
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}
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bool isDeterministic() const override { return false; }
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bool isDeterministicInScopeOfQuery() const override { return false; }
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void executeImpl(Block & block, const ColumnNumbers & arguments, size_t result, size_t input_rows_count) override
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{
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auto col_to = ColumnString::create();
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ColumnString::Chars & data_to = col_to->getChars();
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ColumnString::Offsets & offsets_to = col_to->getOffsets();
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if (input_rows_count == 0)
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{
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block.getByPosition(result).column = std::move(col_to);
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return;
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}
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/// Fill offsets.
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offsets_to.resize(input_rows_count);
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const IColumn & length_column = *block.getByPosition(arguments[0]).column;
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IColumn::Offset offset = 0;
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for (size_t row_num = 0; row_num < input_rows_count; ++row_num)
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{
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size_t length = length_column.getUInt(row_num);
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if (length > (1 << 30))
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throw Exception("Too large string size in function " + getName(), ErrorCodes::TOO_LARGE_STRING_SIZE);
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offset += length + 1;
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offsets_to[row_num] = offset;
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}
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/// Fill random bytes.
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data_to.resize(offsets_to.back());
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pcg64_fast rng(randomSeed()); /// TODO It is inefficient. We should use SIMD PRNG instead.
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auto * pos = data_to.data();
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auto * end = pos + data_to.size();
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while (pos < end)
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{
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unalignedStore<UInt64>(pos, rng());
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pos += sizeof(UInt64); // We have padding in column buffers that we can overwrite.
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}
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/// Put zero bytes in between.
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pos = data_to.data();
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for (size_t row_num = 0; row_num < input_rows_count; ++row_num)
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pos[offsets_to[row_num] - 1] = 0;
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block.getByPosition(result).column = std::move(col_to);
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}
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};
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void registerFunctionRandomString(FunctionFactory & factory)
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{
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factory.registerFunction<FunctionRandomString>();
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}
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}
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