ClickHouse/docs/en/operations/system-tables/stack_trace.md

---
slug: /en/operations/system-tables/stack_trace
---
# stack_trace

Contains stack traces of all server threads. Allows developers to introspect the server state.

To analyze stack frames, use the `addressToLine`, `addressToLineWithInlines`, `addressToSymbol` and `demangle` [introspection functions](../../sql-reference/functions/introspection.md).

Columns:

- `thread_name` ([String](../../sql-reference/data-types/string.md)) — Thread name.
- `thread_id` ([UInt64](../../sql-reference/data-types/int-uint.md)) — Thread identifier.
- `query_id` ([String](../../sql-reference/data-types/string.md)) — Query identifier that can be used to get details about a query that was running from the [query_log](../system-tables/query_log.md) system table.
- `trace` ([Array(UInt64)](../../sql-reference/data-types/array.md)) — A [stack trace](https://en.wikipedia.org/wiki/Stack_trace) which represents a list of physical addresses where the called methods are stored.

:::tip
Check out the Knowledge Base for some handy queries, including [how to see what threads are currently running](https://clickhouse.com/docs/knowledgebase/find-expensive-queries) and [useful queries for troubleshooting](https://clickhouse.com/docs/knowledgebase/useful-queries-for-troubleshooting).
:::

**Example**

Enabling introspection functions:

``` sql
SET allow_introspection_functions = 1;
```

Getting symbols from ClickHouse object files:

``` sql
WITH arrayMap(x -> demangle(addressToSymbol(x)), trace) AS all SELECT thread_name, thread_id, query_id, arrayStringConcat(all, '\n') AS res FROM system.stack_trace LIMIT 1 \G;
```

``` text
Row 1:
──────
thread_name: QueryPipelineEx
thread_id:   743490
query_id:    dc55a564-febb-4e37-95bb-090ef182c6f1
res:         memcpy
large_ralloc
arena_ralloc
do_rallocx
Allocator<true, true>::realloc(void*, unsigned long, unsigned long, unsigned long)
HashTable<unsigned long, HashMapCell<unsigned long, char*, HashCRC32<unsigned long>, HashTableNoState, PairNoInit<unsigned long, char*>>, HashCRC32<unsigned long>, HashTableGrowerWithPrecalculation<8ul>, Allocator<true, true>>::resize(unsigned long, unsigned long)
void DB::Aggregator::executeImplBatch<false, false, true, DB::AggregationMethodOneNumber<unsigned long, HashMapTable<unsigned long, HashMapCell<unsigned long, char*, HashCRC32<unsigned long>, HashTableNoState, PairNoInit<unsigned long, char*>>, HashCRC32<unsigned long>, HashTableGrowerWithPrecalculation<8ul>, Allocator<true, true>>, true, false>>(DB::AggregationMethodOneNumber<unsigned long, HashMapTable<unsigned long, HashMapCell<unsigned long, char*, HashCRC32<unsigned long>, HashTableNoState, PairNoInit<unsigned long, char*>>, HashCRC32<unsigned long>, HashTableGrowerWithPrecalculation<8ul>, Allocator<true, true>>, true, false>&, DB::AggregationMethodOneNumber<unsigned long, HashMapTable<unsigned long, HashMapCell<unsigned long, char*, HashCRC32<unsigned long>, HashTableNoState, PairNoInit<unsigned long, char*>>, HashCRC32<unsigned long>, HashTableGrowerWithPrecalculation<8ul>, Allocator<true, true>>, true, false>::State&, DB::Arena*, unsigned long, unsigned long, DB::Aggregator::AggregateFunctionInstruction*, bool, char*) const
DB::Aggregator::executeImpl(DB::AggregatedDataVariants&, unsigned long, unsigned long, std::__1::vector<DB::IColumn const*, std::__1::allocator<DB::IColumn const*>>&, DB::Aggregator::AggregateFunctionInstruction*, bool, bool, char*) const
DB::Aggregator::executeOnBlock(std::__1::vector<COW<DB::IColumn>::immutable_ptr<DB::IColumn>, std::__1::allocator<COW<DB::IColumn>::immutable_ptr<DB::IColumn>>>, unsigned long, unsigned long, DB::AggregatedDataVariants&, std::__1::vector<DB::IColumn const*, std::__1::allocator<DB::IColumn const*>>&, std::__1::vector<std::__1::vector<DB::IColumn const*, std::__1::allocator<DB::IColumn const*>>, std::__1::allocator<std::__1::vector<DB::IColumn const*, std::__1::allocator<DB::IColumn const*>>>>&, bool&) const
DB::AggregatingTransform::work()
DB::ExecutionThreadContext::executeTask()
DB::PipelineExecutor::executeStepImpl(unsigned long, std::__1::atomic<bool>*)
void std::__1::__function::__policy_invoker<void ()>::__call_impl<std::__1::__function::__default_alloc_func<DB::PipelineExecutor::spawnThreads()::$_0, void ()>>(std::__1::__function::__policy_storage const*)
ThreadPoolImpl<ThreadFromGlobalPoolImpl<false>>::worker(std::__1::__list_iterator<ThreadFromGlobalPoolImpl<false>, void*>)
void std::__1::__function::__policy_invoker<void ()>::__call_impl<std::__1::__function::__default_alloc_func<ThreadFromGlobalPoolImpl<false>::ThreadFromGlobalPoolImpl<void ThreadPoolImpl<ThreadFromGlobalPoolImpl<false>>::scheduleImpl<void>(std::__1::function<void ()>, Priority, std::__1::optional<unsigned long>, bool)::'lambda0'()>(void&&)::'lambda'(), void ()>>(std::__1::__function::__policy_storage const*)
void* std::__1::__thread_proxy[abi:v15000]<std::__1::tuple<std::__1::unique_ptr<std::__1::__thread_struct, std::__1::default_delete<std::__1::__thread_struct>>, void ThreadPoolImpl<std::__1::thread>::scheduleImpl<void>(std::__1::function<void ()>, Priority, std::__1::optional<unsigned long>, bool)::'lambda0'()>>(void*)
```

Getting filenames and line numbers in ClickHouse source code:

``` sql
WITH arrayMap(x -> addressToLine(x), trace) AS all, arrayFilter(x -> x LIKE '%/dbms/%', all) AS dbms SELECT thread_name, thread_id, query_id, arrayStringConcat(notEmpty(dbms) ? dbms : all, '\n') AS res FROM system.stack_trace LIMIT 1 \G;
```

``` text
Row 1:
──────
thread_name: clickhouse-serv

thread_id: 686
query_id:  cad353e7-1c29-4b2e-949f-93e597ab7a54
res:       /lib/x86_64-linux-gnu/libc-2.27.so
/build/obj-x86_64-linux-gnu/../src/Storages/System/StorageSystemStackTrace.cpp:182
/build/obj-x86_64-linux-gnu/../contrib/libcxx/include/vector:656
/build/obj-x86_64-linux-gnu/../src/Interpreters/InterpreterSelectQuery.cpp:1338
/build/obj-x86_64-linux-gnu/../src/Interpreters/InterpreterSelectQuery.cpp:751
/build/obj-x86_64-linux-gnu/../contrib/libcxx/include/optional:224
/build/obj-x86_64-linux-gnu/../src/Interpreters/InterpreterSelectWithUnionQuery.cpp:192
/build/obj-x86_64-linux-gnu/../src/Interpreters/executeQuery.cpp:384
/build/obj-x86_64-linux-gnu/../src/Interpreters/executeQuery.cpp:643
/build/obj-x86_64-linux-gnu/../src/Server/TCPHandler.cpp:251
/build/obj-x86_64-linux-gnu/../src/Server/TCPHandler.cpp:1197
/build/obj-x86_64-linux-gnu/../contrib/poco/Net/src/TCPServerConnection.cpp:57
/build/obj-x86_64-linux-gnu/../contrib/libcxx/include/atomic:856
/build/obj-x86_64-linux-gnu/../contrib/poco/Foundation/include/Poco/Mutex_POSIX.h:59
/build/obj-x86_64-linux-gnu/../contrib/poco/Foundation/include/Poco/AutoPtr.h:223
/lib/x86_64-linux-gnu/libpthread-2.27.so
/lib/x86_64-linux-gnu/libc-2.27.so
```

**See Also**

- [Introspection Functions](../../sql-reference/functions/introspection.md) — Which introspection functions are available and how to use them.
- [system.trace_log](../system-tables/trace_log.md) — Contains stack traces collected by the sampling query profiler.
- [arrayMap](../../sql-reference/functions/array-functions.md#array-map) — Description and usage example of the `arrayMap` function.
- [arrayFilter](../../sql-reference/functions/array-functions.md#array-filter) — Description and usage example of the `arrayFilter` function.