system.instrumentation

Querying in ClickHouse CloudThe data in this system table is held locally on each node in ClickHouse Cloud. Obtaining a complete view of all data, therefore, requires the clusterAllReplicas function. See here for further details.

Description

Contains the instrumentation points using LLVM’s XRay feature. Availability system.instrumentation is present only in ClickHouse builds compiled with LLVM XRay support (USE_XRAY). On builds without it, the table does not exist and queries against it will fail with UNKNOWN_TABLE. You can check whether your build has it enabled with:

SELECT value FROM system.build_options WHERE name = 'USE_XRAY';

Columns

id (UInt32) — ID of the instrumentation point
function_id (Int32) — ID assigned to the function in xray_instr_map section of elf-binary.
function_name (LowCardinality(String)) — Name used to instrument the function.
handler (LowCardinality(String)) — Handler that was patched into instrumentation points of the function.
entry_type (Enum8(‘Entry’ = 0, ‘Exit’ = 1, ‘EntryAndExit’ = 2)) — Entry type for the patch.
symbol (LowCardinality(String)) — Complete and demangled symbol name.
arguments (Array(Dynamic)) — Arguments for the handler call.

Example

SELECT * FROM system.instrumentation FORMAT Vertical;

Row 1:
──────
id:            0
function_id:   231280
function_name: QueryMetricLog::startQuery
handler:       log
entry_type:    Entry
symbol:        DB::QueryMetricLog::startQuery(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>> const&, std::__1::chrono::time_point<std::__1::chrono::system_clock, std::__1::chrono::duration<long long, std::__1::ratio<1l, 1000000l>>>, unsigned long)
arguments:     ['test']

Row 2:
──────
id:            1
function_id:   231280
function_name: QueryMetricLog::startQuery
handler:       profile
entry_type:    EntryAndExit
symbol:        DB::QueryMetricLog::startQuery(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>> const&, std::__1::chrono::time_point<std::__1::chrono::system_clock, std::__1::chrono::duration<long long, std::__1::ratio<1l, 1000000l>>>, unsigned long)
arguments:     []

Row 3:
──────
id:            2
function_id:   231280
function_name: QueryMetricLog::startQuery
handler:       sleep
entry_type:    Exit
symbol:        DB::QueryMetricLog::startQuery(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>> const&, std::__1::chrono::time_point<std::__1::chrono::system_clock, std::__1::chrono::duration<long long, std::__1::ratio<1l, 1000000l>>>, unsigned long)
arguments:     [0.3]

3 rows in set. Elapsed: 0.302 sec.

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