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52 lines
1.4 KiB
C++
52 lines
1.4 KiB
C++
#pragma once
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#include <Core/Block.h>
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namespace DB
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{
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/** Merging consecutive passed blocks to specified minimum size.
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*
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* (But if one of input blocks has already at least specified size,
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* then don't merge it with neighbours, even if neighbours are small.)
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*
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* Used to prepare blocks to adequate size for INSERT queries,
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* because such storages as Memory, StripeLog, Log, TinyLog...
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* store or compress data in blocks exactly as passed to it,
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* and blocks of small size are not efficient.
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*
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* Order of data is kept.
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*/
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class SquashingTransform
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{
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public:
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/// Conditions on rows and bytes are OR-ed. If one of them is zero, then corresponding condition is ignored.
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SquashingTransform(size_t min_block_size_rows_, size_t min_block_size_bytes_, bool reserve_memory_ = false);
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/** Add next block and possibly returns squashed block.
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* At end, you need to pass empty block. As the result for last (empty) block, you will get last Result with ready = true.
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*/
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Block add(Block && block);
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Block add(const Block & block);
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private:
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size_t min_block_size_rows;
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size_t min_block_size_bytes;
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bool reserve_memory;
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Block accumulated_block;
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template <typename ReferenceType>
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Block addImpl(ReferenceType block);
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template <typename ReferenceType>
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void append(ReferenceType block);
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bool isEnoughSize(const Block & block);
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bool isEnoughSize(size_t rows, size_t bytes) const;
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};
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}
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