ClickHouse/src/Storages/StorageDistributed.cpp

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#include <Storages/StorageDistributed.h>
#include <DataStreams/OneBlockInputStream.h>
#include <Databases/IDatabase.h>
#include <Disks/DiskSpaceMonitor.h>
#include <Disks/DiskLocal.h>
#include <DataTypes/DataTypeFactory.h>
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#include <DataTypes/DataTypesNumber.h>
#include <Storages/Distributed/DirectoryMonitor.h>
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#include <Storages/Distributed/DistributedBlockOutputStream.h>
#include <Storages/StorageFactory.h>
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#include <Storages/AlterCommands.h>
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#include <Columns/ColumnConst.h>
#include <Common/Macros.h>
#include <Common/escapeForFileName.h>
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#include <Common/typeid_cast.h>
#include <Common/quoteString.h>
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#include <Parsers/ASTDropQuery.h>
#include <Parsers/ASTExpressionList.h>
#include <Parsers/ASTIdentifier.h>
#include <Parsers/ASTInsertQuery.h>
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#include <Parsers/ASTLiteral.h>
#include <Parsers/ASTSelectQuery.h>
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#include <Parsers/ASTTablesInSelectQuery.h>
#include <Parsers/ParserAlterQuery.h>
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#include <Parsers/TablePropertiesQueriesASTs.h>
#include <Parsers/parseQuery.h>
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#include <Interpreters/ClusterProxy/SelectStreamFactory.h>
#include <Interpreters/ClusterProxy/executeQuery.h>
#include <Interpreters/ExpressionAnalyzer.h>
#include <Interpreters/InterpreterAlterQuery.h>
#include <Interpreters/InterpreterDescribeQuery.h>
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#include <Interpreters/InterpreterSelectQuery.h>
#include <Interpreters/TranslateQualifiedNamesVisitor.h>
#include <Interpreters/SyntaxAnalyzer.h>
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#include <Interpreters/createBlockSelector.h>
#include <Interpreters/evaluateConstantExpression.h>
#include <Interpreters/getClusterName.h>
#include <Interpreters/getTableExpressions.h>
#include <Core/Field.h>
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#include <IO/ReadHelpers.h>
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#include <Poco/DirectoryIterator.h>
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#include <memory>
#include <filesystem>
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namespace
{
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const UInt64 FORCE_OPTIMIZE_SKIP_UNUSED_SHARDS_HAS_SHARDING_KEY = 1;
const UInt64 FORCE_OPTIMIZE_SKIP_UNUSED_SHARDS_ALWAYS = 2;
}
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namespace DB
{
namespace ErrorCodes
{
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extern const int NOT_IMPLEMENTED;
extern const int STORAGE_REQUIRES_PARAMETER;
extern const int BAD_ARGUMENTS;
extern const int NUMBER_OF_ARGUMENTS_DOESNT_MATCH;
extern const int INCORRECT_NUMBER_OF_COLUMNS;
extern const int INFINITE_LOOP;
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extern const int TYPE_MISMATCH;
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extern const int TOO_MANY_ROWS;
extern const int UNABLE_TO_SKIP_UNUSED_SHARDS;
extern const int LOGICAL_ERROR;
}
namespace ActionLocks
{
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extern const StorageActionBlockType DistributedSend;
}
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namespace
{
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/// select query has database, table and table function names as AST pointers
/// Creates a copy of query, changes database, table and table function names.
ASTPtr rewriteSelectQuery(const ASTPtr & query, const std::string & database, const std::string & table, ASTPtr table_function_ptr = nullptr)
{
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auto modified_query_ast = query->clone();
ASTSelectQuery & select_query = modified_query_ast->as<ASTSelectQuery &>();
if (table_function_ptr)
select_query.addTableFunction(table_function_ptr);
else
select_query.replaceDatabaseAndTable(database, table);
/// Restore long column names (cause our short names are ambiguous).
/// TODO: aliased table functions & CREATE TABLE AS table function cases
if (!table_function_ptr)
{
RestoreQualifiedNamesVisitor::Data data;
data.distributed_table = DatabaseAndTableWithAlias(*getTableExpression(query->as<ASTSelectQuery &>(), 0));
data.remote_table.database = database;
data.remote_table.table = table;
data.rename = true;
RestoreQualifiedNamesVisitor(data).visit(modified_query_ast);
}
return modified_query_ast;
}
/// The columns list in the original INSERT query is incorrect because inserted blocks are transformed
/// to the form of the sample block of the Distributed table. So we rewrite it and add all columns from
/// the sample block instead.
ASTPtr createInsertToRemoteTableQuery(const std::string & database, const std::string & table, const Block & sample_block_non_materialized)
{
auto query = std::make_shared<ASTInsertQuery>();
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query->table_id = StorageID(database, table);
auto columns = std::make_shared<ASTExpressionList>();
query->columns = columns;
query->children.push_back(columns);
for (const auto & col : sample_block_non_materialized)
columns->children.push_back(std::make_shared<ASTIdentifier>(col.name));
return query;
}
/// Calculate maximum number in file names in directory and all subdirectories.
/// To ensure global order of data blocks yet to be sent across server restarts.
UInt64 getMaximumFileNumber(const std::string & dir_path)
{
UInt64 res = 0;
std::filesystem::recursive_directory_iterator begin(dir_path);
std::filesystem::recursive_directory_iterator end;
for (auto it = begin; it != end; ++it)
{
const auto & file_path = it->path();
if (!std::filesystem::is_regular_file(*it) || !endsWith(file_path.filename().string(), ".bin"))
continue;
UInt64 num = 0;
try
{
num = parse<UInt64>(file_path.filename().stem().string());
}
catch (Exception & e)
{
e.addMessage("Unexpected file name " + file_path.filename().string() + " found at " + file_path.parent_path().string() + ", should have numeric base name.");
throw;
}
if (num > res)
res = num;
}
return res;
}
std::string makeFormattedListOfShards(const ClusterPtr & cluster)
{
std::ostringstream os;
bool head = true;
os << "[";
for (const auto & shard_info : cluster->getShardsInfo())
{
(head ? os : os << ", ") << shard_info.shard_num;
head = false;
}
os << "]";
return os.str();
}
ExpressionActionsPtr buildShardingKeyExpression(const ASTPtr & sharding_key, const Context & context, const NamesAndTypesList & columns, bool project)
{
ASTPtr query = sharding_key;
auto syntax_result = SyntaxAnalyzer(context).analyze(query, columns);
return ExpressionAnalyzer(query, syntax_result, context).getActions(project);
}
class ReplacingConstantExpressionsMatcher
{
public:
using Data = Block;
static bool needChildVisit(ASTPtr &, const ASTPtr &)
{
return true;
}
static void visit(ASTPtr & node, Block & block_with_constants)
{
if (!node->as<ASTFunction>())
return;
std::string name = node->getColumnName();
if (block_with_constants.has(name))
{
auto result = block_with_constants.getByName(name);
if (!isColumnConst(*result.column))
return;
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node = std::make_shared<ASTLiteral>(assert_cast<const ColumnConst &>(*result.column).getField());
}
}
};
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void replaceConstantExpressions(ASTPtr & node, const Context & context, const NamesAndTypesList & columns, ConstStoragePtr storage)
{
auto syntax_result = SyntaxAnalyzer(context).analyze(node, columns, storage);
Block block_with_constants = KeyCondition::getBlockWithConstants(node, syntax_result, context);
InDepthNodeVisitor<ReplacingConstantExpressionsMatcher, true> visitor(block_with_constants);
visitor.visit(node);
}
QueryProcessingStage::Enum getQueryProcessingStageImpl(const Context & context, QueryProcessingStage::Enum to_stage, const ClusterPtr & cluster)
{
const Settings & settings = context.getSettingsRef();
size_t num_local_shards = cluster->getLocalShardCount();
size_t num_remote_shards = cluster->getRemoteShardCount();
size_t result_size = (num_remote_shards * settings.max_parallel_replicas) + num_local_shards;
if (settings.distributed_group_by_no_merge)
return QueryProcessingStage::Complete;
/// Nested distributed query cannot return Complete stage,
/// since the parent query need to aggregate the results after.
if (to_stage == QueryProcessingStage::WithMergeableState)
return QueryProcessingStage::WithMergeableState;
return result_size == 1 ? QueryProcessingStage::Complete
: QueryProcessingStage::WithMergeableState;
}
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}
/// For destruction of std::unique_ptr of type that is incomplete in class definition.
StorageDistributed::~StorageDistributed() = default;
NamesAndTypesList StorageDistributed::getVirtuals() const
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{
/// NOTE This is weird. Most of these virtual columns are part of MergeTree
/// tables info. But Distributed is general-purpose engine.
return NamesAndTypesList{
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NameAndTypePair("_table", std::make_shared<DataTypeString>()),
NameAndTypePair("_part", std::make_shared<DataTypeString>()),
NameAndTypePair("_part_index", std::make_shared<DataTypeUInt64>()),
NameAndTypePair("_partition_id", std::make_shared<DataTypeString>()),
NameAndTypePair("_sample_factor", std::make_shared<DataTypeFloat64>()),
NameAndTypePair("_shard_num", std::make_shared<DataTypeUInt32>()),
};
}
StorageDistributed::StorageDistributed(
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const StorageID & id_,
const ColumnsDescription & columns_,
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const ConstraintsDescription & constraints_,
const String & remote_database_,
const String & remote_table_,
const String & cluster_name_,
const Context & context_,
const ASTPtr & sharding_key_,
const String & storage_policy_,
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const String & relative_data_path_,
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bool attach_)
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: IStorage(id_)
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, remote_database(remote_database_)
, remote_table(remote_table_)
, global_context(context_)
, cluster_name(global_context.getMacros()->expand(cluster_name_))
, has_sharding_key(sharding_key_)
, storage_policy(storage_policy_)
, relative_data_path(relative_data_path_)
{
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setColumns(columns_);
setConstraints(constraints_);
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if (sharding_key_)
{
sharding_key_expr = buildShardingKeyExpression(sharding_key_, global_context, getColumns().getAllPhysical(), false);
sharding_key_column_name = sharding_key_->getColumnName();
}
if (!relative_data_path.empty())
createStorage();
/// Sanity check. Skip check if the table is already created to allow the server to start.
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if (!attach_ && !cluster_name.empty())
{
size_t num_local_shards = global_context.getCluster(cluster_name)->getLocalShardCount();
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if (num_local_shards && remote_database == id_.database_name && remote_table == id_.table_name)
throw Exception("Distributed table " + id_.table_name + " looks at itself", ErrorCodes::INFINITE_LOOP);
}
}
StorageDistributed::StorageDistributed(
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const StorageID & id_,
const ColumnsDescription & columns_,
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const ConstraintsDescription & constraints_,
ASTPtr remote_table_function_ptr_,
const String & cluster_name_,
const Context & context_,
const ASTPtr & sharding_key_,
const String & storage_policy_,
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const String & relative_data_path_,
bool attach)
: StorageDistributed(id_, columns_, constraints_, String{}, String{}, cluster_name_, context_, sharding_key_, storage_policy_, relative_data_path_, attach)
{
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remote_table_function_ptr = std::move(remote_table_function_ptr_);
}
void StorageDistributed::createStorage()
{
/// Create default policy with the relative_data_path_
if (storage_policy.empty())
{
std::string path(global_context.getPath());
/// Disk must ends with '/'
if (!path.ends_with('/'))
path += '/';
auto disk = std::make_shared<DiskLocal>("default", path, 0);
volume = std::make_shared<Volume>("default", std::vector<DiskPtr>{disk}, 0);
}
else
{
auto policy = global_context.getStoragePolicySelector()->get(storage_policy);
if (policy->getVolumes().size() != 1)
throw Exception("Policy for Distributed table, should have exactly one volume", ErrorCodes::BAD_ARGUMENTS);
volume = policy->getVolume(0);
}
}
StoragePtr StorageDistributed::createWithOwnCluster(
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const StorageID & table_id_,
const ColumnsDescription & columns_,
const String & remote_database_, /// database on remote servers.
const String & remote_table_, /// The name of the table on the remote servers.
ClusterPtr owned_cluster_,
const Context & context_)
{
auto res = create(table_id_, columns_, ConstraintsDescription{}, remote_database_, remote_table_, String{}, context_, ASTPtr(), String(), String(), false);
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res->owned_cluster = std::move(owned_cluster_);
return res;
}
StoragePtr StorageDistributed::createWithOwnCluster(
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const StorageID & table_id_,
const ColumnsDescription & columns_,
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ASTPtr & remote_table_function_ptr_,
ClusterPtr & owned_cluster_,
const Context & context_)
{
auto res = create(table_id_, columns_, ConstraintsDescription{}, remote_table_function_ptr_, String{}, context_, ASTPtr(), String(), String(), false);
res->owned_cluster = owned_cluster_;
return res;
}
bool StorageDistributed::canForceGroupByNoMerge(const Context &context, QueryProcessingStage::Enum to_stage, const ASTPtr & query_ptr) const
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{
const auto & settings = context.getSettingsRef();
std::string reason;
if (settings.distributed_group_by_no_merge)
return true;
/// Distributed-over-Distributed (see getQueryProcessingStageImpl())
if (to_stage == QueryProcessingStage::WithMergeableState)
return false;
if (!settings.optimize_skip_unused_shards)
return false;
if (!has_sharding_key)
return false;
const auto & select = query_ptr->as<ASTSelectQuery &>();
if (select.orderBy())
return false;
if (select.distinct)
{
for (auto & expr : select.select()->children)
{
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const auto * id = expr->as<ASTIdentifier>();
if (!id)
return false;
if (!sharding_key_expr->getSampleBlock().has(id->name))
return false;
}
reason = "DISTINCT " + backQuote(serializeAST(*select.select(), true));
}
// This can use distributed_group_by_no_merge but in this case limit stage
// should be done later (which is not the case right now).
if (select.limitBy() || select.limitLength())
return false;
const ASTPtr group_by = select.groupBy();
if (!group_by)
{
if (!select.distinct)
return false;
}
else
{
// injective functions are optimized out in optimizeGroupBy()
// hence all we need to check is that column in GROUP BY matches sharding expression
auto & group_exprs = group_by->children;
if (group_exprs.empty())
throw Exception("No ASTExpressionList in GROUP BY", ErrorCodes::LOGICAL_ERROR);
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const auto * id = group_exprs[0]->as<ASTIdentifier>();
if (!id)
return false;
if (!sharding_key_expr->getSampleBlock().has(id->name))
return false;
reason = "GROUP BY " + backQuote(serializeAST(*group_by, true));
}
LOG_DEBUG(log, "Force distributed_group_by_no_merge for " << reason << " (injective)");
return true;
}
QueryProcessingStage::Enum StorageDistributed::getQueryProcessingStage(const Context &context, QueryProcessingStage::Enum to_stage, const ASTPtr & query_ptr) const
{
if (canForceGroupByNoMerge(context, to_stage, query_ptr))
return QueryProcessingStage::Complete;
auto cluster = getOptimizedCluster(context, query_ptr);
return getQueryProcessingStageImpl(context, to_stage, cluster);
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}
Pipes StorageDistributed::read(
const Names & column_names,
const SelectQueryInfo & query_info,
const Context & context,
QueryProcessingStage::Enum processed_stage,
const size_t /*max_block_size*/,
const unsigned /*num_streams*/)
{
auto cluster = getOptimizedCluster(context, query_info.query);
const auto & modified_query_ast = rewriteSelectQuery(
query_info.query, remote_database, remote_table, remote_table_function_ptr);
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Block header =
InterpreterSelectQuery(query_info.query, context, SelectQueryOptions(processed_stage)).getSampleBlock();
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const Scalars & scalars = context.hasQueryContext() ? context.getQueryContext().getScalars() : Scalars{};
bool has_virtual_shard_num_column = std::find(column_names.begin(), column_names.end(), "_shard_num") != column_names.end();
if (has_virtual_shard_num_column && !isVirtualColumn("_shard_num"))
has_virtual_shard_num_column = false;
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ClusterProxy::SelectStreamFactory select_stream_factory = remote_table_function_ptr
? ClusterProxy::SelectStreamFactory(
header, processed_stage, remote_table_function_ptr, scalars, has_virtual_shard_num_column, context.getExternalTables())
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: ClusterProxy::SelectStreamFactory(
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header, processed_stage, StorageID{remote_database, remote_table}, scalars, has_virtual_shard_num_column, context.getExternalTables());
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return ClusterProxy::executeQuery(
select_stream_factory, cluster, modified_query_ast, context, context.getSettingsRef(), query_info);
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}
BlockOutputStreamPtr StorageDistributed::write(const ASTPtr &, const Context & context)
{
auto cluster = getCluster();
const auto & settings = context.getSettingsRef();
/// Ban an attempt to make async insert into the table belonging to DatabaseMemory
if (!volume && !owned_cluster && !settings.insert_distributed_sync)
{
throw Exception("Storage " + getName() + " must has own data directory to enable asynchronous inserts",
ErrorCodes::BAD_ARGUMENTS);
}
/// If sharding key is not specified, then you can only write to a shard containing only one shard
if (!has_sharding_key && ((cluster->getLocalShardCount() + cluster->getRemoteShardCount()) >= 2))
{
throw Exception("Method write is not supported by storage " + getName() + " with more than one shard and no sharding key provided",
ErrorCodes::STORAGE_REQUIRES_PARAMETER);
}
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/// Force sync insertion if it is remote() table function
bool insert_sync = settings.insert_distributed_sync || owned_cluster;
auto timeout = settings.insert_distributed_timeout;
/// DistributedBlockOutputStream will not own cluster, but will own ConnectionPools of the cluster
return std::make_shared<DistributedBlockOutputStream>(
context, *this, createInsertToRemoteTableQuery(remote_database, remote_table, getSampleBlockNonMaterialized()), cluster,
insert_sync, timeout);
}
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void StorageDistributed::checkAlterIsPossible(const AlterCommands & commands, const Settings & /* settings */)
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{
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for (const auto & command : commands)
{
if (command.type != AlterCommand::Type::ADD_COLUMN
&& command.type != AlterCommand::Type::MODIFY_COLUMN
&& command.type != AlterCommand::Type::DROP_COLUMN
&& command.type != AlterCommand::Type::COMMENT_COLUMN)
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throw Exception("Alter of type '" + alterTypeToString(command.type) + "' is not supported by storage " + getName(),
ErrorCodes::NOT_IMPLEMENTED);
}
}
void StorageDistributed::alter(const AlterCommands & params, const Context & context, TableStructureWriteLockHolder & table_lock_holder)
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{
lockStructureExclusively(table_lock_holder, context.getCurrentQueryId(), context.getSettingsRef().lock_acquire_timeout);
auto table_id = getStorageID();
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checkAlterIsPossible(params, context.getSettingsRef());
StorageInMemoryMetadata metadata = getInMemoryMetadata();
params.apply(metadata);
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DatabaseCatalog::instance().getDatabase(table_id.database_name)->alterTable(context, table_id, metadata);
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setColumns(std::move(metadata.columns));
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}
void StorageDistributed::startup()
{
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if (remote_database.empty() && !remote_table_function_ptr)
LOG_WARNING(log, "Name of remote database is empty. Default database will be used implicitly.");
if (!volume)
return;
for (const DiskPtr & disk : volume->disks)
createDirectoryMonitors(disk->getPath());
for (const String & path : getDataPaths())
{
UInt64 inc = getMaximumFileNumber(path);
if (inc > file_names_increment.value)
file_names_increment.value.store(inc);
}
LOG_DEBUG(log, "Auto-increment is " << file_names_increment.value);
}
void StorageDistributed::shutdown()
{
monitors_blocker.cancelForever();
std::lock_guard lock(cluster_nodes_mutex);
cluster_nodes_data.clear();
}
Strings StorageDistributed::getDataPaths() const
{
Strings paths;
if (relative_data_path.empty())
return paths;
for (const DiskPtr & disk : volume->disks)
paths.push_back(disk->getPath() + relative_data_path);
return paths;
}
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void StorageDistributed::truncate(const ASTPtr &, const Context &, TableStructureWriteLockHolder &)
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{
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std::lock_guard lock(cluster_nodes_mutex);
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for (auto it = cluster_nodes_data.begin(); it != cluster_nodes_data.end();)
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{
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it->second.shutdownAndDropAllData();
it = cluster_nodes_data.erase(it);
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}
}
StoragePolicyPtr StorageDistributed::getStoragePolicy() const
{
if (storage_policy.empty())
return {};
return global_context.getStoragePolicySelector()->get(storage_policy);
}
void StorageDistributed::createDirectoryMonitors(const std::string & disk)
{
const std::string path(disk + relative_data_path);
Poco::File{path}.createDirectories();
std::filesystem::directory_iterator begin(path);
std::filesystem::directory_iterator end;
for (auto it = begin; it != end; ++it)
if (std::filesystem::is_directory(*it))
requireDirectoryMonitor(disk, it->path().filename().string());
}
StorageDistributedDirectoryMonitor& StorageDistributed::requireDirectoryMonitor(const std::string & disk, const std::string & name)
{
const std::string path(disk + relative_data_path + name);
const std::string key(disk + name);
std::lock_guard lock(cluster_nodes_mutex);
auto & node_data = cluster_nodes_data[key];
if (!node_data.directory_monitor)
{
node_data.conneciton_pool = StorageDistributedDirectoryMonitor::createPool(name, *this);
node_data.directory_monitor = std::make_unique<StorageDistributedDirectoryMonitor>(
*this, path, node_data.conneciton_pool, monitors_blocker, global_context.getDistributedSchedulePool());
}
return *node_data.directory_monitor;
}
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size_t StorageDistributed::getShardCount() const
{
return getCluster()->getShardCount();
}
std::pair<const std::string &, const std::string &> StorageDistributed::getPath()
{
return {volume->getNextDisk()->getPath(), relative_data_path};
}
ClusterPtr StorageDistributed::getCluster() const
{
return owned_cluster ? owned_cluster : global_context.getCluster(cluster_name);
}
ClusterPtr StorageDistributed::getOptimizedCluster(const Context & context, const ASTPtr & query_ptr) const
{
ClusterPtr cluster = getCluster();
const Settings & settings = context.getSettingsRef();
auto table_id = getStorageID();
if (!settings.optimize_skip_unused_shards)
return cluster;
if (has_sharding_key)
{
ClusterPtr optimized = skipUnusedShards(cluster, query_ptr, context);
if (optimized)
{
LOG_DEBUG(log, "Reading from " << table_id.getNameForLogs() << ": "
"Skipping irrelevant shards - the query will be sent to the following shards of the cluster (shard numbers): "
" " << makeFormattedListOfShards(cluster));
return optimized;
}
}
LOG_DEBUG(log, "Reading from " << table_id.getNameForLogs() <<
(has_sharding_key ? "" : " (no sharding key)") << ": "
"Unable to figure out irrelevant shards from WHERE/PREWHERE clauses - "
"the query will be sent to all shards of the cluster");
UInt64 force = settings.force_optimize_skip_unused_shards;
if (force)
{
std::stringstream exception_message;
if (!has_sharding_key)
exception_message << "No sharding key";
else
exception_message << "Sharding key " << sharding_key_column_name << " is not used";
if (force == FORCE_OPTIMIZE_SKIP_UNUSED_SHARDS_ALWAYS)
throw Exception(exception_message.str(), ErrorCodes::UNABLE_TO_SKIP_UNUSED_SHARDS);
if (force == FORCE_OPTIMIZE_SKIP_UNUSED_SHARDS_HAS_SHARDING_KEY && has_sharding_key)
throw Exception(exception_message.str(), ErrorCodes::UNABLE_TO_SKIP_UNUSED_SHARDS);
}
return cluster;
}
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void StorageDistributed::ClusterNodeData::flushAllData() const
{
directory_monitor->flushAllData();
}
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void StorageDistributed::ClusterNodeData::shutdownAndDropAllData() const
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{
directory_monitor->shutdownAndDropAllData();
}
IColumn::Selector StorageDistributed::createSelector(const ClusterPtr cluster, const ColumnWithTypeAndName & result) const
{
const auto & slot_to_shard = cluster->getSlotToShard();
// If result.type is DataTypeLowCardinality, do shard according to its dictionaryType
#define CREATE_FOR_TYPE(TYPE) \
if (typeid_cast<const DataType##TYPE *>(result.type.get())) \
return createBlockSelector<TYPE>(*result.column, slot_to_shard); \
else if (auto * type_low_cardinality = typeid_cast<const DataTypeLowCardinality *>(result.type.get())) \
if (typeid_cast<const DataType ## TYPE *>(type_low_cardinality->getDictionaryType().get())) \
return createBlockSelector<TYPE>(*result.column->convertToFullColumnIfLowCardinality(), slot_to_shard);
CREATE_FOR_TYPE(UInt8)
CREATE_FOR_TYPE(UInt16)
CREATE_FOR_TYPE(UInt32)
CREATE_FOR_TYPE(UInt64)
CREATE_FOR_TYPE(Int8)
CREATE_FOR_TYPE(Int16)
CREATE_FOR_TYPE(Int32)
CREATE_FOR_TYPE(Int64)
#undef CREATE_FOR_TYPE
throw Exception{"Sharding key expression does not evaluate to an integer type", ErrorCodes::TYPE_MISMATCH};
}
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/// Returns a new cluster with fewer shards if constant folding for `sharding_key_expr` is possible
/// using constraints from "PREWHERE" and "WHERE" conditions, otherwise returns `nullptr`
ClusterPtr StorageDistributed::skipUnusedShards(ClusterPtr cluster, const ASTPtr & query_ptr, const Context & context) const
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{
const auto & select = query_ptr->as<ASTSelectQuery &>();
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if (!select.prewhere() && !select.where())
{
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return nullptr;
}
ASTPtr condition_ast;
if (select.prewhere() && select.where())
{
condition_ast = makeASTFunction("and", select.prewhere()->clone(), select.where()->clone());
}
else
{
condition_ast = select.prewhere() ? select.prewhere()->clone() : select.where()->clone();
}
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replaceConstantExpressions(condition_ast, context, getColumns().getAll(), shared_from_this());
const auto blocks = evaluateExpressionOverConstantCondition(condition_ast, sharding_key_expr);
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// Can't get definite answer if we can skip any shards
if (!blocks)
{
return nullptr;
}
std::set<int> shards;
for (const auto & block : *blocks)
{
if (!block.has(sharding_key_column_name))
throw Exception("sharding_key_expr should evaluate as a single row", ErrorCodes::TOO_MANY_ROWS);
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const ColumnWithTypeAndName & result = block.getByName(sharding_key_column_name);
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const auto selector = createSelector(cluster, result);
shards.insert(selector.begin(), selector.end());
}
return cluster->getClusterWithMultipleShards({shards.begin(), shards.end()});
}
ActionLock StorageDistributed::getActionLock(StorageActionBlockType type)
{
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if (type == ActionLocks::DistributedSend)
return monitors_blocker.cancel();
return {};
}
void StorageDistributed::flushClusterNodesAllData()
{
std::lock_guard lock(cluster_nodes_mutex);
/// TODO: Maybe it should be executed in parallel
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for (auto & node : cluster_nodes_data)
node.second.flushAllData();
}
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void StorageDistributed::rename(const String & new_path_to_table_data, const StorageID & new_table_id)
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{
if (!relative_data_path.empty())
renameOnDisk(new_path_to_table_data);
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renameInMemory(new_table_id);
}
void StorageDistributed::renameOnDisk(const String & new_path_to_table_data)
{
for (const DiskPtr & disk : volume->disks)
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{
const String path(disk->getPath());
auto new_path = path + new_path_to_table_data;
Poco::File(path + relative_data_path).renameTo(new_path);
LOG_DEBUG(log, "Updating path to " << new_path);
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std::lock_guard lock(cluster_nodes_mutex);
for (auto & node : cluster_nodes_data)
node.second.directory_monitor->updatePath(new_path);
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}
relative_data_path = new_path_to_table_data;
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}
void registerStorageDistributed(StorageFactory & factory)
{
factory.registerStorage("Distributed", [](const StorageFactory::Arguments & args)
{
/** Arguments of engine is following:
* - name of cluster in configuration;
* - name of remote database;
* - name of remote table;
* - policy to store data in;
*
* Remote database may be specified in following form:
* - identifier;
* - constant expression with string result, like currentDatabase();
* -- string literal as specific case;
* - empty string means 'use default database from cluster'.
*/
ASTs & engine_args = args.engine_args;
if (engine_args.size() < 3 || engine_args.size() > 5)
throw Exception(
"Storage Distributed requires from 3 to 5 parameters - "
"name of configuration section with list of remote servers, "
"name of remote database, "
"name of remote table, "
"sharding key expression (optional), "
"policy to store data in (optional).",
ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
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String cluster_name = getClusterNameAndMakeLiteral(engine_args[0]);
engine_args[1] = evaluateConstantExpressionOrIdentifierAsLiteral(engine_args[1], args.local_context);
engine_args[2] = evaluateConstantExpressionOrIdentifierAsLiteral(engine_args[2], args.local_context);
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String remote_database = engine_args[1]->as<ASTLiteral &>().value.safeGet<String>();
String remote_table = engine_args[2]->as<ASTLiteral &>().value.safeGet<String>();
const auto & sharding_key = engine_args.size() >= 4 ? engine_args[3] : nullptr;
const auto & storage_policy = engine_args.size() >= 5 ? engine_args[4]->as<ASTLiteral &>().value.safeGet<String>() : "";
/// Check that sharding_key exists in the table and has numeric type.
if (sharding_key)
{
auto sharding_expr = buildShardingKeyExpression(sharding_key, args.context, args.columns.getAllPhysical(), true);
const Block & block = sharding_expr->getSampleBlock();
if (block.columns() != 1)
throw Exception("Sharding expression must return exactly one column", ErrorCodes::INCORRECT_NUMBER_OF_COLUMNS);
auto type = block.getByPosition(0).type;
if (!type->isValueRepresentedByInteger())
throw Exception("Sharding expression has type " + type->getName() +
", but should be one of integer type", ErrorCodes::TYPE_MISMATCH);
}
return StorageDistributed::create(
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args.table_id, args.columns, args.constraints,
remote_database, remote_table, cluster_name,
args.context,
sharding_key,
storage_policy,
args.relative_data_path,
args.attach);
},
{
.source_access_type = AccessType::REMOTE,
});
}
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}