> ## Documentation Index > Fetch the complete documentation index at: https://private-7c7dfe99-framing-web-ui.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#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.

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#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#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(...) DB::Aggregator::executeOnBlock(DB::Block const&, ...) 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. The function accepts a constant argument only, so the call is evaluated during query analysis and replaced by its result. The message is therefore emitted once while the query is analyzed, and not once per processed [Block](/resources/develop-contribute/introduction/architecture#block): the number of rows and the setting `max_block_size` have no effect on how many messages appear in the log. **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 │ └───────┘ ```