> ## Documentation Index > Fetch the complete documentation index at: https://private-7c7dfe99-mintlify-8a08bda2.mintlify.site/llms.txt > Use this file to discover all available pages before exploring further. > Documentation for Introspection Functions # Introspection Functions You can use functions described in this chapter to introspect [ELF](https://en.wikipedia.org/wiki/Executable_and_Linkable_Format) and [DWARF](https://en.wikipedia.org/wiki/DWARF) for query profiling. These functions are slow and may impose security considerations. For proper operation of introspection functions: * Install the `clickhouse-common-static-dbg` package. * Set the [allow\_introspection\_functions](/reference/settings/session-settings#allow_introspection_functions) setting to 1. For security reasons introspection functions are disabled by default. ClickHouse saves profiler reports to the [trace\_log](/reference/system-tables/trace_log) system table. Make sure the table and profiler are configured properly. {/*AUTOGENERATED_START*/}

addressToLine

Introduced in: v20.1.0 Converts a virtual memory address inside the ClickHouse server process to a filename and line number in ClickHouse's source code. This function is slow and may impose security considerations. To enable this introspection function: * Install the `clickhouse-common-static-dbg` package. * Set setting [`allow_introspection_functions`](/reference/settings/session-settings#allow_introspection_functions) to `1`. **Syntax** ```sql theme={null} addressToLine(address_of_binary_instruction) ``` **Arguments** * `address_of_binary_instruction` — Address of instruction in a running process. [`UInt64`](/reference/data-types/int-uint) **Returned value** Returns a source code filename and line number delimited by a colon, for example, `/build/obj-x86_64-linux-gnu/../src/Common/ThreadPool.cpp:199`. Returns the name of a binary, if no debug information could be found, otherwise an empty string, if the address is not valid. [`String`](/reference/data-types/string) **Examples** **Selecting the first string from the `trace_log` system table** ```sql title=Query theme={null} SET allow_introspection_functions=1; SELECT * FROM system.trace_log LIMIT 1 \G; ``` ```response title=Response theme={null} -- The `trace` field contains the stack trace at the moment of sampling. Row 1: ────── event_date: 2019-11-19 event_time: 2019-11-19 18:57:23 revision: 54429 timer_type: Real thread_number: 48 query_id: 421b6855-1858-45a5-8f37-f383409d6d72 trace: [140658411141617,94784174532828,94784076370703,94784076372094,94784076361020,94784175007680,140658411116251,140658403895439] ``` **Getting the source code filename and the line number for a single address** ```sql title=Query theme={null} SET allow_introspection_functions=1; SELECT addressToLine(94784076370703) \G; ``` ```response title=Response theme={null} Row 1: ────── addressToLine(94784076370703): /build/obj-x86_64-linux-gnu/../src/Common/ThreadPool.cpp:199 ``` **Applying the function to the whole stack trace** ```sql title=Query theme={null} -- The arrayMap function in this example processing each individual element of the trace array by the addressToLine function. -- The result of this processing is seen in the trace_source_code_lines column of output. SELECT arrayStringConcat(arrayMap(x -> addressToLine(x), trace), '\n') AS trace_source_code_lines FROM system.trace_log LIMIT 1 \G ``` ```response title=Response theme={null} Row 1: ────── trace_source_code_lines: /lib/x86_64-linux-gnu/libpthread-2.27.so /usr/lib/debug/usr/bin/clickhouse /build/obj-x86_64-linux-gnu/../src/Common/ThreadPool.cpp:199 /build/obj-x86_64-linux-gnu/../src/Common/ThreadPool.h:155 /usr/include/c++/9/bits/atomic_base.h:551 /usr/lib/debug/usr/bin/clickhouse /lib/x86_64-linux-gnu/libpthread-2.27.so /build/glibc-OTsEL5/glibc-2.27/misc/../sysdeps/unix/sysv/linux/x86_64/clone.S:97 ```

addressToLineWithInlines

Introduced in: v22.2.0 Similar to `addressToLine`, but returns an Array with all inline functions. As a result of this, it is slower than `addressToLine`. To enable this introspection function: * Install the `clickhouse-common-static-dbg` package. * Set setting [`allow_introspection_functions`](/reference/settings/session-settings#allow_introspection_functions) to `1`. **Syntax** ```sql theme={null} addressToLineWithInlines(address_of_binary_instruction) ``` **Arguments** * `address_of_binary_instruction` — The address of an instruction in a running process. [`UInt64`](/reference/data-types/int-uint) **Returned value** Returns an array whose first element is the source code filename and line number delimited by a colon. The second, third, etc. element list inline functions' source code filenames, line numbers and function names. If no debug information could be found, then an array with a single element equal to the name of the binary is returned, otherwise an empty array is returned if the address is not valid. [`Array(String)`](/reference/data-types/array) **Examples** **Applying the function to an address** ```sql title=Query theme={null} SET allow_introspection_functions=1; SELECT addressToLineWithInlines(531055181::UInt64); ``` ```response title=Response theme={null} ┌─addressToLineWithInlines(CAST('531055181', 'UInt64'))────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐ │ ['./src/Functions/addressToLineWithInlines.cpp:98','./build_normal_debug/./src/Functions/addressToLineWithInlines.cpp:176:DB::(anonymous namespace)::FunctionAddressToLineWithInlines::implCached(unsigned long) const'] │ └──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘ ``` **Applying the function to the whole stack trace** ```sql title=Query theme={null} SET allow_introspection_functions=1; -- The arrayJoin function will split array to rows SELECT ta, addressToLineWithInlines(arrayJoin(trace) AS ta) FROM system.trace_log WHERE query_id = '5e173544-2020-45de-b645-5deebe2aae54'; ``` ```response title=Response theme={null} ┌────────ta─┬─addressToLineWithInlines(arrayJoin(trace))───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐ │ 365497529 │ ['./build_normal_debug/./contrib/libcxx/include/string_view:252'] │ │ 365593602 │ ['./build_normal_debug/./src/Common/Dwarf.cpp:191'] │ │ 365593866 │ ['./build_normal_debug/./src/Common/Dwarf.cpp:0'] │ │ 365592528 │ ['./build_normal_debug/./src/Common/Dwarf.cpp:0'] │ │ 365591003 │ ['./build_normal_debug/./src/Common/Dwarf.cpp:477'] │ │ 365590479 │ ['./build_normal_debug/./src/Common/Dwarf.cpp:442'] │ │ 365590600 │ ['./build_normal_debug/./src/Common/Dwarf.cpp:457'] │ │ 365598941 │ ['./build_normal_debug/./src/Common/Dwarf.cpp:0'] │ │ 365607098 │ ['./build_normal_debug/./src/Common/Dwarf.cpp:0'] │ │ 365590571 │ ['./build_normal_debug/./src/Common/Dwarf.cpp:451'] │ │ 365598941 │ ['./build_normal_debug/./src/Common/Dwarf.cpp:0'] │ │ 365607098 │ ['./build_normal_debug/./src/Common/Dwarf.cpp:0'] │ │ 365590571 │ ['./build_normal_debug/./src/Common/Dwarf.cpp:451'] │ │ 365598941 │ ['./build_normal_debug/./src/Common/Dwarf.cpp:0'] │ │ 365607098 │ ['./build_normal_debug/./src/Common/Dwarf.cpp:0'] │ │ 365590571 │ ['./build_normal_debug/./src/Common/Dwarf.cpp:451'] │ │ 365598941 │ ['./build_normal_debug/./src/Common/Dwarf.cpp:0'] │ │ 365597289 │ ['./build_normal_debug/./src/Common/Dwarf.cpp:807'] │ │ 365599840 │ ['./build_normal_debug/./src/Common/Dwarf.cpp:1118'] │ │ 531058145 │ ['./build_normal_debug/./src/Functions/addressToLineWithInlines.cpp:152'] │ │ 531055181 │ ['./src/Functions/addressToLineWithInlines.cpp:98','./build_normal_debug/./src/Functions/addressToLineWithInlines.cpp:176:DB::(anonymous namespace)::FunctionAddressToLineWithInlines::implCached(unsigned long) const'] │ │ 422333613 │ ['./build_normal_debug/./src/Functions/IFunctionAdaptors.h:21'] │ │ 586866022 │ ['./build_normal_debug/./src/Functions/IFunction.cpp:216'] │ │ 586869053 │ ['./build_normal_debug/./src/Functions/IFunction.cpp:264'] │ │ 586873237 │ ['./build_normal_debug/./src/Functions/IFunction.cpp:334'] │ │ 597901620 │ ['./build_normal_debug/./src/Interpreters/ExpressionActions.cpp:601'] │ │ 597898534 │ ['./build_normal_debug/./src/Interpreters/ExpressionActions.cpp:718'] │ │ 630442912 │ ['./build_normal_debug/./src/Processors/Transforms/ExpressionTransform.cpp:23'] │ │ 546354050 │ ['./build_normal_debug/./src/Processors/ISimpleTransform.h:38'] │ │ 626026993 │ ['./build_normal_debug/./src/Processors/ISimpleTransform.cpp:89'] │ │ 626294022 │ ['./build_normal_debug/./src/Processors/Executors/ExecutionThreadContext.cpp:45'] │ │ 626293730 │ ['./build_normal_debug/./src/Processors/Executors/ExecutionThreadContext.cpp:63'] │ │ 626169525 │ ['./build_normal_debug/./src/Processors/Executors/PipelineExecutor.cpp:213'] │ │ 626170308 │ ['./build_normal_debug/./src/Processors/Executors/PipelineExecutor.cpp:178'] │ │ 626166348 │ ['./build_normal_debug/./src/Processors/Executors/PipelineExecutor.cpp:329'] │ │ 626163461 │ ['./build_normal_debug/./src/Processors/Executors/PipelineExecutor.cpp:84'] │ │ 626323536 │ ['./build_normal_debug/./src/Processors/Executors/PullingAsyncPipelineExecutor.cpp:85'] │ │ 626323277 │ ['./build_normal_debug/./src/Processors/Executors/PullingAsyncPipelineExecutor.cpp:112'] │ │ 626323133 │ ['./build_normal_debug/./contrib/libcxx/include/type_traits:3682'] │ │ 626323041 │ ['./build_normal_debug/./contrib/libcxx/include/tuple:1415'] │ └───────────┴──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘ ```

addressToSymbol

Introduced in: v20.1.0 Converts virtual memory address inside the ClickHouse server process to a symbol from ClickHouse's object files. **Syntax** ```sql theme={null} addressToSymbol(address_of_binary_instruction) ``` **Arguments** * `address_of_binary_instruction` — Address of instruction in a running process. [`UInt64`](/reference/data-types/int-uint) **Returned value** Returns the symbol from ClickHouse object files or an empty string, if the address is not valid. [`String`](/reference/data-types/string) **Examples** **Selecting the first string from the `trace_log` system table** ```sql title=Query theme={null} SET allow_introspection_functions=1; SELECT * FROM system.trace_log LIMIT 1 \G; ``` ```response title=Response theme={null} -- The `trace` field contains the stack trace at the moment of sampling. Row 1: ────── event_date: 2019-11-20 event_time: 2019-11-20 16:57:59 revision: 54429 timer_type: Real thread_number: 48 query_id: 724028bf-f550-45aa-910d-2af6212b94ac trace: [94138803686098,94138815010911,94138815096522,94138815101224,94138815102091,94138814222988,94138806823642,94138814457211,94138806823642,94138814457211,94138806823642,94138806795179,94138806796144,94138753770094,94138753771646,94138753760572,94138852407232,140399185266395,140399178045583] ``` **Getting a symbol for a single address** ```sql title=Query theme={null} SET allow_introspection_functions=1; SELECT addressToSymbol(94138803686098) \G; ``` ```response title=Response theme={null} Row 1: ────── addressToSymbol(94138803686098): _ZNK2DB24IAggregateFunctionHelperINS_20AggregateFunctionSumImmNS_24AggregateFunctionSumDataImEEEEE19addBatchSinglePlaceEmPcPPKNS_7IColumnEPNS_5ArenaE ``` **Applying the function to the whole stack trace** ```sql title=Query theme={null} SET allow_introspection_functions=1; -- The arrayMap function allows to process each individual element of the trace array by the addressToSymbols function. -- The result of this processing is shown in the trace_symbols column of output. SELECT arrayStringConcat(arrayMap(x -> addressToSymbol(x), trace), '\n') AS trace_symbols FROM system.trace_log LIMIT 1 \G ``` ```response title=Response theme={null} Row 1: ────── trace_symbols: _ZNK2DB24IAggregateFunctionHelperINS_20AggregateFunctionSumImmNS_24AggregateFunctionSumDataImEEEEE19addBatchSinglePlaceEmPcPPKNS_7IColumnEPNS_5ArenaE _ZNK2DB10Aggregator21executeWithoutKeyImplERPcmPNS0_28AggregateFunctionInstructionEPNS_5ArenaE _ZN2DB10Aggregator14executeOnBlockESt6vectorIN3COWINS_7IColumnEE13immutable_ptrIS3_EESaIS6_EEmRNS_22AggregatedDataVariantsERS1_IPKS3_SaISC_EERS1_ISE_SaISE_EERb _ZN2DB10Aggregator14executeOnBlockERKNS_5BlockERNS_22AggregatedDataVariantsERSt6vectorIPKNS_7IColumnESaIS9_EERS6_ISB_SaISB_EERb _ZN2DB10Aggregator7executeERKSt10shared_ptrINS_17IBlockInputStreamEERNS_22AggregatedDataVariantsE _ZN2DB27AggregatingBlockInputStream8readImplEv _ZN2DB17IBlockInputStream4readEv _ZN2DB26ExpressionBlockInputStream8readImplEv _ZN2DB17IBlockInputStream4readEv _ZN2DB26ExpressionBlockInputStream8readImplEv _ZN2DB17IBlockInputStream4readEv _ZN2DB28AsynchronousBlockInputStream9calculateEv _ZNSt17_Function_handlerIFvvEZN2DB28AsynchronousBlockInputStream4nextEvEUlvE_E9_M_invokeERKSt9_Any_data _ZN14ThreadPoolImplI20ThreadFromGlobalPoolE6workerESt14_List_iteratorIS0_E _ZZN20ThreadFromGlobalPoolC4IZN14ThreadPoolImplIS_E12scheduleImplIvEET_St8functionIFvvEEiSt8optionalImEEUlvE1_JEEEOS4_DpOT0_ENKUlvE_clEv _ZN14ThreadPoolImplISt6threadE6workerESt14_List_iteratorIS0_E execute_native_thread_routine start_thread clone ```

demangle

Introduced in: v20.1.0 Converts a symbol to a C++ function name. The symbol is usually returned by function `addressToSymbol`. **Syntax** ```sql theme={null} demangle(symbol) ``` **Arguments** * `symbol` — Symbol from an object file. [`String`](/reference/data-types/string) **Returned value** Returns the name of the C++ function, or an empty string if the symbol is not valid. [`String`](/reference/data-types/string) **Examples** **Selecting the first string from the `trace_log` system table** ```sql title=Query theme={null} SELECT * FROM system.trace_log LIMIT 1 \G; ``` ```response title=Response theme={null} -- The `trace` field contains the stack trace at the moment of sampling. Row 1: ────── event_date: 2019-11-20 event_time: 2019-11-20 16:57:59 revision: 54429 timer_type: Real thread_number: 48 query_id: 724028bf-f550-45aa-910d-2af6212b94ac trace: [94138803686098,94138815010911,94138815096522,94138815101224,94138815102091,94138814222988,94138806823642,94138814457211,94138806823642,94138814457211,94138806823642,94138806795179,94138806796144,94138753770094,94138753771646,94138753760572,94138852407232,140399185266395,140399178045583] ``` **Getting a function name for a single address** ```sql title=Query theme={null} SET allow_introspection_functions=1; SELECT demangle(addressToSymbol(94138803686098)) \G; ``` ```response title=Response theme={null} Row 1: ────── demangle(addressToSymbol(94138803686098)): DB::IAggregateFunctionHelper > >::addBatchSinglePlace(unsigned long, char*, DB::IColumn const**, DB::Arena*) const ``` **Applying the function to the whole stack trace** ```sql title=Query theme={null} SET allow_introspection_functions=1; -- The arrayMap function allows to process each individual element of the trace array by the demangle function. -- The result of this processing is shown in the trace_functions column of output. SELECT arrayStringConcat(arrayMap(x -> demangle(addressToSymbol(x)), trace), '\n') AS trace_functions FROM system.trace_log LIMIT 1 \G ``` ```response title=Response theme={null} Row 1: ────── trace_functions: DB::IAggregateFunctionHelper > >::addBatchSinglePlace(unsigned long, char*, DB::IColumn const**, DB::Arena*) const DB::Aggregator::executeWithoutKeyImpl(char*&, unsigned long, DB::Aggregator::AggregateFunctionInstruction*, DB::Arena*) const DB::Aggregator::executeOnBlock(std::vector::immutable_ptr, std::allocator::immutable_ptr > >, unsigned long, DB::AggregatedDataVariants&, std::vector >&, std::vector >, std::allocator > > >&, bool&) DB::Aggregator::executeOnBlock(DB::Block const&, DB::AggregatedDataVariants&, std::vector >&, std::vector >, std::allocator > > >&, bool&) DB::Aggregator::execute(std::shared_ptr const&, DB::AggregatedDataVariants&) DB::AggregatingBlockInputStream::readImpl() DB::IBlockInputStream::read() DB::ExpressionBlockInputStream::readImpl() DB::IBlockInputStream::read() DB::ExpressionBlockInputStream::readImpl() DB::IBlockInputStream::read() DB::AsynchronousBlockInputStream::calculate() std::_Function_handler::_M_invoke(std::_Any_data const&) ThreadPoolImpl::worker(std::_List_iterator) ThreadFromGlobalPool::ThreadFromGlobalPool::scheduleImpl(std::function, int, std::optional)::{lambda()#3}>(ThreadPoolImpl::scheduleImpl(std::function, int, std::optional)::{lambda()#3}&&)::{lambda()#1}::operator()() const ThreadPoolImpl::worker(std::_List_iterator) execute_native_thread_routine start_thread clone ```

isMergeTreePartCoveredBy

Introduced in: v25.6.0 Function which checks if the part of the first argument is covered by the part of the second argument. **Syntax** ```sql theme={null} isMergeTreePartCoveredBy(nested_part, covering_part) ``` **Arguments** * `nested_part` — Name of expected nested part. [`String`](/reference/data-types/string) * `covering_part` — Name of expected covering part. [`String`](/reference/data-types/string) **Returned value** Returns `1` if it covers, `0` otherwise. [`UInt8`](/reference/data-types/int-uint) **Examples** **Basic example** ```sql title=Query theme={null} WITH 'all_12_25_7_4' AS lhs, 'all_7_100_10_20' AS rhs SELECT isMergeTreePartCoveredBy(rhs, lhs), isMergeTreePartCoveredBy(lhs, rhs); ``` ```response title=Response theme={null} ┌─isMergeTreePartCoveredBy(rhs, lhs)─┬─isMergeTreePartCoveredBy(lhs, rhs)─┐ │ 0 │ 1 │ └────────────────────────────────────┴────────────────────────────────────┘ ```

logTrace

Introduced in: v20.12.0 Emits a trace log message to the server log for each [Block](/resources/develop-contribute/introduction/architecture#block). **Syntax** ```sql theme={null} logTrace(message) ``` **Arguments** * `message` — Message that is emitted to the server log. [`const String`](/reference/data-types/string) **Returned value** Returns `0` always. [`UInt8`](/reference/data-types/int-uint) **Examples** **Basic example** ```sql title=Query theme={null} SELECT logTrace('logTrace message'); ``` ```response title=Response theme={null} ┌─logTrace('logTrace message')─┐ │ 0 │ └──────────────────────────────┘ ```

mergeTreePartInfo

Introduced in: v25.6.0 Function that helps to cut the useful values out of the `MergeTree` part name. **Syntax** ```sql theme={null} mergeTreePartInfo(part_name) ``` **Arguments** * `part_name` — Name of part to unpack. [`String`](/reference/data-types/string) **Returned value** Returns a Tuple with subcolumns: `partition_id`, `min_block`, `max_block`, `level`, `mutation`. [`Tuple`](/reference/data-types/tuple) **Examples** **Basic example** ```sql title=Query theme={null} WITH mergeTreePartInfo('all_12_25_7_4') AS info SELECT info.partition_id, info.min_block, info.max_block, info.level, info.mutation; ``` ```response title=Response theme={null} ┌─info.partition_id─┬─info.min_block─┬─info.max_block─┬─info.level─┬─info.mutation─┐ │ all │ 12 │ 25 │ 7 │ 4 │ └───────────────────┴────────────────┴────────────────┴────────────┴───────────────┘ ```

tid

Introduced in: v20.12.0 Returns id of the thread, in which the current [Block](/resources/develop-contribute/introduction/architecture#block) is processed. **Syntax** ```sql theme={null} tid() ``` **Arguments** * None. **Returned value** Returns the current thread id. [`UInt64`](/reference/data-types/int-uint) **Examples** **Usage example** ```sql title=Query theme={null} SELECT tid(); ``` ```response title=Response theme={null} ┌─tid()─┐ │ 3878 │ └───────┘ ```