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58 lines
2.0 KiB
C++
58 lines
2.0 KiB
C++
#pragma once
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#include <Columns/IColumn.h>
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#include <DataStreams/IBlockStream_fwd.h>
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#include <vector>
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namespace DB
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{
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class IDictionarySource;
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using DictionarySourcePtr = std::unique_ptr<IDictionarySource>;
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/** Data-provider interface for external dictionaries,
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* abstracts out the data source (file, MySQL, ClickHouse, external program, network request et cetera)
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* from the presentation and memory layout (the dictionary itself).
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*/
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class IDictionarySource
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{
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public:
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/// Returns an input stream with all the data available from this source.
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virtual BlockInputStreamPtr loadAll() = 0;
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/// Returns an input stream with updated data available from this source.
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virtual BlockInputStreamPtr loadUpdatedAll() = 0;
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/** Indicates whether this source supports "random access" loading of data
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* loadId and loadIds can only be used if this function returns true.
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*/
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virtual bool supportsSelectiveLoad() const = 0;
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/** Returns an input stream with the data for a collection of identifiers.
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* It must be guaranteed, that 'ids' array will live at least until all data will be read from returned stream.
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*/
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virtual BlockInputStreamPtr loadIds(const std::vector<UInt64> & ids) = 0;
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/** Returns an input stream with the data for a collection of composite keys.
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* `requested_rows` contains indices of all rows containing unique keys.
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* It must be guaranteed, that 'requested_rows' array will live at least until all data will be read from returned stream.
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*/
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virtual BlockInputStreamPtr loadKeys(const Columns & key_columns, const std::vector<size_t> & requested_rows) = 0;
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/// indicates whether the source has been modified since last load* operation
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virtual bool isModified() const = 0;
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/// Returns true if update field is defined
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virtual bool hasUpdateField() const = 0;
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virtual DictionarySourcePtr clone() const = 0;
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/// returns an informal string describing the source
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virtual std::string toString() const = 0;
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virtual ~IDictionarySource() = default;
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};
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}
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