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65 lines
2.3 KiB
C++
65 lines
2.3 KiB
C++
#pragma once
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#include <Columns/IColumn.h>
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#include <Columns/ColumnsCommon.h>
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#include <Columns/ColumnsNumber.h>
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namespace DB
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{
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/// Support methods for implementation of WHERE, PREWHERE and HAVING.
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/// Analyze if the column for filter is constant thus filter is always false or always true.
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struct ConstantFilterDescription
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{
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bool always_false = false;
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bool always_true = false;
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ConstantFilterDescription() = default;
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explicit ConstantFilterDescription(const IColumn & column);
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};
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struct IFilterDescription
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{
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/// has_one can be pre-compute during creating the filter description in some cases
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Int64 has_one = -1;
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virtual ColumnPtr filter(const IColumn & column, ssize_t result_size_hint) const = 0;
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virtual size_t countBytesInFilter() const = 0;
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virtual ~IFilterDescription() = default;
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bool hasOne() { return has_one >= 0 ? has_one : hasOneImpl();}
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protected:
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/// Calculate if filter has a non-zero from the filter values, may update has_one
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virtual bool hasOneImpl() = 0;
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};
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/// Obtain a filter from non constant Column, that may have type: UInt8, Nullable(UInt8).
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struct FilterDescription final : public IFilterDescription
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{
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const IColumn::Filter * data = nullptr; /// Pointer to filter when it is not always true or always false.
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ColumnPtr data_holder; /// If new column was generated, it will be owned by holder.
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explicit FilterDescription(const IColumn & column);
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ColumnPtr filter(const IColumn & column, ssize_t result_size_hint) const override { return column.filter(*data, result_size_hint); }
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size_t countBytesInFilter() const override { return DB::countBytesInFilter(*data); }
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protected:
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bool hasOneImpl() override { return data ? (has_one = !memoryIsZero(data->data(), 0, data->size())) : false; }
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};
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struct SparseFilterDescription final : public IFilterDescription
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{
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const ColumnUInt64 * filter_indices = nullptr;
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explicit SparseFilterDescription(const IColumn & column);
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ColumnPtr filter(const IColumn & column, ssize_t) const override { return column.index(*filter_indices, 0); }
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size_t countBytesInFilter() const override { return filter_indices->size(); }
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protected:
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bool hasOneImpl() override { return filter_indices && !filter_indices->empty(); }
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};
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struct ColumnWithTypeAndName;
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}
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