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