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This commit is contained in:
akazz 2019-09-05 15:49:20 +03:00
parent 838957f0e2
commit d374a6fb58
1 changed files with 9 additions and 7 deletions
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16
dbms/src/Common/RWLock.cpp
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@ -108,9 +108,6 @@ RWLockImpl::LockHolder RWLockImpl::getLock(RWLockImpl::Type type, const String &
: ProfileEvents::RWLockWritersWaitMilliseconds, watch.elapsedMilliseconds());
};
GroupsContainer::iterator it_group;
ClientsContainer::iterator it_client;
/// This object is placed above unique_lock, because it may lock in destructor.
LockHolder res;
@ -157,9 +154,13 @@ RWLockImpl::LockHolder RWLockImpl::getLock(RWLockImpl::Type type, const String &
* We will throw an exception instead.
*/
GroupsContainer::iterator it_group;
/// A locking request is considered potentially dangerous if it needs to wait in the queue and
/// its associated query_id already holds at least one Read lock. We raise an exception in such case
if (type == Type::Write || queue.empty() || queue.back().type == Type::Write)
{
if (type == Type::Read && !queue.empty() && queue.back().type == Type::Write && request_has_query_id)
if (type == Type::Read && request_has_query_id && !queue.empty())
all_read_locks.check(query_id);
/// Create new group of clients
@ -167,13 +168,14 @@ RWLockImpl::LockHolder RWLockImpl::getLock(RWLockImpl::Type type, const String &
}
else
{
if (type == Type::Read && request_has_query_id && queue.size() > 1)
all_read_locks.check(query_id);
/// Will append myself to last group
it_group = std::prev(queue.end());
if (it_group != queue.begin() && request_has_query_id)
all_read_locks.check(query_id);
}
ClientsContainer::iterator it_client;
/// Append myself to the end of chosen group
auto & clients = it_group->clients;
try