Basically `DATABASE()` and `SCHEMA()` are aliases in MySQL.
This helps with allowing MySQL Shell to get one step closer to a
functioning connection.
To see what MySQL Shell does:
```
mysqlsh --verbose=4 --log-sql=unfiltered mysql://default@127.0.0.1:9004
```
This might also bring other tools a step closer to working with the
MySQL compatibility of ClickHouse.
Ref: #9336
Signed-off-by: Daniël van Eeden <git@myname.nl>
Usually functions are validated before index analysis, however it is
not the case for parallel replicas, and it requires additional checks
before interpreting function arguments.
<details>
<summary>stack trace</summary>
```
==172==WARNING: MemorySanitizer: use-of-uninitialized-value
0 0x55cf82aedd6c in DB::ASTFunction* typeid_cast<DB::ASTFunction*, DB::IAST>(DB::IAST*) build_docker/./src/Common/typeid_cast.h:42:73
1 0x55cf82aedd6c in DB::TypePromotion<DB::IAST>::CastHelper<DB::ASTFunction, false, false>::value(DB::IAST*) build_docker/./src/Common/TypePromotion.h:38:43
2 0x55cf82aedd6c in std::__1::invoke_result<decltype(&CastHelper<DB::ASTFunction, false>::value), DB::TypePromotion<DB::IAST>::CastHelper<DB::ASTFunction, false, std::is_reference_v<DB::ASTFunction>>, DB::IAST*>::type DB::TypePromotion<DB::IAST>::as<DB::ASTFunction>() build_docker/./src/>
3 0x55cf82aedd6c in DB::MergeTreeIndexConditionSet::operatorFromAST(std::__1::shared_ptr<DB::IAST>&) build_docker/./src/Storages/MergeTree/MergeTreeIndexSet.cpp:602:25
4 0x55cf82ae5bc1 in DB::MergeTreeIndexConditionSet::traverseAST(std::__1::shared_ptr<DB::IAST>&) const build_docker/./src/Storages/MergeTree/MergeTreeIndexSet.cpp:547:9
5 0x55cf82ae5de6 in DB::MergeTreeIndexConditionSet::traverseAST(std::__1::shared_ptr<DB::IAST>&) const build_docker/./src/Storages/MergeTree/MergeTreeIndexSet.cpp:552:13
6 0x55cf82ae06db in DB::MergeTreeIndexConditionSet::MergeTreeIndexConditionSet() build_docker/.>
...
12 0x55cf82aef09c in DB::MergeTreeIndexSet::createIndexCondition() const build_docker/./src/Storages/MergeTree/MergeTreeIndexSet.cpp:703:12
13 0x55cf84951cd4 in DB::buildIndexes()
14 0x55cf84955ed3 in DB::ReadFromMergeTree::selectRangesToReadImpl()
15 0x55cf8494caef in DB::ReadFromMergeTree::selectRangesToRead()
16 0x55cf82a409a9 in DB::MergeTreeDataSelectExecutor::estimateNumMarksToRead()
17 0x55cf827f728d in DB::MergeTreeData::canUseParallelReplicasBasedOnPKAnalysis()
18 0x55cf827f627e in DB::MergeTreeData::getQueryProcessingStage()
19 0x55cf7f2f4969 in DB::InterpreterSelectQuery::getSampleBlockImpl() build_docker/./src/Interpreters/InterpreterSelectQuery.cpp:937:31
20 0x55cf7f2daa00 in DB::InterpreterSelectQuery::InterpreterSelectQuery()
24 0x55cf7f520b98 in DB::InterpreterSelectWithUnionQuery::buildCurrentChildInterpreter()
25 0x55cf7f51b6cd in DB::InterpreterSelectWithUnionQuery::InterpreterSelectWithUnionQuery()
27 0x55cf7f1d4ea9 in DB::InterpreterFactory::get(std::__1::shared_ptr<DB::IAST>&, std::__1::shared_ptr<DB::Context>, DB::SelectQueryOptions const&) build_docker/./src/Interpreters/InterpreterFactory.cpp:162:16
28 0x55cf8012e485 in DB::executeQueryImpl(char const*, char const*, std::__1::shared_ptr<DB::Context>, bool, DB::QueryProcessingStage::Enum, DB::ReadBuffer*) build_docker/./src/Interpreters/executeQuery.cpp:1032:31
29 0x55cf80121bc1 in DB::executeQuery(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>> const&, std::__1::shared_ptr<DB::Context>, bool, DB::QueryProcessingStage::Enum) build_docker/./src/Interpreters/executeQuery.cpp:1229:30
30 0x55cf8389295f in DB::TCPHandler::runImpl() build_docker/./src/Server/TCPHandler.cpp:424:24
31 0x55cf838d7dfb in DB::TCPHandler::run() build_docker/./src/Server/TCPHandler.cpp:2050:9
```
</details>
CI: https://s3.amazonaws.com/clickhouse-test-reports/53214/d99b10c340909ed4ee2e6edf0921e8a2f8561b0d/fuzzer_astfuzzermsan/report.html
Signed-off-by: Azat Khuzhin <a.khuzhin@semrush.com>
