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CLICKHOUSEDOCS-121: Update by the comments.
This commit is contained in:
Sergei Shtykov
parent
6d11f96106
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22399ad7be
@ -1011,7 +1011,6 @@ Lower values mean higher priority. Threads with low `nice` priority values are e
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Default value: 0.
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<<<<<<< HEAD
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## allow_introspection_functions {#settings-allow_introspection_functions}
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Enables of disables [introspections functions](../../query_language/functions/introspection.md) for query profiling.
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@ -1023,7 +1022,6 @@ Possible values:
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Default value: 0.
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=======
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## input_format_parallel_parsing
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- Type: bool
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@ -1037,6 +1035,5 @@ Enable order-preserving parallel parsing of data formats. Supported only for TSV
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- Default value: 1 MiB
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The minimum chunk size in bytes, which each thread will parse in parallel.
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>>>>>>> da754943d87c78168b9c2f5510b727def69b600c
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[Original article](https://clickhouse.yandex/docs/en/operations/settings/settings/) <!-- hide -->
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@ -1,6 +1,6 @@
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# Introspection Functions
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You can use functions described in this chapter to introspect ELF and DWARF for query profiling.
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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.
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!!! warning "Warning"
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These functions are slow and may impose security considerations.
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@ -16,7 +16,9 @@ ClickHouse saves profiler reports to the [trace_log](../../operations/system_tab
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## addressToLine {#addresstoline}
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Converts virtual memory address inside ClickHouse server process to the filename and the number of a string in ClickHouse source code, using the debug information installed by the `clickhouse-common-static-dbg` package.
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Converts virtual memory address inside ClickHouse server process to the filename and the line number in ClickHouse source code.
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If you use official ClickHouse packages, you need to install the `clickhouse-common-static-dbg` package.
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**Syntax**
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@ -26,11 +28,16 @@ addressToLine(address_of_binary_instruction)
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**Parameters**
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- `address_of_binary_instruction` ([UInt64](../../data_types/int_uint.md)) — Address of code instruction that have been executed at the moment of sampling.
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- `address_of_binary_instruction` ([UInt64](../../data_types/int_uint.md)) — Address of instruction in a running process.
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**Returned value**
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- Source code filename and the number of string in this file.
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- Source code filename and the line number in this file delimited by colon.
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For example, `/build/obj-x86_64-linux-gnu/../dbms/src/Common/ThreadPool.cpp:199`, where `199` is a line number.
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- Name of a binary, if the function couldn't find the debug information.
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- Empty string, if the address is not valid.
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Type: [String](../../data_types/string.md).
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@ -44,9 +51,38 @@ SET allow_introspection_functions=1
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Selecting the first string from the `trace_log` system table:
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```sql
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SELECT * FROM system.trace_log LIMIT 1 \G
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```
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```text
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Row 1:
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──────
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event_date: 2019-11-19
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event_time: 2019-11-19 18:57:23
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revision: 54429
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timer_type: Real
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thread_number: 48
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query_id: 421b6855-1858-45a5-8f37-f383409d6d72
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trace: [140658411141617,94784174532828,94784076370703,94784076372094,94784076361020,94784175007680,140658411116251,140658403895439]
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```
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The `trace` field contains the stack trace at the moment of sampling.
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Getting the source code filename and the line number for a single address:
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```sql
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SELECT addressToLine(94784076370703) \G
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```
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```text
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Row 1:
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──────
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addressToLine(94784076370703): /build/obj-x86_64-linux-gnu/../dbms/src/Common/ThreadPool.cpp:199
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```
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Applying the function to the whole stack trace:
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```sql
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SELECT
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*,
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arrayStringConcat(arrayMap(x -> addressToLine(x), trace), '\n') AS trace_source_code_lines
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FROM system.trace_log
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LIMIT 1
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@ -58,13 +94,6 @@ The [arrayMap](higher_order_functions.md#higher_order_functions-array-map) funct
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```text
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Row 1:
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──────
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event_date: 2019-11-19
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event_time: 2019-11-19 18:57:23
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revision: 54429
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timer_type: Real
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thread_number: 48
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query_id: 421b6855-1858-45a5-8f37-f383409d6d72
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trace: [140658411141617,94784174532828,94784076370703,94784076372094,94784076361020,94784175007680,140658411116251,140658403895439]
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trace_source_code_lines: /lib/x86_64-linux-gnu/libpthread-2.27.so
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/usr/lib/debug/usr/bin/clickhouse
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/build/obj-x86_64-linux-gnu/../dbms/src/Common/ThreadPool.cpp:199
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@ -88,11 +117,12 @@ addressToSymbol(address_of_binary_instruction)
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**Parameters**
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- `address_of_binary_instruction` ([UInt64](../../data_types/int_uint.md)) — Address of code instruction that have been executed at the moment of sampling.
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- `address_of_binary_instruction` ([UInt64](../../data_types/int_uint.md)) — Address of instruction in a running process.
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**Returned value**
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- Symbol from ClickHouse object files.
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- Empty string, if the address is not valid.
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Type: [String](../../data_types/string.md).
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@ -106,9 +136,38 @@ SET allow_introspection_functions=1
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Selecting the first string from the `trace_log` system table:
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```sql
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SELECT * FROM system.trace_log LIMIT 1 \G
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```
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```text
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Row 1:
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──────
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event_date: 2019-11-20
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event_time: 2019-11-20 16:57:59
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revision: 54429
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timer_type: Real
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thread_number: 48
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query_id: 724028bf-f550-45aa-910d-2af6212b94ac
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trace: [94138803686098,94138815010911,94138815096522,94138815101224,94138815102091,94138814222988,94138806823642,94138814457211,94138806823642,94138814457211,94138806823642,94138806795179,94138806796144,94138753770094,94138753771646,94138753760572,94138852407232,140399185266395,140399178045583]
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```
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The `trace` field contains the stack trace at the moment of sampling.
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Getting a symbol for a single address:
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```sql
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SELECT addressToSymbol(94138803686098) \G
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```
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```text
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Row 1:
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──────
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addressToSymbol(94138803686098): _ZNK2DB24IAggregateFunctionHelperINS_20AggregateFunctionSumImmNS_24AggregateFunctionSumDataImEEEEE19addBatchSinglePlaceEmPcPPKNS_7IColumnEPNS_5ArenaE
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```
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Applying the function to the whole stack trace:
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```sql
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SELECT
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*,
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arrayStringConcat(arrayMap(x -> addressToSymbol(x), trace), '\n') AS trace_symbols
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FROM system.trace_log
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LIMIT 1
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@ -121,13 +180,6 @@ The [arrayMap](higher_order_functions.md#higher_order_functions-array-map) funct
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```text
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Row 1:
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──────
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event_date: 2019-11-20
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event_time: 2019-11-20 16:57:59
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revision: 54429
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timer_type: Real
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thread_number: 48
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query_id: 724028bf-f550-45aa-910d-2af6212b94ac
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trace: [94138803686098,94138815010911,94138815096522,94138815101224,94138815102091,94138814222988,94138806823642,94138814457211,94138806823642,94138814457211,94138806823642,94138806795179,94138806796144,94138753770094,94138753771646,94138753760572,94138852407232,140399185266395,140399178045583]
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trace_symbols: _ZNK2DB24IAggregateFunctionHelperINS_20AggregateFunctionSumImmNS_24AggregateFunctionSumDataImEEEEE19addBatchSinglePlaceEmPcPPKNS_7IColumnEPNS_5ArenaE
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_ZNK2DB10Aggregator21executeWithoutKeyImplERPcmPNS0_28AggregateFunctionInstructionEPNS_5ArenaE
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_ZN2DB10Aggregator14executeOnBlockESt6vectorIN3COWINS_7IColumnEE13immutable_ptrIS3_EESaIS6_EEmRNS_22AggregatedDataVariantsERS1_IPKS3_SaISC_EERS1_ISE_SaISE_EERb
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@ -167,6 +219,7 @@ demangle(symbol)
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**Returned value**
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- Name of the C++ function.
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- Empty string if a symbol is not valid.
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Type: [String](../../data_types/string.md).
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@ -181,17 +234,8 @@ SET allow_introspection_functions=1
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Selecting the first string from the `trace_log` system table:
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```sql
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SELECT
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*,
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arrayStringConcat(arrayMap(x -> demangle(addressToSymbol(x)), trace), '\n') AS trace_functions
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FROM system.trace_log
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LIMIT 1
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\G
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SELECT * FROM system.trace_log LIMIT 1 \G
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```
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The [arrayMap](higher_order_functions.md#higher_order_functions-array-map) function allows to process each individual element of the `trace` array by the `demangle` function. The result of this processing you see in the `trace_functions` column of output.
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```text
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Row 1:
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──────
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@ -202,6 +246,36 @@ timer_type: Real
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thread_number: 48
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query_id: 724028bf-f550-45aa-910d-2af6212b94ac
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trace: [94138803686098,94138815010911,94138815096522,94138815101224,94138815102091,94138814222988,94138806823642,94138814457211,94138806823642,94138814457211,94138806823642,94138806795179,94138806796144,94138753770094,94138753771646,94138753760572,94138852407232,140399185266395,140399178045583]
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```
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The `trace` field contains the stack trace at the moment of sampling.
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Getting a function name for a single address:
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```sql
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SELECT demangle(addressToSymbol(94138803686098)) \G
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```
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```text
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Row 1:
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──────
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demangle(addressToSymbol(94138803686098)): DB::IAggregateFunctionHelper<DB::AggregateFunctionSum<unsigned long, unsigned long, DB::AggregateFunctionSumData<unsigned long> > >::addBatchSinglePlace(unsigned long, char*, DB::IColumn const**, DB::Arena*) const
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```
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Applying the function to the whole stack trace:
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```sql
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SELECT
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arrayStringConcat(arrayMap(x -> demangle(addressToSymbol(x)), trace), '\n') AS trace_functions
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FROM system.trace_log
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LIMIT 1
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\G
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```
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The [arrayMap](higher_order_functions.md#higher_order_functions-array-map) function allows to process each individual element of the `trace` array by the `demangle` function. The result of this processing you see in the `trace_functions` column of output.
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```text
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Row 1:
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──────
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trace_functions: DB::IAggregateFunctionHelper<DB::AggregateFunctionSum<unsigned long, unsigned long, DB::AggregateFunctionSumData<unsigned long> > >::addBatchSinglePlace(unsigned long, char*, DB::IColumn const**, DB::Arena*) const
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DB::Aggregator::executeWithoutKeyImpl(char*&, unsigned long, DB::Aggregator::AggregateFunctionInstruction*, DB::Arena*) const
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DB::Aggregator::executeOnBlock(std::vector<COW<DB::IColumn>::immutable_ptr<DB::IColumn>, std::allocator<COW<DB::IColumn>::immutable_ptr<DB::IColumn> > >, unsigned long, DB::AggregatedDataVariants&, std::vector<DB::IColumn const*, std::allocator<DB::IColumn const*> >&, std::vector<std::vector<DB::IColumn const*, std::allocator<DB::IColumn const*> >, std::allocator<std::vector<DB::IColumn const*, std::allocator<DB::IColumn const*> > > >&, bool&)
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