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480 lines
26 KiB
Markdown
480 lines
26 KiB
Markdown
---
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slug: /en/sql-reference/functions/introspection
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sidebar_position: 65
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sidebar_label: Introspection
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---
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# Introspection Functions
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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
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These functions are slow and may impose security considerations.
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:::
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For proper operation of introspection functions:
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- Install the `clickhouse-common-static-dbg` package.
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- Set the [allow_introspection_functions](../../operations/settings/settings.md#settings-allow_introspection_functions) setting to 1.
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For security reasons introspection functions are disabled by default.
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ClickHouse saves profiler reports to the [trace_log](../../operations/system-tables/trace_log.md#system_tables-trace_log) system table. Make sure the table and profiler are configured properly.
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## addressToLine
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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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``` sql
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addressToLine(address_of_binary_instruction)
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```
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**Arguments**
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- `address_of_binary_instruction` ([UInt64](../../sql-reference/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 line number in this file delimited by colon.
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For example, `/build/obj-x86_64-linux-gnu/../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](../../sql-reference/data-types/string.md).
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**Example**
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Enabling introspection functions:
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``` sql
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SET allow_introspection_functions=1;
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```
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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/../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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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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\G
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```
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The [arrayMap](../../sql-reference/functions/array-functions.md#array-map) function allows to process each individual element of the `trace` array by the `addressToLine` function. The result of this processing you see in the `trace_source_code_lines` column of output.
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``` text
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Row 1:
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──────
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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/../src/Common/ThreadPool.cpp:199
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/build/obj-x86_64-linux-gnu/../src/Common/ThreadPool.h:155
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/usr/include/c++/9/bits/atomic_base.h:551
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/usr/lib/debug/usr/bin/clickhouse
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/lib/x86_64-linux-gnu/libpthread-2.27.so
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/build/glibc-OTsEL5/glibc-2.27/misc/../sysdeps/unix/sysv/linux/x86_64/clone.S:97
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```
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## addressToLineWithInlines
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Similar to `addressToLine`, but it will return an Array with all inline functions, and will be much slower as a price.
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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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``` sql
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addressToLineWithInlines(address_of_binary_instruction)
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```
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**Arguments**
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- `address_of_binary_instruction` ([UInt64](../../sql-reference/data-types/int-uint.md)) — Address of instruction in a running process.
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**Returned value**
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- Array which first element is source code filename and the line number in this file delimited by colon. And from second element, inline functions' source code filename and line number and function name are listed.
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- Array with single element which is name of a binary, if the function couldn’t find the debug information.
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- Empty array, if the address is not valid.
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Type: [Array(String)](../../sql-reference/data-types/array.md).
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**Example**
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Enabling introspection functions:
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``` sql
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SET allow_introspection_functions=1;
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```
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Applying the function to address.
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```sql
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SELECT addressToLineWithInlines(531055181::UInt64);
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```
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``` text
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┌─addressToLineWithInlines(CAST('531055181', 'UInt64'))────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
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│ ['./src/Functions/addressToLineWithInlines.cpp:98','./build_normal_debug/./src/Functions/addressToLineWithInlines.cpp:176:DB::(anonymous namespace)::FunctionAddressToLineWithInlines::implCached(unsigned long) const'] │
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└──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
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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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ta, addressToLineWithInlines(arrayJoin(trace) as ta)
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FROM system.trace_log
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WHERE
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query_id = '5e173544-2020-45de-b645-5deebe2aae54';
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```
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The [arrayJoin](../../sql-reference/functions/array-functions.md#array-functions-join) functions will split array to rows.
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``` text
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┌────────ta─┬─addressToLineWithInlines(arrayJoin(trace))───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
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│ 365497529 │ ['./build_normal_debug/./contrib/libcxx/include/string_view:252'] │
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│ 365593602 │ ['./build_normal_debug/./src/Common/Dwarf.cpp:191'] │
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│ 365593866 │ ['./build_normal_debug/./src/Common/Dwarf.cpp:0'] │
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│ 365592528 │ ['./build_normal_debug/./src/Common/Dwarf.cpp:0'] │
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│ 365591003 │ ['./build_normal_debug/./src/Common/Dwarf.cpp:477'] │
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│ 365590479 │ ['./build_normal_debug/./src/Common/Dwarf.cpp:442'] │
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│ 365590600 │ ['./build_normal_debug/./src/Common/Dwarf.cpp:457'] │
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│ 365598941 │ ['./build_normal_debug/./src/Common/Dwarf.cpp:0'] │
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│ 365607098 │ ['./build_normal_debug/./src/Common/Dwarf.cpp:0'] │
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│ 365590571 │ ['./build_normal_debug/./src/Common/Dwarf.cpp:451'] │
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│ 365598941 │ ['./build_normal_debug/./src/Common/Dwarf.cpp:0'] │
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│ 365607098 │ ['./build_normal_debug/./src/Common/Dwarf.cpp:0'] │
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│ 365590571 │ ['./build_normal_debug/./src/Common/Dwarf.cpp:451'] │
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│ 365598941 │ ['./build_normal_debug/./src/Common/Dwarf.cpp:0'] │
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│ 365607098 │ ['./build_normal_debug/./src/Common/Dwarf.cpp:0'] │
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│ 365590571 │ ['./build_normal_debug/./src/Common/Dwarf.cpp:451'] │
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│ 365598941 │ ['./build_normal_debug/./src/Common/Dwarf.cpp:0'] │
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│ 365597289 │ ['./build_normal_debug/./src/Common/Dwarf.cpp:807'] │
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│ 365599840 │ ['./build_normal_debug/./src/Common/Dwarf.cpp:1118'] │
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│ 531058145 │ ['./build_normal_debug/./src/Functions/addressToLineWithInlines.cpp:152'] │
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│ 531055181 │ ['./src/Functions/addressToLineWithInlines.cpp:98','./build_normal_debug/./src/Functions/addressToLineWithInlines.cpp:176:DB::(anonymous namespace)::FunctionAddressToLineWithInlines::implCached(unsigned long) const'] │
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│ 422333613 │ ['./build_normal_debug/./src/Functions/IFunctionAdaptors.h:21'] │
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│ 586866022 │ ['./build_normal_debug/./src/Functions/IFunction.cpp:216'] │
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│ 586869053 │ ['./build_normal_debug/./src/Functions/IFunction.cpp:264'] │
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│ 586873237 │ ['./build_normal_debug/./src/Functions/IFunction.cpp:334'] │
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│ 597901620 │ ['./build_normal_debug/./src/Interpreters/ExpressionActions.cpp:601'] │
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│ 597898534 │ ['./build_normal_debug/./src/Interpreters/ExpressionActions.cpp:718'] │
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│ 630442912 │ ['./build_normal_debug/./src/Processors/Transforms/ExpressionTransform.cpp:23'] │
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│ 546354050 │ ['./build_normal_debug/./src/Processors/ISimpleTransform.h:38'] │
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│ 626026993 │ ['./build_normal_debug/./src/Processors/ISimpleTransform.cpp:89'] │
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│ 626294022 │ ['./build_normal_debug/./src/Processors/Executors/ExecutionThreadContext.cpp:45'] │
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│ 626293730 │ ['./build_normal_debug/./src/Processors/Executors/ExecutionThreadContext.cpp:63'] │
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│ 626169525 │ ['./build_normal_debug/./src/Processors/Executors/PipelineExecutor.cpp:213'] │
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│ 626170308 │ ['./build_normal_debug/./src/Processors/Executors/PipelineExecutor.cpp:178'] │
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│ 626166348 │ ['./build_normal_debug/./src/Processors/Executors/PipelineExecutor.cpp:329'] │
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│ 626163461 │ ['./build_normal_debug/./src/Processors/Executors/PipelineExecutor.cpp:84'] │
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│ 626323536 │ ['./build_normal_debug/./src/Processors/Executors/PullingAsyncPipelineExecutor.cpp:85'] │
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│ 626323277 │ ['./build_normal_debug/./src/Processors/Executors/PullingAsyncPipelineExecutor.cpp:112'] │
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│ 626323133 │ ['./build_normal_debug/./contrib/libcxx/include/type_traits:3682'] │
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│ 626323041 │ ['./build_normal_debug/./contrib/libcxx/include/tuple:1415'] │
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└───────────┴──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
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```
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## addressToSymbol
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Converts virtual memory address inside ClickHouse server process to the symbol from ClickHouse object files.
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**Syntax**
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``` sql
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addressToSymbol(address_of_binary_instruction)
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```
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**Arguments**
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- `address_of_binary_instruction` ([UInt64](../../sql-reference/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](../../sql-reference/data-types/string.md).
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**Example**
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Enabling introspection functions:
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``` sql
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SET allow_introspection_functions=1;
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```
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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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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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\G
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```
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The [arrayMap](../../sql-reference/functions/array-functions.md#array-map) function allows to process each individual element of the `trace` array by the `addressToSymbols` function. The result of this processing you see in the `trace_symbols` column of output.
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``` text
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Row 1:
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──────
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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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_ZN2DB10Aggregator14executeOnBlockERKNS_5BlockERNS_22AggregatedDataVariantsERSt6vectorIPKNS_7IColumnESaIS9_EERS6_ISB_SaISB_EERb
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_ZN2DB10Aggregator7executeERKSt10shared_ptrINS_17IBlockInputStreamEERNS_22AggregatedDataVariantsE
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_ZN2DB27AggregatingBlockInputStream8readImplEv
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_ZN2DB17IBlockInputStream4readEv
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_ZN2DB26ExpressionBlockInputStream8readImplEv
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_ZN2DB17IBlockInputStream4readEv
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_ZN2DB26ExpressionBlockInputStream8readImplEv
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_ZN2DB17IBlockInputStream4readEv
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_ZN2DB28AsynchronousBlockInputStream9calculateEv
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_ZNSt17_Function_handlerIFvvEZN2DB28AsynchronousBlockInputStream4nextEvEUlvE_E9_M_invokeERKSt9_Any_data
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_ZN14ThreadPoolImplI20ThreadFromGlobalPoolE6workerESt14_List_iteratorIS0_E
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_ZZN20ThreadFromGlobalPoolC4IZN14ThreadPoolImplIS_E12scheduleImplIvEET_St8functionIFvvEEiSt8optionalImEEUlvE1_JEEEOS4_DpOT0_ENKUlvE_clEv
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_ZN14ThreadPoolImplISt6threadE6workerESt14_List_iteratorIS0_E
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execute_native_thread_routine
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start_thread
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clone
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```
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## demangle
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Converts a symbol that you can get using the [addressToSymbol](#addresstosymbol) function to the C++ function name.
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**Syntax**
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``` sql
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demangle(symbol)
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```
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**Arguments**
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- `symbol` ([String](../../sql-reference/data-types/string.md)) — Symbol from an object file.
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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](../../sql-reference/data-types/string.md).
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**Example**
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Enabling introspection functions:
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``` sql
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SET allow_introspection_functions=1;
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```
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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 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](../../sql-reference/functions/array-functions.md#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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DB::Aggregator::executeOnBlock(DB::Block const&, 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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||
DB::Aggregator::execute(std::shared_ptr<DB::IBlockInputStream> 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<void (), DB::AsynchronousBlockInputStream::next()::{lambda()#1}>::_M_invoke(std::_Any_data const&)
|
||
ThreadPoolImpl<ThreadFromGlobalPool>::worker(std::_List_iterator<ThreadFromGlobalPool>)
|
||
ThreadFromGlobalPool::ThreadFromGlobalPool<ThreadPoolImpl<ThreadFromGlobalPool>::scheduleImpl<void>(std::function<void ()>, int, std::optional<unsigned long>)::{lambda()#3}>(ThreadPoolImpl<ThreadFromGlobalPool>::scheduleImpl<void>(std::function<void ()>, int, std::optional<unsigned long>)::{lambda()#3}&&)::{lambda()#1}::operator()() const
|
||
ThreadPoolImpl<std::thread>::worker(std::_List_iterator<std::thread>)
|
||
execute_native_thread_routine
|
||
start_thread
|
||
clone
|
||
```
|
||
## tid
|
||
|
||
Returns id of the thread, in which current [Block](https://clickhouse.com/docs/en/development/architecture/#block) is processed.
|
||
|
||
**Syntax**
|
||
|
||
``` sql
|
||
tid()
|
||
```
|
||
|
||
**Returned value**
|
||
|
||
- Current thread id. [Uint64](../../sql-reference/data-types/int-uint.md#uint-ranges).
|
||
|
||
**Example**
|
||
|
||
Query:
|
||
|
||
``` sql
|
||
SELECT tid();
|
||
```
|
||
|
||
Result:
|
||
|
||
``` text
|
||
┌─tid()─┐
|
||
│ 3878 │
|
||
└───────┘
|
||
```
|
||
|
||
## logTrace
|
||
|
||
Emits trace log message to server log for each [Block](https://clickhouse.com/docs/en/development/architecture/#block).
|
||
|
||
**Syntax**
|
||
|
||
``` sql
|
||
logTrace('message')
|
||
```
|
||
|
||
**Arguments**
|
||
|
||
- `message` — Message that is emitted to server log. [String](../../sql-reference/data-types/string.md#string).
|
||
|
||
**Returned value**
|
||
|
||
- Always returns 0.
|
||
|
||
**Example**
|
||
|
||
Query:
|
||
|
||
``` sql
|
||
SELECT logTrace('logTrace message');
|
||
```
|
||
|
||
Result:
|
||
|
||
``` text
|
||
┌─logTrace('logTrace message')─┐
|
||
│ 0 │
|
||
└──────────────────────────────┘
|
||
```
|
||
|