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【 TiDB 版本】v7.0.0
【 Bug 的影响】多次重复查询，并copr_cache_hit_ratio一直为0
【可能的问题复现步骤】
任意一张表:explain analyze select count(*) from t,多次重复查询。
【看到的非预期行为】
copr_cache_hit_ratio=0
【期望看到的行为】
copr_cache_hit_ratio > 0
mysql> show config where name like 'tikv-client.copr-cache.capacity-mb';
+------+---------------------+------------------------------------+-------+
| Type | Instance | Name | Value |
+------+---------------------+------------------------------------+-------+
| tidb | 192.168.31.201:4000 | tikv-client.copr-cache.capacity-mb | 1000 |
+------+---------------------+------------------------------------+-------+
1 row in set (0.01 sec)
mysql> show config where name like 'storage.engine';
+------+----------------------+----------------+----------+
| Type | Instance | Name | Value |
+------+----------------------+----------------+----------+
| tikv | 192.168.31.201:20160 | storage.engine | raft-kv2 |
+------+----------------------+----------------+----------+
1 row in set (0.01 sec)
mysql> explain analyze select count(*) from tpch100.customer;
+----------------------------+-------------+----------+-----------+----------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+-----------+------+
| id | estRows | actRows | task | access object | execution info | operator info | memory | disk |
+----------------------------+-------------+----------+-----------+----------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+-----------+------+
| HashAgg_11 | 1.00 | 1 | root | | time:19.7s, loops:2, RRU:64191.095707, WRU:0.000000, partial_worker:{wall_time:19.707367785s, concurrency:5, task_num:1, tot_wait:1m38.535453168s, tot_exec:44.681µs, tot_time:1m38.535514877s, max:19.707113388s, p95:19.707113388s}, final_worker:{wall_time:0s, concurrency:5, task_num:1, tot_wait:1m38.535629349s, tot_exec:28.337µs, tot_time:1m38.535658973s, max:19.707135779s, p95:19.707135779s} | funcs:count(Column#10)->Column#9 | 11.1 KB | N/A |
| └─TableReader_12 | 1.00 | 34 | root | | time:19.7s, loops:2, cop_task: {num: 34, max: 13s, min: 4.9s, avg: 7.77s, p95: 12.5s, max_proc_keys: 467300, p95_proc_keys: 467198, tot_proc: 2m54s, tot_wait: 82.3ms, rpc_num: 34, rpc_time: 4m24.2s, copr_cache_hit_ratio: 0.00, build_task_duration: 683.4µs, max_distsql_concurrency: 15} | data:HashAgg_5 | 404 Bytes | N/A |
| └─HashAgg_5 | 1.00 | 34 | cop[tikv] | | tikv_task:{proc max:13s, min:4.89s, avg: 7.77s, p80:9.25s, p95:12.5s, iters:14662, tasks:34}, scan_detail: {total_process_keys: 15000000, total_process_keys_size: 405000000, total_keys: 15000034, get_snapshot_time: 6.36ms, rocksdb: {key_skipped_count: 15000000, block: {cache_hit_count: 83, read_count: 99868, read_byte: 1.60 GB, read_time: 50.2s}}} | funcs:count(1)->Column#10 | N/A | N/A |
| └─TableFullScan_10 | 15000000.00 | 15000000 | cop[tikv] | table:customer | tikv_task:{proc max:13s, min:4.89s, avg: 7.77s, p80:9.25s, p95:12.5s, iters:14662, tasks:34} | keep order:false, stats:pseudo | N/A | N/A |
+----------------------------+-------------+----------+-----------+----------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+-----------+------+
4 rows in set (19.71 sec)
mysql> explain analyze select count(*) from tpch100.customer;
+----------------------------+-------------+----------+-----------+----------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+-----------+------+
| id | estRows | actRows | task | access object | execution info | operator info | memory | disk |
+----------------------------+-------------+----------+-----------+----------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+-----------+------+
| HashAgg_11 | 1.00 | 1 | root | | time:950.4ms, loops:2, RRU:8918.221802, WRU:0.000000, partial_worker:{wall_time:950.366723ms, concurrency:5, task_num:1, tot_wait:4.751215875s, tot_exec:21.739µs, tot_time:4.751242336s, max:950.25069ms, p95:950.25069ms}, final_worker:{wall_time:0s, concurrency:5, task_num:1, tot_wait:4.751279297s, tot_exec:10.061µs, tot_time:4.751291593s, max:950.264823ms, p95:950.264823ms} | funcs:count(Column#10)->Column#9 | 11.1 KB | N/A |
| └─TableReader_12 | 1.00 | 34 | root | | time:950.2ms, loops:2, cop_task: {num: 34, max: 666ms, min: 199.8ms, avg: 376.9ms, p95: 643.5ms, max_proc_keys: 467300, p95_proc_keys: 467198, tot_proc: 8.19s, tot_wait: 32.7ms, rpc_num: 34, rpc_time: 12.8s, copr_cache_hit_ratio: 0.00, build_task_duration: 29.8µs, max_distsql_concurrency: 15} | data:HashAgg_5 | 389 Bytes | N/A |
| └─HashAgg_5 | 1.00 | 34 | cop[tikv] | | tikv_task:{proc max:666ms, min:198ms, avg: 370.4ms, p80:427ms, p95:629ms, iters:14662, tasks:34}, scan_detail: {total_process_keys: 15000000, total_process_keys_size: 405000000, total_keys: 15000034, get_snapshot_time: 17.2ms, rocksdb: {key_skipped_count: 15000000, block: {cache_hit_count: 99951}}} | funcs:count(1)->Column#10 | N/A | N/A |
| └─TableFullScan_10 | 15000000.00 | 15000000 | cop[tikv] | table:customer | tikv_task:{proc max:666ms, min:198ms, avg: 369ms, p80:427ms, p95:629ms, iters:14662, tasks:34} | keep order:false, stats:pseudo | N/A | N/A |
+----------------------------+-------------+----------+-----------+----------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+-----------+------+
4 rows in set (0.95 sec)
mysql> explain analyze select count(*) from tpch100.customer;
+----------------------------+-------------+----------+-----------+----------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+-----------+------+
| id | estRows | actRows | task | access object | execution info | operator info | memory | disk |
+----------------------------+-------------+----------+-----------+----------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+-----------+------+
| HashAgg_11 | 1.00 | 1 | root | | time:928.9ms, loops:2, RRU:8790.317043, WRU:0.000000, partial_worker:{wall_time:928.874944ms, concurrency:5, task_num:1, tot_wait:4.643754282s, tot_exec:17.086µs, tot_time:4.643777282s, max:928.757591ms, p95:928.757591ms}, final_worker:{wall_time:928.912445ms, concurrency:5, task_num:1, tot_wait:4.64387552s, tot_exec:12.804µs, tot_time:4.64389074s, max:928.797034ms, p95:928.797034ms} | funcs:count(Column#10)->Column#9 | 11.1 KB | N/A |
| └─TableReader_12 | 1.00 | 34 | root | | time:928.7ms, loops:2, cop_task: {num: 34, max: 588.2ms, min: 245.5ms, avg: 365.4ms, p95: 581.3ms, max_proc_keys: 467300, p95_proc_keys: 467198, tot_proc: 7.81s, tot_wait: 21.5ms, rpc_num: 34, rpc_time: 12.4s, copr_cache_hit_ratio: 0.00, build_task_duration: 31.8µs, max_distsql_concurrency: 15} | data:HashAgg_5 | 383 Bytes | N/A |
| └─HashAgg_5 | 1.00 | 34 | cop[tikv] | | tikv_task:{proc max:557ms, min:245ms, avg: 354.9ms, p80:400ms, p95:551ms, iters:14662, tasks:34}, scan_detail: {total_process_keys: 15000000, total_process_keys_size: 405000000, total_keys: 15000034, get_snapshot_time: 480.2µs, rocksdb: {key_skipped_count: 15000000, block: {cache_hit_count: 99951}}} | funcs:count(1)->Column#10 | N/A | N/A |
| └─TableFullScan_10 | 15000000.00 | 15000000 | cop[tikv] | table:customer | tikv_task:{proc max:551ms, min:244ms, avg: 353.1ms, p80:399ms, p95:547ms, iters:14662, tasks:34} | keep order:false, stats:pseudo | N/A | N/A |
+----------------------------+-------------+----------+-----------+----------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+-----------+------+
4 rows in set (0.93 sec)
当前数据库只有该查询，多次重复查询后copr_cache_hit_ratio一直是0。