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# pragma once
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# include <Core/Names.h>
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# include <Core/QueryProcessingStage.h>
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# include <DataStreams/IBlockStream_fwd.h>
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# include <Databases/IDatabase.h>
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# include <Interpreters/CancellationCode.h>
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# include <Storages/IStorage_fwd.h>
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# include <Interpreters/StorageID.h>
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# include <Storages/SelectQueryInfo.h>
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# include <Storages/TableLockHolder.h>
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# include <Storages/CheckResults.h>
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# include <Storages/StorageInMemoryMetadata.h>
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# include <Storages/ColumnDependency.h>
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# include <Storages/SelectQueryDescription.h>
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# include <Common/ActionLock.h>
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# include <Common/Exception.h>
# include <Common/RWLock.h>
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# include <Common/TypePromotion.h>
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# include <optional>
# include <shared_mutex>
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namespace DB
{
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namespace ErrorCodes
{
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extern const int NOT_IMPLEMENTED ;
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}
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class Context ;
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using StorageActionBlockType = size_t ;
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class ASTCreateQuery ;
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struct Settings ;
class AlterCommands ;
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class MutationCommands ;
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struct PartitionCommand ;
using PartitionCommands = std : : vector < PartitionCommand > ;
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class IProcessor ;
using ProcessorPtr = std : : shared_ptr < IProcessor > ;
using Processors = std : : vector < ProcessorPtr > ;
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class Pipe ;
using Pipes = std : : vector < Pipe > ;
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class StoragePolicy ;
using StoragePolicyPtr = std : : shared_ptr < const StoragePolicy > ;
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struct ColumnSize
{
size_t marks = 0 ;
size_t data_compressed = 0 ;
size_t data_uncompressed = 0 ;
void add ( const ColumnSize & other )
{
marks + = other . marks ;
data_compressed + = other . data_compressed ;
data_uncompressed + = other . data_uncompressed ;
}
} ;
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/** Storage. Describes the table. Responsible for
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* - storage of the table data ;
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* - the definition in which files ( or not in files ) the data is stored ;
* - data lookups and appends ;
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* - data storage structure ( compression , etc . )
* - concurrent access to data ( locks , etc . )
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*/
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class IStorage : public std : : enable_shared_from_this < IStorage > , public TypePromotion < IStorage >
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{
public :
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IStorage ( ) = delete ;
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/// Storage metadata can be set separately in setInMemoryMetadata method
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explicit IStorage ( StorageID storage_id_ )
: storage_id ( std : : move ( storage_id_ ) )
, metadata ( std : : make_unique < StorageInMemoryMetadata > ( ) ) { } //-V730
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virtual ~ IStorage ( ) = default ;
IStorage ( const IStorage & ) = delete ;
IStorage & operator = ( const IStorage & ) = delete ;
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/// The main name of the table type (for example, StorageMergeTree).
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virtual std : : string getName ( ) const = 0 ;
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/// The name of the table.
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StorageID getStorageID ( ) const ;
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/// Returns true if the storage receives data from a remote server or servers.
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virtual bool isRemote ( ) const { return false ; }
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/// Returns true if the storage is a view of a table or another view.
virtual bool isView ( ) const { return false ; }
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/// Returns true if the storage supports queries with the SAMPLE section.
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virtual bool supportsSampling ( ) const { return getInMemoryMetadataPtr ( ) - > hasSamplingKey ( ) ; }
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/// Returns true if the storage supports queries with the FINAL section.
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virtual bool supportsFinal ( ) const { return false ; }
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/// Returns true if the storage supports queries with the PREWHERE section.
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virtual bool supportsPrewhere ( ) const { return false ; }
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/// Returns true if the storage replicates SELECT, INSERT and ALTER commands among replicas.
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virtual bool supportsReplication ( ) const { return false ; }
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/// Returns true if the storage supports parallel insert.
virtual bool supportsParallelInsert ( ) const { return false ; }
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/// Returns true if the storage supports deduplication of inserted data blocks.
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virtual bool supportsDeduplication ( ) const { return false ; }
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/// Returns true if the storage supports settings.
virtual bool supportsSettings ( ) const { return false ; }
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/// Returns true if the blocks shouldn't be pushed to associated views on insert.
virtual bool noPushingToViews ( ) const { return false ; }
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/// Read query returns streams which automatically distribute data between themselves.
/// So, it's impossible for one stream run out of data when there is data in other streams.
/// Example is StorageSystemNumbers.
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virtual bool hasEvenlyDistributedRead ( ) const { return false ; }
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/// Optional size information of each physical column.
/// Currently it's only used by the MergeTree family for query optimizations.
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using ColumnSizeByName = std : : unordered_map < std : : string , ColumnSize > ;
virtual ColumnSizeByName getColumnSizes ( ) const { return { } ; }
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public :
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/// Get mutable version (snapshot) of storage metadata. Metadata object is
/// multiversion, so it can be concurrently chaged, but returned copy can be
/// used without any locks.
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StorageInMemoryMetadata getInMemoryMetadata ( ) const { return * metadata . get ( ) ; }
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/// Get immutable version (snapshot) of storage metadata. Metadata object is
/// multiversion, so it can be concurrently chaged, but returned copy can be
/// used without any locks.
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StorageMetadataPtr getInMemoryMetadataPtr ( ) const { return metadata . get ( ) ; }
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/// Update storage metadata. Used in ALTER or initialization of Storage.
/// Metadata object is multiversion, so this method can be called without
/// any locks.
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void setInMemoryMetadata ( const StorageInMemoryMetadata & metadata_ )
{
metadata . set ( std : : make_unique < StorageInMemoryMetadata > ( metadata_ ) ) ;
}
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/// Return list of virtual columns (like _part, _table, etc). In the vast
/// majority of cases virtual columns are static constant part of Storage
/// class and don't depend on Storage object. But sometimes we have fake
/// storages, like Merge, which works as proxy for other storages and it's
/// virtual columns must contain virtual columns from underlying table.
///
/// User can create columns with the same name as virtual column. After that
/// virtual column will be overriden and inaccessible.
///
/// By default return empty list of columns.
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virtual NamesAndTypesList getVirtuals ( ) const ;
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protected :
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/// Returns whether the column is virtual - by default all columns are real.
/// Initially reserved virtual column name may be shadowed by real column.
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bool isVirtualColumn ( const String & column_name , const StorageMetadataPtr & metadata_snapshot ) const ;
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private :
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StorageID storage_id ;
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mutable std : : mutex id_mutex ;
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/// Multiversion storage metadata. Allows to read/write storage metadata
/// without locks.
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MultiVersionStorageMetadataPtr metadata ;
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private :
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RWLockImpl : : LockHolder tryLockTimed (
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const RWLock & rwlock , RWLockImpl : : Type type , const String & query_id , const std : : chrono : : milliseconds & acquire_timeout ) const ;
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public :
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/// Lock table for share. This lock must be acuqired if you want to be sure,
/// that table will be not dropped while you holding this lock. It's used in
/// variety of cases starting from SELECT queries to background merges in
/// MergeTree.
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TableLockHolder lockForShare ( const String & query_id , const std : : chrono : : milliseconds & acquire_timeout ) ;
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/// Lock table for alter. This lock must be acuqired in ALTER queries to be
/// sure, that we execute only one simultaneous alter. Doesn't affect share lock.
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TableLockHolder lockForAlter ( const String & query_id , const std : : chrono : : milliseconds & acquire_timeout ) ;
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/// Lock table exclusively. This lock must be acuired if you want to be
/// sure, that no other thread (SELECT, merge, ALTER, etc.) doing something
/// with table. For example it allows to wait all threads before DROP or
/// truncate query.
///
/// NOTE: You have to be 100% sure that you need this lock. It's extremely
/// heavyweight and makes table irresponsive.
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TableExclusiveLockHolder lockExclusively ( const String & query_id , const std : : chrono : : milliseconds & acquire_timeout ) ;
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/** Returns stage to which query is going to be processed in read() function.
* ( Normally , the function only reads the columns from the list , but in other cases ,
* for example , the request can be partially processed on a remote server . )
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*
* SelectQueryInfo is required since the stage can depends on the query
* ( see Distributed ( ) engine and optimize_skip_unused_shards ) .
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*
* QueryProcessingStage : : Enum required for Distributed over Distributed ,
* since it cannot return Complete for intermediate queries never .
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*/
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QueryProcessingStage : : Enum getQueryProcessingStage ( const Context & context ) const
{
return getQueryProcessingStage ( context , QueryProcessingStage : : Complete , { } ) ;
}
virtual QueryProcessingStage : : Enum getQueryProcessingStage ( const Context & , QueryProcessingStage : : Enum /*to_stage*/ , const ASTPtr & ) const
{
return QueryProcessingStage : : FetchColumns ;
}
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/** Watch live changes to the table.
* Accepts a list of columns to read , as well as a description of the query ,
* from which information can be extracted about how to retrieve data
* ( indexes , locks , etc . )
* Returns a stream with which you can read data sequentially
* or multiple streams for parallel data reading .
* The ` processed_stage ` info is also written to what stage the request was processed .
* ( Normally , the function only reads the columns from the list , but in other cases ,
* for example , the request can be partially processed on a remote server . )
*
* context contains settings for one query .
* Usually Storage does not care about these settings , since they are used in the interpreter .
* But , for example , for distributed query processing , the settings are passed to the remote server .
*
* num_streams - a recommendation , how many streams to return ,
* if the storage can return a different number of streams .
*
* It is guaranteed that the structure of the table will not change over the lifetime of the returned streams ( that is , there will not be ALTER , RENAME and DROP ) .
*/
virtual BlockInputStreams watch (
const Names & /*column_names*/ ,
const SelectQueryInfo & /*query_info*/ ,
const Context & /*context*/ ,
QueryProcessingStage : : Enum & /*processed_stage*/ ,
size_t /*max_block_size*/ ,
unsigned /*num_streams*/ )
{
throw Exception ( " Method watch is not supported by storage " + getName ( ) , ErrorCodes : : NOT_IMPLEMENTED ) ;
}
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/** Read a set of columns from the table.
* Accepts a list of columns to read , as well as a description of the query ,
* from which information can be extracted about how to retrieve data
* ( indexes , locks , etc . )
* Returns a stream with which you can read data sequentially
* or multiple streams for parallel data reading .
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* The ` processed_stage ` must be the result of getQueryProcessingStage ( ) function .
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*
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* context contains settings for one query .
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* Usually Storage does not care about these settings , since they are used in the interpreter .
* But , for example , for distributed query processing , the settings are passed to the remote server .
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*
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* num_streams - a recommendation , how many streams to return ,
* if the storage can return a different number of streams .
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*
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* metadata_snapshot is consistent snapshot of table metadata , it should be
* passed in all parts of the returned pipeline . Storage metadata can be
* changed during lifetime of the returned pipeline , but the snapshot is
* guaranteed to be immutable .
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*/
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virtual Pipes read (
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const Names & /*column_names*/ ,
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const StorageMetadataPtr & /*metadata_snapshot*/ ,
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const SelectQueryInfo & /*query_info*/ ,
const Context & /*context*/ ,
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QueryProcessingStage : : Enum /*processed_stage*/ ,
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size_t /*max_block_size*/ ,
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unsigned /*num_streams*/ )
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{
throw Exception ( " Method read is not supported by storage " + getName ( ) , ErrorCodes : : NOT_IMPLEMENTED ) ;
}
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/** Writes the data to a table.
* Receives a description of the query , which can contain information about the data write method .
* Returns an object by which you can write data sequentially .
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*
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* metadata_snapshot is consistent snapshot of table metadata , it should be
* passed in all parts of the returned streams . Storage metadata can be
* changed during lifetime of the returned streams , but the snapshot is
* guaranteed to be immutable .
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*/
virtual BlockOutputStreamPtr write (
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const ASTPtr & /*query*/ ,
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const StorageMetadataPtr & /*metadata_snapshot*/ ,
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const Context & /*context*/ )
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{
throw Exception ( " Method write is not supported by storage " + getName ( ) , ErrorCodes : : NOT_IMPLEMENTED ) ;
}
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/** Delete the table data. Called before deleting the directory with the data.
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* The method can be called only after detaching table from Context ( when no queries are performed with table ) .
* The table is not usable during and after call to this method .
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* If some queries may still use the table , then it must be called under exclusive lock .
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* If you do not need any action other than deleting the directory with data , you can leave this method blank .
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*/
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virtual void drop ( ) { }
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/** Clear the table data and leave it empty.
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* Must be called under exclusive lock ( lockExclusively ) .
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*/
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virtual void truncate (
const ASTPtr & /*query*/ ,
const StorageMetadataPtr & /* metadata_snapshot */ ,
const Context & /* context */ ,
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TableExclusiveLockHolder & )
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{
throw Exception ( " Truncate is not supported by storage " + getName ( ) , ErrorCodes : : NOT_IMPLEMENTED ) ;
}
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/** Rename the table.
* Renaming a name in a file with metadata , the name in the list of tables in the RAM , is done separately .
* In this function , you need to rename the directory with the data , if any .
* Called when the table structure is locked for write .
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* Table UUID must remain unchanged , unless table moved between Ordinary and Atomic databases .
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*/
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virtual void rename ( const String & /*new_path_to_table_data*/ , const StorageID & new_table_id )
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{
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renameInMemory ( new_table_id ) ;
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}
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/**
* Just updates names of database and table without moving any data on disk
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* Can be called directly only from DatabaseAtomic .
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*/
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virtual void renameInMemory ( const StorageID & new_table_id ) ;
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/** ALTER tables in the form of column changes that do not affect the change
* to Storage or its parameters . Executes under alter lock ( lockForAlter ) .
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*/
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virtual void alter ( const AlterCommands & params , const Context & context , TableLockHolder & alter_lock_holder ) ;
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/** Checks that alter commands can be applied to storage. For example, columns can be modified,
* or primary key can be changes , etc .
*/
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virtual void checkAlterIsPossible ( const AlterCommands & commands , const Settings & settings ) const ;
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/** ALTER tables with regard to its partitions.
* Should handle locks for each command on its own .
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*/
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virtual Pipes alterPartition ( const ASTPtr & /* query */ , const StorageMetadataPtr & /* metadata_snapshot */ , const PartitionCommands & /* commands */ , const Context & /* context */ )
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{
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throw Exception ( " Partition operations are not supported by storage " + getName ( ) , ErrorCodes : : NOT_IMPLEMENTED ) ;
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}
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/// Checks that partition commands can be applied to storage.
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virtual void checkAlterPartitionIsPossible ( const PartitionCommands & commands , const StorageMetadataPtr & metadata_snapshot , const Settings & settings ) const ;
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/** Perform any background work. For example, combining parts in a MergeTree type table.
* Returns whether any work has been done .
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*/
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virtual bool optimize (
const ASTPtr & /*query*/ ,
const StorageMetadataPtr & /*metadata_snapshot*/ ,
const ASTPtr & /*partition*/ ,
bool /*final*/ ,
bool /*deduplicate*/ ,
const Context & /*context*/ )
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{
throw Exception ( " Method optimize is not supported by storage " + getName ( ) , ErrorCodes : : NOT_IMPLEMENTED ) ;
}
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/// Mutate the table contents
virtual void mutate ( const MutationCommands & , const Context & )
{
throw Exception ( " Mutations are not supported by storage " + getName ( ) , ErrorCodes : : NOT_IMPLEMENTED ) ;
}
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/// Cancel a mutation.
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virtual CancellationCode killMutation ( const String & /*mutation_id*/ )
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{
throw Exception ( " Mutations are not supported by storage " + getName ( ) , ErrorCodes : : NOT_IMPLEMENTED ) ;
}
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/** If the table have to do some complicated work on startup,
* that must be postponed after creation of table object
* ( like launching some background threads ) ,
* do it in this method .
* You should call this method after creation of object .
* By default , does nothing .
* Cannot be called simultaneously by multiple threads .
*/
virtual void startup ( ) { }
/** If the table have to do some complicated work when destroying an object - do it in advance.
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* For example , if the table contains any threads for background work - ask them to complete and wait for completion .
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* By default , does nothing .
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* Can be called simultaneously from different threads , even after a call to drop ( ) .
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*/
virtual void shutdown ( ) { }
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/// Asks table to stop executing some action identified by action_type
/// If table does not support such type of lock, and empty lock is returned
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virtual ActionLock getActionLock ( StorageActionBlockType /* action_type */ )
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{
return { } ;
}
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std : : atomic < bool > is_dropped { false } ;
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/// Does table support index for IN sections
virtual bool supportsIndexForIn ( ) const { return false ; }
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/// Provides a hint that the storage engine may evaluate the IN-condition by using an index.
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virtual bool mayBenefitFromIndexForIn ( const ASTPtr & /* left_in_operand */ , const Context & /* query_context */ , const StorageMetadataPtr & /* metadata_snapshot */ ) const { return false ; }
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/// Checks validity of the data
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virtual CheckResults checkData ( const ASTPtr & /* query */ , const Context & /* context */ ) { throw Exception ( " Check query is not supported for " + getName ( ) + " storage " , ErrorCodes : : NOT_IMPLEMENTED ) ; }
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/// Checks that table could be dropped right now
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/// Otherwise - throws an exception with detailed information.
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/// We do not use mutex because it is not very important that the size could change during the operation.
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virtual void checkTableCanBeDropped ( ) const { }
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/// Checks that Partition could be dropped right now
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/// Otherwise - throws an exception with detailed information.
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/// We do not use mutex because it is not very important that the size could change during the operation.
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virtual void checkPartitionCanBeDropped ( const ASTPtr & /*partition*/ ) { }
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/// Returns data paths if storage supports it, empty vector otherwise.
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virtual Strings getDataPaths ( ) const { return { } ; }
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/// Returns storage policy if storage supports it.
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virtual StoragePolicyPtr getStoragePolicy ( ) const { return { } ; }
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/// If it is possible to quickly determine exact number of rows in the table at this moment of time, then return it.
/// Used for:
/// - Simple count() opimization
/// - For total_rows column in system.tables
///
/// Does takes underlying Storage (if any) into account.
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virtual std : : optional < UInt64 > totalRows ( ) const { return { } ; }
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/// If it is possible to quickly determine exact number of bytes for the table on storage:
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/// - memory (approximated, resident)
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/// - disk (compressed)
///
/// Used for:
/// - For total_bytes column in system.tables
//
/// Does not takes underlying Storage (if any) into account
/// (since for Buffer we still need to know how much bytes it uses).
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///
/// Memory part should be estimated as a resident memory size.
/// In particular, alloctedBytes() is preferable over bytes()
/// when considering in-memory blocks.
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virtual std : : optional < UInt64 > totalBytes ( ) const { return { } ; }
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/// Number of rows INSERTed since server start.
///
/// Does not takes underlying Storage (if any) into account.
virtual std : : optional < UInt64 > lifetimeRows ( ) const { return { } ; }
/// Number of bytes INSERTed since server start.
///
/// Does not takes underlying Storage (if any) into account.
virtual std : : optional < UInt64 > lifetimeBytes ( ) const { return { } ; }
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private :
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/// Lock required for alter queries (lockForAlter). Always taken for write
/// (actually can be replaced with std::mutex, but for consistency we use
/// RWLock). Allows to execute only one simultaneous alter query. Also it
/// should be taken by DROP-like queries, to be sure, that all alters are
/// finished.
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mutable RWLock alter_lock = RWLockImpl : : create ( ) ;
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/// Lock required for drop queries. Every thread that want to ensure, that
/// table is not dropped have to tabke this lock for read (lockForShare).
/// DROP-like queries take this lock for write (lockExclusively), to be sure
/// that all table threads finished.
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mutable RWLock drop_lock = RWLockImpl : : create ( ) ;
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} ;
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}