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47 lines
1.2 KiB
C++
47 lines
1.2 KiB
C++
#pragma once
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#include <DB/Parsers/IAST.h>
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#include <DB/Storages/IStorage.h>
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#include <DB/Client/ConnectionPool.h>
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namespace DB
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{
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struct Settings;
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class Context;
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class Cluster;
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namespace ClusterProxy
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{
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class IQueryConstructor;
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/// This class is designed for distributed queries execution. It hides from
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/// the caller the details about the actual locations at which a distributed
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/// query is performed. Depending on the type of query to be performed,
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/// (currently SELECT, DESCRIBE, or ALTER (for resharding)), a so-called
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/// query constructor is specified. Such an object states, among other things,
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/// how connections must be allocated for remote execution.
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class Query
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{
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public:
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Query(IQueryConstructor & query_constructor_, const Cluster & cluster_,
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ASTPtr query_ast_, const Context & context_, const Settings & settings_, bool enable_shard_multiplexing_);
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/// For each location at which we perform the query, create an input stream
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/// from which we can fetch the result.
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BlockInputStreams execute();
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private:
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IQueryConstructor & query_constructor;
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const Cluster & cluster;
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ASTPtr query_ast;
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const Context & context;
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const Settings & settings;
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bool enable_shard_multiplexing;
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};
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}
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}
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