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123 lines
3.4 KiB
C++
123 lines
3.4 KiB
C++
#include <DataStreams/DistinctBlockInputStream.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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DistinctBlockInputStream::DistinctBlockInputStream(const BlockInputStreamPtr & input, const SizeLimits & set_size_limits_, UInt64 limit_hint_, const Names & columns_)
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: columns_names(columns_)
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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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children.push_back(input);
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}
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Block DistinctBlockInputStream::readImpl()
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{
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/// Execute until end of stream or until
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/// a block with some new records will be gotten.
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while (true)
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{
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if (no_more_rows)
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return Block();
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/// Stop reading if we already reach the limit.
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if (limit_hint && data.getTotalRowCount() >= limit_hint)
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return Block();
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Block block = children[0]->read();
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if (!block)
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return Block();
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const ColumnRawPtrs column_ptrs(getKeyColumns(block));
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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 & elem : block)
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elem.column = elem.column->cut(0, 1);
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return block;
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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 size_t old_set_size = data.getTotalRowCount();
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const size_t rows = block.rows();
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IColumn::Filter filter(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, 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 block 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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continue;
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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 & elem : block)
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elem.column = elem.column->filter(filter, -1);
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return block;
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}
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}
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template <typename Method>
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void DistinctBlockInputStream::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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ColumnRawPtrs DistinctBlockInputStream::getKeyColumns(const Block & block) const
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{
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size_t columns = columns_names.empty() ? block.columns() : columns_names.size();
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ColumnRawPtrs column_ptrs;
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column_ptrs.reserve(columns);
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for (size_t i = 0; i < columns; ++i)
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{
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auto & column = columns_names.empty()
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? block.safeGetByPosition(i).column
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: block.getByName(columns_names[i]).column;
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/// Ignore all constant columns.
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if (!isColumnConst(*column))
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column_ptrs.emplace_back(column.get());
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}
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return column_ptrs;
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}
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}
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