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62 lines
2.4 KiB
C++
62 lines
2.4 KiB
C++
#pragma once
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#include <deque>
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#include <mutex>
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#include <map>
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namespace DB
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{
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/// ALTERs in StorageReplicatedMergeTree have to be executed sequentially (one
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/// by one). But ReplicatedMergeTreeQueue execute all entries almost
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/// concurrently. The only dependency between entries is data parts, but they are
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/// not suitable in alters case.
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///
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/// This class stores information about current alters in
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/// ReplicatedMergeTreeQueue, and control their order of execution. Actually
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/// it's a part of ReplicatedMergeTreeQueue and shouldn't be used directly by
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/// other classes, also methods have to be called under ReplicatedMergeTreeQueue
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/// state lock.
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class ReplicatedMergeTreeAltersSequence
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{
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private:
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/// In general case alter consist of two stages Alter data and alter
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/// metadata. First we alter storage metadata and then we can apply
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/// corresponding data changes (MUTATE_PART). After that, we can remove
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/// alter from this sequence (alter is processed).
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struct AlterState
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{
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bool metadata_finished = false;
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bool data_finished = false;
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};
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/// alter_version -> AlterState.
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std::map<int, AlterState> queue_state;
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public:
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/// Add mutation for alter (alter data stage).
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void addMutationForAlter(int alter_version, std::lock_guard<std::mutex> & /*state_lock*/);
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/// Add metadata for alter (alter metadata stage).
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void addMetadataAlter(int alter_version, std::lock_guard<std::mutex> & /*state_lock*/);
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/// Finish metadata alter. If corresponding data alter finished, than we can remove
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/// alter from sequence.
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void finishMetadataAlter(int alter_version, std::unique_lock <std::mutex> & /*state_lock*/);
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/// Finish data alter. If corresponding metadata alter finished, than we can remove
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/// alter from sequence.
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void finishDataAlter(int alter_version, std::lock_guard<std::mutex> & /*state_lock*/);
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/// Check that we can execute this data alter. If it's metadata stage finished.
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bool canExecuteDataAlter(int alter_version, std::unique_lock<std::mutex> & /*state_lock*/) const;
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/// Check that we can execute metadata alter with version.
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bool canExecuteMetaAlter(int alter_version, std::unique_lock<std::mutex> & /*state_lock*/) const;
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/// Just returns smallest alter version in sequence (first entry)
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int getHeadAlterVersion(std::unique_lock<std::mutex> & /*state_lock*/) const;
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};
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}
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