Source originale: https://bohutang.me/2020/06/08/clickhouse-and-friends-mysql-protocol-write-stack/
L' appel MySQL Protocol and Read de l'article précédent a présenté la pile d'appels d'une instruction de requête ClickHouse. Cet article continue de présenter la pile d'appels écrite et ouverte dans son ensemble.
Ecrire la demande
Construisez une table:
mysql> CREATE TABLE test(a UInt8, b UInt8, c UInt8) ENGINE=MergeTree() PARTITION BY (a, b) ORDER BY c;
Query OK, 0 rows affected (0.03 sec)
entrée de données:
INSERT INTO test VALUES(1,1,1), (2,2,2);
Analyse de la pile d'appels
1. Obtenez le moteur de stockage OutputStream
DB::StorageMergeTree::write(std::__1::shared_ptr<DB::IAST> const&, DB::Context const&) StorageMergeTree.cpp:174
DB::PushingToViewsBlockOutputStream::PushingToViewsBlockOutputStream(std::__1::shared_ptr<DB::IStorage> const&, DB::Context const&, std::__1::shared_ptr<DB::IAST> const&, bool) PushingToViewsBlockOutputStream.cpp:110
DB::InterpreterInsertQuery::execute() InterpreterInsertQuery.cpp:229
DB::executeQueryImpl(const char *, const char *, DB::Context &, bool, DB::QueryProcessingStage::Enum, bool, DB::ReadBuffer *) executeQuery.cpp:364
DB::executeQuery(DB::ReadBuffer&, DB::WriteBuffer&, bool, DB::Context&, std::__1::function<void (std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&)>) executeQuery.cpp:696
DB::MySQLHandler::comQuery(DB::ReadBuffer&) MySQLHandler.cpp:311
DB::MySQLHandler::run() MySQLHandler.cpp:141
2. Assemblez InputStream à partir de SQL
(1,1,1), (2,2,2) Comment assembler en structure de flux d'entrée?
DB::InputStreamFromASTInsertQuery::InputStreamFromASTInsertQuery(std::__1::shared_ptr<DB::IAST> const&, DB::ReadBuffer*,
DB::InterpreterInsertQuery::execute() InterpreterInsertQuery.cpp:300
DB::executeQueryImpl(char const*, char const*, DB::Context&, bool, DB::QueryProcessingStage::Enum, bool, DB::ReadBuffer*) executeQuery.cpp:386
DB::MySQLHandler::comQuery(DB::ReadBuffer&) MySQLHandler.cpp:313
DB::MySQLHandler::run() MySQLHandler.cpp:150
puis
res.in = std::make_shared<InputStreamFromASTInsertQuery>(query_ptr, nullptr, query_sample_block, context, nullptr);
res.in = std::make_shared<NullAndDoCopyBlockInputStream>(res.in, out_streams.at(0));
Construisez un bloc via la méthode copyData de NullAndDoCopyBlockInputStream:
DB::ValuesBlockInputFormat::readRow(std::__1::vector<COW<DB::IColumn>::mutable_ptr<DB::IColumn>, std::__1::allocator<COW<DB::IColumn>::mutable_ptr<DB::IColumn> > >&, unsigned long) ValuesBlockInputFormat.cpp:93
DB::ValuesBlockInputFormat::generate() ValuesBlockInputFormat.cpp:55
DB::ISource::work() ISource.cpp:48
DB::InputStreamFromInputFormat::readImpl() InputStreamFromInputFormat.h:48
DB::IBlockInputStream::read() IBlockInputStream.cpp:57
DB::InputStreamFromASTInsertQuery::readImpl() InputStreamFromASTInsertQuery.h:31
DB::IBlockInputStream::read() IBlockInputStream.cpp:57
void DB::copyDataImpl<DB::copyData(DB::IBlockInputStream&, DB::IBlockOutputStream&, std::__1::atomic<bool>*)::$_0&, void (&)(DB::Block const&)>(DB::IBlockInputStream&, DB::IBlockOutputStream&, DB::copyData(DB::IBlockInputStream&, DB::IBlockOutputStream&, std::__1::atomic<bool>*)::$_0&, void (&)(DB::Block const&)) copyData.cpp:26
DB::copyData(DB::IBlockInputStream&, DB::IBlockOutputStream&, std::__1::atomic<bool>*) copyData.cpp:62
DB::NullAndDoCopyBlockInputStream::readImpl() NullAndDoCopyBlockInputStream.h:47
DB::IBlockInputStream::read() IBlockInputStream.cpp:57
void DB::copyDataImpl<std::__1::function<bool ()> const&, std::__1::function<void (DB::Block const&)> const&>(DB::IBlockInputStream&, DB::IBlockOutputStream&, std::__1::function<bool ()> const&, std::__1::function<void (DB::Block const&)> const&) copyData.cpp:26
DB::copyData(DB::IBlockInputStream&, DB::IBlockOutputStream&, std::__1::function<bool ()> const&, std::__1::function<void (DB::Block const&)> const&) copyData.cpp:73
DB::executeQuery(DB::ReadBuffer&, DB::WriteBuffer&, bool, DB::Context&, std::__1::function<void (std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&)>) executeQuery.cpp:785
DB::MySQLHandler::comQuery(DB::ReadBuffer&) MySQLHandler.cpp:313
DB::MySQLHandler::run() MySQLHandler.cpp:150
3. Assemblez le OutputStream
DB::InterpreterInsertQuery::execute() InterpreterInsertQuery.cpp:107
DB::executeQueryImpl(const char *, const char *, DB::Context &, bool, DB::QueryProcessingStage::Enum, bool, DB::ReadBuffer *) executeQuery.cpp:364
DB::executeQuery(DB::ReadBuffer&, DB::WriteBuffer&, bool, DB::Context&, std::__1::function<void (std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&)>) executeQuery.cpp:696
DB::MySQLHandler::comQuery(DB::ReadBuffer&) MySQLHandler.cpp:311
DB::MySQLHandler::run() MySQLHandler.cpp:141
Séquence d'assemblage:
NullAndDoCopyBlockInputStream
CountingBlockOutputStream
AddingDefaultBlockOutputStream
SquashingBlockOutputStream
PushingToViewsBlockOutputStream
MergeTreeBlockOutputStream
4. Ecrire dans OutputStream
DB::MergeTreeBlockOutputStream::write(DB::Block const&) MergeTreeBlockOutputStream.cpp:17
DB::PushingToViewsBlockOutputStream::write(DB::Block const&) PushingToViewsBlockOutputStream.cpp:145
DB::SquashingBlockOutputStream::finalize() SquashingBlockOutputStream.cpp:30
DB::SquashingBlockOutputStream::writeSuffix() SquashingBlockOutputStream.cpp:50
DB::AddingDefaultBlockOutputStream::writeSuffix() AddingDefaultBlockOutputStream.cpp:25
DB::CountingBlockOutputStream::writeSuffix() CountingBlockOutputStream.h:37
DB::copyDataImpl<DB::copyData(DB::IBlockInputStream&, DB::IBlockOutputStream&, std::__1::atomic<bool>*)::<lambda()>&, void (&)(const DB::Block&)>(DB::IBlockInputStream &, DB::IBlockOutputStream &, <lambda()> &, void (&)(const DB::Block &)) copyData.cpp:52
DB::copyData(DB::IBlockInputStream&, DB::IBlockOutputStream&, std::__1::atomic<bool>*) copyData.cpp:138
DB::NullAndDoCopyBlockInputStream::readImpl() NullAndDoCopyBlockInputStream.h:57
DB::IBlockInputStream::read() IBlockInputStream.cpp:60
void DB::copyDataImpl<std::__1::function<bool ()> const&, std::__1::function<void (DB::Block const&)> const&>(DB::IBlockInputStream&, DB::IBlockOutputStream&, std::__1::function<bool ()> const&, std::__1::function<void (DB::Block const&)> const&) copyData.cpp:29
DB::copyData(DB::IBlockInputStream&, DB::IBlockOutputStream&, std::__1::function<bool ()> const&, std::__1::function<void (DB::Block const&)> const&) copyData.cpp:154
DB::executeQuery(DB::ReadBuffer&, DB::WriteBuffer&, bool, DB::Context&, std::__1::function<void (std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&)>) executeQuery.cpp:748
DB::MySQLHandler::comQuery(DB::ReadBuffer&) MySQLHandler.cpp:311
DB::MySQLHandler::run() MySQLHandler.cpp:141
Grâce à la méthode copyData, les données sont transmises de manière transparente entre les couches OutputStream, jusqu'à MergeTreeBlockOutputStream.
5. Retour au client
DB::MySQLOutputFormat::finalize() MySQLOutputFormat.cpp:62
DB::IOutputFormat::doWriteSuffix() IOutputFormat.h:78
DB::OutputStreamToOutputFormat::writeSuffix() OutputStreamToOutputFormat.cpp:18
DB::MaterializingBlockOutputStream::writeSuffix() MaterializingBlockOutputStream.h:22
void DB::copyDataImpl<std::__1::function<bool ()> const&, std::__1::function<void (DB::Block const&)> const&>(DB::IBlockInputStream&, DB::IBlockOutputStream&, std::__1::function<bool ()> const&, std::__1::function<void (DB::Block const&)> const&) copyData.cpp:52
DB::copyData(DB::IBlockInputStream&, DB::IBlockOutputStream&, std::__1::function<bool ()> const&, std::__1::function<void (DB::Block const&)> const&) copyData.cpp:154
DB::executeQuery(DB::ReadBuffer&, DB::WriteBuffer&, bool, DB::Context&, std::__1::function<void (std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&)>) executeQuery.cpp:748
DB::MySQLHandler::comQuery(DB::ReadBuffer&) MySQLHandler.cpp:311
DB::MySQLHandler::run() MySQLHandler.cpp:141
Pour résumer
INSERT INTO test VALUES(1,1,1), (2,2,2);
Tout d'abord, le noyau analyse l'instruction SQL pour générer un AST, et obtient Interpreter: InterpreterInsertQuery selon l'AST. Deuxièmement, Interpreter ajoute à son tour le OutputStream correspondant. Ensuite, lisez les données d'InputStream et écrivez dans OutputStream. Stream pénétrera couche par couche et écrira dans le moteur de stockage sous-jacent. Enfin, écrivez dans Socket Output et renvoyez le résultat.
La disposition OutputStream de ClickHouse est encore plus compliquée, manquant de planification et d'orchestration de type pipeline, mais en raison de la solidification du modèle, cela semble clair pour le moment.
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