SHOW [GLOBAL|SESSION] VARIABLES
SHOW [GLOBAL|SESSION] VARIABLES 语句用于显示 GLOBAL 或 SESSION 范围的变量列表。如果未指定范围，则应用默认范围 SESSION。
语法图
- ShowVariablesStmt
- ShowLikeOrWhere
ShowVariablesStmt ::=
"SHOW" ("GLOBAL" | "SESSION")? VARIABLES ShowLikeOrWhere?
ShowLikeOrWhere ::=
"LIKE" SimpleExpr
| "WHERE" Expression
示例
查看 TiDB 定义的专用系统变量，关于这些变量的含义参见系统变量和语法。
SHOW GLOBAL VARIABLES LIKE 'tidb%';
+-------------------------------------+---------------------+
| Variable_name | Value |
+-------------------------------------+---------------------+
| tidb_allow_batch_cop | 0 |
| tidb_allow_remove_auto_inc | 0 |
| tidb_auto_analyze_end_time | 23:59 +0000 |
| tidb_auto_analyze_ratio | 0.5 |
| tidb_auto_analyze_start_time | 00:00 +0000 |
| tidb_backoff_lock_fast | 100 |
| tidb_backoff_weight | 2 |
| tidb_batch_commit | 0 |
| tidb_batch_delete | 0 |
| tidb_build_stats_concurrency | 4 |
| tidb_capture_plan_baselines | off |
| tidb_check_mb4_value_in_utf8 | 1 |
| tidb_checksum_table_concurrency | 4 |
| tidb_config | |
| tidb_constraint_check_in_place | 0 |
| tidb_current_ts | 0 |
| tidb_ddl_error_count_limit | 512 |
| tidb_ddl_reorg_batch_size | 256 |
| tidb_ddl_reorg_priority | PRIORITY_LOW |
| tidb_ddl_reorg_worker_cnt | 4 |
| tidb_disable_txn_auto_retry | 1 |
| tidb_distsql_scan_concurrency | 15 |
| tidb_dml_batch_size | 20000 |
| tidb_enable_cascades_planner | 0 |
| tidb_enable_chunk_rpc | 1 |
| tidb_enable_collect_execution_info | 1 |
| tidb_enable_index_merge | 0 |
| tidb_enable_noop_functions | 0 |
| tidb_enable_radix_join | 0 |
| tidb_enable_slow_log | 1 |
| tidb_enable_stmt_summary | 1 |
| tidb_enable_table_partition | on |
| tidb_enable_vectorized_expression | 1 |
| tidb_enable_window_function | 1 |
| tidb_evolve_plan_baselines | off |
| tidb_evolve_plan_task_end_time | 23:59 +0000 |
| tidb_evolve_plan_task_max_time | 600 |
| tidb_evolve_plan_task_start_time | 00:00 +0000 |
| tidb_expensive_query_time_threshold | 60 |
| tidb_force_priority | NO_PRIORITY |
| tidb_general_log | 0 |
| tidb_hash_join_concurrency | 5 |
| tidb_hashagg_final_concurrency | 4 |
| tidb_hashagg_partial_concurrency | 4 |
| tidb_index_join_batch_size | 25000 |
| tidb_index_lookup_concurrency | 4 |
| tidb_index_lookup_join_concurrency | 4 |
| tidb_index_lookup_size | 20000 |
| tidb_index_serial_scan_concurrency | 1 |
| tidb_init_chunk_size | 32 |
| tidb_isolation_read_engines | tikv, tiflash, tidb |
| tidb_low_resolution_tso | 0 |
| tidb_max_chunk_size | 1024 |
| tidb_max_delta_schema_count | 1024 |
| tidb_mem_quota_hashjoin | 34359738368 |
| tidb_mem_quota_indexlookupjoin | 34359738368 |
| tidb_mem_quota_indexlookupreader | 34359738368 |
| tidb_mem_quota_mergejoin | 34359738368 |
| tidb_mem_quota_nestedloopapply | 34359738368 |
| tidb_mem_quota_query | 1073741824 |
| tidb_mem_quota_sort | 34359738368 |
| tidb_mem_quota_topn | 34359738368 |
| tidb_metric_query_range_duration | 60 |
| tidb_metric_query_step | 60 |
| tidb_opt_agg_push_down | 0 |
| tidb_opt_concurrency_factor | 3 |
| tidb_opt_copcpu_factor | 3 |
| tidb_opt_correlation_exp_factor | 1 |
| tidb_opt_correlation_threshold | 0.9 |
| tidb_opt_cpu_factor | 3 |
| tidb_opt_desc_factor | 3 |
| tidb_opt_disk_factor | 1.5 |
| tidb_opt_distinct_agg_push_down | 0 |
| tidb_opt_insubq_to_join_and_agg | 1 |
| tidb_opt_join_reorder_threshold | 0 |
| tidb_opt_memory_factor | 0.001 |
| tidb_opt_network_factor | 1 |
| tidb_opt_scan_factor | 1.5 |
| tidb_opt_seek_factor | 20 |
| tidb_opt_write_row_id | 0 |
| tidb_optimizer_selectivity_level | 0 |
| tidb_pprof_sql_cpu | 0 |
| tidb_projection_concurrency | 4 |
| tidb_query_log_max_len | 4096 |
| tidb_record_plan_in_slow_log | 1 |
| tidb_replica_read | leader |
| tidb_retry_limit | 10 |
| tidb_row_format_version | 2 |
| tidb_scatter_region | 0 |
| tidb_skip_isolation_level_check | 0 |
| tidb_skip_utf8_check | 0 |
| tidb_slow_log_threshold | 300 |
| tidb_slow_query_file | tidb-slow.log |
| tidb_snapshot | |
| tidb_stmt_summary_history_size | 24 |
| tidb_stmt_summary_internal_query | 0 |
| tidb_stmt_summary_max_sql_length | 4096 |
| tidb_stmt_summary_max_stmt_count | 3000 |
| tidb_stmt_summary_refresh_interval | 1800 |
| tidb_store_limit | 0 |
| tidb_txn_mode | |
| tidb_use_plan_baselines | on |
| tidb_wait_split_region_finish | 1 |
| tidb_wait_split_region_timeout | 300 |
| tidb_window_concurrency | 4 |
+-------------------------------------+---------------------+
108 rows in set (0.01 sec)
SHOW GLOBAL VARIABLES LIKE 'time_zone%';
+---------------+--------+
| Variable_name | Value |
+---------------+--------+
| time_zone | SYSTEM |
+---------------+--------+
1 row in set (0.00 sec)
SHOW VARIABLES WHERE Variable_name="tidb_window_concurrency";
+-------------------------+-------+
| Variable_name | Value |
+-------------------------+-------+
| tidb_window_concurrency | -1 |
+-------------------------+-------+
1 row in set (0.00 sec)
SHOW VARIABLES WHERE Value=300;
+--------------------------------+-------+
| Variable_name | Value |
+--------------------------------+-------+
| ddl_slow_threshold | 300 |
| delayed_insert_timeout | 300 |
| innodb_purge_batch_size | 300 |
| key_cache_age_threshold | 300 |
| slave_checkpoint_period | 300 |
| tidb_slow_log_threshold | 300 |
| tidb_wait_split_region_timeout | 300 |
+--------------------------------+-------+
7 rows in set (0.00 sec)
MySQL 兼容性
SHOW [GLOBAL|SESSION] VARIABLES 语句与 MySQL 完全兼容。如发现任何兼容性差异，请尝试 TiDB 支持资源。