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115 lines
3.1 KiB
C++
115 lines
3.1 KiB
C++
#include <Processors/Transforms/DistinctTransform.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 SET_SIZE_LIMIT_EXCEEDED;
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}
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DistinctTransform::DistinctTransform(
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const Block & header_,
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const SizeLimits & set_size_limits_,
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UInt64 limit_hint_,
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const Names & columns_)
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: ISimpleTransform(header_, header_, true)
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, limit_hint(limit_hint_)
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, set_size_limits(set_size_limits_)
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{
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size_t num_columns = columns_.empty() ? header_.columns() : columns_.size();
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key_columns_pos.reserve(columns_.size());
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for (size_t i = 0; i < num_columns; ++i)
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{
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auto pos = columns_.empty() ? i
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: header_.getPositionByName(columns_[i]);
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auto & col = header_.getByPosition(pos).column;
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if (!(col && isColumnConst(*col)))
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key_columns_pos.emplace_back(pos);
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}
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}
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template <typename Method>
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void DistinctTransform::buildFilter(
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Method & method,
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const ColumnRawPtrs & columns,
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IColumn::Filter & filter,
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size_t rows,
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SetVariants & variants) const
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{
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typename Method::State state(columns, key_sizes, nullptr);
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for (size_t i = 0; i < rows; ++i)
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{
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auto emplace_result = state.emplaceKey(method.data, i, variants.string_pool);
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/// Emit the record if there is no such key in the current set yet.
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/// Skip it otherwise.
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filter[i] = emplace_result.isInserted();
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}
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}
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void DistinctTransform::transform(Chunk & chunk)
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{
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auto num_rows = chunk.getNumRows();
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auto columns = chunk.detachColumns();
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/// Stop reading if we already reach the limit.
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if (no_more_rows || (limit_hint && data.getTotalRowCount() >= limit_hint))
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{
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stopReading();
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return;
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}
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ColumnRawPtrs column_ptrs;
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column_ptrs.reserve(key_columns_pos.size());
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for (auto pos : key_columns_pos)
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column_ptrs.emplace_back(columns[pos].get());
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if (column_ptrs.empty())
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{
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/// Only constants. We need to return single row.
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no_more_rows = true;
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for (auto & column : columns)
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column = column->cut(0, 1);
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chunk.setColumns(std::move(columns), 1);
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return;
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}
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if (data.empty())
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data.init(SetVariants::chooseMethod(column_ptrs, key_sizes));
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const auto old_set_size = data.getTotalRowCount();
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IColumn::Filter filter(num_rows);
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switch (data.type)
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{
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case SetVariants::Type::EMPTY:
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break;
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#define M(NAME) \
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case SetVariants::Type::NAME: \
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buildFilter(*data.NAME, column_ptrs, filter, num_rows, data); \
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break;
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APPLY_FOR_SET_VARIANTS(M)
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#undef M
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}
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/// Just go to the next chunk if there isn't any new record in the current one.
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if (data.getTotalRowCount() == old_set_size)
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return;
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if (!set_size_limits.check(data.getTotalRowCount(), data.getTotalByteCount(), "DISTINCT", ErrorCodes::SET_SIZE_LIMIT_EXCEEDED))
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return;
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for (auto & column : columns)
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column = column->filter(filter, -1);
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chunk.setColumns(std::move(columns), data.getTotalRowCount() - old_set_size);
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}
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}
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