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DocumentationTDSQL-C for MySQLOperation GuideParallel QuerySetting Parallel QueryParallel Query Metrics
Parallel Query Metrics
Last updated: 2024-07-31 10:03:33
This document describes the monitoring metrics offered by TDSQL-C for MySQL to help you monitor the operations related to parallel database query in real time.
Prerequisites
Database version: TDSQL-C for MySQL 8.0 on kernel version 3.1.8 or later.
Parallel Query of Monitoring Metrics
Metric | Parameter | Unit | Description | Data Aggregation Method |
Parallelly Queried Threads | txsql_parallel_threads_currently_used | - | The number of threads currently used for parallel queries. | MAX |
Failed Parallel Queries | txsql_parallel_stmt_error | - | The number of parallel query statements that report errors. | SUM |
Executed Parallel Queries | txsql_parallel_stmt_executed | - | The number of executed parallel query statements. | SUM |
Parallel-to-Serial Queries | txsql_parallel_stmt_fallback | - | The number of parallel-to-serial query statements. | SUM |
Practical Tutorial for Monitoring Metrics
The following lists some special issues for which you should check the metrics and their solutions.
Example 1:
The value of Parallelly Queried Threads is always equal to the value set by
txsql_max_parallel_worker_threads.
Solution:
This example indicates that the threads are always fully loaded. We recommend you increase the value of the txsql_max_parallel_worker_threads parameter when the CPU utilization is low.Example 2:
The value of Failed Parallel Queries increases.
Solution:
Check the CPU utilization and memory utilization. If the load becomes significantly higher, we recommend you reduce the value of
txsql_parallel_degree to 1/4 of the number of CPU cores.Example 3:
The value of Parallel-to-Serial Queries increases.
Solution:
This example indicates that the currently executed SQL statement does not meet the conditions for parallel query. We recommend you increase the total number of threads (
txsql_max_parallel_worker_threads) or the maximum memory (txsql_optimizer_context_max_mem_size) of the parallel query plan environment that a single statement can apply for, so as to ensure that parallel query can be used for SQL statements.Was this page helpful?
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