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Fix UUID overlap in DROP TABLE for internal DDL from MaterializeMySQL

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This will fix race with DatabaseCatalog::loadMarkedAsDroppedTables(),
since MaterializeMySQL, and MaterializedMySQLSyncThread in background,
will be started earlier then
DatabaseCatalog::loadMarkedAsDroppedTables() and will move those tables
to metadata_dropped, and after loadMarkedAsDroppedTables() will start
and try to load partially dropped tables and will hit UUID overlap:

    12:02:51.536783 [ 3026034 ] {} <Information> Application: starting up
    12:02:53.019282 [ 3026034 ] {} <Information> DatabaseMaterializeMySQL<Atomic> (mysql): Total 9 tables and 0 dictionaries.
    12:02:53.041699 [ 3026200 ] {} <Debug> mysql.data (7143b65f-6982-4600-b143-b65f6982e600): Loading data parts
    12:02:53.041740 [ 3026200 ] {} <Debug> mysql.data (7143b65f-6982-4600-b143-b65f6982e600): There are no data parts
    12:02:53.620382 [ 3026034 ] {} <Information> DatabaseMaterializeMySQL<Atomic> (mysql): Starting up tables.
    12:03:00.669730 [ 3026183 ] {} <Debug> executeQuery: (internal) /*Materialize MySQL step 1: execute MySQL DDL for dump data*/ DROP TABLE mysql.data
    12:03:00.741894 [ 3026269 ] {} <Information> DatabaseCatalog: Trying load partially dropped table mysql.data (7143b65f-6982-4600-b143-b65f6982e600) from /var/lib/clickhouse/metadata_dropped/mysql.data.7143b65f-6982-4600-b143-b65f6982e600.sql
    12:03:00.742582 [ 3026269 ] {} <Debug> mysql.data (7143b65f-6982-4600-b143-b65f6982e600): Loading data parts
    12:03:00.742650 [ 3026269 ] {} <Debug> mysql.data (7143b65f-6982-4600-b143-b65f6982e600): There are no data parts
    12:03:00.773137 [ 3026034 ] {} <Error> Application: Caught exception while loading metadata: Code: 57, e.displayText() = DB::Exception: Mapping for table with UUID=7143b65f-6982-4600-b143-b65f6982e600 already exists. It happened due to UUID collision, most likely because some not random UUIDs were manually specified in CREATE queries., Stack trace (when copying this message, always include the lines below):
    12:03:01.224557 [ 3026034 ] {} <Error> Application: DB::Exception: Mapping for table with UUID=7143b65f-6982-4600-b143-b65f6982e600 already exists. It happened due to UUID collision, most likely because some not random UUIDs were manually specified in CREATE queries.

Cc: @zhang2014
This commit is contained in:
Azat Khuzhin 2021-09-02 21:05:13 +03:00
parent b85f98d2f4
commit bf6ba796f8
3 changed files with 5 additions and 2 deletions
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4
programs/server/Server.cpp
View File

@ -1131,6 +1131,10 @@ if (ThreadFuzzer::instance().isEffective())
global_context->setSystemZooKeeperLogAfterInitializationIfNeeded();
/// After the system database is created, attach virtual system tables (in addition to query_log and part_log)
attachSystemTablesServer(*database_catalog.getSystemDatabase(), has_zookeeper);
/// Firstly remove partially dropped databases, to avoid race with MaterializedMySQLSyncThread,
/// that may execute DROP before loadMarkedAsDroppedTables() in background,
/// and so loadMarkedAsDroppedTables() will find it and try to add, and UUID will overlap.
database_catalog.loadMarkedAsDroppedTables();
/// Then, load remaining databases
loadMetadata(global_context, default_database);
database_catalog.loadDatabases();

1
src/Interpreters/DatabaseCatalog.cpp
View File

@ -146,7 +146,6 @@ void DatabaseCatalog::initializeAndLoadTemporaryDatabase()
void DatabaseCatalog::loadDatabases()
{
loadMarkedAsDroppedTables();
auto task_holder = getContext()->getSchedulePool().createTask("DatabaseCatalog", [this](){ this->dropTableDataTask(); });
drop_task = std::make_unique<BackgroundSchedulePoolTaskHolder>(std::move(task_holder));
(*drop_task)->activate();

2
src/Interpreters/DatabaseCatalog.h
View File

@ -130,6 +130,7 @@ public:
void initializeAndLoadTemporaryDatabase();
void loadDatabases();
void loadMarkedAsDroppedTables();
/// Get an object that protects the table from concurrently executing multiple DDL operations.
DDLGuardPtr getDDLGuard(const String & database, const String & table);
@ -241,7 +242,6 @@ private:
};
using TablesMarkedAsDropped = std::list<TableMarkedAsDropped>;
void loadMarkedAsDroppedTables();
void dropTableDataTask();
void dropTableFinally(const TableMarkedAsDropped & table);