Otherwise you can see something like this for the following query:
```sql
WITH
arrayMap(x -> demangle(addressToSymbol(x)), s.trace) AS trace_array,
arrayStringConcat(trace_array, '\n') AS trace_string
SELECT
p.thread_id,
p.query_id,
p.query,
trace_string
FROM
(
SELECT
query_id,
query,
arrayJoin(thread_ids) AS thread_id
FROM system.processes
) AS p
INNER JOIN system.stack_trace AS s ON p.thread_id = s.thread_id
ORDER BY p.query_id ASC
SETTINGS enable_global_with_statement = 0, allow_introspection_functions = 1
FORMAT PrettyCompactNoEscapes
```
Lots of the following:
```sql
INSERT INTO buffer (...) VALUES
__lll_lock_wait
pthread_mutex_lock
std::__1::mutex::lock()
DB::StorageBuffer::reschedule()
DB::BufferBlockOutputStream::write(DB::Block const&)
```
That will wait one of this:
```
INSERT INTO buffer (...) VALUES
...
DB::PushingToViewsBlockOutputStream::write(DB::Block const&)
DB::AddingDefaultBlockOutputStream::write(DB::Block const&)
DB::SquashingBlockOutputStream::finalize()
DB::SquashingBlockOutputStream::writeSuffix()
DB::PushingToViewsBlockOutputStream::writeSuffix()
DB::StorageBuffer::writeBlockToDestination(DB::Block const&, std::__1::shared_ptr<DB::IStorage>)
DB::StorageBuffer::flushBuffer(DB::StorageBuffer::Buffer&, bool, bool, bool)
```
P.S. we cannot simply unlock the buffer during flushing, see comments in
the code
Do not use subquery result, when value is unknown, for constant folding.
v2: fix simple subqueries, fixes 00597_push_down_predicate.
v3:
- use identity over introducing yet another cast analog (as suggested by @akuzm)
- simpler suitable_for_const_folding check
v4: use identity(cast()) since only cast() can provide corrent type (for
data types that does not have it's own type, i.e. DateTime)
v5: do not optimize consts if only_analyze isset, regardless the block
content
Without this setting the test will pass only when the table will be
actually removed by the background worker of the Atomic engine.
In CI this is not required since
database_atomic_wait_for_drop_and_detach_synchronously is set explicitly
in via tests/users.d.
