TODO (suggested by Nikolai)
1. Build query plan fro current query (inside storage::read) up to WithMergableState
2. Check, that plan is simple enough: Aggregating - Expression - Filter - ReadFromStorage (or simplier)
3. Check, that filter is the same as filter in projection, and also expression calculates the same aggregation keys as in projection
4. Return WithMergableState if projection applies
3 will be easier to do with ActionsDAG, cause it sees all functions, and dependencies are direct (but it is possible with ExpressionActions also)
Also need to figure out how prewhere works for projections, and
row_filter_policies.
wip
This is not the problem for plain DROP DATABASE query since it first
remove tables.
(gdb) bt
0 __lll_lock_wait () at ../sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:103
1 0x00007f353c262774 in __GI___pthread_mutex_lock (mutex=mutex@entry=0x11049288 <DB::DatabaseCatalog::init(DB::Context const*)::database_catalog+8>) at ../nptl/pthread_mutex_lock.c:80
2 0x0000000004fd5d1e in DB::pthread_mutex_lock (arg=arg@entry=0x11049288 <DB::DatabaseCatalog::init(DB::Context const*)::database_catalog+8>) at ../src/Common/ThreadFuzzer.cpp:253
3 0x000000000c70b3a9 in std::__1::__libcpp_mutex_lock (__m=__m@entry=0x11049288 <DB::DatabaseCatalog::init(DB::Context const*)::database_catalog+8>) at ../contrib/libcxx/include/__threading_support:322
4 std::__1::mutex::lock (this=this@entry=0x11049288 <DB::DatabaseCatalog::init(DB::Context const*)::database_catalog+8>) at ../contrib/libcxx/src/mutex.cpp:33
5 0x0000000008acd4e2 in std::__1::lock_guard<std::__1::mutex>::lock_guard (__m=..., this=<synthetic pointer>) at ../contrib/libcxx/include/__mutex_base:90
6 DB::DatabaseCatalog::removeDependency (this=this@entry=0x11049280 <DB::DatabaseCatalog::init(DB::Context const*)::database_catalog>, from=..., where=...) at ../src/Interpreters/DatabaseCatalog.cpp:388
7 0x000000000975044b in DB::StorageMaterializedView::shutdown (this=0x7f338d178a00) at ../src/Storages/StorageMaterializedView.cpp:362
8 0x0000000008a79602 in DB::DatabaseWithOwnTablesBase::shutdown (this=0x7f353be3cc60) at ../contrib/libcxx/include/__tree:184
9 0x0000000009546196 in DB::DatabaseWithDictionaries::shutdown (this=0x7f353be3cc60) at ../src/Databases/DatabaseWithDictionaries.cpp:265
10 0x0000000008acecdb in DB::DatabaseCatalog::detachDatabase (this=0x11049280 <DB::DatabaseCatalog::init(DB::Context const*)::database_catalog>, database_name=..., drop=drop@entry=false, check_empty=check_empty@entry=false) at ../contrib/libcxx/include/memory:3826
11 0x0000000004bf0aa5 in DB::InterpreterCreateQuery::createDatabase (this=0x7ffd6e1bab80, create=...) at ../src/Interpreters/InterpreterCreateQuery.cpp:162
12 0x0000000008b04327 in DB::InterpreterCreateQuery::execute (this=this@entry=0x7ffd6e1bab80) at ../src/Interpreters/InterpreterCreateQuery.cpp:722
13 0x0000000008d0fdaa in DB::executeCreateQuery (has_force_restore_data_flag=false, file_name=..., database=..., context=..., query=...) at ../src/Interpreters/loadMetadata.cpp:48
14 DB::loadDatabase (context=..., database=..., database_path=..., force_restore_data=<optimized out>) at ../src/Interpreters/loadMetadata.cpp:72
15 0x0000000008d103c3 in DB::loadMetadata (context=...) at ../src/Interpreters/loadMetadata.cpp:111
16 0x0000000004f4d25e in DB::Server::main (this=<optimized out>) at ../contrib/libcxx/include/memory:2582
17 0x000000000bbc8963 in Poco::Util::Application::run (this=this@entry=0x7ffd6e1bcc60) at ../contrib/poco/Util/src/Application.cpp:334
18 0x0000000004ffe1de in DB::Server::run (this=0x7ffd6e1bcc60) at ../programs/server/Server.cpp:178
19 0x0000000004ff36cc in mainEntryClickHouseServer (argc=3, argv=0x7f353be58bc0) at ../programs/server/Server.cpp:1060
20 0x0000000004f49b99 in main (argc_=<optimized out>, argv_=<optimized out>) at ../contrib/libcxx/include/vector:655
